Siege of Yorktown

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Siege of Yorktown
Part of the Yorktown Campaign and the American Revolutionary War
Surrender of Lord Cornwallis by John Trumbull, depicts the British surrendering to Benjamin Lincoln, flanked by French (left) and American troops. Oil on canvas, 1820.
Date September 28 – October 19, 1781 (3 weeks) Location Gloucester and Yorktown, Virginia 37°14′21″N 76°30′38″WCoordinates: 37°14′21″N 76°30′38″W Result Franco-American victory End of major land operations in North America Beginning of peace negotiations
Belligerents
United States  France	Great Britain Hesse-Cassel Ansbach-Bayreuth  Loyalists
Commanders and leaders
George Washington Benjamin Lincoln Henry Knox Alexander Hamilton Baron von Steuben Thomas Nelson Moses Hazen Henry Dearborn / Marquis de Lafayette Comte de Rochambeau Comte d'Aboville Marquis de Choisy Comte de Grasse	Lord Cornwallis  Charles O'Hara  Banastre Tarleton  Robert Abercromby  Thomas Dundas  Thomas Symonds  Matthias von Fuchs  August Voit von Salzburg  Johann von Seybothen
Strength
Americans: 8,000–9,000 men 5,000–5,900 regular troops 3,000–3,100 militia (not engaged) French: 7,500–8,800 men and 29 warships Total: 15,500–17,800 (fewer engaged)	British: 7,000+ German: Fewer than 3,000 Total: 9,000
Casualties and losses
88 killed 301 wounded	142–309 killed; 326–595 wounded prisoners; 7,416–7,685 captured

Location within Virginia

The siege of Yorktown, also known as the Battle of Yorktown, the surrender at Yorktown, or the German battle (from the presence of Germans in all three armies), beginning on September 28, 1781, and ending on October 19, 1781, at Yorktown, Virginia, was a decisive victory by a combined force of the American Continental Army troops led by General George Washington and Gilbert du Motier, Marquis de Lafayette, and French Army troops led by Comte de Rochambeau over a British army commanded by British peer and Lieutenant General Charles Cornwallis. The culmination of the Yorktown Campaign, the siege proved to be the last major land battle of the American Revolutionary War in the North American region, as the surrender by Cornwallis, and the capture of both him and his army, prompted the British government to negotiate an end to the conflict.

In 1780, about 5,500 French soldiers landed in Rhode Island to help their American allies fight the British troops who controlled New York City. Following the arrival of dispatches from France that included the possibility of support from the French West Indies fleet of the Comte de Grasse, disagreements arose between Washington and Rochambeau on whether to ask de Grasse for assistance in besieging New York or in military operations against a British army in Virginia. On the advice of Rochambeau, de Grasse informed them of his intent to sail to the Chesapeake Bay, where Cornwallis had taken command of the army. Cornwallis, at first given confusing orders by his superior officer, Henry Clinton, was eventually ordered to build a defensible deep-water port, which he began to do in Yorktown. Cornwallis' movements in Virginia were shadowed by a Continental Army force led by the Marquis de Lafayette.

The French and American armies united north of New York City during the summer of 1781. When word of de Grasse's decision arrived, both armies began moving south toward Virginia, engaging in tactics of deception to lead the British to believe a siege of New York was planned. De Grasse sailed from the West Indies and arrived at the Chesapeake Bay at the end of August, bringing additional troops and creating a naval blockade of Yorktown. He was transporting 500,000 silver pesos collected from the citizens of Havana, Cuba, to fund supplies for the siege and payroll for the Continental Army. While in Santo Domingo, de Grasse met with Francisco Saavedra de Sangronis, an agent of Carlos III of Spain. De Grasse had planned to leave several of his warships in Santo Domingo. Saavedra promised the assistance of the Spanish navy to protect the French merchant fleet, enabling de Grasse to sail north with all of his warships. In the beginning of September, he defeated a British fleet led by Sir Thomas Graves that came to relieve Cornwallis at the Battle of the Chesapeake. As a result of this victory, de Grasse blocked any reinforcement or escape by sea for Cornwallis and also disembarked the heavy siege guns required by the allied land forces. By late September, Washington and Rochambeau arrived, and the army and naval forces completely surrounded Cornwallis.

After initial preparations, the Americans and French built their first parallel and began the bombardment. With the British defense weakened, on October 14, 1781, Washington sent two columns to attack the last major remaining British outer defenses. A French column under Wilhelm of the Palatinate-Zweibrücken took Redoubt No. 9 and an American column under Alexander Hamilton took Redoubt No. 10. With these defenses taken, the allies were able to finish their second parallel. With the Franco-American artillery closer and its bombardment more intense than ever, the British position began to deteriorate rapidly. Cornwallis asked for capitulation terms on October 17. After two days of negotiation, the surrender ceremony occurred on October 19; Cornwallis was absent from the ceremony. With the capture of more than 7,000 British soldiers, negotiations between the United States and Great Britain began, resulting in the Treaty of Paris of 1783.

The battlegrounds are preserved and interpreted today as part of Colonial National Historical Park.

Prelude

Main article: Yorktown campaign

 

A plan of the Battle of Yorktown drawn in 1875

Franco-American cooperation

Main articles: Franco-American alliance and Southern theater of the American Revolutionary War

On December 20, 1780, Benedict Arnold sailed from New York with 1,500 British troops to Portsmouth, Virginia. He first raided Richmond, defeating the defending militia, from January 5–7 before falling back to Portsmouth. Admiral Destouches, who arrived in Newport, Rhode Island, in July 1780 with a fleet transporting 5,500 soldiers, was encouraged by Washington and French Lieutenant General Rochambeau to move his fleet south, and launch a joint land-naval attack on Arnold's troops. The Marquis de Lafayette was sent south with 1,200 men to help with the assault. However, Destouches was reluctant to dispatch many ships, and in February sent only three. After they proved ineffective, he took a larger force of 8 ships in March 1781, and fought a tactically inconclusive battle with the British fleet of Marriot Arbuthnot at the mouth of the Chesapeake Bay. Destouches withdrew due to the damage sustained to his fleet, leaving Arbuthnot and the British fleet in control of the bay's mouth.

On March 26, Arnold was joined by 2,300 troops under command of Major General William Phillips, who took command of the combined forces. Phillips resumed raiding, defeating the militia at Blandford, then burning the tobacco warehouses at Petersburg on April 25. Richmond was about to suffer the same fate, but Lafayette arrived. The British, not wanting to engage in a major battle, withdrew to Petersburg on May 10.

National Park Service map of the W3R Route

On May 20, Charles Cornwallis arrived at Petersburg with 1,500 men after suffering heavy casualties at the Battle of Guilford Courthouse. He immediately assumed command, as Phillips had recently died of a fever. Cornwallis had not received permission to abandon the Carolinas from his superior, Henry Clinton, but he believed that Virginia would be easier to capture, feeling that it would approve of an invading British army.

With the arrival of Cornwallis and more reinforcements from New York, the British Army numbered 7,200 men. Cornwallis wanted to push Lafayette, whose force now numbered 3,000 men with the arrival of Virginia militia. On May 24, he set out after Lafayette, who withdrew from Richmond, and linked forces with those under the command of Baron von Steuben and Anthony Wayne. Cornwallis did not pursue Lafayette. Instead, he sent raiders into central Virginia, where they attacked depots and supply convoys, before being recalled on June 20. Cornwallis then headed for Williamsburg, and Lafayette's force of now 4,500 followed him. General Clinton, in a confusing series of orders, ordered Cornwallis first to Portsmouth and then Yorktown, where he was instructed to build fortifications for a deep water port.

On July 6, the French and American armies met at White Plains, north of New York City. Although Rochambeau had almost 40 years of warfare experience, he never challenged Washington's authority, telling Washington he had come to serve, not to command.

Washington and Rochambeau discussed where to launch a joint attack. Washington believed an attack on New York was the best option, since the Americans and French now outnumbered the British defenders 3 to 1. Rochambeau disagreed, arguing the fleet in the West Indies under Admiral de Grasse was going to sail to the American coast, where easier options than attacking New York could be attempted.

In early July, Washington suggested an attack be made at the northern part of Manhattan Island, but his officers and Rochambeau all disagreed. Washington continued to probe the New York area until August 14, when he received a letter from de Grasse stating he was headed for Virginia with 28 warships and 3,200 soldiers, but could only remain there until October 14. De Grasse encouraged Washington to move south so they could launch a joint operation. Washington abandoned his plan to take New York, and began to prepare his army for the march south to Virginia.

March to Virginia

On August 19, the "celebrated march" to Yorktown led by Washington and Rochambeau began. 7,000 soldiers (4,000 French and 3,000 American) began the march in Newport, Rhode Island, while the rest remained behind to protect the Hudson Valley. Washington wanted to maintain complete secrecy of their destination. To ensure this, he sent out fake dispatches that reached Clinton revealing that the Franco-American army was going to launch an attack on New York, and that Cornwallis was not in danger.

The French and American armies marched through Philadelphia from September 2 to 4, where the American soldiers announced they would not leave Maryland until they received one month's pay in coin, rather than in the worthless Continental paper currency. "Count de Rochabeau very readily agreed at Chester to supply at the Head of Elk twenty thousand hard dollars", half of his supply of gold Spanish coins. This would be the last time the men would be paid. This strengthened French and American relations. On September 5, Washington learned of the arrival of de Grasse's fleet off the Virginia Capes. De Grasse debarked his French troops to join Lafayette, and then sent his empty transports to pick up the American troops. Washington made a visit to his home, Mount Vernon, on his way to Yorktown.

