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Monday, February 2, 2015

Asteroid mining


From Wikipedia, the free encyclopedia


Artist's concept of asteroid mining

433 Eros is a stony asteroid in a near-Earth orbit

Asteroid mining refers to the possibility of exploiting raw materials from asteroids and other minor planets, including near-Earth objects.[1] Minerals and volatiles could be mined from an asteroid or spent comet then taken back to Earth or used in space for construction materials. Materials that could be mined or extracted include iron, nickel, titanium for construction, water, and oxygen to sustain the lives of prospector-astronauts on site, as well as hydrogen and oxygen for use as rocket propellant. In space exploration, using resources gathered while on a journey is referred to as in-situ resource utilization.

Purpose

Based on known terrestrial reserves and growing consumption in developing countries along with excessive exploitation by developed countries, there is speculation that key elements needed for modern industry and food production, including phosphorus, antimony, zinc, tin, silver, lead, indium, gold, and copper, could be exhausted on Earth within 50–60 years.[2] In response, it has been suggested that platinum, cobalt and other valuable elements from asteroids may be mined and sent to Earth for profit, used to build solar-power satellites and space habitats,[3][4] and water processed from ice to refuel orbiting propellant depots.[5][6][7]

In fact, all the gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium, ruthenium, and tungsten mined from Earth's crust, and that are essential for economic and technological progress, came originally from the rain of asteroids that hit Earth after the crust cooled.[8][9][10] This is because although asteroids and Earth accreted from the same starting materials, Earth's relatively stronger gravity pulled all heavy siderophilic (iron-loving) elements into its core during its molten youth more than four billion years ago.[10] This left the crust depleted of such valuable elements[10] until asteroid impacts re-infused the depleted crust with metals (some flow from core to surface does occur, e.g. at the Bushveld Igneous Complex, a famously rich source of platinum-group metals).

In 2006, the Keck Observatory announced that the binary Jupiter trojan 617 Patroclus,[11] and possibly large numbers of other Jupiter trojans, are likely extinct comets and consist largely of water ice. Similarly, Jupiter-family comets, and possibly near-Earth asteroids that are extinct comets, might also economically provide water. The process of in-situ resource utilization—using materials native to space for propellant, tankage, radiation shielding, and other high-mass components of space infrastructure—could lead to radical reductions in its cost.[1]

Ice would satisfy one of two necessary conditions to enable "human expansion into the Solar System" (the ultimate goal for human space flight proposed by the 2009 "Augustine Commission" Review of United States Human Space Flight Plans Committee): physical sustainability and economic sustainability.[12]

From the astrobiological perspective, asteroid prospecting could provide scientific data for the search for extraterrestrial intelligence (SETI). Some astrophysicists have suggested that if advanced extraterrestrial civilizations employed asteroid mining long ago, the hallmarks of these activities might be detectable.[13][14][15]

Asteroid selection

Comparison of delta-v requirements
Mission Δv
Earth surface to LEO 8.0 km/s
LEO to near-Earth asteroid 5.5 km/s[note 1]
LEO to lunar surface 6.3 km/s
LEO to moons of Mars 8.0 km/s
An important factor to consider in target selection is orbital economics, in particular the change in velocity (Δv) and travel time to and from the target. More of the extracted native material must be expended as propellant in higher Δv trajectories, thus less returned as payload. Direct Hohmann trajectories are faster than Hohmann trajectories assisted by planetary and/or lunar flybys, which in turn are faster than those of the Interplanetary Transport Network, but the latter have lower Δv than the former.

Near-Earth asteroids are considered likely candidates for early mining activity. Their low Δv makes them suitable for use in extracting construction materials for near-Earth space-based facilities, greatly reducing the economic cost of transporting supplies into Earth orbit.[16]

The table at right shows a comparison of Δv requirements for various missions. In terms of propulsion energy requirements, a mission to a near-Earth asteroid compares favorably to alternative mining missions.

An example of a potential target for an early asteroid mining expedition is 4660 Nereus.[17] This body has a very low Δv compared to lifting materials from the surface of the Moon. However it would require a much longer round-trip to return the material.

Multiple types of asteroids have been identified but the three main types would include the C-type, S-type, and M-type asteroids.
  1. C-type asteroids have a high abundance of water which is not currently of use for mining but could be used in an exploration effort beyond the asteroid. Mission costs could be reduced by using the available water from the asteroid. C-type asteroids also have a lot of organic carbon, phosphorus, and other key ingredients for fertilizer which could be used to grow food.[18]
  2. S-type asteroids carry little water but look more attractive because they contain numerous metals including: nickel, cobalt and more valuable metals such as gold, platinum and rhodium. A small 10-meter S-type asteroid contains about 650,000 kg (1,433,000 lb) of metal with 50 kg (110 lb) in the form of rare metals like platinum and gold.[18]
  3. M-type asteroids are rare but contain up to 10 times more metal than S-types[18]

