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Sunday, November 10, 2024

Seven heavens

From Wikipedia, the free encyclopedia
Wood carving 1475; pointing to 7 celestial bodies consisted 5 planets that can be seen with naked eye, the Sun and the Moon, each floating in a heaven layer, (Arabic Felaq in ancient cosmology)

In mythological or religious cosmology, the seven heavens refer to seven levels or divisions of the Heavens. The concept, also found in the ancient Mesopotamian religions, can be found in Judaism and Islam; the Christian Bible does not mention seven levels of heaven. Some of these traditions, including Jainism, also have a concept of seven earths or seven underworlds both with the metaphysical realms of deities and with observed celestial bodies such as the classical planets and fixed stars.

Beliefs in the plurality of the heavens were not restricted to the belief in seven heavens. Ancient near eastern cosmology largely accepted the existence of three heavens. In Jewish cosmologies (albeit absent from the Hebrew Bible), the number of heavens could range from 3 to 365, with 7 being the most popular figure.

Origins

The notion or belief in a cosmos structured or tiered into seven heavens likely originates or derives from the seven visible heavenly bodies (Mercury, Venus, Mars, Jupiter, Saturn, the Moon, and the Sun).

Greek astronomy and cosmology

Each of the seven heavens corresponds to one of the seven classical planets known in antiquity. Ancient observers noticed that these heavenly objects (the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn) moved at different paces in the sky both from each other and from the fixed stars beyond them. Unlike comets, which appeared in the sky with no warning, they moved in regular patterns that could be predicted. They also observed that objects in the sky influenced objects on Earth as when movements of the sun affect the behavior of plants or movements of the Moon affect ocean tides.

Mesopotamian cosmology

The concept of seven heavens as developed in ancient Mesopotamia where it took on a symbolic or magical meaning as opposed to a literal one. The concept of a seven-tiered was likely In the Sumerian language, the words for heavens (or sky) and Earth are An and Ki. The ancient Mesopotamians regarded the sky as a series of domes (usually three, but sometimes seven) covering the flat Earth. Each dome was made of a different kind of precious stone. The lowest dome of the heavens was made of jasper and was the home of the stars. The middle dome of heaven was made of saggilmut stone and was the abode of the Igigi. The highest and outermost dome of the heavens was made of luludānītu stone and was personified as An, the god of the sky. The celestial bodies were equated with specific deities as well. The planet Venus was believed to be Inanna, the goddess of love, sex, and war. The Sun was her brother Utu, the god of justice and the Moon was their father Nanna. Ordinary mortals could not go to the heavens because it was the abode of the gods alone. Instead, after a person died, his or her soul went to Kur (later known as Irkalla), a dark shadowy underworld, located deep below the surface of the Earth. Sumerian incantations of the late second millennium BCE make references to seven heavens and seven earths. One such incantation is: "an-imin-bi ki-imin-bi" (the heavens are seven, the earths are seven.)

The understanding that the heavens can influence things on Earth lent heavenly, magical properties to the number seven itself, as in stories of seven demons, seven churches, seven spirits, or seven thrones. The number seven appears frequently in Babylonian magical rituals. The seven Jewish and the seven Islamic heavens may have had their origin in Babylonian astronomy.

In general, the heavens is not a place for humans in Mesopotamian religion. As Gilgamesh says to his friend Enkidu, in the Epic of Gilgamesh: "Who can go up to the heavens, my friend? Only the gods dwell with Shamash forever". Along with the idea of seven heavens, the idea of three heavens was also common in ancient Mesopotamia.

Abrahamic religions

Judaism

In the Talmud, it is suggested that the upper part of the universe is made up of seven heavens (Hebrew: shamayim):

  1. Vilon (וילון), see (Isa 40:22)
  2. Raki'a (רקיע), see (Gen 1:17)
  3. Shehaqim (שחקים), see (Ps 78:23, Midr. Teh. to Ps. xix. 7)
  4. Zebul (זבול), see (Isa 63:15, 1 Kings 8:13)
  5. Ma'on (מעון), see (Deut 26:15, Ps 42:9)
  6. Machon (מכון), see (1 Kings 8:39, Deut 28:12)
  7. Araboth (ערבות), The seventh Heaven where ophanim, the seraphim, and the hayyoth and the Throne of God are located.

The Jewish Merkavah and Hekhalot literature was devoted to discussing the details of these heavens, sometimes in connection with traditions relating to Enoch, such as the Third Book of Enoch.

Apocryphal texts

The Second Book of Enoch, also written in the first century CE, describes the mystical ascent of the patriarch Enoch through a hierarchy of Ten Heavens. Enoch passes through the Garden of Eden in the Third Heaven on his way to meet the Lord face-to-face in the Tenth (chapter 22). Along the way, he encounters vividly described populations of angels who torment wrongdoers; he sees homes, olive oil, and flowers.

The book's depiction of ten heavens represented an expansion of the ancient seven-heaven model. This expanded cosmology was developed further in medieval Christianity.

Christianity

La materia della Divina commedia di Dante Alighieri, Plate VI: "The Ordering of Paradise" by Michelangelo Caetani (1804–1882)

The New Testament does not refer to the concept of seven heavens. However, an explicit reference to a third heaven appears in the Second Epistle to the Corinthians, penned in Macedonia around 55 CE. It describes the following mystical experience:

I know a person in Christ who fourteen years ago was caught up to the third heaven—whether in the body or out of the body I do not know; God knows. And I know that such a person—whether in the body or out of the body I do not know; God knows—was caught up into Paradise and heard things that are not to be told, that no mortal is permitted to repeat.

— (2 Corinthians 12.2–4 NRSV)

The description is usually taken as an oblique reference by the author to himself. The passage appears to reflect first-century beliefs among Jews and Christians that the realm of Paradise existed in a different heaven than the highest one—an impression that may find support in the original Greek wording (closer to "caught away" than "caught up").

In the second century, Irenaeus also knows seven heavens (see his Demonstration of Apostolic Preaching 9; cf. Against Heresies 1.5.2).

Over the course of the Middle Ages, Christian thinkers expanded the ancient Mesopotamian seven-heaven model into a system of ten heavens. This cosmology, taught in the first European universities by the Scholastics, reached its supreme literary expression in The Divine Comedy by Dante Alighieri. The idea of seven heavens is carried over into the esoteric Christian cabala.

Islam

A Persian miniature depicting Seven Heavens from The History of Mohammed, Bibliothèque nationale de France, Paris.

The Quran and Hadith frequently mention the existence of seven samāwāt (سماوات), the plural of samāʾ (سماء), meaning 'heaven, sky, celestial sphere', and cognate with Hebrew shamāyim (שמים). Some of the verses in the Quran mentioning the samaawat are Q41:12, Q65:12 and Q71:15. The seven heavens are not final destinations for the dead after the Day of Judgment, but regions distinct from the earth, guarded by angels and inhabited by souls whose abode depends on their good deeds (fasting, jihad, Hajj, charity), with the highest layer, the closest to God. According to Quran and Hadiths, each of the skies has its own Qibla or a structure which became direction of prayer, similar to Kaaba of the mortal world, where the Qibla of highest heaven is called Bayt al-Ma'mur, while the Qibla building for the lowest sky is called Bayt al-Izza.

In other sources, the concept is presented in metaphorical terms. Each of the seven heavens is depicted as being composed of a different material, and Islamic prophets are resident in each. The names are taken from Suyuti's Al-Hay’a as-samya fi l-hay’a as-sunmya:

  1. Raqi'a (رقيعاء): The first heaven is described as being made of water and is the home of Adam and Eve, as well as the angels of each star. According to some narratives, Muhammad encountered the angel Habib here.
  2. Araqlun (أرفلون): The second heaven is described as being made of white pearls and is the home of Yahya (John the Baptist) and Isa (Jesus).
  3. Qaydum (قيدوم): The third heaven is described as being made of iron (alternatively pearls or other dazzling stones); Joseph and the Angel of Death (named Azrael) are resident there.
  4. Maʿuna (ماعونا): The fourth heaven is described as being made of brass (alternatively white gold); Idris (conventionally identified with Enoch) and the "Angel of Tears" reside there.
  5. Di'a (ريقا): The fifth heaven is described as being made of silver; Aaron holds court over this heaven. Sometimes, the guardian of hellfire is assigned to this place.
  6. Daqua (دقناء): The sixth heaven is described as being composed of gold (alternatively garnets and rubies); Moses can be found here.
  7. ʿAriba (عريبا): The seventh heaven, which borrows some concepts from its Jewish counterpart, is depicted as being composed of divine light incomprehensible to the mortal man (alternatively emerald). Abraham is a resident there and Sidrat al-Muntaha, a large enigmatic Lote tree, marks the end of the seventh heaven and the utmost extremity for all of God's creatures and heavenly knowledge.