Main article: Battle of the Chesapeake

In August, Admiral Sir Thomas Graves led a fleet from New York to attack de Grasse's fleet. Graves did not realize how large the French fleet was, and neither did Cornwallis. The British fleet was defeated by de Grasse's fleet in the Battle of the Chesapeake on September 5, and forced to fall back to New York. On September 14, Washington arrived in Williamsburg, Virginia.

The siege

See also: Yorktown order of battle

 

Siège de Yorktown by Auguste Couder, c. 1836. Rochambeau and Washington giving their last orders before the battle.

Initial movements

On September 26, transports with artillery, siege tools, and some French infantry and shock troops from Head of Elk, the northern end of the Chesapeake Bay, arrived, giving Washington command of an army of 7,800 Frenchmen, 3,100 militia, and 8,000 Continentals. Early on September 28, Washington led the army out of Williamsburg to surround Yorktown. The French took the positions on the left while the Americans took the position of honor on the right. Cornwallis had a chain of seven redoubts and batteries linked by earthworks along with batteries that covered the narrows of the York River at Gloucester Point. That day, Washington reconnoitered the British defenses, and decided that they could be bombarded into submission. The Americans and the French spent the night of the 28th sleeping out in the open, while work parties built bridges over the marsh. Some of the American soldiers hunted down wild hogs to eat.

On September 29, Washington moved the army closer to Yorktown, and British gunners opened fire on the infantry. Throughout the day, several British cannon fired on the Americans, but there were few casualties. Fire was also exchanged between American riflemen and Hessian Jägers.

Cornwallis pulled back from all of his outer defenses, except for the Fusilier's redoubt on the west side of the town and redoubts 9 and 10 in the east. Cornwallis had his forces occupy the earthworks immediately surrounding the town because he had received a letter from Clinton that promised relief force of 5,000 men within a week and he wished to tighten his lines. The Americans and the French occupied the abandoned defenses and began to establish their batteries there. With the British outer defenses in their hands, allied engineers began to lay out positions for the artillery. The men improved their works and deepened their trenches. The British also worked on improving their defenses.

On September 30, the French attacked the British Fusiliers redoubt. The skirmish lasted two hours, in which the French were repulsed, suffering several casualties. On October 1, the allies learned from British deserters that, to preserve their food, the British had slaughtered hundreds of horses and thrown them on the beach. In the American camp, thousands of trees were cut down to provide wood for earthworks. Preparations for the parallel also began.

As the allies began to put their artillery into place, the British kept up a steady fire to disrupt them. British fire increased on the 2nd and the allies suffered moderate casualties. General Washington continued to make visits to the front, despite concern shown by several of his officers over the increasing enemy fire. On the night of October 2, the British opened a storm of fire to cover up the movement of the British cavalry to Gloucester where they were to escort infantrymen on a foraging party. On the 3rd, the foraging party, led by Banastre Tarleton, went out but collided with Lauzun's Legion, and John Mercer's Virginia militia, led by the Marquis de Choisy. The British cavalry quickly retreated behind their defensive lines, losing 50 men.

By October 5, Washington was almost ready to open the first parallel. That night the sappers and miners worked, putting strips of pine on the wet sand to mark the path of the trenches. The main/ initial movements of this battle were walking and riding horses.

Bombardment

After nightfall on October 6, troops moved out in stormy weather to dig the first parallel: the heavily overcast sky negated the waning full moon and shielded the massive digging operation from the eyes of British sentries. Washington ceremoniously struck several blows with his pickaxe to begin the trench. The trench was to be 2,000 yards (1,800 m) long, running from the head of Yorktown to the York River. Half of the trench was to be commanded by the French, the other half by the Americans. On the northernmost end of the French line, a support trench was dug so that they could bombard the British ships in the river. The French were ordered to distract the British with a false attack, but the British were told of the plan by a French deserter and the British artillery fire turned on the French from the Fusiliers redoubt.

Washington firing the first gun

On October 7, the British saw the new allied trench just out of musket-range. Over the next two days, the allies completed the gun placements and dragged the artillery into line. The British fire began to weaken when they saw the large number of guns the allies had.

By October 9, all of the French and American guns were in place. Among the American guns there were three twenty-four pounders, three eighteen pounders, two eight-inch (203 mm) howitzers and six mortars, totaling fourteen guns. At 3:00 pm, the French guns opened the barrage and drove the British frigate HMS Guadeloupe across the York River, where she was scuttled to prevent capture. At 5:00 pm, the Americans opened fire. Washington fired the first gun; legend has it that this shot smashed into a table where British officers were eating. The Franco-American guns began to tear apart the British defenses. Washington ordered that the guns fire all night so that the British could not make repairs. All of the British guns on the left were soon silenced. The British soldiers began to pitch their tents in their trenches and soldiers began to desert in large numbers. Some British ships were also damaged by cannonballs that flew across the town into the harbor.

On October 10, the Americans spotted a large house in Yorktown. Believing that Cornwallis might be stationed there, they aimed at it and quickly destroyed it. Cornwallis sank more than a dozen of his ships in the harbor. The French began to fire at the British ships and scored a hit on the British HMS Charon, which caught fire, and in turn set two or three other ships on fire. Cornwallis received word from Clinton that the British fleet was to depart on October 12, however Cornwallis responded by saying that he would not be able to hold out for long.

On the night of October 11, Washington ordered that the Americans dig a second parallel. It was 400 yards (370 m) closer to the British lines, but could not be extended to the river because the British number 9 and 10 redoubts were in the way. During the night, the British fire continued to land in the old line; Cornwallis did not suspect that a new parallel was being dug. By morning of the 12th, the allied troops were in position on the new line.

Assault on the redoubts

Storming of Redoubt #10

 

The storming of Redoubt No. 10, by Eugène Lami

By October 14, the trenches were within 150 yards (140 m) of redoubts No. 9 and No. 10. Washington ordered that all guns within range begin blasting the redoubts to weaken them for an assault that evening. Washington planned to use the cover of a moonless night to gain the element of surprise. To reinforce the darkness, he added silence, ordering that no soldier should load his musket until reaching the fortifications; the advance would be made with only "cold steel." Redoubt 10 was near the river and held only 70 men, while redoubt 9 was a quarter-mile inland, and was held by 120 British and Germans. Both redoubts were heavily fortified with rows of abatis surrounding them, along with muddy ditches that surrounded the redoubts at about 25 yards (23 m). Washington devised a plan in which the French would launch a diversionary attack on the Fusiliers redoubt, and then a half an hour later, the French would assault redoubt 9 and the Americans redoubt 10. Redoubt 9 would be assaulted by 400 French regular soldiers of the Royal Deux-Ponts Regiment under the command of the Count of Deux-Ponts and redoubt 10 would be assaulted by 400 light infantry troops under the command of Alexander Hamilton. There was a brief dispute as to who should lead the attack on Redoubt No. 10. Lafayette named his aide, Jean-Joseph Sourbader de Gimat, who commanded a battalion of Continental light infantry. However, Hamilton protested, saying that he was the senior officer. Washington concurred with Hamilton and gave him command of the attack.

Storming of Redoubt #9

At 6:30 pm, gunfire announced the diversionary attack on the Fusiliers redoubt. At other places in the line, movements were made as if preparing for an assault on Yorktown itself, which caused the British to panic. With bayonets fixed, the Americans marched towards Redoubt No. 10. Hamilton sent Lieutenant Colonel John Laurens around to the rear of the redoubt to prevent the British from escaping. The Americans reached the redoubt and began chopping through the British wooden defenses with their axes. A British sentry called a challenge, and then fired at the Americans. The Americans responded by charging with their bayonets towards the redoubt. They hacked through the abatis, crossed a ditch and climbed the parapet into the redoubt. The Americans forced their way into the redoubt, falling into giant shell holes created by the preparatory bombardment. The British fire was heavy, but the Americans overwhelmed them. Someone in the front shouted, "Rush on boys! The fort's ours!" The British threw hand grenades at the Americans with little effect. Men in the trench stood on the shoulders of their comrades to climb into the redoubt. The bayonet fight cleared the British from the redoubt and almost the entire garrison was captured, including the commander of the redoubt, Major Campbell. In the assault, the Americans lost 9 dead and 25 wounded.

The French assault began at the same time, but they were halted by the abatis, which was undamaged by the artillery fire. The French began to hack at the abatis and a Hessian sentry came out and asked who was there. When there was no response, the sentry opened fire as did other Hessians on the parapet. The French soldiers fired back, and then charged the redoubt. The Germans charged the Frenchmen climbing over the walls but the French fired a volley, driving them back. The Hessians then took a defensive position behind some barrels but threw down their arms and surrendered when the French prepared a bayonet charge.

With the capture of redoubts 9 and 10, Washington was able to have his artillery shell the town from three directions and the allies moved some of their artillery into the redoubts. On October 15, Cornwallis turned all of his guns onto the nearest allied position. He then ordered a storming party of 350 British troops under the command of Colonel Robert Abercromby to attack the allied lines and spike the American and French cannon (i.e., plug the touch hole with an iron spike). The allies were sleeping and unprepared. As the British charged Abercromby shouted "Push on my brave boys, and skin the bastards!" The British party spiked several cannon in the parallel and then spiked the guns on an unfinished redoubt. A French party came and drove them out of the allied lines and back to Yorktown. The British had been able to spike six guns, but by the morning they were all repaired. The bombardment resumed with the American and French troops engaged in competition to see who could do the most damage to the enemy defenses.

