Hominid Evolution

Human Evolution and the Fossil Record

Scientists continue to debate the history of man. It is generally agreed upon by the scientific community, however, that humans evolved from lesser beings, and this essay will function to provide evidence to support this claim. Several points will be outlined, including the general physical changes that occurred between several key species on the phylogeny of man, and a discussion of dating methods used to pinpoint the age of the fossils. This essay will begin with a brief discussion of dating techniques. In the study of hominid evolution, two main methods of dating are used: carbon-14 and potassium-argon dating. Carbon-14 dating involves the decay of radioactive
C-14, which has a half life of 5770
This species, which lived between three and four million years ago, is believed to be the first real hominid because it is the oldest, and "most primitive of any definite hominid form thus far found."(Turnbaugh, 281) Evidence from fossilized footprints, as well as pelvic and leg bones which were similar to modern hominids, led scientists to believe that they could walk upright. Its teeth resembled more those of primates, due to their large size. Its skull capacity ranged from 350 to 500 cm3. This species, though it had some hominid characteristics, was still more like an ape. Its face portruded outwards near the mouth region, and it did not have a definable chin. Finally, their craniums had large, portruding ridges over either eye. Another important being in the human timeline is Australopithecus africanus. Many scientists believe that it is the next in the sequence leading to man, however, a few believe that it belongs to a lineage on its own. A. africanus fossils have been dated back to the time period between two and three million years ago. It had a greater body size than A. afarensis, and a skull volume ranging between 420 and 500 cm3. It averaged a little higher in
Because they are believed to have evolved apart from Homo hominids, it is not important to cover these species in detail. Homo erectus lived between 300,000 and 1,800,000 years ago, and still had portruding jaws and a "keel" effect on the top of the cranium. It, like its predecessors, had no definable chin, and thick brow ridges. However, skull capacity in these hominids jumped from an average of 650 cm3 in H. habilis to an average of 900 cm3 in early specimens and 1100 cm3 in later specimens. The skeleton "is more robust than those of modern humans, implying greater strength."(Foley, n.pag.) Due to their larger brain sizes, they are believed to have possessed greater intelligence, and evidence of this has been found in their probably use of fire, as shown by traces of burnt bones in cave floors, and the finding of more sophisticated tools than H. habilis. They were shorter, on average, than Homo sapiens, and their craniums showed a Nuchal torus, or a ridge, across the back of the head. This species also had keeled craniums. Archaic Homo sapiens, which first appeared 500,000 years ago,