There are two interpretations of using the number "seven". One viewpoint is that the number "seven" here simply means "many" and is not to be taken literally (the number is often used to imply that in the Arabic language). But many other commentators use the number literally.

One modern interpretation of "heavens" is that all the stars and galaxies (including the Milky Way) are all part of the "first heaven", and "beyond that six still bigger worlds are there," which have yet to be discovered by scientists.

Gnosticism

The Gnostic text On the Origin of the World states that seven heavens were created in Chaos by Yaldabaoth below the higher realms, and each of them are ruled over by an Archon. During the end times, these heavens will collapse on each and the heaven of Yaldabaoth will split in two, causing its stars to fall upon the Earth, therefore causing it to sink into the Abyss.

In the Coptic Apocalypse of Paul, the apostle Paul ascends through the lower Seven Heavens. At the seventh heaven, he meets an old man who opens the gate to the realm beyond the material universe, and Paul then ascends to the eighth, ninth, and tenth heavens.

In Mandaeism, a series of maṭartas, or "toll houses," are located between the World of Light (alma ḏ-nhūra) from Tibil (Earth). The term maṭarta has variously been translated as "watch-station", "toll-station", "way-station", or "purgatory". Maṭartas are guarded by various uthras (celestial beings from the World of Light) and demons. In the Ginza Rabba, seven maṭartas are listed and described in Chapter 3 in Book 5 of the Right Ginza. However, the number of maṭartas is not always seven; Book 6 of the Right Ginza (also known as the "Book of Dinanukht") lists six, and Chapter 4 in Book 1 of the Left Ginza lists eight. Alternatively, the Seven Heavens can also be seen as corresponding to the Seven Planets, who form part of the entourage of Ruha in the World of Darkness.

Hinduism

According to all Puranas, the Brahmanda is divided into fourteen worlds known as lokas. Seven are upper worlds: Bhuloka (the Earth and sky), Bhuvarloka, Svargaloka, Maharloka, Janarloka, Tapaloka and Satyaloka; and seven are lower worlds: Atala, Vitala, Sutala, Talatala, Mahatala, Rasatala and Patala.

Celestial spheres

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Celestial_spheres
Geocentric celestial spheres; Peter Apian's Cosmographia (Antwerp, 1539)

The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others. In these celestial models, the apparent motions of the fixed stars and planets are accounted for by treating them as embedded in rotating spheres made of an aetherial, transparent fifth element (quintessence), like gems set in orbs. Since it was believed that the fixed stars did not change their positions relative to one another, it was argued that they must be on the surface of a single starry sphere.

In modern thought, the orbits of the planets are viewed as the paths of those planets through mostly empty space. Ancient and medieval thinkers, however, considered the celestial orbs to be thick spheres of rarefied matter nested one within the other, each one in complete contact with the sphere above it and the sphere below. When scholars applied Ptolemy's epicycles, they presumed that each planetary sphere was exactly thick enough to accommodate them. By combining this nested sphere model with astronomical observations, scholars calculated what became generally accepted values at the time for the distances to the Sun: about 4 million miles (6.4 million kilometres), to the other planets, and to the edge of the universe: about 73 million miles (117 million kilometres). The nested sphere model's distances to the Sun and planets differ significantly from modern measurements of the distances, and the size of the universe is now known to be inconceivably large and continuously expanding.

Albert Van Helden has suggested that from about 1250 until the 17th century, virtually all educated Europeans were familiar with the Ptolemaic model of "nesting spheres and the cosmic dimensions derived from it". Even following the adoption of Copernicus's heliocentric model of the universe, new versions of the celestial sphere model were introduced, with the planetary spheres following this sequence from the central Sun: Mercury, Venus, Earth-Moon, Mars, Jupiter and Saturn.

Mainstream belief in the theory of celestial spheres did not survive the Scientific Revolution. In the early 1600s, Kepler continued to discuss celestial spheres, although he did not consider that the planets were carried by the spheres but held that they moved in elliptical paths described by Kepler's laws of planetary motion. In the late 1600s, Greek and medieval theories concerning the motion of terrestrial and celestial objects were replaced by Newton's law of universal gravitation and Newtonian mechanics, which explain how Kepler's laws arise from the gravitational attraction between bodies.

History

Early ideas of spheres and circles

In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC. In his cosmology both the Sun and Moon are circular open vents in tubular rings of fire enclosed in tubes of condensed air; these rings constitute the rims of rotating chariot-like wheels pivoting on the Earth at their centre. The fixed stars are also open vents in such wheel rims, but there are so many such wheels for the stars that their contiguous rims all together form a continuous spherical shell encompassing the Earth. All these wheel rims had originally been formed out of an original sphere of fire wholly encompassing the Earth, which had disintegrated into many individual rings. Hence, in Anaximanders's cosmogony, in the beginning was the sphere, out of which celestial rings were formed, from some of which the stellar sphere was in turn composed. As viewed from the Earth, the ring of the Sun was highest, that of the Moon was lower, and the sphere of the stars was lowest.

Following Anaximander, his pupil Anaximenes (c. 585 – c. 528/4) held that the stars, Sun, Moon, and planets are all made of fire. But whilst the stars are fastened on a revolving crystal sphere like nails or studs, the Sun, Moon, and planets, and also the Earth, all just ride on air like leaves because of their breadth. And whilst the fixed stars are carried around in a complete circle by the stellar sphere, the Sun, Moon and planets do not revolve under the Earth between setting and rising again like the stars do, but rather on setting they go laterally around the Earth like a cap turning halfway around the head until they rise again. And unlike Anaximander, he relegated the fixed stars to the region most distant from the Earth. The most enduring feature of Anaximenes' cosmos was its conception of the stars being fixed on a crystal sphere as in a rigid frame, which became a fundamental principle of cosmology down to Copernicus and Kepler.

After Anaximenes, Pythagoras, Xenophanes and Parmenides all held that the universe was spherical. And much later in the fourth century BC Plato's Timaeus proposed that the body of the cosmos was made in the most perfect and uniform shape, that of a sphere containing the fixed stars. But it posited that the planets were spherical bodies set in rotating bands or rings rather than wheel rims as in Anaximander's cosmology.

Emergence of the planetary spheres

Instead of bands, Plato's student Eudoxus developed a planetary model using concentric spheres for all the planets, with three spheres each for his models of the Moon and the Sun and four each for the models of the other five planets, thus making 26 spheres in all. Callippus modified this system, using five spheres for his models of the Sun, Moon, Mercury, Venus, and Mars and retaining four spheres for the models of Jupiter and Saturn, thus making 33 spheres in all. Each planet is attached to the innermost of its own particular set of spheres. Although the models of Eudoxus and Callippus qualitatively describe the major features of the motion of the planets, they fail to account exactly for these motions and therefore cannot provide quantitative predictions. Although historians of Greek science have traditionally considered these models to be merely geometrical representations, recent studies have proposed that they were also intended to be physically real or have withheld judgment, noting the limited evidence to resolve the question.