On the morning of October 16, more allied guns were in line and the fire intensified. In desperation, Cornwallis attempted to evacuate his troops across the York River to Gloucester Point. At Gloucester Point, the troops might be able to break through the allied lines and escape into Virginia and then march to New York. One wave of boats made it across, but a squall hit when they returned to take more soldiers, making the evacuation impossible.

British surrender

Overview of the capitulation of the British army at Yorktown, with the blockade of the French squadron

The fire on Yorktown from the allies was heavier than ever as new artillery pieces joined the line. Cornwallis talked with his officers that day and they agreed that their situation was hopeless.

On the morning of October 17, a drummer appeared, followed by an officer waving a white handkerchief. The bombardment ceased, and the officer was blindfolded and led behind the French and American lines. Negotiations began at the Moore House on October 18 between Lieutenant Colonel Thomas Dundas and Major Alexander Ross (who represented the British) and Lieutenant Colonel Laurens (who represented the Americans) and Marquis de Noailles (who represented the French). To make sure that nothing fell apart between the French and Americans at the last minute, Washington ordered that the French be given an equal share in every step of the surrender process. At 2:00 pm the allied army entered the British positions, with the French on the left and the Americans on the right.

The surrender of Lord Cornwallis, October 19, 1781, at Yorktown

The British had asked for the traditional honors of war, which would allow the army to march out with flags flying, bayonets fixed, and the band playing an American or French tune as a tribute to the victors. However, Washington firmly refused to grant the British the honors that they had denied the defeated American army the year before at the siege of Charleston. Consequently, the British and Hessian troops marched with flags furled and muskets shouldered, while the band was forced to play "a British or German march." American history books recount the legend that the British band played "The World Turn'd Upside Down", but the story may be apocryphal.

Surrender of Cornwallis. At York-town, VA Oct. 1781, Nathaniel Currier. D'Amour Museum of Fine Arts

Cornwallis refused to attend the surrender ceremony, citing illness. Instead, Brigadier General Charles O'Hara led the British army onto the field. O'Hara first attempted to surrender to Rochambeau, who shook his head and pointed to Washington. O'Hara then offered his sword to Washington, who also refused and motioned to Benjamin Lincoln, his second-in-command. The surrender finally took place when Lincoln accepted the sword of Cornwallis' deputy.

The British soldiers marched out and laid down their arms in between the French and American armies, while many civilians watched. At this time, the troops on the other side of the river in Gloucester also surrendered. The British soldiers had been issued new uniforms hours before the surrender and until prevented by General O'Hara some threw down their muskets with the apparent intention of smashing them. Others wept or appeared to be drunk. In all, 8,000 soldiers, 214 artillery pieces, thousands of muskets, 24 transport ships, wagons and horses were captured.

Casualties

60 French died and 194 were injured. 28 Americans died and 107 were wounded.

156 British were killed and 326 were wounded with 70 missing.

Effect of disease

Malaria was endemic in the marshlands of eastern Virginia during the time, and Cornwallis's army suffered greatly from the disease; he estimated during the surrender that half of his army was unable to fight as a result. The Continental Army enjoyed an advantage, in that most of their members had grown up with malaria, and hence had acquired resistance to the disease. As malaria has a month-long incubation period, most of the French soldiers had not begun to exhibit symptoms before the surrender.

Articles of capitulation

The articles of capitulation, outlining the terms and conditions of surrender for officers, soldiers, military supplies, and personal property, were signed on October 19, 1781. Signatories included Washington, Rochambeau, the Comte de Barras (on behalf of the French Navy), Cornwallis, and Captain Thomas Symonds (the senior Royal Navy officer present). Cornwallis' British men were declared prisoners of war, promised good treatment in American camps, and officers were permitted to return home after taking their parole.

Articles of Capitulation, Yorktown

Article 10 controversy

George Washington refused to accept the Tenth Article of the Yorktown Articles of Capitulation, which granted immunity to provincials, and Cornwallis failed to make any effort to press the matter. "The outcry against the Tenth Article was vociferous and immediate, as Americans on both sides of the Atlantic proclaimed their sense of betrayal."

Aftermath

The victory at Yorktown and the American Revolution were honored in Libertas Americana, a 1783 medallion minted in Paris and designed there by US Ambassador Benjamin Franklin.

Following the surrender, the American and French officers entertained the British officers to dinner. The British officers were "overwhelmed" by the civility their erstwhile foes extended to them, with some French officers offering "profuse" sympathies for the defeat, as one British officer, Captain Samuel Graham, commented. Equally, the French aide to Rochambeau, Cromot du Bourg, noted the coolness of the British officers, particularly O'Hara, considering the defeat they had endured.

Five days after the battle ended, on October 24, 1781, the British fleet sent by Clinton to rescue the British army arrived. The fleet picked up several provincials who had escaped on October 18, and they informed Admiral Thomas Graves that they believed Cornwallis had surrendered. Graves picked up several more provincials along the coast, and they confirmed this fact. Graves sighted the French Fleet, but chose to leave because he was outnumbered by nine ships, and thus he sent the fleet back to New York.

After the British surrender, Washington sent Tench Tilghman to report the victory to Congress. After a difficult journey, he arrived in Philadelphia, which celebrated for several days. The British Prime Minister, Lord North, is reported to have exclaimed "Oh God, it's all over" when told of the defeat. Washington moved his army to New Windsor, New York where they remained stationed until the Treaty of Paris was signed on September 3, 1783, formally ending the war. Although the peace treaty did not happen for two years following the end of the battle, the Yorktown Campaign proved to be decisive; there was no significant battle or campaign on the North American mainland after the Battle of Yorktown and in March 1782, "the British Parliament had agreed to cease hostilities."

Legacy

US Postage Stamp, 1931 issue, depicting Rochambeau, George Washington and De Grasse, commemorating 150th anniversary of the victory at Yorktown, 1781

On October 19, 1881, an elaborate ceremony took place to honor the battle's centennial. U.S. naval vessels floated on Chesapeake Bay, and special markers highlighted where Washington and Lafayette's siege guns were placed. President Chester Arthur, sworn in only thirty days before, following James Garfield's death, made his first public speech as president. Also present were descendants of Lafayette, Rochambeau, de Grasse, and Steuben. To close the ceremony, Arthur gave an order to salute the British flag.

There is a belief that General Cornwallis's sword, surrendered by Charles O'Hara after the battle, is to this day on display at the White House. However, U.S. National Park Service historian Jerome Green, in his 2005 history of the siege, The Guns of Independence, concurs with the 1881 centennial account by Johnston, noting simply that when Brigadier General O'Hara presented the sword to Major General Lincoln, he held it for a moment and immediately returned it to O'Hara.

The siege of Yorktown is also known in some German historiographies as "die deutsche Schlacht" ("the German battle"), because Germans played significant roles in all three armies, accounting for roughly one third of all forces involved. According to one estimate more than 2,500 German soldiers served at Yorktown with each of the British and French armies, and more than 3,000 German-Americans were in Washington's army.

Four Army National Guard units (113th Inf, 116th Inf, 175th Inf and 198th Sig Bn) and one active Regular Army Field Artillery battalion (1–5th FA) are derived from American units that participated in the Battle of Yorktown. There are thirty current U.S. Army units with lineages that go back to the colonial era.

Yorktown Victory Monument

Yorktown Victory Monument

Five days after the British surrendered, Congress passed a resolution agreeing to erect a structure dedicated to commemorating those who participated in the battle. Construction of the monument was delayed, however, as the Confederation government had several other financial obligations that were considered to be of a more urgent nature. In 1834, the citizens of Yorktown asked Congress for the monument to be constructed, and then followed up once again in 1836, but still no action was taken. The desirability of the project was recognized in 1876 "when a memorial from the Common Council of Fredericksburg, Virginia was before Congress."

The project was postponed once again until the battle's centennial sparked renewed enthusiasm in the resolution and prompted the government to begin building the monument in 1881 amid national support. The crowning figure was set on August 12, 1884; the structure was officially reported in a communication as complete on January 5, 1885, and currently resides within Colonial National Historical Park. The artists commissioned by the Secretary of War for the monument project included Mr. R. M. Hunt (Chairman) and Mr. J. Q. A. Ward (Architect) of New York and Mr. Henry Van Brunt (Sculptor) of Boston.

Yorktown sesquicentennial and bicentennial celebrations

A four-day celebration to commemorate the 150th anniversary of the siege took place in Yorktown on October 16–19, 1931. It was presided over by the Governor of Virginia John Garland Pollard and attended by then President Herbert Hoover along with French representatives. The event included the official dedication of the Colonial National Historical Park, which also includes Historic Jamestown. President Ronald Reagan visited Yorktown in 1981 for the bicentennial celebration.

Spider silk

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Spider_silk 

A garden spider spinning its web

 

A female specimen of Argiope bruennichi wraps her prey in silk.

 

Indian Summer by Józef Chełmoński (1875, National Museum in Warsaw) depicts a peasant woman with a thread of gossamer in her hand.

