James Priest couldn’t make sense of it. He was examining the DNA of a desperately ill baby, searching for a genetic mutation that threatened to stop her heart. But the results looked as if they had come from two different infants.

“I was just flabbergasted,” said Dr. Priest, a pediatric cardiologist at Stanford University.

The baby, it turned out, carried a mixture of genetically distinct cells, a condition known as mosaicism. Some of her cells carried the deadly mutation, but others did not. They could have belonged to a healthy child.

Continue reading “Every Cell in Your Body Has the Same DNA. Except It Doesn’t.” →

Scientists reported on Wednesday that they have recovered DNA from the oldest viruses known to have infected humans — and have succeeded in resurrecting some of them in the laboratory.

The viruses were all strains of hepatitis B. Two teams of researchers independently discovered its DNA in 15 ancient skeletons, the oldest a farmer who lived 7,000 years ago in what is now Germany.

Until now, the oldest viral DNA ever recovered from human remains was just 450 years old.

Continue reading “In Ancient Skeletons, Scientists Discover a Modern Foe: Hepatitis B” →

The animal kingdom is one of life’s great success stories — a collection of millions of species that swim, burrow, run and fly across the planet. All that diversity, from ladybugs to killer whales, evolved from a common ancestor that likely lived over 650 million years ago.

No one has found a fossil of the ur-animal, so we can’t say for sure what it looked like. But two scientists in Britain have done the next best thing. They’ve reconstructed its genome.

Their study, published in Nature Communications, offers an important clue to how the animal kingdom arose: with an evolutionary burst of new genes.

Continue reading “The Very First Animal Appeared Amid an Explosion of DNA” →

Nine years later, Erin Wessling can still remember the first time she visited Fongoli, a savanna in southeast Senegal.

“You feel like you walk into an oven,” she said.

Temperatures at Fongoli can reach 110 degrees Fahrenheit or more. During every dry season, brush fires sweep across the parched landscape, leaving behind leafless trees and baked, orange soil.

“It’s really nuts,” said Ms. Wessling, now a graduate student at the Max Planck Institute for Evolutionary Anthropology.

Continue reading “Hints of Human Evolution in Chimpanzees That Endure a Savanna’s Heat” →

We are the products of evolution, and not just evolution that occurred billions of years ago. As scientists peer deeper into our genes, they are discovering instances of human evolution in just the past few thousand years.

People in Tibet and Ethiopian highlands have adapted to living at high altitudes, for example. Cattle-herding people in East Africa and northern Europe have gained a mutation that helps them digest milk as adults.

On Thursday in the journal Cell, a team of researchers reported a new kind of adaptation — not to air or to food, but to the ocean. A group of sea-dwelling people in Southeast Asia have evolved into better divers.

Continue reading “Bodies Remodeled for a Life at Sea” →