Evolution Comes in Bursts, Gene Study Finds

Brian Handwerk
for National Geographic News
October 5, 2006

Evolution is not always a gradual process but often a series of genetic fits and starts, a new report suggests.

Looking back over evolutionary "family trees," it appears that adaptations—such as changes in skin color or beak shape—occur in spurts, the study says. And those spurts seem to occur when new species arise.

This suggests that genetic mutations are more likely to succeed—to be passed on to future generations and gradually adopted across a species—when a species is relatively young and trying to find its place in the world.

These times of supercharged evolution are separated by long stretches with relatively few adaptations, according to the study, which looked at genetic histories of plants, animals, and fungi.

(See our quick overview of human genetics.)

"It seems to be the case that speciation can accelerate evolution," said Mark Page, a professor of biological sciences at the University of Reading in the United Kingdom.

"There's something special about it."

(Related: "'Instant' Evolution Seen in Darwin's Finches, Study Says' [July 14, 2006].)

Punctuated Equilibrium

The controversial concept of "punctuated equilibrium"—the idea of golden ages of evolution separated by "calmer" times—arose from studies of the fossil record more than three decades ago.

Instead of studying fossils for their new report, Page and his colleagues examined the evolutionary family trees of 122 species—charting their genetic changes over millions of years.

Their report, to be published in the journal Science tomorrow, compares the genetic changes in species (changes not drastic enough to qualify is indicators of entirely new species) to the number of "speciation events"—the debuts of new species—in those family trees.

Continued on Next Page >>




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