 

Spider cocoon

Spider silk is a protein fibre spun by spiders. Spiders use their silk to make webs or other structures, which function as sticky nets to catch other animals, or as nests or cocoons to protect their offspring, or to wrap up prey. They can also use their silk to suspend themselves, to float through the air, or to glide away from predators. Most spiders vary the thickness and stickiness of their silk for different uses.

In some cases, spiders may even use silk as a source of food. While methods have been developed to collect silk from a spider by force, it is difficult to gather silk from many spiders compared to silk-spinning organisms such as silkworms.

All spiders produce silk, and even in non-web building spiders, silk is intimately tied to courtship and mating. Silk produced by females provides a transmission channel for male vibratory courtship signals, while webs and draglines provide a substrate for female sex pheromones. Observations of male spiders producing silk during sexual interactions are also common across phylogenetically widespread taxa. However, the function of male-produced silk in mating has received very little study.

Biodiversity

Uses

All spiders produce silks, and a single spider can produce up to seven different types of silk for different uses.^[4] This is in contrast to insect silks, where an individual usually only produces one type of silk. Spider silks may be used in many different ecological ways, each with properties to match the silk's function. As spiders have evolved, so has their silks' complexity and diverse uses, for example from primitive tube webs 300–400 million years ago to complex orb webs 110 million years ago.

Use	Example
Prey capture	The orb webs produced by the Araneidae (typical orb-weavers); tube webs; tangle webs; sheet webs; lace webs, dome webs; single thread used by the Bolas spiders for "fishing".
Prey immobilisation	Silk used as "swathing bands" to wrap up prey. Often combined with immobilising prey using a venom. In species of Scytodes the silk is combined with venom and squirted from the chelicerae.
Reproduction	Male spiders may produce sperm webs; spider eggs are covered in silk cocoons.
Dispersal	"Ballooning" or "kiting" used by smaller spiders to float through the air, for instance for dispersal.
Source of food	The kleptoparasitic Argyrodes eating the silk of host spider webs. Some daily weavers of temporary webs also eat their own unused silk daily, thus mitigating a heavy metabolic expense.
Nest lining and nest construction	Tube webs used by "primitive" spiders such as the European tube web spider (Segestria florentina). Threads radiate out of nest to provide a sensory link to the outside. Silk is a component of the lids of spiders that use "trapdoors", such as members of the family Ctenizidae, and the "water" or "diving bell" spider Argyroneta aquatica builds its diving bell of silk.
Guide lines	Some spiders that venture from shelter will leave a trail of silk by which to find their way home again.
Drop lines and anchor lines	Many spiders, such as the Salticidae, that venture from shelter and leave a trail of silk, use that as an emergency line in case of falling from inverted or vertical surfaces. Many others, even web dwellers, will deliberately drop from a web when alarmed, using a silken thread as a drop line by which they can return in due course. Some, such as species of Paramystaria, also will hang from a drop line when feeding.
Alarm lines	Some spiders that do not spin actual trap webs do lay out alarm webs that the feet of their prey (such as ants) can disturb, cueing the spider to rush out and secure the meal if it is small enough, or to avoid contact if the intruder seems too formidable.
Pheromonal trails	Some wandering spiders will leave a largely continuous trail of silk impregnated with pheromones that the opposite sex can follow to find a mate.

Types

A female Argiope picta immobilizing prey by wrapping a curtain of aciniform silk around the insect for later consumption

Meeting the specification for all these ecological uses requires different types of silk suited to different broad properties, as either a fibre, a structure of fibres, or a silk-globule. These types include glues and fibres. Some types of fibres are used for structural support, others for constructing protective structures. Some can absorb energy effectively, whereas others transmit vibration efficiently. In a spider, these silk types are produced in different glands; so the silk from a particular gland can be linked to its use by the spider.

Gland	Silk Use
Ampullate (major)	Dragline silk – used for the web's outer rim and spokes, also for the lifeline and for ballooning.
Ampullate (minor)	Used for temporary scaffolding during web construction.
Flagelliform	Capture-spiral silk – used for the capturing lines of the web.
Tubuliform	Egg cocoon silk – used for protective egg sacs.
Aciniform	Used to wrap and secure freshly captured prey; used in the male sperm webs; used in stabilimenta.
Aggregate	A silk glue of sticky globules.
Piriform	Used to form bonds between separate threads for attachment points.

Properties

Mechanical properties

Each spider and each type of silk has a set of mechanical properties optimised for their biological function.

Most silks, in particular dragline silk, have exceptional mechanical properties. They exhibit a unique combination of high tensile strength and extensibility (ductility). This enables a silk fibre to absorb a large amount of energy before breaking (toughness, the area under a stress-strain curve).

An illustration of the differences between toughness, stiffness and strength

A frequent mistake made in the mainstream media is to confuse strength and toughness, when comparing silk to other materials. Weight for weight, silk is stronger than steel, but not as strong as Kevlar. Silk is, however, tougher than both.

The variability of mechanical properties of spider silk fibres may be important and it is related to their degree of molecular alignment. Mechanical properties depend strongly on the ambient conditions, i.e. humidity and temperature.

Strength

A dragline silk's tensile strength is comparable to that of high-grade alloy steel (450−2000 MPa), and about half as strong as aramid filaments, such as Twaron or Kevlar (3000 MPa).

Density

Consisting of mainly protein, silks are about a sixth of the density of steel (1.3 g/cm³). As a result, a strand long enough to circle the Earth would weigh less than 500 grams (18 oz). (Spider dragline silk has a tensile strength of roughly 1.3 GPa. The tensile strength listed for steel might be slightly higher – e.g. 1.65 GPa, but spider silk is a much less dense material, so that a given weight of spider silk is five times as strong as the same weight of steel.

Energy density

The energy density of dragline spider silk is roughly 1.2×10⁸ J/m³.

Extensibility

Silks are also extremely ductile, with some able to stretch up to five times their relaxed length without breaking.

Toughness

The combination of strength and ductility gives dragline silks a very high toughness (or work to fracture), which "equals that of commercial polyaramid (aromatic nylon) filaments, which themselves are benchmarks of modern polymer fibre technology".

Temperature

While unlikely to be relevant in nature, dragline silks can hold their strength below -40 °C (-40 °F) and up to 220 °C (428 °F). As occurs in many materials, spider silk fibres undergo a glass transition. The glass-transition temperature depends on the humidity, as water is a plasticiser for the silk.

Supercontraction

When exposed to water, dragline silks undergo supercontraction, shrinking up to 50% in length and behaving like a weak rubber under tension. Many hypotheses have been suggested as to its use in nature, with the most popular being to automatically tension webs built in the night using the morning dew.

Highest-performance

The toughest known spider silk is produced by the species Darwin's bark spider (Caerostris darwini): "The toughness of forcibly silked fibers averages 350 MJ/m³, with some samples reaching 520 MJ/m³. Thus, C. darwini silk is more than twice as tough as any previously described silk, and over 10 times tougher than Kevlar".

Adhesive properties

Silk fibre is a two-compound pyriform secretion, spun into patterns (called "attachment discs") that are employed to adhere silk threads to various surfaces using a minimum of silk substrate. The pyriform threads polymerise under ambient conditions, become functional immediately, and are usable indefinitely, remaining biodegradable, versatile and compatible with numerous other materials in the environment. The adhesive and durability properties of the attachment disc are controlled by functions within the spinnerets. Some adhesive properties of the silk resemble glue, consisting of microfibrils and lipid enclosures.

Types of silk

Many species of spiders have different glands to produce silk with different properties for different purposes, including housing, web construction, defence, capturing and detaining prey, egg protection, and mobility (fine "gossamer" thread for ballooning, or for a strand allowing the spider to drop down as silk is extruded). Different specialised silks have evolved with properties suitable for different uses. For example, Argiope argentata has five different types of silk, each used for a different purpose:

Silk	Use
major-ampullate (dragline) silk	Used for the web's outer rim and spokes and also for the lifeline. Can be as strong per unit weight as steel, but much tougher.
capture-spiral (flagelliform) silk	Used for the capturing lines of the web. Sticky, extremely stretchy and tough. The capture spiral is sticky due to droplets of aggregate (a spider glue) that is placed on the spiral. The elasticity of flagelliform allows for enough time for the aggregate to adhere to the aerial prey flying into the web.
tubiliform (a.k.a. cylindriform) silk	Used for protective egg sacs. Stiffest silk.
aciniform silk	Used to wrap and secure freshly captured prey. Two to three times as tough as the other silks, including dragline.
minor-ampullate silk	Used for temporary scaffolding during web construction.

Structural

Macroscopic structure down to protein hierarchy

Structure of spider silk. Inside a typical fibre there are crystalline regions separated by amorphous linkages. The crystals are beta-sheets that have assembled together.

Silks, like many other biomaterials, have a hierarchical structure. The primary structure is the amino acid sequence of its proteins (spidroin), mainly consisting of highly repetitive glycine and alanine blocks, which is why silks are often referred to as a block co-polymer. On a secondary structure level, the short side chained alanine is mainly found in the crystalline domains (beta sheets) of the nanofibril, glycine is mostly found in the so-called amorphous matrix consisting of helical and beta turn structures. It is the interplay between the hard crystalline segments, and the strained elastic semi-amorphous regions, that gives spider silk its extraordinary properties. Various compounds other than protein are used to enhance the fibre's properties. Pyrrolidine has hygroscopic properties which keeps the silk moist while also warding off ant invasion. It occurs in especially high concentration in glue threads. Potassium hydrogen phosphate releases hydrogen ions in aqueous solution, resulting in a pH of about 4, making the silk acidic and thus protecting it from fungi and bacteria that would otherwise digest the protein. Potassium nitrate is believed to prevent the protein from denaturing in the acidic milieu.

