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That Tiny Little Bit?

Only a small sliver of human DNA is functional, say researchers from the University of Oxford in PLOS Genetics. They calculate that 8.2 percent of the human genome is under negative selection and thus likely to be functional.

That's higher than some previous estimates, but much lower than what the ENCODE group reported in 2012, LiveScience notes.

To come to this figure, researchers led by Oxford's Gerton Lunter compared the genome sequences of dozen mammals to gauge how much those sequences had changed since their most recent common ancestor. From this, they homed in on regions that evolved slower than expected, a sign, they said, of natural selection on a functional sequence. A functional sequence, by the researchers' definition, is one that is important enough to be evolutionarily conserved.

"Scientifically speaking, we have no evidence that 92 [percent] of our genome is contributing to our biology at all," Lunter tells the Guardian.

Others, though, argue that that DNA stretches that are not so well conserved can be important.

"Many [DNA] elements that play important roles in human disease are not evolutionarily conserved, " Manolis Kellis, a computational biologist at MIT, says in the Guardian. "We cannot simply ignore the remaining 90 [percent] of the genome that is not evolutionarily conserved."

"Evolution can tell you whether something is important or not important, but it doesn't tell you what that something actually does," he adds.