CORVALLIS, Ore. In research that will help address a long-running debate and apparent contradiction between short- and long-term evolutionary change, scientists have discovered that although evolution is a constant and sometimes rapid process, the changes that hit and stick tend to take a long time.
Give or take a little, one million years seems to be the magic number.
A new study, published this week in Proceedings of the National Academy of Sciences, combined for the first time data from short periods such as 10-100 years with much longer evidence found in the fossil record over millions of years.
It determined that rapid changes in local populations often don't continue, stand the test of time or spread through a species.
In other words, just because humans are two or three inches taller now than they were 200 years ago, it doesn't mean that process will continue and we'll be two or three feet taller in 2,000 years. Or even as tall in one million years as we are now.
"Rapid evolution is clearly a reality over fairly short time periods, sometimes just a few generations," said Josef Uyeda, lead author of the study and a zoologist at Oregon State University. "But those rapid changes do not always persist and may be confined to small populations. For reasons that are not completely clear, the data show the long-term dynamics of evolution to be quite slow."
Across a broad range of species, the research found that for a major change to persist and for changes to accumulate, it took about one million years. The researchers wrote that this occurred repeatedly in a "remarkably consistent pattern."
"What's interesting is not that we have so much biological diversity and evolutionary change, but that we have so little," Uyeda said. "It's a paradox as to why evolution should be so slow."
Long periods of little change, Uyeda said, are called "stasis," a pattern that originally led to the conc
|Contact: Josef Uyeda|
Oregon State University