Paleoanthropology

Human evolution scheme.svg

Paleoanthropology is a sub-discipline of anthropology and paleontology, and is also known as human anthropology. Studying hominid fossil evidence, such as petrified bones and footprints, as well as artifacts such as tools, and even incorporating knowledge of current primate species, paleoanthropologists essentially study the origin of human beings.

Contents

Of great interest to this field is the theory of human evolution, including the pattern and process of evolution, or the search for the "missing link" between the apes and humans. Many paleoanthropologists have made their name through finding fossils purported to be of such an intermediate species, such as Davidson Black, who discovered "Peking Man," Eugene Dubois with "Java Man," Richard Leakey and his "Turkana Boy," and Donald Johanson who discovered the 3.2 million year old Australopithecine fossil " Lucy." Beyond the excitement of finding such examples, these scientists also debate the geographical origins of humankind, with each find supporting or disproving the various theories. Historically, a major source of controversy has been the process by which humans have developed, whether by a force with a random component (natural selection) or by the creative force of a Creator God. Abrahamic religions believe in a single-point origin of modern humans, beginning with an "Adam and Eve."

Etymology

The word paleoanthropology is an academic creation that combines the Ancient Greek paleo, which refers to prehistoric time periods, with "anthropology," itself a combination of Greek words which mean "study of man."[1]

Paleoanthropology is actually a sub-division of two different larger fields of study: Anthropology and paleontology, and is sometimes known as human paleontology. Anthropology is concerned with the study of humankind's cultural and biological evolution through all time. Paleontology is the study of prehistoric life forms on Earth through the examination of fossils. Hence, paleoanthropology studies the prehistoric ancestors of humankind, referred to in a group as hominids. The discipline often overlaps with geology (the study of rocks and rock formations) as well as with botany, biology, zoology, and ecology—fields concerned with life forms and how they interact.

Origins

Reconstruction of a Neanderthal child, made using modern techniques of computer-assisted paleoanthropology from the Gibraltar 2 Neanderthal specimen.

The modern field of paleoanthropology (study of human origins) began in the nineteenth century with the discovery of "Neanderthal man" (the eponymous skeleton was found in 1856, but there had been finds elsewhere since 1830). However, fossils of Neanderthals were widely misinterpreted as skeletons of modern humans with deformation or disease.[2]

Research activities

Paleoanthropologists usually operate in one of two arenas: searching for physical remains and evidence in the field, or analyzing finds in a laboratory. In the field, discovering physical remains and other fossils follows painstaking procedures similar to those archaeologists use when uncovering cultural remains.

Areas where evidence is thought to be buried are systematically noted for geological data before layers of earth are removed slowly. Noting the condition and details of the location of the find is just as crucial as uncovering fossils. Once remains are discovered, they are usually sent to a laboratory or research center where they are carefully studied, using chemical and physical dating methods, X-Rays, MRIs, and other special tools. Paleoanthropologists are most interested in noting how the finds are similar and how they are different from already established ancestral lines.

Africa and Asia are two of the most popular sites for paleoanthropologists in the field, for they have historically yielded the oldest and most promising evidence. However, as recent finds in South America and Europe push the date of humankind's origin further back, paleoanthropologists can be found worldwide seeking to make a discovery of ancient human remains.

Theories and findings

Charles Darwin (1809-1882) in his later years.

The science of paleoanthropology is based upon the scientific theories of Human evolution. These involve both the pattern of evolution (descent with modification, the non-causal relations between ancestral and descendant species) and the process of evolution (various theories involving mechanisms and causes for the pattern observed, including fundamental concepts such as natural selection, punctuated equilibrium, and design, and specific scenarios, such as those involving movement from trees, use of tools, "out of Africa," and so forth).

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 significantly advanced 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 helped make the theory of natural selection 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.

Substantial evidence has been marshaled for the fact that humans have descended from common ancestors by a process of branching (descent with modification) and for a primate origin of humans. However, proposals for the specific ancestral-descendant relationships and for the process leading to humans tend to be speculative. And, while the theory of natural selection typically is central to scientific explanations for the process, evidence for natural selection being the directive or creative force is limited to extrapolation from the microevolutionary level (changes within the level of species).

Since the time of Carolus Linnaeus in the eighteenth century, the great apes were considered the closest relatives of human beings, based on morphological similarity. In the nineteenth century, it was speculated that the closest living relatives to human beings were chimpanzees and gorillas. Based on the natural range of these creatures, it was surmised that humans share a common ancestor with other African apes and that fossils of these ancestors would ultimately be found in Africa.

It was not until the 1920s that hominid fossils were discovered in Africa. In 1924, Raymond Dart described Australopithecus africanus. The specimen was the Taung Child, an australopithecine infant discovered in a cave deposit at Taung, South Africa. The remains were a remarkably well-preserved tiny skull and an endocranial cast of the individual's brain. Although the brain was small (410 cm3), its shape was rounded, unlike that of chimpanzees and gorillas, and more like a modern human brain. Also, the specimen exhibited short canine teeth, and the position of the foramen magnum (the hole in the skull where the spine enters) was evidence of bipedal locomotion. All of these traits convinced Dart that the Taung baby was a bipedal human ancestor, a transitional form between apes and humans.[3] However, the prevailing view of the time was that a large brain evolved before bipedality, it being thought that intelligence on par with modern humans was a prerequisite to bipedalism. Another twenty years would pass before Dart's claims were taken seriously, following the discovery of more fossils that resembled his find.

