Humans: An Evolutionary History ORIGINS - Rebecca Stefoff Part 5 pptx

By the end of 2002 the team had discovered additional Sahelanthropus

teeth and fragments of lower jaws. No body parts below the skull have been

found. The search continues for additional fossils that may answer some of

scientists’ questions about Sahelanthropus. Was this animal truly bipedal?

Was it related to other known species of early humanlike animals? Was it,

perhaps, related to human ancestors?

Orrorin, “Original Man”: Unlike the date for Sahelanthropus, the date for the

second-oldest fossil with humanlike features is established by direct evi￾dence. That fossil is Orrorin tugensis, found in the East African nation of Kenya.

In 1974, while excavating for fossils in an area called the Tugen Hills west

of Lake Baringo in Kenya, a Kenyan-born paleontologist named Martin Pick￾ford found a molar tooth from an unknown primate species. Pickford

reported his find in the science journal Nature but did not have enough evi￾dence to determine what it was.

Pickford was unable to resume work in the Tugen Hills until 2000, when

he returned to the area as part of a French-Kenyan team. The team uncov￾ered fossils that appeared to be related to the 1974 tooth: more loose

teeth; two jaw fragments with teeth; part of an arm bone; and several finger

bones. They also found two femurs, or thighbones. These are especially

interesting because few post-cranial (below the head) fossils of hominids

have been recovered. The scientists decided that their finds represented a

new genus and species, which they named Orrorin tugenensis (orrorin means

“original man” in the local language of the Tugen Hills).

Some of the Orrorin fossils were found between two layers of volcanic

rock that could be dated. The layer below the fossils is about 6.2 million

years old; the layer above them is 5.65 million years old. Researchers there￾fore estimate that Orrorin lived between 5.8 and 6 million years ago.16

Orrorin’s teeth were more apelike than those of Sahelanthropus.The long,

large canine teeth moved against other teeth called premolars in a way that

sharpened the canines. This is an ape trait that appears to be missing from

ORIGINS

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