Asteroid cataloging

The B612 Foundation is a private nonprofit foundation with headquarters in the United States, dedicated to protecting Earth from asteroid strikes. As a non-governmental organization it has conducted two lines of related research to help detect asteroids that could one day strike Earth, and find the technological means to divert their path to avoid such collisions.
The foundation's current goal is to design and build a privately financed asteroid-finding space telescope, Sentinel, to be launched in 2017–2018. The Sentinel's infrared telescope, once parked in an orbit similar to that of Venus, will help identify threatening asteroids by cataloging 90% of those with diameters larger than 140 metres (460 ft), as well as surveying smaller Solar System objects.[19][20][21]

Data gathered by Sentinel will be provided through an existing scientific data-sharing network that includes NASA and academic institutions such as the Minor Planet Center in Cambridge, Massachusetts. Given the satellite's telescopic accuracy, Sentinel's data may prove valuable for other possible future missions, such as asteroid mining.[20][21][22]

Mining considerations

There are three options for mining:[16]
  1. Bring raw asteroidal material to Earth for use.
  2. Process it on-site to bring back only processed materials, and perhaps produce propellant for the return trip.
  3. Transport the asteroid to a safe orbit around the Moon, Earth or to the ISS.[7] This can hypothetically allow for most materials to be used and not wasted.[4] (see Methods for asteroid retrieval or catching)
Processing in situ for the purpose of extracting high-value minerals will reduce the energy requirements for transporting the materials, although the processing facilities must first be transported to the mining site.

Mining operations require special equipment to handle the extraction and processing of ore in outer space.[16] The machinery will need to be anchored to the body,[citation needed] but once in place, the ore can be moved about more readily due to the lack of gravity. Docking with an asteroid can be performed using a harpoon-like process, where a projectile penetrates the surface to serve as an anchor then an attached cable is used to winch the vehicle to the surface, if the asteroid is rigid enough for a harpoon to be effective.[23]

Due to the distance from Earth to an asteroid selected for mining, the round-trip time for communications will be several minutes or more, except during occasional close approaches to Earth by near-Earth asteroids. Thus any mining equipment will either need to be highly automated, or a human presence will be needed nearby.[16] Humans would also be useful for troubleshooting problems and for maintaining the equipment. On the other hand, multi-minute communications delays have not prevented the success of robotic exploration of Mars, and automated systems would be much less expensive to build and deploy.[24]

Technology being developed by Planetary Resources to locate and harvest these asteroids has resulted in the creation of 3 different types of satellites.
  1. Arkyd Series 100 (The Leo Space telescope) Less expensive instrument that will be used to find, analyze, and see what resources are available on nearby asteroids.[18]
  2. Arkyd Series 200 (The Interceptor) Satellite that would actually land on the asteroid to get a closer analysis of the available resources.[18]
  3. Arkyd Series 300 (Rendezvous Prospector) Satellite developed for research and finding resources deeper in space.[18]
Technology being developed by Deep Space Industries to examine, sample, and harvest asteroids is divided into three families of spacecraft.
  1. FireFlies are launched in waves of three nearly identical spacecraft to different targets in inexpensive CubeSat form factors to rendezvous and examine candidate asteroids for their resource value.[25]
  2. DragonFlies also are launched in waves of three nearly identical spacecraft to gather small samples (5–10 kg) and return them to Earth for detailed analysis of their value.[25]
  3. Harvestors voyage out to confirmed high-value asteroid to gather hundreds of tons of material for return to high Earth orbit for processing into products useful for high-value in-space markets.[26]
Asteroid mining could potentially revolutionize space exploration. The C-type asteroids high abundance of water could be used to produce fuel by splitting water into hydrogen and oxygen. This would make space travel a more feasible option by lowering cost of fuel.

Extraction techniques

Surface mining

On some types of asteroids, material may be scraped off the surface using a scoop or auger, or for larger pieces, an "active grab."[16] There is strong evidence that many asteroids consist of rubble piles,[27] making this approach possible.

Shaft mining

A mine can be dug into the asteroid, and the material extracted through the shaft. This requires precise knowledge to engineer accuracy of astro-location under the surface regolith and a transportation system to carry the desired ore to the processing facility.

Magnetic rakes

Asteroids with a high metal content may be covered in loose grains that can be gathered by means of a magnet.[16][28]

Heating

For volatile materials in extinct comets, heat can be used to melt and vaporize the matrix.[16][29]

Self-replicating machines

A 1980 NASA study entitled Advanced Automation for Space Missions proposed a complex automated factory on the Moon that would work over several years to build a copy of itself.[30]
Exponential growth of factories over many years could refine large amounts of lunar regolith. Since 1980 there has been major progress in miniaturization, nanotechnology, materials science, and additive manufacturing.

The power of self-replication is compelling. For example, a 1 kg solar-powered self-replicating machine that takes one month to make a copy of itself would, after just two and a half years (30 doublings), refine over one billion kilograms of asteroidal material without any human intervention. Ten months later you would have one trillion kg of whatever metal(s) are used to make the devices, which could then be "harvested" at any time. No large mass of equipment need be delivered to the asteroid; in effect, only the information that went into designing the device plus the 1 kg device itself.