Hominin species distributed through time

Debates

While there are many aspects of human evolution that paleoanthropologist agree upon, there are several puzzles in regards to the human evolutionary line. One of the most contested issues is from where humans originated. There are two dominant views on the issue of human origins, the Out of Africa position and the multiregional position. There are also various combinations of these ideas.

The Out of Africa (or Out of Africa II, or replacement) model holds that there was a migration of Homo erectus (or Homo ergaster) out of Africa and into Europe and Asia, but that these populations did not subsequently contribute significant amounts of genetic material (or, some say, contributed absolutely nothing) to later populations along the lineage to Homo sapiens.[4] Later, approximately 200,000 years ago, there was a second migration of hominids out of Africa, and this was modern Homo sapiens that replaced the populations that then occupied Europe and Asia.[4] This view maintains a specific speciation event that led to Homo sapiens in Africa, and this is the modern human.

The multiregional (or continuity) camp hold that since the origin of Homo erectus, there have been populations of hominids living in the Old World and that these all contributed to successive generations in their regions.[4] According to this view, hominids in China and Indonesia are the most direct ancestors of modern East Asians, and those in Africa are the most direct ancestors of modern Africans. The European populations either gave rise to modern Europeans or contributed significant genetic material to them, while their origins were in Africa or West Asia.[4] According to this model, there is genetic flow to allow for the maintenance of one species, but not enough to prevent racial differentiation.

Overall, the disagreement between these two camps has caused "fairly severe strife within the paleoanthropologist community."[4] Multiregionalism is often "portrayed as a racist theory," while Out of Africa II "has often been portrayed as a religiously motivated idea" that strives to align with the biblical story of Genesis.[4]

Other issues facing paleoanthropology deal with how current evidence is used to create theories. A major contention is that the fossil record remains fragmentary. No fossils of hominids have been found for the period between 6 and 13 million years ago (mya), the time when branching between the chimpanzee and human lineages is expected to have taken place.[5] Furthermore, as author Ernst Mayr notes "most hominid fossils are extremely incomplete. They may consist of part of a mandible, or the upper part of a skull without face and teeth, or only part of the extremities."[5] Even the famous "Lucy" finding (Australopithecus afarensis) was only a 40 percent complete female skeleton and lacked a head.[6]

Coupled with this is a recurrent problem that interpretation of fossil evidence is heavily influenced by personal beliefs and prejudices. Fossil evidence often allows a variety of interpretations, since the individual specimens may be reconstructed in a variety of ways.[7] As Mayr notes, "subjectivity is inevitable in the reconstruction of the missing parts," and virtually all hominid finds and interpretations are "somewhat controversial!"[5] Another author recounts several examples where the pieces of fossils found offered a variety of reconstructions that were sometimes dramatically different, such as long face versus a short face, a heavy brow, a missing forehead. Different interpretations of two sections of a fossil skull and how to place one of those pieces led Roger Lewin to recount, "How you held it really depended on your preconceptions. It was very interesting what people did with it."[7]

