Dating term descriptions
This species was named in July 2001 from fossils discovered in western Kenya (Senut et al. The fossils include fragmentary arm and thigh bones, lower jaws, and teeth and were discovered in deposits that are about 6 million years old.
The limb bones are about 1.5 times larger than those of Lucy, and suggest that it was about the size of a female chimpanzee.
Most scientists consider this evidence that afarensis was still partially adapted to climbing in trees, others consider it evolutionary baggage. Brain size may also have been slightly larger, ranging between 420 and 500 cc.
This species was named in 2001 from a partial skull found in Kenya with an unusual mixture of features (Leakey et al. This is a little larger than chimp brains (despite a similar body size), but still not advanced in the areas necessary for speech.
This species was named in August 1995 (Leakey et al. The material consists of 9 fossils, mostly found in 1994, from Kanapoi in Kenya, and 12 fossils, mostly teeth found in 1988, from Allia Bay in Kenya (Leakey et al. Anamensis existed between 4.2 and 3.9 million years ago, and has a mixture of primitive features in the skull, and advanced features in the body.
The teeth and jaws are very similar to those of older fossil apes.
It lived in a woodland environment with patches of forest, indicating that bipedalism did not originate in a savannah environment.
A number of fragmentary fossils discovered between 19, and dating from 5.2 to 5.8 million years old, were originally assigned to a new subspecies, Ardipithecus ramidus kadabba (Haile-Selassie 2001), and later to a new species, Ardipithecus kadabba (Haile-Selassie et al. One of these fossils is a toe bone belonging to a bipedal creature, but is a few hundred thousand years younger than the rest of the fossils and so its identification with kadabba is not as firm as the other fossils.
For a good discussion of the hominid/hominin terminology issue, read this article by Lee Berger.
Although the hominid fossil record is far from complete, and the evidence is often fragmentary, there is enough to give a good outline of the evolutionary history of humans.
The time of the split between humans and living apes used to be thought to have occurred 15 to 20 million years ago, or even up to 30 or 40 million years ago.
Each species has a type specimen which was used to define it.
This species was named in July 2002 from fossils discovered in Chad in Central Africa (Brunet et al. It is the oldest known hominid or near-hominid species, dated at between 6 and 7 million years old.