Asteroid prospects

A class of easily recoverable objects (EROs) was identified by a group of researchers in 2013. Twelve asteroids made up the initially identified group, all of which could be potentially mined with present-day rocket technology. Of 9000 asteroids searched in the NEO database, these twelve could all be brought into an Earth-accessible orbit by changing their velocity by less than 500 meters per second (1,800 km/h; 1,100 mph). The dozen asteroids range in size from 2 to 20 meters (10 to 70 ft).[31]

Proposed mining projects

On April 24, 2012 a plan was announced by billionaire entrepreneurs to mine asteroids for their resources. The company is called Planetary Resources and its founders include aerospace entrepreneurs Eric Anderson and Peter Diamandis. Advisers include film director and explorer James Cameron and investors include Google's chief executive Larry Page and its executive chairman Eric Schmidt.[1][32] They also plan to create a fuel depot in space by 2020 by using water from asteroids, which could be broken down in space to liquid oxygen and liquid hydrogen for rocket fuel. From there, it could be shipped to Earth orbit for refueling commercial satellites or spacecraft.[1] The plan has been met with skepticism by some scientists who do not see it as cost-effective, even though platinum and gold are worth nearly £35 per gram (approximately $1,800 per troy ounce). An upcoming NASA mission (OSIRIS-REx) to return just 60 g (two ounces) of material from an asteroid to Earth will cost about $1 billion USD.[1] Planetary Resources admits that, in order to be successful, it will need to develop technologies that bring the cost of space flight down. Planetary Resources also expects that the construction of "space infrastructure" will help to reduce long-term running costs.
For example, fuel costs can be reduced by extracting water from asteroids and converting it to hydrogen using solar energy. In theory, hydrogen fuel mined from asteroids costs significantly less than fuel from Earth due to high costs of escaping Earth's gravity. If successful, investment in "space infrastructure" and economies of scale could reduce operational costs to levels significantly below NASA's upcoming (OSIRIS-REx) mission.[33]

Another similar venture, called Deep Space Industries, was started by David Gump, who had founded other space companies.[34] The company hopes to begin prospecting for asteroids suitable for mining by 2015 and by 2016 return asteroid samples to Earth.[35] By 2023 Deep Space Industries plans to begin mining for asteroids.[36]

Deep Space Industries won a contract to design a bitcoin spacecraft and associated constellation to broadcast the latest completed bitcoin block in April 2014.[37] NASA has awarded the company two contracts for analysis and advice on the space agency's Asteroid Redirect Mission in June 2014.[38]

At ISDC-San Diego 2013,[39] Kepler Energy and Space Engineering (KESE,llc) also announced it was going to mine asteroids, using a simpler, more straightforward approach: KESE plans to use almost exclusively existing guidance, navigation and anchoring technologies from successful missions like the Rosetta/Philae, Dawn, and Hyabusa's Muses-C and current NASA Technology Transfer tooling to build and send a 4-module Automated Mining System (AMS) to a small asteroid with a simple digging tool to collect ~40 tons of asteroid regolith and bring each of the four return modules back to low Earth orbit (LEO) by the end of the decade. Small asteroids are expected to be loose piles of rubble, therefore providing for easy extraction.

In September 2012, the NASA Institute for Advanced Concepts (NIAC) announced the Robotic Asteroid Prospector project, which will examine and evaluate the feasibility of asteroid mining in terms of means, methods, and systems.[40]

Economics

Currently, the quality of the ore and the consequent cost and mass of equipment required to extract it are unknown and can only be speculated. Some economic analyses indicate that the cost of returning asteroidal materials to Earth far outweighs their market value, and that asteroid mining will not attract private investment at current commodity prices and space transportation costs.[41][42] Other studies suggest large profit by using solar power.[43][44] Potential markets for materials can be identified and profit generated if extraction cost is brought down. For example, the delivery of multiple tonnes of water to low Earth orbit for rocket fuel preparation for space tourism could generate a significant profit.[45]

In 1997 it was speculated that a relatively small metallic asteroid with a diameter of 1.6 km (0.99 mi) contains more than $20 trillion USD worth of industrial and precious metals.[6][46] A comparatively small M-type asteroid with a mean diameter of 1 kilometer (0.62 mi) could contain more than two billion metric tons of iron–nickel ore,[47] or two to three times the annual production of 2004.[48] The asteroid 16 Psyche is believed to contain 1.7×1019 kg of nickel–iron, which could supply the world production requirement for several million years. A small portion of the extracted material would also be precious metals.

Although Planetary Resources says that platinum from a 30-meter long asteroid is worth 25–50 billion USD,[49] an economist remarked that any outside source of precious metals could lower prices sufficiently to possibly doom the venture by rapidly increasing the available supply of such metals.[50]

Development of an asteroid-orbit manipulation infrastructure could offer a large return on investment.[51] However, astrophysicists Carl Sagan and Steven J. Ostro raised the concern that altering the trajectories of asteroids in nearby interplanetary space could cause a catastrophic collision with Earth. These scientists concluded[when?] that stringent controls on the misuse of orbit-engineering technology be instituted.[by whom?][51][52][53]

Scarcity

Scarcity is a fundamental economic problem of humans having seemingly unlimited wants in a world of limited resources. Asteroid mining has the potential to provide nearly unlimited resources, which could eliminate scarcity for those materials.[citation needed] Earth's resources are not infinite.

