The Three Steps in Evolution

Topics: Hominina, Australopithecus, Hominidae Pages: 2 (743 words) Published: March 11, 2008
Sahelanthropus tchadensis has a skull with an elongated shape with a relatively short, vertical face, which is set high relative to the skull vault. The eyes are set far apart from each other and have a very large continuous bony brow ridge above them. Examination of the lower jaw reveals that Sahelanthropus had a total of thirty two teeth, which is common in all Old World monkeys, apes, and humans. The foramen magnum (where the skull opens for spinal cord passage) is positioned forward and oriented downward. Sahelanthropus has a nose opening that a midline reaches down to the bony palate, as seen in gibbons and monkeys. By contrast, humans and African apes have a nose opening that is set well above the mouth even at its midline. Sahelanthropus had a very primitive-looking braincase, especially in the back, combined with fairly advanced hominid-looking face and canine teeth. (source: Intro to Physical Anthropology, pg 292). Sahelanthropus' diet is not confirmed, but its flooded grassland/woodland habitat suggests that it probably ate leaves, succulents, and the roots and bulbs of submerged grasses and herbs. Most of the species identified near the Sahelanthropus either have yet to be identified or are long since extinct. These include giant saber-tooth cats, an unidentified leaf-eating monkey, elephants with four tusks, a large water-loving relative of pigs, prehistoric giraffes, three-toed horses, pigs, and an unidentified relative of musk ox. There are also three different hyena species, all abundant and representing genera that are now extinct. The abundance of kob, roan, hippopotami, and the presence of crocodiles and pythons suggest large tracts of flooded grasslands and thin woodlands as occur along the Lake Chad shore today. Discovery of Sahelanthropus' fossils were found in the Djurab Desert of northern Chad, at a site known as Toros-Menalla (source: Intro to Physical Anthro, pg 270). It is estimated that Sahelanthropus is about seven million years...
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