This first very basic model of silk was introduced by Termonia in 1994 who suggested crystallites embedded in an amorphous matrix interlinked with hydrogen bonds. This model has refined over the years: semi-crystalline regions were found as well as a fibrillar skin core model suggested for spider silk, later visualised by AFM and TEM. Sizes of the nanofibrillar structure and the crystalline and semi-crystalline regions were revealed by neutron scattering.

It has been possible to relate microstructural information and macroscopic mechanical properties of the fibres. The results show that ordered regions (i) mainly reorient by deformation for low-stretched fibres and (ii) the fraction of ordered regions increases progressively for higher stretching of the fibres.

• 

  Schematic of the spider's orb web, structural modules, and spider silk structure. On the left is shown a schematic drawing of an orb web. The red lines represent the dragline, radial line, and frame lines, the blue lines represent the spiral line, and the centre of the orb web is called the "hub". Sticky balls drawn in blue are made at equal intervals on the spiral line with viscous material secreted from the aggregate gland. Attachment cement secreted from the piriform gland is used to connect and fix different lines. Microscopically, the spider silk secondary structure is formed of spidroin and is said to have the structure shown on the right side. In the dragline and radial line, a crystalline β-sheet and an amorphous helical structure are interwoven. The large amount of β-spiral structure gives elastic properties to the capture part of the orb web. In the structural modules diagram, a microscopic structure of dragline and radial lines is shown, composed mainly of two proteins of MaSp1 and MaSp2, as shown in the upper central part. In the spiral line, there is no crystalline β-sheet region.

Biosynthesis and fibre spinning

The production of silks, including spider silk, differs in an important aspect from the production of most other fibrous biological materials: rather than being continuously grown as keratin in hair, cellulose in the cell walls of plants, or even the fibres formed from the compacted faecal matter of beetles; it is "spun" on demand from liquid silk precursor out of specialised glands.

The spinning process occurs when a fibre is pulled away from the body of a spider, whether by the spider's legs, by the spider's falling under its own weight, or by any other method including being pulled by humans. The term "spinning" is misleading because no rotation of any component occurs, but rather comes from analogy to the textile spinning wheels. Silk production is a pultrusion, similar to extrusion, with the subtlety that the force is induced by pulling at the finished fibre rather than being squeezed out of a reservoir. The unspun silk fibre is pulled through silk glands of which there may be both numerous duplicates and different types of gland on any one spider species.

Silk gland

Schematic of the spiders spinning apparatus and structural hierarchy in silk assembling related to assembly into fibers. In the process of dragline production, the primary structure protein is secreted first from secretory granules in the tail. In the ampullate (neutral environment, pH = 7), the proteins form a soft micelle of several tens of nanometers by self-organization because the hydrophilic terminals are excluded. In ampullate, the concentration of the protein is very high. Then, the micelles are squeezed into the duct. The long axis direction of the molecules is aligned parallel to the duct by a mechanical frictional force and partially oriented. The continuous lowering of pH from 7.5 to 8.0 in the tail to presumably close to 5.0 occurs at the end of the duct. Ion exchange, acidification, and water removal all happen in the duct. The shear and elongational forces lead to phase separation. In the acidic bath of the duct, the molecules attain a high concentration liquid crystal state. Finally, the silk is spun from the taper exterior. The molecules become more stable helixes and β-sheets from the liquid crystal.

The gland's visible, or external, part is termed the spinneret. Depending on the complexity of the species, spiders will have two to eight spinnerets, usually in pairs. There exist highly different specialised glands in different spiders, ranging from simply a sac with an opening at one end, to the complex, multiple-section major ampullate glands of the golden silk orb-weavers.

Behind each spinneret visible on the surface of the spider lies a gland, a generalised form of which is shown in the figure to the right, "Schematic of a generalised gland".

Schematic of a generalised gland of a Golden silk orb-weaver. Each differently coloured section highlights a discrete section of the gland.

Gland characteristics

1. The first section of the gland labelled 1 on Figure 1 is the secretory or tail section of the gland. The walls of this section are lined with cells that secrete proteins Spidroin I and Spidroin II, the main components of this spider's dragline. These proteins are found in the form of droplets that gradually elongate to form long channels along the length of the final fibre, hypothesised to assist in preventing crack formation or even self-healing of the fibre.
2. The second section is the storage sac. This stores and maintains the gel-like unspun silk dope until it is required by the spider. In addition to storing the unspun silk gel, it secretes proteins that coat the surface of the final fibre.
3. The funnel rapidly reduces the large diameter of the storage sac to the small diameter of the tapering duct.
4. The final length is the tapering duct, the site of most of the fibre formation. This consists of a tapering tube with several tight about turns, a valve almost at the end (mentioned in detail at point No. 5 below) ending in a spigot from which the solid silk fibre emerges. The tube here tapers hyperbolically, therefore the unspun silk is under constant elongational shear stress, which is an important factor in fibre formation. This section of the duct is lined with cells that exchange ions, reduce the dope pH from neutral to acidic, and remove water from the fibre. Collectively, the shear stress and the ion and pH changes induce the liquid silk dope to undergo a phase transition and condense into a solid protein fibre with high molecular organisation. The spigot at the end has lips that clamp around the fibre, controlling fibre diameter and further retaining water.
5. Almost at the end of the tapering duct is a valve, approximate position marked "5" on figure 1. Though discovered some time ago, the precise purpose of this valve is still under discussion. It is believed to assist in restarting and rejoining broken fibres, acting much in the way of a helical pump, regulating the thickness of the fibre, and/or clamping the fibre as a spider falls upon it. There is some discussion of the similarity of the silk worm's silk press and the roles each of these valves play in the production of silk in these two organisms.

Throughout the process the unspun silk appears to have a nematic texture, in a similar manner to a liquid crystal, arising in part due to the extremely high protein concentration of silk dope (around 30% in terms of weight per volume). This allows the unspun silk to flow through the duct as a liquid but maintain a molecular order.

As an example of a complex spinning field, the spinneret apparatus of an adult Araneus diadematus (garden cross spider) consists of the glands shown below. Similar multiple gland architecture exists in the black widow spider.

• 500 pyriform glands for attachment points
• 4 ampullate glands for the web frame
• about 300 aciniform glands for the outer lining of egg sacs, and for ensnaring prey
• 4 tubuliform glands for egg sac silk
• 4 aggregate glands for adhesive functions
• 2 coronate glands for the thread of adhesion lines

Artificial synthesis

Single strand of artificial spider silk produced under laboratory conditions

To artificially synthesise spider silk into fibres, there are two broad areas that must be covered. These are synthesis of the feedstock (the unspun silk dope in spiders), and synthesis of the spinning conditions (the funnel, valve, tapering duct, and spigot). There have been a number of different approaches but few of these methods have produced silk that can efficiently be synthesised into fibres.

Feedstock

The molecular structure of unspun silk is both complex and extremely long. Though this endows the silk fibres with their desirable properties, it also makes replication of the fibre somewhat of a challenge. Various organisms have been used as a basis for attempts to replicate some components or all of some or all of the proteins involved. These proteins must then be extracted, purified and then spun before their properties can be tested.

Organism	Details	Average Maximum breaking stress (MPa)	Average Strain (%)
Darwin's bark spider (Caerostris darwini)	Malagasy spider famed for making webs with strands up to 25 m long, across rivers. "C. darwini silk is more than twice as tough as any previously described silk"	1850 ±350	33 ±0.08
Nephila clavipes	Typical golden orb weaving spider	710–1200	18–27
Bombyx mori Silkworms	Silkworms were genetically altered to express spider proteins and fibres measured.	660	18.5
E. coli	Synthesising a large and repetitive molecule (~300 kDa) is complex, but required for the strongest silk. Here E. coli was engineered to produce a 556 kDa protein. Fibers spun from these synthetic spidroins are the first to fully replicate the mechanical performance of natural spider silk by all common metrics.	1030 ±110	18 ±6
Goats	Goats were genetically modified to secrete silk proteins in their milk, which could then be purified.	285–250	30–40
Tobacco & potato plants	Tobacco and potato plants were genetically modified to produce silk proteins. Patents were granted, but no fibres have yet been described in the literature.	n/a	n/a

Geometry

Spider silks with comparatively simple molecular structure need complex ducts to be able to spin an effective fibre. There have been a number of methods used to produce fibres, of which the main types are briefly discussed below.

Syringe and needle

Feedstock is simply forced through a hollow needle using a syringe. This method has been shown to make fibres successfully on multiple occasions.

Although very cheap and easy to produce, the shape and conditions of the gland are very loosely approximated. Fibres created using this method may need encouragement to change from liquid to solid by removing the water from the fibre with such chemicals as the environmentally undesirable methanol or acetone, and also may require post-stretching of the fibre to attain fibres with desirable properties.

Microfluidics

As the field of microfluidics matures, it is likely that more attempts to spin fibres will be made using microfluidics. These have the advantage of being very controllable and able to test spin very small volumes of unspun fibre but setup and development costs are likely to be high. A patent has been granted in this area for spinning fibres in a method mimicking the process found in nature, and fibres are successfully being continuously spun by a commercial company.