The idea of exhausting resources is not new, Thomas Malthus wrote in 1798 that, because resources are ultimately limited, the exponential growth in a population would result in falls in income per capita until poverty and starvation would result as a constricting factor on population.[54] Malthus's analysis was based on two types of reserves on Earth, including proven and conditional reserves.[citation needed] These make up the group of measured reserves that is estimated to contain about 20% of Earth's deposits.[clarification needed]
  • Proven reserves are deposits of mineral resources that are already discovered and known to be economically extractable under present or similar demand, price and other economic and technological conditions.[54]
  • Conditional reserves are discovered deposits that are not yet economically viable.[citation needed]
  • Indicated reserves are less intensively measured deposits whose data is derived from surveys and geological projections. Hypothetical reserves and speculative resources make up this group of reserves. Inferred reserves are deposits that have been located but not yet exploited.[54]
Continued development in asteroid mining techniques and technology will help to increase mineral discoveries found on the Moon and asteroids which could make mining more intriguing.[citation needed] As the cost of extracting mineral resources, especially platinum group metals, on Earth rises, the cost of extracting the same resources from celestial bodies declines due to technological innovations around space exploration.[54]

Financial feasibility

Space ventures are high-risk, with long lead times and heavy capital investment, and that is no different for asteroid-mining projects. These types of ventures could be funded through private investment or through government investment. If a government venture were to be sought, maximizing its cost–benefit ratio and financial returns are a must. For a commercial venture it can be highly profitable as long as the revenue earned is greater than total costs (costs for extraction and costs for marketing).[55] The costs involving an asteroid-mining venture have been estimated to be around $100 billion US.[55]

There are six categories of cost considered for an asteroid mining venture:[55]
  1. Research and development costs
  2. Exploration and prospecting costs
  3. Construction and infrastructure development costs
  4. Operational and engineering costs
  5. Environmental costs
  6. Time cost
Determining financial feasibility is best represented through net present value.[55] One requirement needed for financial feasibility is a high return on investments estimating around 30%.[55] On September 5, 2008 platinum was valued at US$1,340 per ounce, or US$43,000 per kilogram. With a 10% return on investment, 173,400 kilograms (5,575,000 ozt) of platinum would have to be extracted for every 1,155,00 tons of asteroid ore. With a 50% return on investment 1,703,000 kilograms (54,750,000 ozt) of platinum would have to be extracted for every 11,350,000 tons of asteroid ore. The higher return on investment required, the more economically, technologically, and practically unfeasible the venture becomes.[55]

The payback period and the high risk involved make asteroid mining a less competitive venture compared to terrestrial projects. Launching costs may be the most significant, which can only lower over time through increased competition and technological innovation. Asteroid mining will become more viable when fixed costs lower due to development in infrastructure.[citation needed]

In fiction

The first mention of asteroid mining in science fiction is apparently Garrett P. Serviss' story Edison's Conquest of Mars, New York Evening Journal, 1898.[56][57]

The 1979 film Alien, directed by Ridley Scott, is about the crew of the Nostromo, a commercially operated spaceship on a return trip to Earth hauling a refinery and 20 million tons of mineral ore mined from an asteroid. C. J. Cherryh's novel, Heavy Time focuses on the plight of asteroid miners in the Alliance-Union universe, while Moon is a 2009 British science fiction drama film depicting a lunar facility that mines the alternative fuel helium-3 needed to provide energy on Earth. It was notable for its realism and drama, winning several awards internationally.[58][59][60]

In several science fiction video games, asteroid mining is a possibility. For example, in the space-MMO, EVE Online, asteroid mining is a very popular career, due to its simplicity.[61][62][63]

Gallery

  • Artist's concept from the 1970s of asteroid mining
  • Artist's concept of an asteroid mining vehicle as seen in 1984
  • Artist's concept of an asteroid moved by a space tether
  • A future space telescope designed by Planetary Resources company to find asteroids

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Paleoanthropology


From Wikipedia, the free encyclopedia


Fossil Hominid Skull Display at The Museum of Osteology.

Paleoanthropology (English: Palaeoanthropology; from Greek: παλαιός (palaeos) "old, ancient"), anthrōpos (ἄνθρωπος), "man", understood to mean humanity, and -logia (-λογία), "discourse" or "study"), which combines the disciplines of paleontology and physical anthropology, is the study of ancient humans as found in fossil hominid evidence such as petrifacted bones and footprints.

History of paleoanthropology

18th Century

Since the time of Carl Linnaeus, the great apes were considered the closest relatives of human beings, based on morphological similarity. In the 19th century, it was speculated that the closest living relatives to humans were chimpanzees and gorillas, and based on the natural range of these creatures, it was surmised that humans shared a common ancestor with African apes and that fossils of these ancestors would ultimately be found in Africa.[1]

19th century


Charles Robert Darwin.