Renowned paleoanthropologists

  • Robert Ardrey (1908-1980), wrote African Genesis (1961), The Territorial Imperative (1966), The Social Contract (1970), and The Hunting Hypothesis (1976) detailing the mid-twentieth century transition in paleoanthropologist studies and methodology.
Zhoukoudian Peking Man Site—the Museum (taken in July 2004). At the center: What Peking Man looked like.
  • Davidson Black (1884-1934) discovered Sinanthropus pekinensis (now Homo erectus pekinensis) or the “Peking Man.” Despite the fact that Africa was later found to be the origin of humankind, proving Black's theory of an Asian origination wrong, Black's work greatly advanced our knowledge of the development of human beings in Asia.[8]
  • Carleton S. Coon (1904-1981), in such works as The Origin of Races (1962), The Story of Man (1954), and "The Races of Europe" (1939), concluded that sometimes different racial types had annihilated other types while in other cases warfare and/or settlement had only led to the partial displacement of racial types.
  • Eugene Dubois (1858-1940) discovered several fossils of seemingly hominid origin, and called his finds Pithecanthropus erectus, or Java Man—"a species in between humans and apes." Later, they were classified as Homo erectus. What Dubois found in 1890s was a set of teeth, a skullcap, and a left femur (thigh bone). The femur suggested that its owner had walked erect. From the teeth and the skull, Dubois argued that the specimen was exactly between humans and apes on the evolutionary timeline.[9]
  • Johann Carl Fuhlrott (1803-1877) is famous for the discovery of the Neanderthal 1, a Neanderthal specimen found during an archaeology dig in August 1856.
Louis Leakey examining skulls from Olduvai Gorge
  • Louis Leakey (1903-1972) was one of the most renowned paleoanthropologists of all time. Among Leakey’s many extraordinary finds was the 1959 unearthing of Zinjanthropus, a robust hominid that hinted at the great complexity of humankind's evolutionary roots. Leakey called it Zinjanthropus boisei, and believed that it belonged in the line of direct human ancestors. Later, however, it was classified as australopithecus. In 1964, he and his wife discovered the skull and hand of what was recognized as a new species—Homo habilis, or “the human who used tools.” Using the carbon-14 dating technique, researchers from the University of California at Berkeley have estimated that the site where they were found, and the bones themselves, were 1.75 million years old.[10]
  • Mary Leakey (1913-1996) is as famous as her husband Louis. Mary discovered a set of footprints discovered at the Laetoli site located 27 miles (45 kilometers) south of Olduvai Gorge. The site is Pliocene, dated by the Potassium-argon method to 3.7 million years ago. The footprints, preserved in powdery ash from an eruption of the 20 kilometers distant Sadiman volcano, demonstrate that these hominids walked upright habitually, as there are no knuckle-impressions. The feet do not have the mobile big toe of apes; instead, they have an arch (the bending of the sole of the foot) typical of modern humans. The discovery caused serious debate among scientists, requiring them to change their theories concerning the evolution of bipedalism.[11]
  • Richard Leakey (1944- ), the son of Mary and Louis Leakey, built upon the legacy of his parents. In 1969, his discovery of a cranium of Australopithecus boisei caused great excitement. A Homo habilis skull (ER 1470) and a Homo erectus skull (ER 3733), discovered in 1972 and 1975, respectively, were among the most significant finds of Leakey's early expeditions. In 1978, an intact cranium of Homo erectus (KNM-ER 3883) was discovered. In 1984, he made his most important discovery—"Turkana Boy"—the nearly complete skeleton of a young Homo erectus who died 1.6 million years ago. It was one of the first well-preserved skeletons of that origin ever found.[11]
  • André Leroi-Gourhan (1911-1986), created theories about human evolution involving the notion that the transition to bipedality freed the hands for grasping, and the face for gesturing and speaking, and thus that the development of the cortex, of technology, and of language all follow from the adoption of an upright stance.
  • Kenneth Oakley (1911-1981) is known for his work in the relative dating of fossils by fluorine content, which was instrumental in the exposure in the 1950s of the Piltdown Man hoax.[12]

Notes

  1. Dictionary.com, Paleoanthropology, Dictionary.com Unabridged (v 1.1). Retrieved May 05, 2008.
  2. S.J. Gould, "Men of the Thirty-third Division," Natural History (1990): 12-24.
  3. Frances Wheelhouse, Dart: Scientist and Man of Grit (Hornsby, Australia: Transpareon Press, 2001, ISBN 0908021216).
  4. 4.0 4.1 4.2 4.3 4.4 4.5 C.D. Kreger, Homo sapiens: Introduction, Archaeology.info (2005). Retrieved June 2, 2008.
  5. 5.0 5.1 5.2 Ernst Mayr, What Evolution Is (New York: Basic Books, 2001, ISBN 0465044255).
  6. S.J. Gould, "Lucy on the Earth in stasis," Natural History, (1994): 12-20.
  7. 7.0 7.1 Jonathan Wells, Icons of Evolution. (Washington, DC: Regnery Publishing, 2000, ISBN 0895262762)
  8. Encyclopædia Britannica, Davidson Black (2008). Retrieved June 2, 2008.
  9. Pat Shipman, The Man who Found the Missing Link: The Extraordinary Life of Eugene Dubois (Diane Publishing Co, 2001, ISBN 075679160X).
  10. Sonia Cole, Leakey's Luck: The Life of Louis Seymour Bazett Leakey, 1903-1972 (Harcourt, 1975, ISBN 0151494568).
  11. 11.0 11.1 Mary Bowman-Kruhm, The Leakeys: A Biography (Westport, CT: Greenwood Press, 2005, ISBN 0313329850).
  12. Encyclopædia Britannica, Kenneth Oakley (2008). Retrieved June 2, 2008.

References

  • Bowman-Kruhm, Mary. The Leakeys: A Biography. Westport, CT: Greenwood Press, 2005. ISBN 0313329850.
  • Cole, Sonia. Leakey's Luck: The Life of Louis Seymour Bazett Leakey, 1903-1972. Harcourt, 1975. ISBN 0151494568.
  • Mayr, Ernst. What Evolution Is. New York: Basic Books, 2001. ISBN 0465044255.
  • McKie, Robin. Dawn of Man: The Story of Human Evolution. DK Publishing, 2000. ISBN 978-0789462626.
  • Shipman, Pat. The Man who Found the Missing Link: The Extraordinary Life of Eugene Dubois. Diane Publishing Co, 2001. ISBN 075679160X.
  • Wells, Jonathan. Icons of Evolution. Washington, DC: Regnery Publishing, 2000. ISBN 0895262762.
  • Wheelhouse, Frances. Dart: Scientist and Man of Grit. Hornsby, Australia: Transpareon Press, 2001. ISBN 0908021216.

External links

All links retrieved March 17, 2015.

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