Electrospinning

Electrospinning is a very old technique whereby a fluid is held in a container in a manner such that it is able to flow out through capillary action. A conducting substrate is positioned below, and a large difference in electrical potential is applied between the fluid and the substrate. The fluid is attracted to the substrate, and tiny fibres jump almost instantly from their point of emission, the Taylor cone, to the substrate, drying as they travel. This method has been shown to create nano-scale fibres from both silk dissected from organisms and regenerated silk fibroin.

Other artificial shapes formed from silk

Silk can be formed into other shapes and sizes such as spherical capsules for drug delivery, cell scaffolds and wound healing, textiles, cosmetics, coatings, and many others. Spider silk proteins can also self-assemble on superhydrophobic surfaces to generate nanowires, as well as micron-sized circular sheets. It has recently been shown that recombinant spider silk proteins can self-assemble at the liquid air interface of a standing solution to form protein permeable, strong, and flexible nanomembranes that support cell proliferation. Suggested applications include skin transplants, and supportive membranes in organ-on-a-chip. These spider silk nanomembranes have also been used to create a static in-vitro model of a blood vessel.

Human uses

A cape made from Madagascar golden orb spider silk

Peasants in the southern Carpathian Mountains used to cut up tubes built by Atypus and cover wounds with the inner lining. It reportedly facilitated healing, and even connected with the skin. This is believed to be due to antiseptic properties of spider silk and because the silk is rich in vitamin K, which can be effective in clotting blood. Due to the difficulties in extracting and processing substantial amounts of spider silk, the largest known piece of cloth made of spider silk is an 11-by-4-foot (3.4 by 1.2 m) textile with a golden tint made in Madagascar in 2009. Eighty-two people worked for four years to collect over one million golden orb spiders and extract silk from them.

The silk of Nephila clavipes was used in research concerning mammalian neuronal regeneration.

Spider silk has been used as a thread for crosshairs in optical instruments such as telescopes, microscopes, and telescopic rifle sights. In 2011, spider silk fibres were used in the field of optics to generate very fine diffraction patterns over N-slit interferometric signals used in optical communications. In 2012, spider silk fibres were used to create a set of violin strings.

Development of methods to mass-produce spider silk has led to manufacturing of military, medical and consumer goods, such as ballistics armour, athletic footwear, personal care products, breast implant and catheter coatings, mechanical insulin pumps, fashion clothing, and outerwear.

Spider silk is used to suspend inertial confinement fusion targets during laser ignition, as it remains considerably elastic and has a high energy to break at temperatures as low as 10–20 K. In addition, it is made from "light" atomic number elements that won't emit x-rays during irradiation that could preheat the target so that the pressure differential required for fusion is not achieved.

Spider silk has been used to create biolenses that could be used in conjunction with lasers to create high-resolution images of the inside of the human body.

Attempts at producing synthetic spider silk

Proposed framework for producing artificial skin from spider silk to help patients with burns.

Replicating the complex conditions required to produce fibres that are comparable to spider silk has proven difficult in research and early-stage manufacturing. Through genetic engineering, Escherichia coli bacteria, yeasts, plants, silkworms, and animals other than silkworms have been used to produce spider silk proteins, which have different, simpler characteristics than those from a spider. Extrusion of protein fibres in an aqueous environment is known as "wet-spinning". This process has so far produced silk fibres of diameters ranging from 10 to 60 μm, compared to diameters of 2.5–4 μm for natural spider silk. Artificial spider silks have fewer and simpler proteins than natural dragline silk, and are consequently half the diameter, strength, and flexibility of natural dragline silk.

• In March 2010, researchers from the Korea Advanced Institute of Science & Technology succeeded in making spider silk directly using the bacteria E. coli, modified with certain genes of the spider Nephila clavipes. This approach eliminates the need to milk spiders and allows the manufacture of the spider silk in a more cost-effective manner.
• A 556 kDa spider silk protein was manufactured from 192 repeat motifs of the Nephila clavipes dragline spidroin, having similar mechanical characteristics as their natural counterparts, i.e., tensile strength (1.03 ± 0.11 GPa), modulus (13.7 ± 3.0 GPa), extensibility (18 ± 6%), and toughness (114 ± 51 MJ/m3).
• The company AMSilk developed spidroin using bacteria, making it into an artificial spider silk.
• The company Bolt Threads produces a recombinant spidroin using yeast, for use in apparel fibers and personal care. They produced the first commercial apparel products made of recombinant spider silk, trademarked Microsilk, demonstrated in ties and beanies. They have also partnered with vegan activist and luxury designer Stella McCartney as well as Adidas to produce Microsilk garments.
• The company Kraig Biocraft Laboratories used research from the Universities of Wyoming and Notre Dame to create silkworms that were genetically altered to produce spider silk.
• The now defunct Canadian biotechnology company Nexia successfully produced spider silk protein in transgenic goats that carried the gene for it; the milk produced by the goats contained significant quantities of the protein, 1–2 grams of silk proteins per litre of milk. Attempts to spin the protein into a fibre similar to natural spider silk resulted in fibres with tenacities of 2–3 grams per denier. Nexia used wet spinning and squeezed the silk protein solution through small extrusion holes in order to simulate the behavior of the spinneret, but this procedure was not sufficient to replicate the stronger properties of native spider silk.
• The company Spiber has produced a synthetic spider silk that they are calling Q/QMONOS. In partnership with Goldwin, a ski parka made from this synthetic spider silk is currently in testing and is to be in mass production soon for less than $120,000 YEN.

Bioarchaeology

From Wikipedia, the free encyclopedia

The term bioarchaeology has been attributed to British archaeologist Grahame Clark who, in 1972, defined it as the study of animal and human bones from archaeological sites. Redefined in 1977 by Jane Buikstra, bioarchaeology in the United States now refers to the scientific study of human remains from archaeological sites, a discipline known in other countries as osteoarchaeology, osteology or palaeo-osteology. Compared to bioarchaeology, osteoarchaeology is the scientific study that solely focus on the human skeleton. The human skeleton is used to tell us about health, lifestyle, diet, mortality and physique of the past. Furthermore, palaeo-osteology is simple the study of ancient bones.

In contrast, the term bioarchaeology is used in Europe to describe the study of all biological remains from archaeological sites. Although Clark used it to describe just human remains and animal remains (zoology/archaeozoology), increasingly modern archaeologists also include botanical remains (botany/archaeobotany) 

Bioarchaeology was largely born from the practices of New Archaeology, which developed in the United States in the 1970s as a reaction to a mainly cultural-historical approach to understanding the past. Proponents of New Archaeology advocated using processual methods to test hypotheses about the interaction between culture and biology, or a biocultural approach. Some archaeologists advocate a more holistic approach to bioarchaeology that incorporates critical theory and is more relevant to modern descent populations.

If possible, human remains from archaeological sites are analyzed to determine sex, age, and health. which all fall under the term 'Bioarchaeology'.

Paleodemography

Paleodemography is the field that attempts to identify demographic characteristics from the past population. The information gathered is used to make interpretations. Bioarchaeologists use paleodemography sometimes and create life tables, a type of cohort analysis, to understand the demographic characteristics (such as risk of death or sex ratio) of a given age cohort within a population. Age and sex are crucial variables in the construction of a life table, although this information is often not available to bioarchaeologists. Therefore, it is often necessary to estimate the age and sex of individuals based on specific morphological characteristics of the skeleton.

Age estimation

The estimation of age in bioarchaeology and osteology actually refers to an approximation of skeletal or biological age-at-death. The primary assumption in age estimation is that an individual's skeletal age is closely associated with their chronological age. Age estimation can be based on patterns of growth and development or degenerative changes in the skeleton. Many methods tracking these types of changes have been developed using a variety of skeletal series. For instance, in children age is typically estimated by assessing their dental development, ossification and fusion of specific skeletal elements, or long bone length. For children, the different points of time at which different teeth erupt from the gums are best known for telling a child's age down to the exact year. But once the teeth are fully developed, age in hard to be determined using teeth. In adults, degenerative changes to the pubic symphysis, the auricular surface of the ilium, the sternal end of the 4th rib, and dental attrition are commonly used to estimate skeletal age.

When using bones to determine age, there might be problems that you might face. Until the age of about 30, the human bones are still growing. Different bones are fusing at different points of growth. Some bones might not follow the correct stages of growth which can mess with your analysis. Also, as you get older there is wear and tear on the humans' bones and the age estimate becomes less precise as the bone gets older. The bones then become categorized as either 'young' (20–35 years), 'middle' (35–50 years), or 'old' (50+ years).

Sex determination

Differences in male and female skeletal anatomy are used by bioarchaeologists to determine the biological sex of human skeletons. Humans are sexually dimorphic, although overlap in body shape and sexual characteristics is possible. Not all skeletons can be assigned a sex, and some may be wrongly identified as male or female. Sexing skeletons is based on the observation that biological males and biological females differ most in the skull and pelvis; bioarchaeologists focus on these parts of the body when determining sex, although other body parts can also be used. The female pelvis is generally broader than the male pelvis, and the angle between the two inferior pubic rami (the sub-pubic angle) is wider and more U-shaped, while the sub-pubic angle of the male is more V-shaped and less than 90 degrees. Phenice details numerous visual differences between the male and female pelvis.

