How quickly do animals evolve? You'd be surprised.

A new study challenges the presumption that evolution's effects appear only over long periods of time.

Courtesy of John McCormick/Virginia Tech/File
White Plymouth Rock chickens.

A new study by the University of Oxford shows evolution may happen significantly faster than commonly thought.

Researchers used chickens to determine the rate of change in mitochondrial genome mutations, which previous research had estimated to be no quicker than 2 percent for every million years.

The study identified two mutations, signifying the rate of evolution in the avian population was 15 times faster, or 30 percent per million years, according to Oxford University’s Research Laboratory for Archaeology.

The finding opens new questions about whether evolution can only be seen over lengthy time scales, often-measured in millions of years.

The scientists focused on a period of about 50 years, a boundary that was never probed because the scientific community assumed the results would be negligible, says Dr. Greger Larson, a senior author on the study.

Via Skype interview from London, he notes that the common assumption that evolution only happens over long time periods meant no one had tried to measure evolution over a period less than thousands of years.

"The idea that evolution moves quickly is not the rhetoric that evolutionary biologists use," Dr. Larson says. "There’s just this constant refrain that fits into this popular perception. Our observations reveal that evolution is always moving quickly but we tend not to see it because we typically measure it over longer periods."

By determining the genetic sequence of a specific pedigree, in this case the White Plymouth Rock chicken, researchers also found evidence that mitochondrial DNA can be passed down from a father — assumed to be a rare occurrence.

"The one thing everyone knew about mitochondria is that it is almost exclusively passed down the maternal line, but we identified chicks who inherited their mitochondria from their father, meaning so-call paternal leakage can happen in avian populations," said the study’s lead author, University of York’s Dr. Michelle Alexander, in a statement.

"Both of these findings demonstrate the speed and dynamism of evolution when observed over short periods," she added.

In the study, researchers examined DNA extracted from the blood of 12 chickens linked over 47 years through distant maternal lines. The scientists also viewed 385 “mitochondrial transmission” as the basis for their analysis.

"We had a complete pedigree of a vertebrate," Larson says. "Nobody looked at vertebrates. You have a lot more transmission in things that are very quickly reproducing."

The data also suggested that when mitochondrial DNA evolves, negative mutations are removed, causing an increase in short-term outcomes.

This new data on rapid evolution could alter our timelines on when humans first left Africa, says Larson, or when differences began to form between humans and chimpanzees.

"Was it 3 million or 8 million years?" Larson asks. "You’re in serious risk of misestimating the date of any two things you’re trying to figure out."

The results of the study will be published Wednesday in Biology Letters, a scientific journal. 

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