Реферат: The Earliest Hominines Essay Research Paper The

boisei fossils are only 1.3 million years old.

A. boisei is similar to A. robustus in form; however, the East African robust

australopithecine is even more robust than its South African relative. A. boisei s

cranial capacity was 500 to 530 cc and its weight was 34 to 49 kg, compared with

the 32 to 40 kg range of A. robustus.

The Black Skull from Kenya shares some primitive features with

Australopithecus afarensis and, being far earlier than the other A. boisei finds, has

been suggested as being descended from A. afarensis. While your text considers

this specimen to be an early A. boisei, other researchers prefer to place the Black

Skull in a separate species, Australopithecus aethiopicus.

It is uncertain whether A. robustus represents a southern offshoot of the A.

boisei lineage or an example of convergent evolution that evolved from A.

africanus.

A. boisei and A. robustus were both highly efficient “chewing machines” which

had a diet of tough, uncooked vegetation.

The law of competitive exclusion states that when two closely related species

compete for the same niche, one will outcompete the other, bringing about the

“loser s” extinction. The specialized vegetarian robust australopithecines avoided

such competition with early Homo and these two genera were thereby able to

coexist for some 1.5 million years.

Older than Australopithecus afarensis is Australopithecus anamensis. This

species is a recent find, dated to 4.2 to 3.9 mya, and is represented by an arm bone

found in 1965 and two jaws and a tibia found in 1995. The jaws were ape-like with

a shallow palate and large canines, but the tibia was similar to that of A. afarensis

and is the oldest direct evidence of bipedalism yet found.

Older still than Australopithecus anamensis is Ardipithecus ramidus, a species

known from pieces of 17 individuals from Ethiopia dated to 4.4 mya. No pelvic,

foot, or leg bones are among the fossils; however, the shapes of the canines and

vertebral elements are hominine in appearance.