In his Metaphysics, Aristotle developed a physical cosmology of spheres, based on the mathematical models of Eudoxus. In Aristotle's fully developed celestial model, the spherical Earth is at the centre of the universe and the planets are moved by either 47 or 55 interconnected spheres that form a unified planetary system, whereas in the models of Eudoxus and Callippus each planet's individual set of spheres were not connected to those of the next planet. Aristotle says the exact number of spheres, and hence the number of movers, is to be determined by astronomical investigation, but he added additional spheres to those proposed by Eudoxus and Callippus, to counteract the motion of the outer spheres. Aristotle considers that these spheres are made of an unchanging fifth element, the aether. Each of these concentric spheres is moved by its own god—an unchanging divine unmoved mover, and who moves its sphere simply by virtue of being loved by it.

Ptolemaic model of the spheres for Venus, Mars, Jupiter, and Saturn with epicycle, eccentric deferent and equant point. Georg von Peuerbach, Theoricae novae planetarum, 1474.

In his Almagest, the astronomer Ptolemy (fl. c. 150 AD) developed geometrical predictive models of the motions of the stars and planets and extended them to a unified physical model of the cosmos in his Planetary hypotheses. By using eccentrics and epicycles, his geometrical model achieved greater mathematical detail and predictive accuracy than had been exhibited by earlier concentric spherical models of the cosmos. In Ptolemy's physical model, each planet is contained in two or more spheres, but in Book 2 of his Planetary Hypotheses Ptolemy depicted thick circular slices rather than spheres as in its Book 1. One sphere/slice is the deferent, with a centre offset somewhat from the Earth; the other sphere/slice is an epicycle embedded in the deferent, with the planet embedded in the epicyclical sphere/slice. Ptolemy's model of nesting spheres provided the general dimensions of the cosmos, the greatest distance of Saturn being 19,865 times the radius of the Earth and the distance of the fixed stars being at least 20,000 Earth radii.

The planetary spheres were arranged outwards from the spherical, stationary Earth at the centre of the universe in this order: the spheres of the Moon, Mercury, Venus, Sun, Mars, Jupiter, and Saturn. In more detailed models the seven planetary spheres contained other secondary spheres within them. The planetary spheres were followed by the stellar sphere containing the fixed stars; other scholars added a ninth sphere to account for the precession of the equinoxes, a tenth to account for the supposed trepidation of the equinoxes, and even an eleventh to account for the changing obliquity of the ecliptic. In antiquity the order of the lower planets was not universally agreed. Plato and his followers ordered them Moon, Sun, Mercury, Venus, and then followed the standard model for the upper spheres. Others disagreed about the relative place of the spheres of Mercury and Venus: Ptolemy placed both of them beneath the Sun with Venus above Mercury, but noted others placed them both above the Sun; some medieval thinkers, such as al-Bitruji, placed the sphere of Venus above the Sun and that of Mercury below it.

Middle Ages

The Earth within seven celestial spheres, from Bede, De natura rerum, late 11th century

Astronomical discussions

A series of astronomers, beginning with the Muslim astronomer al-Farghānī, used the Ptolemaic model of nesting spheres to compute distances to the stars and planetary spheres. Al-Farghānī's distance to the stars was 20,110 Earth radii which, on the assumption that the radius of the Earth was 3,250 miles (5,230 kilometres), came to 65,357,500 miles (105,182,700 kilometres). An introduction to Ptolemy's Almagest, the Tashil al-Majisti, believed to be written by Thābit ibn Qurra, presented minor variations of Ptolemy's distances to the celestial spheres. In his Zij, Al-Battānī presented independent calculations of the distances to the planets on the model of nesting spheres, which he thought was due to scholars writing after Ptolemy. His calculations yielded a distance of 19,000 Earth radii to the stars.

Around the turn of the millennium, the Arabic astronomer and polymath Ibn al-Haytham (Alhacen) presented a development of Ptolemy's geocentric models in terms of nested spheres. Despite the similarity of this concept to that of Ptolemy's Planetary Hypotheses, al-Haytham's presentation differs in sufficient detail that it has been argued that it reflects an independent development of the concept. In chapters 15–16 of his Book of Optics, Ibn al-Haytham also said that the celestial spheres do not consist of solid matter.

Near the end of the twelfth century, the Spanish Muslim astronomer al-Bitrūjī (Alpetragius) sought to explain the complex motions of the planets without Ptolemy's epicycles and eccentrics, using an Aristotelian framework of purely concentric spheres that moved with differing speeds from east to west. This model was much less accurate as a predictive astronomical model, but it was discussed by later European astronomers and philosophers.

In the thirteenth century the astronomer al-'Urḍi proposed a radical change to Ptolemy's system of nesting spheres. In his Kitāb al-Hayáh, he recalculated the distance of the planets using parameters which he redetermined. Taking the distance of the Sun as 1,266 Earth radii, he was forced to place the sphere of Venus above the sphere of the Sun; as a further refinement, he added the planet's diameters to the thickness of their spheres. As a consequence, his version of the nesting spheres model had the sphere of the stars at a distance of 140,177 Earth radii.

About the same time, scholars in European universities began to address the implications of the rediscovered philosophy of Aristotle and astronomy of Ptolemy. Both astronomical scholars and popular writers considered the implications of the nested sphere model for the dimensions of the universe. Campanus of Novara's introductory astronomical text, the Theorica planetarum, used the model of nesting spheres to compute the distances of the various planets from the Earth, which he gave as 22,612 Earth radii or 73,387,747+100660 miles (118,106,130.55 km). In his Opus Majus, Roger Bacon cited Al-Farghānī's distance to the stars of 20,110 Earth radii, or 65,357,700 miles (105,183,000 km), from which he computed the circumference of the universe to be 410,818,517+37 miles (661,148,316.1 km). Clear evidence that this model was thought to represent physical reality is the accounts found in Bacon's Opus Majus of the time needed to walk to the Moon and in the popular Middle English South English Legendary, that it would take 8,000 years to reach the highest starry heaven. General understanding of the dimensions of the universe derived from the nested sphere model reached wider audiences through the presentations in Hebrew by Moses Maimonides, in French by Gossuin of Metz, and in Italian by Dante Alighieri.

Philosophical and theological discussions

Philosophers were less concerned with such mathematical calculations than with the nature of the celestial spheres, their relation to revealed accounts of created nature, and the causes of their motion.

Adi Setia describes the debate among Islamic scholars in the twelfth century, based on the commentary of Fakhr al-Din al-Razi about whether the celestial spheres are real, concrete physical bodies or "merely the abstract circles in the heavens traced out… by the various stars and planets." Setia points out that most of the learned, and the astronomers, said they were solid spheres "on which the stars turn… and this view is closer to the apparent sense of the Qur'anic verses regarding the celestial orbits." However, al-Razi mentions that some, such as the Islamic scholar Dahhak, considered them to be abstract. Al-Razi himself, was undecided, he said: "In truth, there is no way to ascertain the characteristics of the heavens except by authority [of divine revelation or prophetic traditions]." Setia concludes: "Thus it seems that for al-Razi (and for others before and after him), astronomical models, whatever their utility or lack thereof for ordering the heavens, are not founded on sound rational proofs, and so no intellectual commitment can be made to them insofar as description and explanation of celestial realities are concerned."

Christian and Muslim philosophers modified Ptolemy's system to include an unmoved outermost region, the empyrean heaven, which came to be identified as the dwelling place of God and all the elect. Medieval Christians identified the sphere of stars with the Biblical firmament and sometimes posited an invisible layer of water above the firmament, to accord with Genesis. An outer sphere, inhabited by angels, appeared in some accounts.

Edward Grant, a historian of science, has provided evidence that medieval scholastic philosophers generally considered the celestial spheres to be solid in the sense of three-dimensional or continuous, but most did not consider them solid in the sense of hard. The consensus was that the celestial spheres were made of some kind of continuous fluid.

Later in the century, the mutakallim Adud al-Din al-Iji (1281–1355) rejected the principle of uniform and circular motion, following the Ash'ari doctrine of atomism, which maintained that all physical effects were caused directly by God's will rather than by natural causes. He maintained that the celestial spheres were "imaginary things" and "more tenuous than a spider's web". His views were challenged by al-Jurjani (1339–1413), who maintained that even if the celestial spheres "do not have an external reality, yet they are things that are correctly imagined and correspond to what [exists] in actuality".

