WEIT Chap8

What about us? Chap 8

Darwin firmly believed that humans evolved from other species, apelike creatures, in Africa. This statement created a lot of religious objections. He {{co|It or He?} } took fossils to finally convince the skeptics that humans had indeed evolved. He was the first to discover an Australopithecus africanus. The chapter talks about Darwin's theory, explaining us his theory and the proofs he found. This chapter talks about fossil ancestors, our genetic heritage, the sticky question of race and what about now. We will describe all the chapters briefly.

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Fossil Ancestors

Complete fossil sequences don't exist. Fossil records are very difficult to find, thus rather than hoping to find all the missing link, you have to make a general analysis with the records that you have.

which clearly shows a change from apelike to humanlike features.

The older possible hominin discovered is Sahelanthropus tchadensis, from the Central African desert of Chad, the region known as the Sahel. It dates from between six and seven million years ago, right when molecular evidence tells us that our lineage diverged from that of chimps. The discovery of this species suggests that bipedal walking was one of the first evolutionary innovations to distinguish us from other apes.

After Sachelanthropus we have the six-million-years-old fragments from a species, called Orrorin tugenensis, which has a single leg bone that is an evidence of bipedality.
Then, there's a two-million-years gap with no substantive hominin fossils. That is where crucial information about when be began to walk upright has still to be found. The fossils reappear, beginning about four million years ago and from them we see branches beginning to grow from the hominin tree.
There was still a link missing in the tree of hominins. In 1974 a main dicovered was made in Ethiopa Johannson and Tom Gray discovered a fossil, a female of new spieces which will be called "Lucy". The most important thing is that she walked on two legs. Between the chimp who can't walk on two legs and the homo spaiens who can we needed to find a link between them and this link is the Australopithecus afarensis. Knowing how the attachment of the femur to the pelvis we could know if the fossil was bipedal or not. If the femurs angle toward the middel, it's bipedal, Lucy had almost the same angles as the humans. By fossilizied footprints people had an oder proof to confirm that depending on the way they were walking we could know if the fossils were bipedal or not. The Laetoli footsprints are virtually identical to those made by us. For example the size of the braincase led us know we the fossil was between the "Homo spaiens" and the "chimp". The dental arcades was also a way to know the evolution of the fossil. After A. afarensis, we can notice a chronological progression to a more modern human form: the tooth row gets more parabolic, the brain gets larger, and the skeleton loses its aplike features. To distinguish an Australopithecus from a Homo sapiens you need to look at the size of the brain: a larger brain for Homo sapiens and a smaller brain for Australopithecus. With the growth of the brain Homo sapiens had parts associated with speach and comprehension, the Australopithecus doesn't have these parts. "Habilis" was the first species with spoken language. This robust spieces probably subsisted by eating roots, nuts and so on. The homo herectus was the highly successful spieces, it lived , this spiece is the closest spieces to ours. An important thing to know is that we have no idea if the homo herectus contributed to the gene pool of modern humans. A question remains: what happened? 1.1: From homo herectus simply involved into h.sapiens independtly in several areas, perhaps because there was a natural selection happening all over the world. 1.2 mthe second idea was the africa theory, saying that the modern homo sapiens was replaced by homo erectus and the neanderthals maybe by killing them or by the food.

les filles, il faut qu'on se voit pour une sorte de répartition des taches non?

Etes vous d'accord de faire de votre côté Fossil ancestor (2e sous chapitre) et our genetic heritage (3e sous chapitre)? Julia et moi nous occupons de "what about us, the sticky question of race, what about now" ?

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The Sticky Question of Race

There exist visible differences in human types but many biologists stay as far away from this statement because of racial prejudice. Scientists argued the fact that human races have no link with biology and are more a sociopolitical status. According to biology, a race is a population of a species that is geographically separated and differ genetically in several traits.

What about now?

Natural selection doesn't have produced differences between races, although we can notice some differences between population within ethnic groups. one example of natural selection is the tolerance of milk. Our ancestor had no source of milk after weaning so that's why

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