Chimps and Humans Shared a Common Apelike Ancestor

Humans’ evolutionary break-up from their closest relatives, chimpanzees, may have been more complicated, taken longer and probably occurred more recently than previously thought, scientists said today.

As indicated by the new theory, chimps and humans shared a common apelike ancestor much more recently than was thought. Moreover, when the two emerging species split from each other, it was not a clean break.

However, after comparing the genes or genetic codes, of humans and their closest animal relatives, researchers suggest the initial split took place no more than 6.3 million years ago and probably less than 5.4 million years ago.

The group of scientists revealed that the process of separation may have taken about 4 million years and there could have been some inter-breeding before the final break.
David Reich of the Broad Institute and Harvard Medical School’s Department of Genetics in Massachusetts, said, "The study gave unexpected results about how we separated from our closest relatives, the chimpanzees."

In place of analyzing genetic dissimilarities between humans and chimpanzees, Reich and researchers from the Massachusetts Institute of Technology (MIT) and the Broad Institute of Harvard and MIT, looked at variations in the degree of divergence between the two in different regions of the genomes.

The analytical study, published in the journal Nature, reveals some regions in the human genome are older than others which mean they trace back to different times in the common ancestral population of the two species.

As per the researchers, the youngest regions are unexpectedly recent, which means the separation between the two species was more recent than previously thought.

Reich explicated, "A hybridization event between human and chimpanzee ancestors could help explain both the wide range of divergence times seen across our genomes, as well as the relatively similar X chromosomes."

Hybridization refers to the initial breakup of two species followed by interbreeding and then the final split.

The findings also raise questions about the 7 million year old remains of ’Toumai’ skull unearthed in Chad in 2001 and was thought to be the earliest member of the human family.

The skull, which has an amalgam of primitive and human-like features and dates, was hailed as most likely an essential fossil discovery in living memory because it was thought to belong to an ancient ancestor of modern humans.

Some scientists had debated it was a fossil of a female ape.

Nick Patterson of the Broad Institute and a co-author of the study, said, "It is possible that the Toumai fossil is more recent than previously thought," he added "But if the dating is correct, the Toumai fossil would precede the human-chimp split. The fact that it has human-like features suggests that human-chimp speciation (separation) may have occurred over a long period with episodes of hybridization between the emerging species."

The research is the latest aftermath of the Human Genome Initiative, the effort to transcribe and read out the entire genetic message of human chromosomes, which was completed in 2003.

This narration, by a team of geneticists and biostatisticians from the Broad Institute of the Massachusetts Institute of Technology and Harvard, not only sheds new light on the origin of humans, but also raises questions about how all new species arise.