In general, the male skeleton is more robust than the female skeleton because of the greater muscles mass of the male. Males generally have more pronounced brow ridges, nuchal crests, and mastoid processes. It should be remembered that skeletal size and robustness are influenced by nutrition and activity levels. Pelvic and cranial features are considered to be more reliable indicators of biological sex. Sexing skeletons of young people who have not completed puberty is more difficult and problematic than sexing adults, because the body has not had time to develop fully.

Bioarchaeological sexing of skeletons is not error-proof. In reviewing the sexing of Egyptian skulls from Qua and Badari, Mann found that 20.3% could be assigned to a different sex than the sex indicated in the archaeological literature. A re-evalutaion of Mann's work showed that he did not understand the tomb numbering system of the old excavation and assigned wrong tomb numbers to the skulls. The sexing of the bone material was actually quite correct. However, recording errors and re-arranging of human remains may play a part in this great incidence of misidentification.

Direct testing of bioarchaeological methods for sexing skeletons by comparing gendered names on coffin plates from the crypt at Christ Church, Spitalfields, London to the associated remains resulted in a 98 percent success rate.

Sex-based differences are not inherently a form of inequality, but become an inequality when members of one sex are given privileges based on their sex. This stems from society investing differences with cultural and social meaning. Gendered work patterns may make their marks on the bones and be identifiable in the archaeological record. Molleson found evidence of gendered work patterns by noting extremely arthritic big toes, a collapse of the last dorsal vertebrae, and muscular arms and legs among female skeletons at Abu Hureyra. She interpreted this sex-based pattern of skeletal difference as indicative of gendered work patterns. These kinds of skeletal changes could have resulted from women spending long periods of time kneeling while grinding grain with the toes curled forward. Investigation of gender from mortuary remains is of growing interest to archaeologists.

Non-specific stress indicators

Dental non-specific stress indicators

Enamel hypoplasia

Enamel hypoplasia refers to transverse furrows or pits that form in the enamel surface of teeth when the normal process of tooth growth stops, resulting in a deficit of enamel. Enamel hypoplasias generally form due to disease and/or poor nutrition. Linear furrows are commonly referred to as linear enamel hypoplasias (LEHs); LEHs can range in size from microscopic to visible to the naked eye. By examining the spacing of perikymata grooves (horizontal growth lines), the duration of the stressor can be estimated, although Mays argues that the width of the hypoplasia bears only an indirect relationship to the duration of the stressor.

Studies of dental enamel hypoplasia are used to study child health. Unlike bone, teeth are not remodeled, so they can provide a more reliable indicator of past health events as long as the enamel remains intact. Dental hypoplasias provide an indicator of health status during the time in childhood when the enamel of the tooth crown is being formed. Not all of the enamel layers are visible on the surface of the tooth because enamel layers that are formed early in crown development are buried by later layers. Hypoplasias on this part of the tooth do not show on the surface of the tooth. Because of this buried enamel, teeth record stressors form a few months after the start of the event. The proportion of enamel crown formation time represented by this buried in enamel varies from up to 50 percent in molars to 15-20 percent in anterior teeth. Surface hypoplasias record stressors occurring from about one to seven years, or up to 13 years if the third molar is included.

Skeletal non-specific stress indicators

Porotic hyperostosis/cribra orbitalia

It was long assumed that iron deficiency anemia has marked effects on the flat bones of the cranium of infants and young children. That as the body attempts to compensate for low iron levels by increasing red blood cell production in the young, sieve-like lesions develop in the cranial vaults (termed porotic hyperostosis) and/or the orbits (termed cribra orbitalia). This bone is spongy and soft.

It is however, highly unlikely that iron deficiency anemia is a cause of either porotic hyperostosis or cribra orbitalia. These are more likely the result of vascular activity in these areas and are unlikely to be pathological. The development of cribra orbitalia and porotic hyperostosis could also be attributed to other causes besides an iron deficiency in the diet, such as nutrients lost to intestinal parasites. However, dietary deficiencies are the most probable cause.

Anemia incidence may be a result of inequalities within society, and/or indicative of different work patterns and activities among different groups within society. A study of iron-deficiency among early Mongolian nomads showed that although overall rates of cribra orbitalia declined from 28.7 percent (27.8 percent of the total female population, 28.4 percent of the total male population, 75 percent of the total juvenile population) during the Bronze and Iron Ages, to 15.5 percent during the Hunnu (2209–1907 BP) period, the rate of females with cribra orbitalia remained roughly the same, while the incidence of cribra orbitalia among males and children declined (29.4 percent of the total female population, 5.3 percent of the total male population, and 25 percent of the juvenile population had cribra orbitalia). Bazarsad posits several reasons for this distribution of cribra orbitalia: adults may have lower rates of cribra orbitalia than juveniles because lesions either heal with age or lead to death. Higher rates of cribia orbitalia among females may indicate lesser health status, or greater survival of young females with cribia orbitalia into adulthood.

Harris lines

Harris lines form before adulthood, when bone growth is temporarily halted or slowed down due to some sort of stress (either disease or malnutrition). During this time, bone mineralization continues, but growth does not, or does so at very reduced levels. If and when the stressor is overcome, bone growth will resume, resulting in a line of increased mineral density that will be visible in a radiograph. If there is not recovery from the stressor, no line will be formed.

Hair

The stress hormone cortisol is deposited in hair as it grows. This has been used successfully to detect fluctuating levels of stress in the later lifespan of mummies.

Mechanical stress and activity indicators

Examining the effects that activities and workload has upon the skeleton allows the archaeologist to examine who was doing what kinds of labor, and how activities were structured within society. The division of labor within the household may be divided according to gender and age, or be based on other hierarchical social structures. Human remains can allow archaeologists to uncover patterns in the division of labor.

Living bones are subject to Wolff's law, which states that bones are physically affected and remodeled by physical activity or inactivity. Increases in mechanical stress tend to produce bones that are thicker and stronger. Disruptions in homeostasis caused by nutritional deficiency or disease or profound inactivity/disuse/disability can lead to bone loss. While the acquisition of bipedal locomotion and body mass appear to determine the size and shape of children's bones, activity during the adolescent growth period seems to exert a greater influence on the size and shape of adult bones than exercise later in life.

Muscle attachment sites (also called entheses) have been thought to be impacted in the same way causing what were once called musculoskeletal stress markers, but now widely named entheseal changes. These changes were widely used to study activity-patterns, but research has shown that processes associated with aging have a greater impact than occupational stresses. It has also been shown that geometric changes to bone structure (described above) and entheseal changes differ in their underlying cause with the latter poorly affected by occupation. Joint changes, including osteoarthritis, have also been used to infer occupations but in general these are also manifestations of the aging process.

Markers of occupational stress, which include morphological changes to the skeleton and dentition as well as joint changes at specific locations have also been widely used to infer specific (rather than general) activities. Such markers are often based on single cases described in clinical literature in the late nineteenth century. One such marker has been found to be a reliable indicator of lifestyle: the external auditory exostosis also called surfer's ear, which is a small bony protuberance in the ear canal which occurs in those working in proximity to cold water.

One example of how these changes have been used to study activities is the New York African Burial Ground in New York. This provides evidence of the brutal working conditions under which the enslaved labored; osteoarthritis of the vertebrae was very common, even among the young. The pattern of osteoarthritis combined with the early age of onset provides evidence of labor that resulted in mechanical strain to the neck. One male skeleton shows stress lesions at 37 percent of 33 muscle or ligament attachments, showing he experienced significant musculoskeletal stress. Overall, the interred show signs of significant musculoskeletal stress and heavy workloads, although workload and activities varied among different individuals. Some individuals show high levels of stress, while others do not. This references the variety of types of labor (e.g., domestic vs. carrying heavy loads) labor that enslaved individuals were forced to perform.

Injury and workload

Fractures to bones during or after excavation will appear relatively fresh, with broken surfaces appearing white and unweathered. Distinguishing between fractures around the time of death and post-depositional fractures in bone is difficult, as both types of fractures will show signs of weathering. Unless evidence of bone healing or other factors are present, researchers may choose to regard all weathered fractures as post-depositional.

Evidence of perimortal fractures (or fractures inflicted on a fresh corpse) can be distinguished in unhealed metal blade injuries to the bones. Living or freshly dead bones are somewhat resilient, so metal blade injuries to bone will generate a linear cut with relatively clean edges rather than irregular shattering. Archaeologists have tried using the microscopic parallel scratch marks on cut bones in order to estimate the trajectory of the blade that caused the injury.

Diet and dental health

Caries

Dental caries, commonly referred to as cavities or tooth decay, are caused by localized destruction of tooth enamel, as a result of acids produced by bacteria feeding upon and fermenting carbohydrates in the mouth. Subsistence based upon agriculture is strongly associated with a higher rate of caries than subsistence based upon foraging, because of the higher levels of carbohydrates in diets based upon agriculture. For example, bioarchaeologists have used caries in skeletons to correlate a diet of rice and agriculture with the disease. Females may be more vulnerable to caries compared to men, due to lower saliva flow than males, the positive correlation of estrogens with increased caries rates, and because of physiological changes associated with pregnancy, such as suppression of the immune system and a possible concomitant decrease in antimicrobial activity in the oral cavity.

