Реферат: The Earliest Hominines Essay Research Paper The

equivalent to those of the great apes of today.

What is significant is the fact that at 4 million years ago, there existed a bipedal

hominine. Evidence supporting this fact includes: forward placement of the

foramen magnum indicating a head balanced atop the spinal column; human-like

curvature of the spine; forearms shorter than those of an ape indications of a lower

centre of gravity than apes; the Laetoli footprints; and hip and knee anatomy. On

the other hand, these australopithecines still retained a slightly divergent great toe

and shoulder girdle well suited for climbing.

Bipedal locomotion preceded any increase in brain size; in fact,

australopithecines lacked the prolonged maturation of modern humans and likely

matured as apes do. Upright walking set the stage for larger brain sizes but was

not the sole cause of these later increases.

Robert Broom and John Robinson first discovered Australopithecus robustus,

a larger, more robust australopithecine, in 1948 at the sites of Swartkrans and

Kromdraai (South Africa). While no accurate dates are available, it is believed that

the deposits are 1.8 to 1 million years old.

A. robustus is similar to A. africanus, except for thicker bones relative to size,

with large muscle-markings that included an ape-like sagittal crest on the large

skull.

Cranial capacity of A. robustus was around 530 cc and the crest served to

anchor the massive chewing muscles of powerful jaws. Such chewing apparatus is

also seen in the modern gorilla and is an example of convergent evolution in these

two species.

In East Africa, a robust australopithecine species also exists: Australopithecus

boisei.

First found at Ngorongoro Crater of Olduvai Gorge in 1959 by Mary Leakey,

the original specimen was named Zinjanthropus by Louis Leakey. Further study

revealed it was another australopithecine and it was renamed A. boisei.

Potassium-argon dating places the find at 1.75 million years old; however, another