Medieval astronomers and philosophers developed diverse theories about the causes of the celestial spheres' motions. They attempted to explain the spheres' motions in terms of the materials of which they were thought to be made, external movers such as celestial intelligences, and internal movers such as motive souls or impressed forces. Most of these models were qualitative, although a few incorporated quantitative analyses that related speed, motive force and resistance. By the end of the Middle Ages, the common opinion in Europe was that celestial bodies were moved by external intelligences, identified with the angels of revelation. The outermost moving sphere, which moved with the daily motion affecting all subordinate spheres, was moved by an unmoved mover, the Prime Mover, who was identified with God. Each of the lower spheres was moved by a subordinate spiritual mover (a replacement for Aristotle's multiple divine movers), called an intelligence.

Renaissance

Thomas Digges' 1576 Copernican heliocentric model of the celestial orbs

Early in the sixteenth century Nicolaus Copernicus drastically reformed the model of astronomy by displacing the Earth from its central place in favour of the Sun, yet he called his great work De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres). Although Copernicus does not treat the physical nature of the spheres in detail, his few allusions make it clear that, like many of his predecessors, he accepted non-solid celestial spheres. Copernicus rejected the ninth and tenth spheres, placed the orb of the Moon around the Earth, and moved the Sun from its orb to the center of the universe. The planetary orbs circled the center of the universe in the following order: Mercury, Venus, the great orb containing the Earth and the orb of the Moon, then the orbs of Mars, Jupiter, and Saturn. Finally he retained the eighth sphere of the stars, which he held to be stationary.

The English almanac maker, Thomas Digges, delineated the spheres of the new cosmological system in his Perfit Description of the Caelestiall Orbes … (1576). Here he arranged the "orbes" in the new Copernican order, expanding one sphere to carry "the globe of mortalitye", the Earth, the four classical elements, and the Moon, and expanding the sphere of stars infinitely to encompass all the stars and also to serve as "the court of the Great God, the habitacle of the elect, and of the coelestiall angelles."

Johannes Kepler's diagram of the celestial spheres, and of the spaces between them, following the opinion of Copernicus (Mysterium Cosmographicum, 2nd ed., 1621)

In the sixteenth century, a number of philosophers, theologians, and astronomers—among them Francesco Patrizi, Andrea Cisalpino, Peter Ramus, Robert Bellarmine, Giordano Bruno, Jerónimo Muñoz, Michael Neander, Jean Pena, and Christoph Rothmann—abandoned the concept of celestial spheres. Rothmann argued from observations of the comet of 1585 that the lack of observed parallax indicated that the comet was beyond Saturn, while the absence of observed refraction indicated the celestial region was of the same material as air, hence there were no planetary spheres.

Tycho Brahe's investigations of a series of comets from 1577 to 1585, aided by Rothmann's discussion of the comet of 1585 and Michael Maestlin's tabulated distances of the comet of 1577, which passed through the planetary orbs, led Tycho to conclude that "the structure of the heavens was very fluid and simple." Tycho opposed his view to that of "very many modern philosophers" who divided the heavens into "various orbs made of hard and impervious matter." Edward Grant found relatively few believers in hard celestial spheres before Copernicus and concluded that the idea first became common sometime between the publication of Copernicus's De revolutionibus in 1542 and Tycho Brahe's publication of his cometary research in 1588.

In his early Mysterium Cosmographicum, Johannes Kepler considered the distances of the planets and the consequent gaps required between the planetary spheres implied by the Copernican system, which had been noted by his former teacher, Michael Maestlin. Kepler's Platonic cosmology filled the large gaps with the five Platonic polyhedra, which accounted for the spheres' measured astronomical distance. In Kepler's mature celestial physics, the spheres were regarded as the purely geometric spatial regions containing each planetary orbit rather than as the rotating physical orbs of the earlier Aristotelian celestial physics. The eccentricity of each planet's orbit thereby defined the radii of the inner and outer limits of its celestial sphere and thus its thickness. In Kepler's celestial mechanics, the cause of planetary motion became the rotating Sun, itself rotated by its own motive soul. However, an immobile stellar sphere was a lasting remnant of physical celestial spheres in Kepler's cosmology.

Literary and visual expressions

"Because the medieval universe is finite, it has a shape, the perfect spherical shape, containing within itself an ordered variety....
"The spheres ... present us with an object in which the mind can rest, overwhelming in its greatness but satisfying in its harmony."

C. S. Lewis, The Discarded Image, p. 99.

Dante and Beatrice gaze upon the highest Heaven; from Gustave Doré's illustrations to the Divine Comedy, Paradiso Canto 28, lines 16–39.

In Cicero's Dream of Scipio, the elder Scipio Africanus describes an ascent through the celestial spheres, compared to which the Earth and the Roman Empire dwindle into insignificance. A commentary on the Dream of Scipio by the Roman writer Macrobius, which included a discussion of the various schools of thought on the order of the spheres, did much to spread the idea of the celestial spheres through the Early Middle Ages.

Nicole Oresme, Le livre du Ciel et du Monde, Paris, BnF, Manuscrits, Fr. 565, f. 69 (1377)

Some late medieval figures noted that the celestial spheres' physical order was inverse to their order on the spiritual plane, where God was at the center and the Earth at the periphery. Near the beginning of the fourteenth century Dante, in the Paradiso of his Divine Comedy, described God as a light at the center of the cosmos. Here the poet ascends beyond physical existence to the Empyrean Heaven, where he comes face to face with God himself and is granted understanding of both divine and human nature. Later in the century, the illuminator of Nicole Oresme's Le livre du Ciel et du Monde, a translation of and commentary on Aristotle's De caelo produced for Oresme's patron, King Charles V, employed the same motif. He drew the spheres in the conventional order, with the Moon closest to the Earth and the stars highest, but the spheres were concave upwards, centered on God, rather than concave downwards, centered on the Earth. Below this figure Oresme quotes the Psalms that "The heavens declare the Glory of God and the firmament showeth his handiwork."

The late-16th-century Portuguese epic The Lusiads vividly portrays the celestial spheres as a "great machine of the universe" constructed by God. The explorer Vasco da Gama is shown the celestial spheres in the form of a mechanical model. Contrary to Cicero's representation, da Gama's tour of the spheres begins with the Empyrean, then descends inward toward Earth, culminating in a survey of the domains and divisions of earthly kingdoms, thus magnifying the importance of human deeds in the divine plan.

Domestication of the horse

A Heck Horse, bred to resemble the now-extinct Tarpan

How and when horses became domesticated has been disputed. Although horses appeared in Paleolithic cave art as early as 30,000 BC, these were wild horses and were probably hunted for meat. The clearest evidence of early use of the horse as a means of transport is from chariot burials dated c. 2000 BC. However, an increasing amount of evidence began to support the hypothesis that horses were domesticated in the Eurasian Steppes in approximately 3500 BC. Discoveries in the context of the Botai culture had suggested that Botai settlements in the Akmola Province of Kazakhstan are the location of the earliest domestication of the horse. Warmouth et al. (2012) pointed to horses having been domesticated around 3000 BC in what is now Ukraine and Western Kazakhstan.

Genetic evidence indicates that domestication of the modern horse's ancestors likely occurred in an area known as the Volga–Don, in the Pontic–Caspian steppe region of eastern Europe, around 2200 BC. From there, use of horses spread across Eurasia for transportation, agricultural work, and warfare. Scientists have linked the successful spread of domesticated horses to observed genetic changes. They speculate that stronger backs (GSDMC gene) and increased docility (ZFPM1 gene) may have made horses more suitable for riding.

Background

Terracotta urn in the shape of a horse (Iran, 1000 BCE) at the Lyndon B. Johnson Presidential Library

The date of the domestication of the horse depends to some degree upon the definition of "domestication". Some zoologists define "domestication" as human control over breeding, which can be detected in ancient skeletal samples by changes in the size and variability of ancient horse populations. Other researchers look at the broader evidence, including skeletal and dental evidence of working activity; weapons, art, and spiritual artifacts; and lifestyle patterns of human cultures. There is evidence that horses were kept as a source of meat and milk before they were trained as working animals.

