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The discovery of a number of 10 million year old fossilised teeth of a new Gorilla-like species, will rewrite the evolutionary history of great apes and humans.

Until now, most palaeoanthropologists had thought the gorilla lineage diverged from that of humans and chimpanzees sometime between 6 and 8 million years ago, based on comparisons between the genomes of modern species.

But a team led by the Tokyo University Museum in Japan, have unearthed canine and eight partial molars, from at least three, prehaps six or more, individuals, which the team have named 'Chororapithecus abyssinicus' (Nature, vol 448,p921).

The teeth were unearthed from the Chorora formation in Ethiopia's Afar rift, which ten million years ago was a lush forested area.
The evidence suggests that 'Choroapithecus' may have been a primitive gorilla. For one thing, the teeth are of about the same size and proportions as modern gorilla teeth. The molars also have smaller versions of the long crests that are characteristic of the molars of modern gorilla's, but not other apes. These crests help with cutting tough fibrous material, such as leaves and stems.
Michel Brunet of the University of Poitiers, France, who has seen the teeth, also believes that these teeth must be related to a gorilla group. "If Chororapithecus is indeed an early gorilla, that would push back the origins of gorilla lineage to at least 10 million years ago, and prehaps further".
That could in turn could force researchers to recalibrate their estimates of the rates of genetic change, which in turn would change the timing of many events on the ape family tree.
For example, it would show that the orang-utan lineage may have split off around 20 million years ago, rather than 13 million years ago as previously thought.
The earlier date for the start of the gorilla lineage would also fit well with the age of the earliest known remains from the lineage leading to humans found in Chad, and dated at about 7 million years old.

Precis of article below.
http://www.newscientist.com/article/mg19...ry-history.html

The headline in the link reads, "New ape species rewrites our evolutionary history".

I know journalists have to sell their story but the find hardly lives up to the headline. In fact the find lends support to a view of speciation that is rapidly becoming accepted, and is basically self-evident when you think about it. Species do not separate instantaneously.

The find is totally compatible with the statement, "the gorilla lineage diverged from that of humans and chimpanzees sometime between 6 and 8 million years ago". This is the date indicated by the mitochondrial DNA lines for the split. It's known and accepted that the first step in the development of interspecies infertility is usually infertility of males. Exchange of genes between two evolving species is still possible long after this development though. Genes can still move between what we would probably call subspecies. Therefore the original development of the gorilla type could have started 3 or 4 million years before the 6 to 8 million years date. Fits the evidence. It's been shown the chimp/human split took about 4 million years and so there is no reason why the earler branching off of the gorilla line didn't take about as long.