User:P'tit Pierre/Chimpanzees and Gorilla's ancestry

Chimpanzees and Gorillas ancestry

Today, chimpanzees and gorillas live in tropical forests with acid soils where bones are hardly preserved as fossils. It is considered that no fossil chimpanzees or gorillas have been reported. However, four chimpanzee teeth, about 500 ky old have recently been discovered in the rift valley, where many fossils from the human lineage (hominins) have previously been found <McBrearty and Jablonski, Nature, 2005>. This discovery shows that at the time, some chimpanzees lived close to Homo (erectus or rhodesiensis). It is likely that the same could be true for gorillas too.

Are Paranthropus the ancestors of gorillas ? Robust Australopithecus (Paranthropus) have Gorilla-like cranial crests: the sagittal crest is running at the top of the skull, the very strong jaw muscles (Temporalis muscle) go all the way up to attach on both sides of this crest Paranthropus also have characteristic wide cheek bones (zygomatic arches) projecting forward of the nasal opening and marks along the skull from strong chewing muscles, as well as a dished-shape face. Diet: Large postcanine dentition, thick enamel, robust mandibles, sagittal cresting, flaring zygomatic region are indicative of a diet of hard or tough foods. It is believed that the paranthropus lineage died out, leaving no descendants. Although the many similarities with Gorillas were readily noted in the original papers describing Paranthropus discoveries, the logical conclusion that they could be Gorillas ancestors was not proposed.. Species: A. robustus, A. boisei (or Zinjanthropus), A. aethiopicus Sexual dimorphism: Male average height was 137 cm, weight 50-70 kg, female 125 cm, 34-45 kg. Less sexual dimorphism than today gorillas where males are much stronger (height 170 cm, weight 180kg) than females (140 cm, 100 kg) a few males reaching an height of 180cm and a weigt of more than 200 kg, twice that of females.. However Paranthropus were taller and heavier than other Australopithecus living at the same time, hence their name: Robustus and showed a more pronounced sexual dimorphism , Between 2.7 million and 1.2 million years ago Paranthropus shared the earth with some early examples of the genus Homo, such as H. habilis, H.ergasrter and possibly even H.erectus As far back as 2.5 Mya P. aethiopicus co-existed with A. africanus.

Human evolutionary genetics and chimpanzees ancestry: According to molecular evolution, the common ancestor had as much pre-human traits as chimp-like traits. An Australopithecus 4 million years old (Ardipithecus ramidus 4.4 mya) is close to the last common ancestor (5 million years old) it is thus difficult to place a 4 million years old fossil in a precise lineage because the two have diverged shortly before. Some of the most recent paranthropus fossils are 1 million year old, about one tenth the time since the divergence of humans and gorillas (10 million years). Therefore many of the paranthropus traits are very much like gorillas. In contrast, it is more difficult to place 4 million years old australopithecines in the chimp or human lineages. Most A.africanus seem to be in the human lineage, whereas A.afarensis are in the chimp lineage, probably with the exception of Selam (3.3Mya) who has been placed in A.afarensis, but has more homo traits than Lucy (3.2Mya) for instance, and should be placed in A. africanus

These are not the mainstream conclusions that can be found in the main "human evolution" page, but Similar conclusions were reached by at least two other biologists, independently: the author of the “Paranthropus aethiopicus” page of the Online Biology Dictionary” http://www.macroevolution.net/paranthropus-aethiopicus.html and by [ [Richard Dawkins]] in his book “The ancestor’s tale” 2004 Boston: Houghton Mifflin Eds, "Australopithecines. According to this theory, chimps and bonobos are descended from Australopithecus Gracile type species while gorillas are descended from Australopithecus Robustus type species. These apes were once bipedal but then lost this ability when they were forced back into the semi-forest (presumably by those Australopithecines who eventually became us";

References

McBrearty and Jablonski, Nature, 2005.

"Human Evolutionary Genetics" Jobling M.A., Hurles M., Tyler Smith C.

External links

• example.com

http://www.macroevolution.net/paranthropus-aethiopicus.html

http://en.wikipedia.org/wiki/The_Ancestor's_Tale

http://en.wikipedia.org/wiki/Human_evolution