The science arguably began in the late 19th century when important discoveries occurred that led to the study of human evolution. The discovery of the Neanderthal in Germany, Thomas Huxley's Evidence as to Man's Place in Nature, and Charles Darwin's The Descent of Man were all important to early paleoanthropological research.

The modern field of paleoanthropology began in the 19th century with the discovery of "Neanderthal man" (the eponymous skeleton was found in 1856, but there had been finds elsewhere since 1830), and with evidence of so-called cave men. The idea that humans are similar to certain great apes had been obvious to people for some time, but the idea of the biological evolution of species in general was not legitimized until after Charles Darwin published On the Origin of Species in 1859.

Though Darwin's first book on evolution did not address the specific question of human evolution—"light will be thrown on the origin of man and his history," was all Darwin wrote on the subject—the implications of evolutionary theory were clear to contemporary readers.

Debates between Thomas Huxley and Richard Owen focused on the idea of human evolution. Huxley convincingly illustrated many of the similarities and differences between humans and apes in his 1863 book Evidence as to Man's Place in Nature. By the time Darwin published his own book on the subject, Descent of Man, it was already a well-known interpretation of his theory—and the interpretation which made the theory highly controversial. Even many of Darwin's original supporters (such as Alfred Russel Wallace and Charles Lyell) balked at the idea that human beings could have evolved their apparently boundless mental capacities and moral sensibilities through natural selection.

Asia

Prior to today's general acceptance of Africa as the root of genus Homo, 19th century naturalists sought the origin of man in Asia. So-called "dragon bones" (fossil bones and teeth) from Chinese apothecary shops were known, but it was not until the early 20th century that German paleontologist, Max Schlosser, first described a single human tooth from Beijing. Although Schlosser (1903) was very cautious, identifying the tooth only as “?Anthropoide g. et sp. indet?,” he was hopeful that future work would discover a new anthropoid in China.

Eleven years later, the Swedish geologist Johan Gunnar Andersson was sent to China as a mining advisor and soon developed an interest in “dragon bones”. It was he who, in 1918, discovered the sites around Zhoukoudian, a village about 50 kilometers southwest of Beijing. However, because of the sparse nature of the initial finds, the site was abandoned.

Work did not resume until 1921, when the Austrian paleontologist, Otto Zdansky, fresh with his doctoral degree from Vienna, came to Beijing to work for Andersson. Zdansky conducted short-term excavations at Locality 1 in 1921 and 1923, and recovered only two teeth of significance (one premolar and one molar) that he subsequently described, cautiously, as “?Homo sp.” (Zdansky, 1927). With that done, Zdansky returned to Austria and suspended all fieldwork.

News of the fossil hominin teeth delighted the scientific community in Beijing, and plans for developing a larger, more systematic project at Zhoukoudian were soon formulated. At the epicenter of excitement was Davidson Black, a Canadian-born anatomist working at Peking Union Medical College. Black shared Andersson’s interest, as well as his view that central Asia was a promising home for early humankind. In late 1926, Black submitted a proposal to the Rockefeller Foundation seeking financial support for systematic excavation at Zhoukoudian and the establishment of an institute for the study of human biology in China.

The Zhoukoudian Project came into existence in the spring of 1927, and two years later, the Cenozoic Research Laboratory of the Geological Survey of China was formally established. Being the first institution of its kind, the Cenozoic Laboratory opened up new avenues for the study of paleogeology and paleontology in China. The Laboratory was the precursor of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Science, which took its modern form after 1949.

The first of the major project finds are attributed to the young Swedish paleontologist, Anders Birger Bohlin, then serving as the field advisor at Zhoukoudian. He recovered a left lower molar that Black (1927) identified as unmistakably human (it compared favorably to the previous find made by Zdansky), and subsequently coined it Sinanthropus pekinensis.[2] The news was at first met with skepticism, and many scholars had reservations that a single tooth was sufficient to justify the naming of a new type of early hominin. Yet within a little more than two years, in the winter of 1929, Pei Wenzhong, then the field director at Zhoukoudian, unearthed the first complete calvaria of Peking Man. Twenty-seven years after Schlosser’s initial description, the antiquity of early humans in East Asia was no longer a speculation, but a reality.

The Zhoukoudian Site.

Excavations continued at the site and remained fruitful until the outbreak of the Second Sino-Japanese War in 1937. The decade-long research yielded a wealth of faunal and lithic materials, as well as hominin fossils. These included 5 more complete calvaria, 9 large cranial fragments, 6 facial fragments, 14 partial mandibles, 147 isolated teeth, and 11 postcranial elements—estimated to represent as least 40 individuals. Evidence of fire, marked by ash lenses and burned bones and stones, were apparently also present,[3] although recent studies have challenged this view.[4][5] Franz Weidenreich came to Beijing soon after Black’s untimely death in 1934, and took charge of the study of the hominin specimens.