Attempts to date domestication by genetic study or analysis of physical remains rest on the assumption that there was a separation of the genotypes of domesticated and wild populations. Such a separation appears to have taken place, but dates based on such methods can only produce an estimate of the latest possible date for domestication without excluding the possibility of an unknown period of earlier gene flow between wild and domestic populations (which will occur naturally as long as the domesticated population is kept within the habitat of the wild population).

Whether one adopts the narrower zoological definition of domestication or the broader cultural definition that rests on an array of zoological and archaeological evidence affects the time frame chosen for the domestication of the horse. The date of 4000 BCE is based on evidence that includes the appearance of dental pathologies associated with bitting, changes in butchering practices, changes in human economies and settlement patterns, the depiction of horses as symbols of power in artifacts, and the appearance of horse bones in human graves. On the other hand, measurable changes in size and increases in variability associated with domestication occurred later, about 2500–2000 BCE, as seen in horse remains found at the site of Csepel-Haros in Hungary, a settlement of the Bell Beaker culture.

Use of horses spread across Eurasia for transportation, agricultural work and warfare. Horses and mules in agriculture used a breastplate type harness or a yoke more suitable for oxen, which was not as efficient at utilizing the full strength of the animals as the later-invented padded horse collar that arose several millennia later.

Predecessors to the domestic horse

A horse painting from a cave in Lascaux

A 2005 study analyzed the mitochondrial DNA (mtDNA) of a worldwide range of equids, from 53,000-year-old fossils to contemporary horses. Their analysis placed all equids into a single clade, or group with a single common ancestor, consisting of three genetically divergent species: the South American Hippidion, the North American New World stilt-legged horse, and Equus, the true horse. The true horse included prehistoric horses and the Przewalski's horse, as well as what is now the modern domestic horse, belonged to a single Holarctic species.

The true horse migrated from the Americas to Eurasia via Beringia, becoming broadly distributed from North America to central Europe, north and south of Pleistocene ice sheets. It became extinct in Beringia around 14,200 years ago, and in the rest of the Americas around 10,000 years ago. This clade survived in Eurasia, however, and it is from these horses which all domestic horses appear to have descended. These horses showed little phylogeographic structure, probably reflecting their high degree of mobility and adaptability.

Therefore, the domestic horse today is classified as Equus ferus caballus. No genetic originals of native wild horses currently exist. The Przewalski diverged from the modern horse before domestication. It has 66 chromosomes, as opposed to 64 among modern domesticated horses, and their Mitochondrial DNA (mtDNA) forms a distinct cluster. Genetic evidence suggests that modern Przewalski's horses are descended from a distinct regional gene pool in the eastern part of the Eurasian steppes, not from the same genetic group that gave rise to modern domesticated horses. Nevertheless, evidence such as the cave paintings of Lascaux suggests that the ancient wild horses that some researchers now label the "Tarpan subtype" probably resembled Przewalski horses in their general appearance: big heads, dun coloration, thick necks, stiff upright manes, and relatively short, stout legs.

Equus caballus germanicus front leg, teeth and upper jaw at the Museum für Naturkunde, Berlin

The horses of the Ice Age were hunted for meat in Europe and across the Eurasian steppes and in North America by early modern humans. Numerous kill sites exist and many cave paintings in Europe indicate what they looked like. Many of these Ice Age subspecies died out during the rapid climate changes associated with the end of the last Ice Age or were hunted out by humans, particularly in North America, where the horse became completely extinct.

Classification based on body types and conformation, before the availability of DNA for research, once suggested that there were roughly four basic wild prototypes, thought to have developed with adaptations to their environment before domestication. There were competing theories: some argued that the four prototypes were separate species or subspecies, while others suggested that the prototypes were physically different manifestations of the same species. However, more recent study indicates that there was only one wild species and all different body types were entirely a result of selective breeding or landrace adaptation after domestication. Either way, the most common theories of prototypes include four base prototypes:

  • The "Tarpan subtype"
  • The "Warmblood subspecies" or "Forest Horse" (once proposed as Equus ferus silvaticus, also known as the Diluvial Horse), which evolved into a later variety sometimes called Equus ferus germanicus. This prototype may have contributed to the development of the warmblood horses of northern Europe, as well as older "heavy horses" such as the Ardennais.
  • The "Draft" subspecies, a small, sturdy, heavyset animal with a heavy hair coat, arising in northern Europe, adapted to cold, damp climates, somewhat resembling today's draft horse and even the Shetland pony.
  • The "Oriental" subspecies (once proposed as Equus agilis), a taller, slim, refined and agile animal arising in Western Asia, adapted to hot, dry climates. It is thought to be the progenitor of the modern Arabian horse and Akhal-Teke.

Two "wild" groups, that were believed to be never-domesticated, survived into historic times: Przewalski's horse (Equus ferus przewalski), and the Tarpan (Equus ferus ferus). The Tarpan became extinct in the late 19th century and Przewalski's horse is endangered; it became extinct in the wild during the late 1960s, but was re-introduced in the early 1990s to two preserves in Mongolia. Although researchers such as Marija Gimbutas theorized that the horses of the Chalcolithic (Copper Age) were Przewalski's, more recent genetic studies indicate that Przewalski's horse is not an ancestor to modern domesticated horses.

Genetic evidence

The early stages of domestication were marked by a rapid increase in coat color variation.

A 2014 study compared DNA from ancient horse bones that predated domestication and compared them to DNA of modern horses, discovering 125 genes that correlated to domestication. Some were physical, affecting muscle and limb development, cardiac strength and balance. Others were linked to cognitive function and most likely were critical to the taming of the horse, including social behavior, learning capabilities, fear response, and agreeableness. The DNA used in this study came from horse bones 16,000 to 43,000 years ago, and therefore the precise changes that occurred at the time of domestication have yet to be sequenced.

The domestication of stallions and mares can be analyzed separately by looking at those portions of the DNA that are passed on exclusively along the maternal (mitochondrial DNA or mtDNA) or paternal line (Y-chromosome or Y-DNA). DNA studies indicate that there may have been multiple domestication events for mares, as the number of female lines required to account for the genetic diversity of the modern horse suggests a minimum of 77 different ancestral mares, divided into 17 distinct lineages. Studies of modern horses showed very little Y chromosome diversity, which was originally interpreted as evidence of a single domestication event for a limited number of stallions combined with repeated restocking of wild females into the domesticated herds. However, more recent studies of ancient DNA show that Y chromosome diversity was significantly higher a thousand years ago. The low present diversity may be partially explained by the popularity of Arabian and Turkoman studs, especially the three foundation stallions of the Thoroughbred breed.

A study published in 2012 that performed genomic sampling on 300 work horses from local areas as well as a review of previous studies of archaeology, mitochondrial DNA, and Y-DNA suggested that horses were originally domesticated in the western part of the Eurasian steppe. Both domesticated stallions and mares spread out from this area, and then additional wild mares were added from local herds; wild mares were easier to handle than wild stallions. Most other parts of the world were ruled out as sites for horse domestication, either due to climate unsuitable for an indigenous wild horse population or no evidence of domestication.

Genes located on the Y-chromosome are inherited only from sire to its male offspring and these lines show a very reduced degree of genetic variation (aka genetic homogeneity) in modern domestic horses, far less than expected based on the overall genetic variation in the remaining genetic material. This indicates that a relatively few stallions were domesticated and that it is unlikely that many male offspring originating from unions between wild stallions and domestic mares were included in early domesticated breeding stock.

Genes located in the mitochondrial DNA are passed on along the maternal line from the mother to her offspring. Multiple analyses of the mitochondrial DNA obtained from modern horses as well as from horse bones and teeth from archaeological and palaeological finds consistently shows an increased genetic diversity in the mitochondrial DNA compared to the remaining DNA, showing that a large number of mares has been included into the breeding stock of the originally domesticated horse.

Variation in the mitochondrial DNA is used to determine so-called haplogroups. A haplogroup is a group of closely related haplotypes that share the same common ancestor. In horses, eighteen main haplogroups are recognized (A-R). Several haplogroups are unequally distributed around the world, indicating the addition of local wild mares to the domesticated stock.

