Some of them harbor strains that infected medieval Europeans, but that have been eradicated on the U.K. mainland for centuries.

Just over a year after they were discovered in China, bacteria that can fend off colistin are being found all across the world.

An ancient, robust breed is proving well-suited for the arid American Southwest.

One strange piece of mobile DNA has spread itself throughout the oceans, claiming real estate in the genomes of clams, fish, and more.

Guppies have silver eyes, but when they’re ready for a fight, their irises go dark. An experiment with robots shows why.

Trump’s family-separation policy is horrible, but equating it with genocide is both historically and strategically misguided.

And those who spend the most time babysitting end up with more babies of their own.

People raised in low-income families have worse cognitive functioning after age 50, suggesting that mental decline is a process that starts in childhood.

Nature isn’t cruel—it’s just careless.

Better to run than to have your liver squeezed out.