February 11, 2009

Genetic Change May Have Caused Split In Human-Ape Family Tree

A new study by researchers at the University of Washington shows that the evolutionary split between humans and apes may have been spurred by a fast-track genetic change that occurred in a common ancestor.

Before the primates' family tree split, the code was fairly stable, except in one fascinating area, researchers said.

Sequences of DNA code become duplicated in that area of change and then quickly accelerated, something that could account for the evolutionary break, the research found.

It may provide clues about something that has long baffled scientists: why humans and chimps look and behave so differently, despite the fact they have what is commonly believed to be a nearly identical genetic heritage.

Indeed, human and chimps have genomes that overlap by nearly 99 percent, and their proteins are virtually the same, according to earlier research.

However, the current study found that the range and number of duplicated sequences vary much more than the other parts of genetic code.

"It is unclear why, but the common ancestor of humans, chimps and gorillas had an unusual activity of duplication," Jeffrey Kidd of the University of Washington, the study's co-leader, told the AFP.

Changes in lifespan, population size or instability in the genome may have caused this genetic change, Kidd hypothesized.

But whatever the cause, it likely "had a profound impact on the reproductive success, adaptability and evolution of ancestral hominid populations," the researchers said.

To investigate patterns of genomic duplication during evolution, Kidd and his team compared telltale sequences in four primates: the orangutan, human, macaque and chimpanzee.

Only a small portion of these copied segments were unique to each species, indicating that a large percentage of these duplications must have occurred prior to the evolutionary split, in a common ancestor.

The study also revealed that these regions are changing faster than most others.

"The next challenge will be making sense of all these differences and the genes that affect them," Tomas Marques-Bonet, the study's other co-leader and also a researcher at the University of Washington, told the AFP.

The research was published in the journal Nature.


On the Net: