Ruben Sanchez-Teran
Dr. Neal Endacott
Video Worksheet #4: Becoming Human, Part I
What evolutionary selective pressures likely lead to bipedalism and then much later the
development of human intelligence?
Much of modern anthropological discoveries are made in regions of the Earth that are dry and
desolate; yet, it is known that when our ancient ancestors existed, it was in a land that wetter and
more abundant with life. The following paragraphs will cover bipedalism and intelligence of
Humans in summary.
Australopithecus afarensis exhibited anatomical evidence that they walked upright. The fossils
from Lucy show articulating knees and a pelvic bone more like a Human than a chimpanzee, as
explained by Dr. Don Johanson (Timestamp 11:50 video). Bipedalism is unique to Humans as
stated by, Brian Richmond, in the video (Timestamp 17:37), is “an unusual trait”.
Until the 1990s, there was no fossil record of earlier hominids that predated Lucy or Salam. In
1997, Michel Brunet, a French anthropologist, discovered Sahelanthropus tchadensis,
nicknamed Tumay, and dated at 6 MYA (Timestamp 24:35). It was determined that Tumay
walked on two legs; yet, limited evidence due to only a skull being discovered.
Over the next few million years other hominids were discovered that practiced bipedalism but
still had chimpanzee sized brains: Orrorin tugenensis,dated at six million years ago;
Ardipithecus ramidus dated at 4.4 million years ago; Australopithecus africanus dated at 2.4-3
million years ago; Kenyanthropus platyops dated at 3.5 million years ago. This lasted for about
four million years until the emergence of Homo habilis, nicknamed Handy Man, dated from 1.62.5 million years ago.
As far as intelligence goes, it was Homo habilis that first exhibited the talent for tool making.
This was about one million years from ‘Lucy’ to ‘Handy Man’. He utilized his thumb to create
tools for hunting and eating. Although he was still almost ape, Homo habilis exhibited a larger
brain and cranium shape to house it.
In order for Homo habilus and future progeny to have emerged, there seems to have been a series
of “climate fluxuation” (timestamp 41:45). The change experienced by our ancient ancestors as a
selective pressure was the environmental and climatic change due to volcanic eruptions, sudden
droughts, and an ongoing cycle that eventually allowed for the emergence of the fittest to
survive. The most intelligent and the ones that could move faster and easier.