Following the loss of the Peking Man materials in late 1941, scientific endeavors at Zhoukoudian slowed, primarily because of lack of funding. Frantic search for the missing fossils took place, and continued well into the 1950s. After the establishment of the People’s Republic of China in 1949, excavations resumed at Zhoukoudian. But with political instability and social unrest brewing in China, beginning in 1966, and major discoveries at Olduvai Gorge and East Turkana (Koobi Fora), the paleoanthropological spotlight shifted westward to East Africa. Although China re-opened its doors to the West in the late 1970s, national policy calling for self-reliance, coupled with a widened language barrier, thwarted all the possibilities of renewed scientific relationships. Indeed, Harvard anthropologist K. C. Chang noted, “international collaboration (in developing nations very often a disguise for Western domination) became a thing of the past” (1977: 139).

Africa


Australopithecus africanus.

In South Africa, a notable and rare find came to light in 1924. In a limestone quarry at Taung, Professor Raymond Dart discovered a remarkably well-preserved juvenile specimen (face and brain endocast), which he named Australopithecus africanus. (Australopithecus = Southern Ape). Although the brain was small (410 cm³), its shape was rounded, unlike that of chimpanzees and gorillas, and more like a modern human brain. In addition, the specimen exhibited short canine teeth, and the foramen magnum was more anteriorly placed, suggesting a bipedal mode of locomotion.

All of these traits convinced Dart that the Taung child was a bipedal human ancestor, a transitional form between ape and man. Another 20 years passed before Dart's claims were taken seriously, following the discovery of additional australopith fossils in Africa that resembled his specimen. The prevailing view of the time was that a large brain evolved before bipedality. It was thought that intelligence on par with modern humans was a prerequisite to bipedalism.

The factors that drove human evolution are still the subject of controversy. Dart's savanna hypothesis suggested that bipedalism was caused by a move to the savanna for hunting. However recent evidence suggests that bipedalism existed before the savannas.[6] Several anthropologists, such as Bernard Wood, Kevin Hunt and Philip Tobias, have pronounced the savanna theory defunct. The aquatic ape hypothesis, developed in response to the perceived flaws of the savanna hypothesis, suggests that wading, swimming and diving for food exerted a strong evolutionary effect on the ancestors of the genus Homo and is in part responsible for the split between the common ancestors of humans and other great apes. It is not well accepted by most researchers in paleoanthropology.[7]

Today, the australopiths are considered to be the last common ancestors leading to genus Homo, the group to which modern humans belong. Both australopiths and Homo sapiens are part of the tribe Hominini, but recent morphological data have brought into doubt the position of A. africanus as a direct ancestor of modern humans.

The australopiths were originally grouped based on size as either gracile or robust. The robust variety of Australopithecus has since been renamed Paranthropus (P. robustus from South Africa, and P. boisei and P. aethiopicus from East Africa). In the 1930s, when the robust specimens were first described by Robert Broom, the Paranthropus genus was used. During the 1960s, the robust variety was moved into Australopithecus. The recent consensus has been to return to the original classification as a separate genus.

The real hub of palaeoanthropological activity was in eastern Africa at the famous Olduvai Gorge, Tanzania. The Leakey family became a name associated with human origins, particularly the search for the first human.

In 1975, Colin Groves and Vratislav Mazák announced a new species of human they called Homo ergaster.

Ian Tattersall once noted (Nature 2006, 441:155) that paleoanthropology is distinguished as the "branch of science [that] keeps its primary data secret."

Renowned paleoanthropologists


Hominin species distributed through time edit
Homo Australopithecus Ardipithecus Paranthropus Homo sapiens Homo neandertalensis Homo heidelbergensis Homo erectus Paranthropus robustus Paranthropus boisei Paranthropus aethiopicus Homo ergaster Homo habilis Australopithecus sediba Australopithecus garhi Australopithecus africanus Australopithecus bahrelghazali Australopithecus afarensis Australopithecus anamensis Orrorin tugenensis Sahelanthropus Pleistocene Pliocene Miocene


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Homo


From Wikipedia, the free encyclopedia
Homo is the genus of hominids that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old,[1][2] possibly having evolved from australopithecine ancestors, with the appearance of Homo habilis [3] It is the only genus in the subtribe Hominina. Several species, including Australopithecus garhi, Australopithecus sediba, Australopithecus africanus, and Australopithecus afarensis, have been proposed as the direct ancestor of the Homo lineage.[4][5] These species have morphological features that align them with Homo, but there is no consensus on which gave rise to Homo, assuming it was not an as of yet undiscovered species.

The most salient physiological development between the earlier australopith species and Homo is the increase in cranial capacity, from about 450 cm3 (27 cu in) in A. garhi to 600 cm3 (37 cu in) in H. habilis. Within the Homo genus, cranial capacity again doubled from H. habilis through Homo ergaster or H. erectus to Homo heidelbergensis by 0.6 million years ago. The cranial capacity of H. heidelbergensis overlaps with the range found in modern humans.

The advent of Homo was thought to coincide with the first evidence of stone tools (the Oldowan industry), and thus by definition with the beginning of the Lower Palaeolithic; however, recent evidence from Ethiopia now places the earliest evidence of stone tool usage at before 3.39 million years ago.[6] The emergence of Homo coincides roughly with the onset of Quaternary glaciation, the beginning of the current ice age.

