People who sign up for genetic testing from companies like 23andMe can find out how much of their DNA comes from Neanderthals. For those whose ancestry lies outside Africa, that number usually falls somewhere between 1 percent and 2 percent.

Scientists are still a long way from understanding what inheriting a Neanderthal gene means to people. Some Neanderthal genes may be helpful — improving our defenses against infections, for example — but other bits may leave carriers slightly more prone to certain diseases.

Continue reading “Narrower Skulls, Oblong Brains: How Neanderthal DNA Still Shapes Us” →

Some 252 million years ago, Earth almost died.

In the oceans, 96 percent of all species became extinct. It’s harder to determine how many terrestrial species vanished, but the loss was comparable.

This mass extinction, at the end of the Permian Period, was the worst in the planet’s history, and it happened over a few thousand years at most — the blink of a geological eye.

Continue reading “The Planet Has Seen Sudden Warming Before. It Wiped Out Almost Everything.” →

It felt as if humanity had crossed an important line: In China, a scientist named He Jiankui announced on Monday that twins had been born in November with a gene that he had edited when they were embryos.

But in some ways this news is not new at all. A few genetically modified people already walk among us.

In the mid-1990s, fertility doctors in New Jersey got an idea for how to help women have children. They suspected that some women struggled to become pregnant because of defective material in their eggs.

Continue reading “Genetically Modified People Are Walking Among Us” →

To demonstrate how smart an octopus can be, Piero Amodio points to a YouTube video. It shows an octopus pulling two halves of a coconut shell together to hide inside. Later the animal stacks the shells together like nesting bowls — and carts them away.

“It suggests the octopus is carrying these tools around because it has some understanding they may be useful in the future,” said Mr. Amodio, a graduate student studying animal intelligence at the University of Cambridge in Britain.