By the way, the following is really just a fun little precursor read to the exciting post "Human Evolution - Part 2", so really take your time and let the anticipation build. And once again, no need to thank me. I do it because I love to. Really.
- Human evolution is the part of biological evolution concerning the emergence of humans as a distinct species. It is the subject of a broad scientific inquiry that seeks to understand and describe how this change and development occurred. The study of human evolution encompasses many scientific disciplines, most notably physical anthropology, linguistics and genetics. The term "human", in the context of human evolution, refers to the genus Homo, but studies of human evolution usually include other hominins, such as the australopithecines.
The idea that humans are similar to certain great apes had been discussed and argued for some time, but the idea of the biological evolution of species in general was not legitimized until after Charles Darwin published On the Origin of Species in 1859. Though Darwin's first book on evolution did not address the specific question of human evolution - "light will be thrown on the origin of man and his history," was all Darwin wrote on the subject - the implications of evolutionary theory were clear to contemporary readers.[1]
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, The Descent of Man, it was already a well-known interpretation of his theory—and the interpretation which made the theory highly controversial. Even many of Darwin's original supporters (such as Alfred Russel Wallace and Charles Lyell) balked at the idea that human beings could have evolved their impressive mental capacities and moral sensibilities through natural selection.
Since the time of Carolus Linnaeus, the great apes were considered the closest relatives of human beings, based on morphological similarity. In the 19th century, it was speculated that their closest living relatives were chimpanzees and gorillas, and based on the natural range of these creatures, it was surmised 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.[2] The type specimen was the Taung Child, an australopithecine infant discovered in a cave deposit being mined for concrete 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 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.
Another 20 years would pass before Dart's claims were taken seriously, following the discovery of more fossils that resembled his find. The prevailing view of the time was that a large brain evolved before bipedality. It was thought that intelligence on par with modern humans was a prerequisite to bipedalism.
The australopithecines are now thought to be immediate ancestors of the genus Homo, the group to which modern humans belong.[3] Both australopithecines and Homo sapiens are part of the tribe Hominini, but recent data has brought into doubt the position of A. africanus as a direct ancestor of modern humans; it may well have been a dead-end cousin.[4] The australopithecines were originally classified as either gracile or robust. The robust variety of Australopithecus has since been reclassified as Paranthropus, although it is still regarded as a subgenus of Australopithecus by some authors.[5]
In the 1930s, when the robust specimens were first described, the Paranthropus genus was used. During the 1960s, the robust variety was moved into Australopithecus. The recent trend has been back to the original classification as a separate genus.
No comments:
Post a Comment