The dispersal of the DOM2 genetic lineage, believed to be the ancestor of all modern domesticated horses, is linked with the populations which preceded the Sintashta culture and their expansions.

In 2018, genomic comparison of 42 ancient-horse genomes, 20 of which were from Botai, with 46 published ancient and modern-horse genomes yielded surprising results. It was found that modern domestic horses are not closely related to the horses at Botai. Rather, Przewalski’s horses were identified as feral descendants of horses herded at Botai. Evidence suggested that "a massive genomic turnover" had occurred along with the domestication of horses and large-scale human population expansion in the Early Bronze Age. Subsequent research showed that horse lineages from Iberia and Siberia, also associated with early domestication, had little influence on the genetics of modern domestic horses.

More than 150 scientists collaborated in gathering 264 ancient horse genomes from across Eurasia, dating from 50,000 to 200 B.C.E. In October 2021, results of the analysis were published in Nature. They indicated that domestication of the modern horse's ancestors likely occurred in the Volga-Don region of the Pontic–Caspian steppe grasslands of Western Eurasia. Both Tarpan and Przewalski’s horse were related to different ancestral populations than those underlying the modern domestic horses (DOM2).

In addition, researchers were able to map population changes over time as modern domestic horses expanded rapidly across Eurasia and displaced other local populations, from about 2000 BCE onwards. The genetic profile for DOM2 horses is associated with horses buried in Sintashta kurgans with early spoke-wheeled chariots, and with horses in Central Anatolia where two-wheeled vehicles were depicted. DOM2 horses also occur in some areas prior to the earliest evidence for chariots, suggesting that both horseback riding and chariot use were factors in expansion.

Genetic data may also provide clues as to why this particular domestication event had far more widespread impact than other domestication events in Botai, Iberia, SIberia and Anatolia. The genetic lineage that leads to modern domestic horses shows evidence of strong selection for locomotor and behavioural adaptations. Changes relate to the GSDMC gene and the ZFPM1 gene. The GSDMC gene is linked to back problems in people, and scientists speculate that changes may have made horses' backs stronger. The ZFPM1 gene is related to mood regulation, and scientists speculate that this may have made horses more docile and easier to tame and manage. Strength and docility would have made horses more suitable for riding and other uses.

Archaeological evidence

Chariots of Ramesses II and the Hittites in the Battle of Kadesh, 1274 BCE

Archaeological evidence for the domestication of the horse comes from three kinds of sources: 1) changes in the skeletons and teeth of ancient horses; 2) changes in the geographic distribution of ancient horses, particularly the introduction of horses into regions where no wild horses had existed; and 3) archaeological sites containing artifacts, images, or evidence of changes in human behavior connected with horses.

Examples include horse remains interred in human graves; changes in the ages and sexes of the horses killed by humans; the appearance of horse corrals; equipment such as bits or other types of horse tack; horses interred with equipment intended for use by horses, such as chariots; and depictions of horses used for riding, driving, draught work, or symbols of human power.

Few of these categories, taken alone, provide irrefutable evidence of domestication, but the cumulative evidence becomes increasingly more persuasive.

Drawing of a horse, a mammoth, a rhinoceros in the Shulgan-Tash Cave, 25-10 thousand years B.C.

Horses interred with chariots

The least ancient, but most persuasive, evidence of domestication comes from sites where horse leg bones and skulls, probably originally attached to hides, were interred with the remains of chariots in at least 16 graves of the Sintashta and Petrovka cultures. These were located in the steppes southeast of the Ural Mountains, between the upper Ural and upper Tobol Rivers, a region today divided between southern Russia and northern Kazakhstan. Petrovka was a little later than and probably grew out of Sintashta, and the two complexes together spanned about 2100–1700 BCE. A few of these graves contained the remains of as many as eight sacrificed horses placed in, above, and beside the grave.

In all of the dated chariot graves, the heads and hooves of a pair of horses were placed in a grave that once contained a chariot. Evidence of chariots in these graves was inferred from the impressions of two spoked wheels set in grave floors 1.2–1.6m apart; in most cases the rest of the vehicle left no trace. In addition, a pair of disk-shaped antler "cheekpieces," an ancient predecessor to a modern bit shank or bit ring, were placed in pairs beside each horse head-and-hoof sacrifice. The inner faces of the disks had protruding prongs or studs that would have pressed against the horse's lips when the reins were pulled on the opposite side. Studded cheekpieces were a new and fairly severe kind of control device that appeared simultaneously with chariots.

All of the dated chariot graves contained wheel impressions, horse bones, weapons (arrow and javelin points, axes, daggers, or stone mace-heads), human skeletal remains, and cheekpieces. Because they were buried in teams of two with chariots and studded cheekpieces, the evidence is extremely persuasive that these steppe horses of 2100–1700 BCE were domesticated. Shortly after the period of these burials, the expansion of the domestic horse throughout Europe was little short of explosive. In the space of possibly 500 years, there is evidence of horse-drawn chariots in Greece, Egypt, and Mesopotamia. By another 500 years, the horse-drawn chariot had spread to China.

Skeletal indicators of domestication

Some researchers do not consider an animal to be "domesticated" until it exhibits physical changes consistent with selective breeding, or at least having been born and raised entirely in captivity. Until that point, they classify captive animals as merely "tamed". Those who hold to this theory of domestication point to a change in skeletal measurements detected among horse bones recovered from middens dated about 2500 BCE in eastern Hungary in Bell-Beaker sites, and in later Bronze Age sites in the Russian steppes, Spain, and Eastern Europe. Horse bones from these contexts exhibited an increase in variability, thought to reflect the survival under human care of both larger and smaller individuals than appeared in the wild; and a decrease in average size, thought to reflect penning and restriction in diet. Horse populations that showed this combination of skeletal changes probably were domesticated. Most evidence suggests that horses were increasingly controlled by humans after about 2500 BCE. However, more recently there have been skeletal remains found at a site in Kazakhstan which display the smaller, more slender limbs characteristic of corralled animals, dated to 3500 BCE.

Botai culture

Some of the most intriguing evidence of early domestication comes from the Botai culture, found in northern Kazakhstan. The Botai culture was a culture of foragers who seem to have adopted horseback riding in order to hunt the abundant wild horses of northern Kazakhstan between 3500 and 3000 BCE. Botai sites had no cattle or sheep bones; the only domesticated animals, in addition to horses, were dogs. Botai settlements in this period contained between 50 and 150 pit houses. Garbage deposits contained tens to hundreds of thousands of discarded animal bones, 65% to 99% of which had come from horses. Also, there has been evidence found of horse milking at these sites, with horse milk fats soaked into pottery shards dating to 3500 BCE. Earlier hunter-gatherers who lived in the same region had not hunted wild horses with such success, and lived for millennia in smaller, more shifting settlements, often containing less than 200 wild animal bones.

Entire herds of horses were slaughtered by the Botai hunters, apparently in hunting drives. The adoption of horseback riding might explain the emergence of specialized horse-hunting techniques and larger, more permanent settlements. Domesticated horses could have been adopted from neighboring herding societies in the steppes west of the Ural Mountains, where the Khvalynsk culture had herds of cattle and sheep, and perhaps had domesticated horses, as early as 4800 BCE.

Other researchers have argued that all of the Botai horses were wild, and that the horse-hunters of Botai hunted wild horses on foot. As evidence, they note that zoologists have found no skeletal changes in the Botai horses that indicate domestication. Moreover, because they were hunted for food, the majority of the horse remains found in Botai-culture settlements indeed probably were wild. On the other hand, any domesticated riding horses were probably the same size as their wild cousins and cannot now be distinguished by bone measurements. They also note that the age structure of the horses slaughtered at Botai represents a natural demographic profile for hunted animals, not the pattern expected if they were domesticated and selected for slaughter. However, these arguments were published before a Copper Age corral was discovered at Krasnyi Yar in 2006 and mats of horse-dung at two other Botai sites. Current findings continue to support the Botai as having domesticated horses.