Homo sapiens (modern humans) is the only surviving species in the genus, all others having become extinct. Homo neanderthalensis, traditionally considered the last surviving relative, died out about 40,000 years ago,[7] though recent discoveries suggest that another species, Homo floresiensis, may have lived much more recently. The other extant Homininae—the chimpanzees and gorillas—have a limited geographic range. In contrast, the evolution of humans is a history of migrations and admixture. Humans repeatedly left Africa to populate Eurasia and finally the Americas, Oceania, and the rest of the world.

Naming

In the biological sciences, particularly anthropology and palaeontology, the common name for all members of the genus Homo is "human".[8] The word homo is Latin meaning "human", and came to mean "man" in New Latin. The word "human" itself is from Latin humanus, an adjective cognate to homo, both thought to derive from a Proto-Indo-European word for "earth" reconstructed as *dhǵhem-.[9]
The binomial name Homo sapiens was coined by Carl Linnaeus[10] (1758).[11]

Names for other species were introduced beginning in the second half of the 19th century (H. neanderthalensis 1864, H. erectus 1892). A couple of recently discovered, recently extinct, species in the genus Homo do not have accepted binomial names yet, Denisova hominin, and Red Deer Cave people. Classification of the genus Homo into species and subspecies is poorly defined and subject to incomplete information, leading to difficulties in binomial naming, and the use of common names, such as Neanderthal and Denisovan, even in scientific papers.[12]

Species

The species status of Homo rudolfensis, Homo ergaster, H. georgicus, H. antecessor, H. cepranensis, H. rhodesiensis, Homo neanderthalensis, Denisova hominin, Red Deer Cave people and Homo floresiensis remains under debate. H. heidelbergensis and H. neanderthalensis are closely related to each other and have been considered to be subspecies of H. sapiens. Recently, nuclear DNA from a Neanderthal specimen from Vindija Cave has been sequenced using two different methods that yield similar results regarding Neanderthal and H. sapiens lineages, with both analyses suggesting a date for the split between 460,000 and 700,000 years ago, though a population split of around 370,000 years is inferred. The nuclear DNA results indicate about 30% of derived alleles in H. sapiens are also in the Neanderthal lineage. This high frequency may suggest some gene flow between ancestral human and Neanderthal populations due to mating between the two.[13]
 
Comparative table of Homo species
Species Lived when Ma Lived where Adult height Adult mass Cranial capacity (cm³) Fossil record Discovery / publication of name
Denisova hominin 0.04 Russia 1 site 2010
H. antecessor 1.2 – 0.8 Spain 175 cm (5 ft 9 in) 90 kg (200 lb) 1,000 2 sites 1997
H. cepranensis 0.9 – 0.35 Italy 1,000 1 skull cap 1994/2003
H. erectus 1.9 – 0.2 Africa, Eurasia (Java, China, India, Caucasus) 180 cm (5 ft 11 in) 60 kg (130 lb) 850 (early) – 1,100 (late) Many 1891/1892
H. ergaster 1.9 – 1.4 Eastern and Southern Africa 700–850 Many 1975
H. floresiensis 0.10 – 0.012 Indonesia 100 cm (3 ft 3 in) 25 kg (55 lb) 400 7 individuals 2003/2004
H. gautengensis >2 – 0.6 South Africa 100 cm (3 ft 3 in) 1 individual 2010/2010
H. habilis 2.2 – 1.4 Africa 150 cm (4 ft 11 in) 33–55 kg (73–121 lb) 510–660 Many 1960/1964
H. heidelbergensis 0.6 – 0.35 Europe, Africa, China 180 cm (5 ft 11 in) 90 kg (200 lb) 1,100–1,400 Many 1908
H. neanderthalensis 0.35 – 0.04 Europe, Western Asia 170 cm (5 ft 7 in) 55–70 kg (121–154 lb) (heavily built) 1,200–1,900 Many (1829)/1864
H. rhodesiensis 0.3 – 0.12 Zambia 1,300 Very few 1921
H. rudolfensis 1.9 Kenya 700 2 sites 1972/1986
Red Deer Cave people 0.0145–0.0115 China Very few 2012
H. sapiens idaltu 0.16 – 0.15 Ethiopia 1,450 3 craniums 1997/2003
H. sapiens
(modern humans)		 0.2 – present Worldwide 150 - 190 cm (4 ft 7 in - 6 ft 3 in) 50–100 kg (110–220 lb) 950–1,800 Still living —/1758

Migration and admixture

H. habilis, which is considered the first member of the genus Homo, might have given rise to H. ergaster (however this is questionable, as some finds suggest that the species were contemporaneous).[14] Some of H. ergaster migrated to Asia, where they are named Homo erectus, and to Europe with Homo georgicus. H. ergaster in Africa and H. erectus in Eurasia evolved separately for almost two million years and presumably separated into two different species. Homo rhodesiensis, who were descended from H. ergaster, migrated from Africa to Europe and became Homo heidelbergensis and later (about 250,000 years ago) Homo neanderthalensis and the Denisova hominin in Asia. The first Homo sapiens, descendants of H. rhodesiensis, appeared in Africa about 250,000 years ago. About 100,000 years ago, some H. sapiens sapiens migrated from Africa to the Levant and met with resident Neanderthals, with some admixture.[15] Later, about 70,000 years ago, perhaps after the Toba catastrophe, a small group left the Levant to populate Eurasia, Australia and later the Americas. A subgroup among them met the Denisovans[16] and, after further admixture, migrated to populate Melanesia. In this scenario, non-African people living today are mostly of African origin ("Out of Africa model"). However, there was also some admixture with Neanderthals and Denisovans, who had evolved locally (the "multiregional hypothesis"). Recent genomic results from the group of Svante Pääbo also show that 30,000 years ago at least three major subspecies coexisted: Denisovans, Neanderthals and anatomically modern humans.[17] Today, only H. sapiens remains, with no other extant species.