Stable isotope analysis

Stable isotope analysis of carbon and nitrogen in human bone collagen allows bioarchaeologists to carry out dietary reconstruction and to make nutritional inferences. These chemical signatures reflect long-term dietary patterns, rather than a single meal or feast. Stable isotope analysis monitors the ratio of carbon 13 to carbon 12 (¹³C/¹²C), which is expressed as parts per mil (per thousand) using delta notation (δ¹³C). The ratio of carbon isotopes varies according to the types of plants consumed with different photosynthesis pathways. The three photosynthesis pathways are C3 carbon fixation, C4 carbon fixation and Crassulacean acid metabolism. C4 plants are mainly grasses from tropical and subtropical regions, and are adapted to higher levels of radiation than C3 plants. Corn, millet and sugar cane are some well-known C4 domesticates, while all trees and shrubs use the C3 pathway. C3 plants are more common and numerous than C4 plants. Both types of plants occur in tropical areas, but only C3 plants occur naturally in colder areas. ¹²C and ¹³C occur in a ratio of approximately 98.9 to 1.1.

The ¹³C and ¹²C ratio is either depleted (more negative) or enriched (more positive) relative to the international standard, which is set to an arbitrary zero. The different photosynthesis pathways used by C3 and C4 plants cause them to discriminate differently towards ¹³C The C4 and C3 plants have distinctly different ranges of ¹³C; C4 plants range between -9 and -16 per mil, and C3 plants range between -22 to -34 per mil. δ¹³C studies have been used in North America to document the transition from a C3 to a C4 (native North American plants to corn) diet. The rapid and dramatic increase in ¹³C after the adoption of maize agriculture attests to the change in the southeastern American diet by 1300 CE.

Isotope ratios in food, especially plant food, are directly and predictably reflected in bone chemistry, allowing researchers to partially reconstruct recent diet using stable isotopes as tracers. Nitrogen isotopes (¹⁴N and ¹⁵N) have been used to estimate the relative contributions of legumes verses nonlegumes, as well as terrestrial versus marine resources to the diet.

The increased consumption of legumes, or animals that eat them, causes ¹⁵N in the body to decrease. Nitrogen isotopes in bone collagen are ultimately derived from dietary protein, while carbon can be contributed by protein, carbohydrate, or fat in the diet. Compared to other plants, legumes have lower ¹⁴N/¹⁵N ratios because they can fix molecular nitrogen, rather than having to rely on nitrates and nitrites in the soil. Legumes have δ¹⁵N values close to 0%, while other plants, which have δ15N values that range from 2 to 6%. Nitrogen isotope ratios can be used to index the importance of animal protein in the diet. ¹⁵N increases about 3-4% with each trophic step upward. ¹⁵N values increase with meat consumption, and decrease with legume consumption. The ¹⁴N/¹⁵N ratio could be used to gauge the contribution of meat and legumes to the diet.

Skeletons excavated from the Coburn Street Burial Ground (1750 to 1827 CE) in Cape Town, South Africa, were analyzed using stable isotope data by Cox et al. in order to determine geographical histories and life histories of the interred. The people buried in this cemetery were assumed to be slaves and members of the underclass based on the informal nature of the cemetery; biomechanical stress analysis and stable isotope analysis, combined with other archaeological data, seem to support this supposition.

Based on stable isotope levels, eight Cobern Street Burial Ground individuals consumed a diet based on C4 (tropical) plants in childhood, then consumed more C3 plants, which were more common at the Cape later in their lives. Six of these individuals had dental modifications similar to those carried out by peoples inhabiting tropical areas known to be targeted by slavers who brought enslaved individuals from other parts of Africa to the colony. Based on this evidence, Cox et al. argue that these individuals represent enslaved persons from areas of Africa where C4 plants are consumed and who were brought to the Cape as laborers. Cox et al. do not assign these individuals to a specific ethnicity, but do point out that similar dental modifications are carried out by the Makua, Yao, and Marav peoples. Four individuals were buried with no grave goods, in accordance with Muslim tradition, facing Signal Hill, which is a point of significance for local Muslims. Their isotopic signatures indicate that they grew up in a temperate environment consuming mostly C3 plants, but some C4 plants. Many of the isotopic signatures of interred individuals indicate that they Cox et al. argue that these individuals were from the Indian Ocean area. They also suggest that these individuals were Muslims. Cox et al. argue that stable isotopic analysis of burials, combined with historical and archaeological data can be an effective way in of investigating the worldwide migrations forced by the African Slave Trade, as well as the emergence of the underclass and working class in the colonial Old World.

Stable isotope analysis of strontium and oxygen can also be carried out. The amounts of these isotopes vary in different geological locations. Because bone is a dynamic tissue that is remodeled over time, and because different parts of the skeleton are laid down at particular times over the course of a human life, stable isotope analysis can be used to investigate population movements in the past and indicate where people lived at various points of their lives.

Archaeological uses of DNA

aDNA analysis of past populations is used by archaeology to genetically determine the sex of individuals, determine genetic relatedness, understand marriage patterns, and investigate prehistoric population movements.

An example of Archaeologists using DNA to find evidence, in 2012 archaeologists found skeletal remains of an adult male. He was buried under a car park in England. with the use of DNA evidence, the archaeologists were able to confirm that the remains belonged to Richard III, the former king of England who died in the Battle of Bosworth.

In 2021, Canadian researchers used DNA analysis on skeletal remains found on King William Island, identifying them as belonging to Warrant Officer John Gregory, an engineer serving aboard HMS Erebus in the ill-fated 1845 Franklin Expedition. He was the first expedition member to be identified by DNA analysis.

Bioarchaeological treatments of equality and inequality

Aspects of the relationship between the physical body and socio-cultural conditions and practices can be recognized through the study of human remains. This is most often emphasized in a "biocultural bioarchaeology" model. It has often been the case that bioarchaeology has been regarded as a positivist, science-based discipline, while theories of the living body in the social sciences have been viewed as constructivist in nature. Physical anthropology and bioarchaeology have been criticized for having little to no concern for culture or history. Blakey has argued that scientific or forensic treatments of human remains from archaeological sites construct a view of the past that is neither cultural nor historic, and has suggested that a biocultural version of bioarchaeology will be able to construct a more meaningful and nuanced history that is more relevant to modern populations, especially descent populations. By biocultural, Blakey means a type of bioarchaeology that is not simply descriptive, but combines the standard forensic techniques of describing stature, sex and age with investigations of demography and epidemiology in order to verify or critique socioeconomic conditions experienced by human communities of the past. The incorporation of analysis regarding the grave goods interred with individuals may further the understanding of the daily activities experienced in life.

Currently, some bioarchaeologists are coming to view the discipline as lying at a crucial interface between the science and the humanities; as the human body is non-static, and is constantly being made and re-made by both biological and cultural factors.

Buikstra considers her work to be aligned with Blakey's biocultural version of bioarchaeology because of her emphasis on models stemming from critical theory and political economy. She acknowledges that scholars such as Larsen are productive, but points out that his is a different type of bioarchaeology that focuses on quality of life, lifestyle, behavior, biological relatedness, and population history. It does not closely link skeletal remains to their archaeological context, and is best viewed as a "skeletal biology of the past."

Inequalities exist in all human societies, even so-called “egalitarian” ones. It is important to note that bioarchaeology has helped to dispel the idea that life for foragers of the past was “nasty, brutish and short”; bioarchaeological studies have shown that foragers of the past were often quite healthy, while agricultural societies tend to have increased incidence of malnutrition and disease. However, based on a comparison of foragers from Oakhurst to agriculturalists from K2 and Mapungubwe, Steyn believes that agriculturalists from K2 and Mapungubwe were not subject to the lower nutritional levels expected for this type of subsistence system.

Danforth argues that more “complex” state-level societies display greater health differences between elites and the rest of society, with elites having the advantage, and that this disparity increases as societies become more unequal. Some status differences in society do not necessarily mean radically different nutritional levels; Powell did not find evidence of great nutritional differences between elites and commoners, but did find lower rates of anemia among elites in Moundville.

An area of increasing interest among bioarchaeologists interested in understanding inequality is the study of violence. Researchers analyzing traumatic injuries on human remains have shown that a person's social status and gender can have a significant impact on their exposure to violence. There are numerous researchers studying violence, exploring a range of different types of violent behavior among past human societies. Including intimate partner violence, child abuse, institutional abuse, torture, warfare, human sacrifice, and structural violence.

Archaeological ethics

There are ethical issues with bioarchaeology that revolve around treatment and respect for the dead. Large-scale skeletal collections were first amassed in the US in the 19th century, largely from the remains of Native Americans. No permission was ever granted from surviving family for study and display. Recently, federal laws such as NAGPRA (Native American Graves Protection and Repatriation Act) have allowed Native Americans to regain control over the skeletal remains of their ancestors and associated artifacts in order to reassert their cultural identities.

NAGPRA passed in 1990. At this time, many archaeologists underestimated the public perception of archaeologists as non-productive members of society and grave robbers. Concerns about occasional mistreatment of Native American remains are not unfounded: in a Minnesota excavation 1971, White and Native American remains were treated differently; remains of White people were reburied, while remains of Native American people were placed in cardboard boxes and placed in a natural history museum. Blakey relates the growth in African American bioarchaeology to NAGPRA and its effect of cutting physical anthropologist off from their study of Native American remains.

Bioarchaeology in Europe is not as affected by these repatriation issues as American bioarchaeology but regardless the ethical considerations associated with working with human remains are, and should, be considered. However, because much of European archaeology has been focused on classical roots, artifacts and art have been overemphasized and Roman and post-Roman skeletal remains were nearly completely neglected until the 1980s. Prehistoric archaeology in Europe is a different story, as biological remains began to be analyzed earlier than in classical archaeology.