A study in 2018 revealed that the Botai horses did not contribute significantly to the genetics of modern domesticated horses, and that therefore a subsequent and separate domestication event must have been responsible for the modern domestic horse. Genetic evidence also connects Botai horses with Przewalski's horse in Mongolia, which has led to debates over whether Przewalski's horses should be considered a never-domesticated population or feral descendants of domesticated Botai horses.

Bit wear

A Luristan bronze horse bit

The presence of bit wear is an indicator that a horse was ridden or driven, and the earliest of such evidence from a site in Kazakhstan dates to 3500 BCE. The absence of bit wear on horse teeth is not conclusive evidence against domestication because horses can be ridden and controlled without bits by using a noseband or a hackamore, but such materials do not produce significant physiological changes nor are they apt to be preserved for millennia.

The regular use of a bit to control a horse can create wear facets or bevels on the anterior corners of the lower second premolars. The corners of the horse's mouth normally keep the bit on the "bars" of the mouth, an interdental space where there are no teeth, forward of the premolars. The bit must be manipulated by a human or the horse must move it with its tongue for it to touch the teeth. Wear can be caused by the bit abrading the front corners of the premolars if the horse grasps and releases the bit between its teeth; other wear can be created by the bit striking the vertical front edge of the lower premolars, due to very strong pressure from a human handler.

Modern experiments showed that even organic bits of rope or leather can create significant wear facets, and also showed that facets 3mm (.118 in) deep or more do not appear on the premolars of wild horses. However, other researchers disputed both conclusions.

Wear facets of 3 mm or more were found on seven horse premolars in two sites of the Botai culture, Botai and Kozhai 1, dated about 3500–3000 BCE. The Botai culture premolars are the earliest reported multiple examples of this dental pathology in any archaeological site, and preceded any skeletal change indicators by 1,000 years. While wear facets more than 3 mm deep were discovered on the lower second premolars of a single stallion from Dereivka in Ukraine, an Eneolithic settlement dated about 4000 BCE, dental material from one of the worn teeth later produced a radiocarbon date of 700–200 BCE, indicating that this stallion was actually deposited in a pit dug into the older Eneolithic site during the Iron Age.

Dung and corrals

Soil scientists working with Sandra Olsen of the Carnegie Museum of Natural History at the Chalcolithic settlements of Botai and Krasnyi Yar in northern Kazakhstan found layers of horse dung, discarded in unused house pits in both settlements. The collection and disposal of horse dung suggests that horses were confined in corrals or stables. An actual corral, dated to 3500–3000 BCE was identified at Krasnyi Yar by a pattern of post holes for a circular fence, with the soils inside the fence yielding ten times more phosphorus than the soils outside. The phosphorus could represent the remains of manure.

Geographic expansion

The appearance of horse remains in human settlements in regions where they had not previously been present is another indicator of domestication. Although images of horses appear as early as the Upper Paleolithic period in places such as the caves of Lascaux, France, suggesting that wild horses lived in regions outside of the Eurasian steppes before domestication and may have even been hunted by early humans, concentration of remains suggests animals being deliberately captured and contained, an indicator of domestication, at least for food, if not necessarily use as a working animal.

Around 3500–3000 BCE, horse bones began to appear more frequently in archaeological sites beyond their center of distribution in the Eurasian steppes and were seen in central Europe, the middle and lower Danube valley, and the North Caucasus and Transcaucasia. Evidence of horses in these areas had been rare before, and as numbers increased, larger animals also began to appear in horse remains. This expansion in range was contemporary with the Botai culture, where there are indications that horses were corralled and ridden. This does not necessarily mean that horses were first domesticated in the steppes, but the horse-hunters of the steppes certainly pursued wild horses more than in any other region.

European wild horses were hunted for up to 10% of the animal bones in a handful of Mesolithic and Neolithic settlements scattered across Spain, France, and the marshlands of northern Germany, but in many other parts of Europe, including Greece, the Balkans, the British Isles, and much of central Europe, horse bones do not occur or occur very rarely in Mesolithic, Neolithic or Chalcolithic sites. In contrast, wild horse bones regularly exceeded 40% of the identified animal bones in Mesolithic and Neolithic camps in the Eurasian steppes, west of the Ural Mountains.

Horse bones were rare or absent in Neolithic and Chalcolithic kitchen garbage in western Turkey, Mesopotamia, most of Iran, South and Central Asia, and much of Europe. While horse bones have been identified in Neolithic sites in central Turkey, all equids together totaled less than 3% of the animal bones. Within this three percent, horses were less than 10%, with 90% or more of the equids represented by onagers (Equus hemionus) or another ass-like equid that later became extinct, the hydruntine or European wild ass (Equus hydruntinus). Onagers were the most common native wild equids of the Near East. They were hunted in Syria, Anatolia, Mesopotamia, Iran, and Central Asia; and domesticated asses (Equus asinus) were imported into Mesopotamia, probably from Egypt, but wild horses apparently did not live there.

Other evidence of geographic expansion

Relief depicting Assyrian king Ashurbanipal in a chariot, inspecting booty and prisoners from Babylon

In Northern Caucasus, the Maikop culture settlements and burials of c. 3300 BC contain both horse bones and images of horses. A frieze of nineteen horses painted in black and red colors is found in one of the Maikop graves. The widespread appearance of horse bones and images in Maikop sites suggest to some observers that horseback riding began in the Maikop period.

Later, images of horses, identified by their short ears, flowing manes, and tails that bushed out at the dock, began to appear in artistic media in Mesopotamia during the Akkadian period, 2300–2100 BCE. The word for "horse", literally translated as ass of the mountains, first appeared in Sumerian documents during the Third dynasty of Ur, about 2100–2000 BCE. The kings of the Third Dynasty of Ur apparently fed horses to lions for royal entertainment, perhaps indicating that horses were still regarded as more exotic than useful, but King Shulgi, about 2050 BCE, compared himself to "a horse of the highway that swishes its tail", and one image from his reign showed a man apparently riding a horse at full gallop. Horses were imported into Mesopotamia and the lowland Near East in larger numbers after 2000 BCE in connection with the beginning of chariot warfare, replacing the long-established kunga (a hybrid between the now-extinct Syrian wild ass and a domestic donkey) as the main equid for warfare.

Surroundings of the Shirenzigou archaeological site in Barkol County.

A further expansion, into the lowland Near East and northwestern China, also happened around 2000 BCE. Although Equus bones of uncertain species are found in some Late Neolithic sites in China dated before 2000 BCE, Equus caballus or Equus ferus bones first appeared in multiple sites and in significant numbers in sites of the Qijia and Siba cultures, 2000–1600 BCE, in Gansu and the northwestern provinces of China. Skeletal evidence from sites in Shirenzigou and Xigou in eastern Xinjiang indicate that by the fourth century BCE both horseback riding and mounted archery were practiced along China’s northwest frontier.

In 2008, archaeologists announced the discovery of rock art in Somalia's northern Dhambalin region, which the researchers suggest is one of the earliest known depictions of a hunter on horseback. The rock art is in the Ethiopian-Arabian style, dated to 1000 to 3000 BCE.

Horse images as symbols of power

About 4200-4000 BCE, more than 500 years before the geographic expansion evidenced by the presence of horse bones, new kinds of graves, named after a grave at Suvorovo, appeared north of the Danube delta in the coastal steppes of Ukraine near Izmail. Suvorovo graves were similar to and probably derived from earlier funeral traditions in the steppes around the Dnieper River. Some Suvorovo graves contained polished stone mace-heads shaped like horse heads and horse tooth beads. Earlier steppe graves also had contained polished stone mace-heads, some of them carved in the shape of animal heads.[64] Settlements in the steppes contemporary with Suvorovo, such as Sredni Stog II and Dereivka on the Dnieper River, contained 12–52% horse bones.