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Australopithecine


From Wikipedia, the free encyclopedia

Australopithecines
Temporal range: Pliocene - Pleistocene 4.2–1.2Ma

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Australopithecus sediba.JPG
Australopithecus sediba
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Tribe: Hominini
Subtribe: †Australopithecina
Gregory & Hellman, 1939
Type species
†Australopithecus africanus
Dart, 1925
Genera
The term australopithecine refers generally to any species in the related genera of Australopithecus and Paranthropus. It may also include members of Kenyanthropus,[2] Ardipithecus,[2] and Praeanthropus.[3] The term comes from a former classification as members of a distinct subfamily, the Australopithecinae.[4] They are now classified by some within the Australopithecina subtribe of the Hominini tribe.[5][6] Members of Australopithecus are sometimes referred to as the "gracile australopithecines", while Paranthropus are called the "robust australopithecines".[7][8]

The australopithecines occurred in the Plio-Pleistocene era, and were bipedal and dentally similar to humans, but with a brain size not much larger than that of modern apes, with lesser encephalization than in the genus Homo.[9] Humans (genus Homo) may have descended from australopithecine ancestors, while the genus Ardipithecus is a possible ancestor of the australopithecines.[8]

Phylogeny

Phylogeny of subtribe Australopithecina according to Briggs & Crowther 2008, p. 124.

Physical characteristics

The post-cranial remains of australopithecines show they were adapted to bipedal locomotion, but did not walk identical to humans. They have a high brachial index (forearm/upper arm ratio) when compared to other hominids, and they exhibit greater sexual dimorphism than members of Homo or Pan but less so than Gorilla or Pongo. It is thought that they averaged heights of 1.2–1.5 metres (3.9–4.9 ft) and weighed between 30 and 55 kilograms (66 and 121 lb). The brain size may have been 350 cc to 600 cc. The postcanines (the teeth behind the canines) were relatively large, and had more enamel compared to contemporary apes and humans, while the incisors and canines were relatively small, and there was little difference between the males' and females' canines compared to modern apes.[8]

Relation to Homo

Most scientists maintain one of the australopithecine species evolved into the Homo genus in Africa around two million years ago. However there is no consensus on which species:
"Determining which species of australopithecine (if any) is ancestral to the genus Homo is a question that is a top priority for many paleoanthropologists, but one that will likely elude any conclusive answers for years to come. Nearly every possible species has been suggested as a likely candidate, but none are overwhelmingly convincing. Presently, it appears that A. garhi has the potential to occupy this coveted place in paleoanthropology, but the lack of fossil evidence is a serious problem. Another problem presents itself in the fact that it has been very difficult to assess which hominid represents the first member of the genus Homo. Without knowing this, it is not possible to determine which species of australopithecine may have been ancestral to Homo."[10]
Marc Verhaegen has argued that an australopithecines species could have also been ancestral to the Pan genus (i.e. chimpanzees).[11]

Asian australopithecines?

A minority held viewpoint among palaeoanthropologists is that australopithecines moved outside of Africa. A notable proponent of this theory is Jens Lorenz Franzen, formerly Head of Paleoanthropology at the Research Institute Senckenberg. Franzen argues that robust australopithecines had reached not only Indonesia, as Meganthropus, but also China:
"In this way we arrive at the conclusion that the recognition of australopithecines in Asia would not confuse but could help to clarify the early evolution of hominids on that continent. This concept would explain the scanty remains from Java and China as relic of an Asian offshoot of an early radiation of Australopithecus, which was followed much later by an [African] immigration of Homo erectus, and finally became extinct after a period of coexistence."[12]
In 1957, an Early Pleistocene Chinese fossil tooth of unknown province was described as resembling P. robustus. Three fossilized molars from Jianshi, China (Longgudong Cave) were later identified as belonging to an Australopithecus species (Gao, 1975). However further examination questioned this interpretation; Zhang (1984) argued the Jianshi teeth and unidentified tooth belong to H. erectus. Liu et al. (2010) also dispute the Jianshi-australopithecine link and argue the Jianshi molars fall within the range of Homo erectus:
"No marked difference in dental crown shape is shown between the Jianshi hominin and other Chinese Homo erectus, and there is also no evidence in support of the Jianshi hominin's closeness to Australopithecus."
Wolpoff (1999) though points out that in China "persistent claims of australopithecine or australopithecine-like remains continue".

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