When Suvorovo graves appeared in the Danube delta grasslands, horse-head maces also appeared in some of the indigenous farming towns of the Trypillia and Gumelnitsa cultures in present-day Romania and Moldova, near the Suvorovo graves. These agricultural cultures had not previously used polished-stone maces, and horse bones were rare or absent in their settlement sites. Probably their horse-head maces came from the Suvorovo immigrants. The Suvorovo people in turn acquired many copper ornaments from the Trypillia and Gumelnitsa towns. After this episode of contact and trade, but still during the period 4200–4000 BCE, about 600 agricultural towns in the Balkans and the lower Danube valley, some of which had been occupied for 2000 years, were abandoned. Copper mining ceased in the Balkan copper mines, and the cultural traditions associated with the agricultural towns were terminated in the Balkans and the lower Danube valley. This collapse of "Old Europe" has been attributed to the immigration of mounted Indo-European warriors. The collapse could have been caused by intensified warfare, for which there is some evidence; and warfare could have been worsened by mounted raiding; and the horse-head maces have been interpreted as indicating the introduction of domesticated horses and riding just before the collapse.

However, mounted raiding is just one possible explanation for this complex event. Environmental deterioration, ecological degradation from millennia of farming, and the exhaustion of easily mined oxide copper ores also are cited as causal factors.

Artifacts

Perforated antler objects discovered at Derievka (mistakenly, Dereivka) and other sites contemporary with Suvorovo have been identified as cheekpieces or psalia for horse bits. This identification is no longer widely accepted, as the objects in question have not been found associated with horse bones, and could have had a variety of other functions. However, through studies of microscopic wear, it has been established that many of the bone tools at Botai were used to smooth rawhide thongs, and rawhide thongs might have been used to manufacture of rawhide cords and ropes, useful for horse tack. Similar bone thong-smoothers are known from many other steppe settlements, but it cannot be known how the thongs were used. The oldest artifacts clearly identified as horse tack—bits, bridles, cheekpieces, or any other kind of horse gear—are the antler disk-shaped cheekpieces associated with the invention of the chariot, at the Sintashta-Petrovka sites.

Horses interred in human graves

The oldest possible archaeological indicator of a changed relationship between horses and humans is the appearance about 4800–4400 BCE of horse bones and carved images of horses in Chalcolithic graves of the early Khvalynsk culture and the Samara culture in the middle Volga region of Russia. At the Khvalynsk cemetery near the town of Khvalynsk, 158 graves of this period were excavated. Of these, 26 graves contained parts of sacrificed domestic animals, and additional sacrifices occurred in ritual deposits on the original ground surface above the graves. Ten graves contained parts of lower horse legs; two of these also contained the bones of domesticated cattle and sheep. At least 52 domesticated sheep or goats, 23 domesticated cattle, and 11 horses were sacrificed at Khvalynsk. The inclusion of horses with cattle and sheep and the exclusion of obviously wild animals together suggest that horses were categorized symbolically with domesticated animals.

At S'yezzhe, a contemporary cemetery of the Samara culture, parts of two horses were placed above a group of human graves. The pair of horses here was represented by the head and hooves, probably originally attached to hides. The same ritual—using the hide with the head and lower leg bones as a symbol for the whole animal—was used for many domesticated cattle and sheep sacrifices at Khvalynsk. Horse images carved from bone were placed in the above-ground ochre deposit at S’yezzhe and occurred at several other sites of the same period in the middle and lower Volga region. Together these archaeological clues suggest that horses had a symbolic importance in the Khvalynsk and Samara cultures that they had lacked earlier, and that they were associated with humans, domesticated cattle, and domesticated sheep. Thus, the earliest phase in the domestication of the horse might have begun during the period 4800-4400 BCE.

Methods of domestication

Equidae died out in the Western Hemisphere at the end of the last glacial period. A question raised is why and how horses avoided this fate on the Eurasian continent. It has been theorized that domestication saved the species. While the environmental conditions for equine survival were somewhat more favorable in Eurasia than in the Americas, the same stressors that led to extinction for the mammoth had an effect upon horse populations. Thus, some time after 8000 BCE, the approximate date of extinction in the Americas, humans in Eurasia may have begun to keep horses as a livestock food source, and by keeping them in captivity, may have helped to preserve the species. Horses also fit the six core criteria for livestock domestication, and thus, it could be argued, "chose" to live in close proximity to humans.

One model of horse domestication starts with individual foals being kept as pets while the adult horses were slaughtered for meat. Foals are relatively small and easy to handle. Horses behave as herd animals and need companionship to thrive. Both historic and modern data shows that foals can and will bond to humans and other domestic animals to meet their social needs. Thus domestication may have started with young horses being repeatedly made into pets over time, preceding the great discovery that these pets could be ridden or otherwise put to work.

However, there is disagreement over the definition of the term domestication. One interpretation of domestication is that it must include physiological changes associated with being selectively bred in captivity, and not merely "tamed." It has been noted that traditional peoples worldwide (both hunter-gatherers and horticulturists) routinely tame individuals from wild species, typically by hand-rearing infants whose parents have been killed, and these animals are not necessarily "domesticated." 

On the other hand, some researchers look to examples from historical times to hypothesize how domestication occurred. For example, while Native American cultures captured and rode horses from the 16th century onwards, most tribes did not exert significant control over their breeding, thus their horses developed a genotype and phenotype adapted to the uses and climatological conditions in which they were kept, making them more of a landrace than a planned breed as defined by modern standards, but nonetheless "domesticated".

Driving versus riding

A difficult question is if domesticated horses were first ridden or driven. While the most unequivocal evidence shows horses first being used to pull chariots in warfare, there is strong, though indirect, evidence for riding occurring first, particularly by the Botai. Bit wear may correlate to riding, though, as the modern hackamore demonstrates, horses can be ridden without a bit by using rope and other evanescent materials to make equipment that fastens around the nose. So the absence of unequivocal evidence of early riding in the record does not settle the question.

Thus, on one hand, logic suggests that horses would have been ridden long before they were driven. But it is also far more difficult to gather evidence of this, as the materials required for riding—simple hackamores or blankets—would not survive as artifacts, and other than tooth wear from a bit, the skeletal changes in an animal that was ridden would not necessarily be particularly noticeable. Direct evidence of horses being driven is much stronger.

Horses in historic warfare

While riding may have been practiced during the 4th and 3rd millennia BCE, and the disappearance of "Old European" settlements may be related to attacks by horseback-mounted warriors, the clearest influence by horses on ancient warfare was by pulling chariots, introduced around 2000 BCE.

Horses in the Bronze Age were relatively small by modern standards, which led some theorists to believe the ancient horses were too small to be ridden and so must have been used for driving. Herodotus' description of the Sigynnae, a steppe people who bred horses too small to ride but extremely efficient at drawing chariots, illustrates this stage. However, as horses remained generally smaller than modern equines well into the Middle Ages, this theory is highly questionable.

The Iron Age in Mesopotamia saw the rise of mounted cavalry as a tool of war, as evidenced by the notable successes of mounted archer tactics used by various invading eurasian nomads such as the Parthians. Over time, the chariot gradually became obsolete.

The horse of the Iron Age was still relatively small, perhaps 12.2 to 14.2 hands (50 to 58 inches, 127 to 147 cm) high (measured at the withers.) This was shorter overall than the average height of modern riding horses, which range from about 14.2 to 17.2 hands (58 to 70 inches, 147 to 178 cm). However, small horses were used successfully as light cavalry for many centuries. For example, Fell ponies, believed to be descended from Roman cavalry horses, are comfortably able to carry fully grown adults (although with rather limited ground clearance) at an average height of 13.2 hands (54 inches, 137 cm) Likewise, the Arabian horse is noted for a short back and dense bone, and the successes of the Muslims against the heavy mounted knights of Europe demonstrated that a horse standing 14.2 hands (58 inches, 147 cm) can easily carry a full-grown human adult into battle.

Mounted warriors such as the Scythians, Huns and Vandals of late Roman antiquity, the Turks and Mongols who invaded eastern Europe in the 7th century through 14th centuries CE, the Arab warriors of the 7th through 14th centuries CE, and the Native Americans in the 16th through 19th centuries each demonstrated effective forms of light cavalry.

Representation of a Lie group

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