In 1980, a Buddhist monk in Tibet entered a sacred cave to pray. On the floor, he found half of a human jawbone, studded with two teeth.

A team of scientists on Wednesday reported that the fossil belonged to a 160,000-year-old Denisovan, a member of a lineage of mysterious, Neanderthal-like humans that disappeared about 50,000 years ago.

The fossil is the first evidence of this species found outside the Denisova Cave in Siberia, buttressing the theory that these relatives of modern humans once lived across much of central and eastern Asia.

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There’s never been a study like it before, and there probably never will be again.

Starting in March 2015, astronaut Scott Kelly spent 340 days aboard the International Space Station. A team of scientists tracked his body’s responses to long-term spaceflight in painstaking detail. They simultaneously tracked his identical twin brother, Mark, on Earth.

On Thursday, the scientists began publishing the huge trove of results from the so-called NASA Twins Study — 90 pages, all told, and that’s just the first installment. Here’s a guide to what they’ve found … so far.

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In a cave in the Philippines, scientists have discovered a new branch of the human family tree.

At least 50,000 years ago, an extinct human species lived on what is now the island of Luzon, researchers reported on Wednesday. It’s possible that Homo luzonensis, as they’re calling the species, stood less than three feet tall.

The discovery adds growing complexity to the story of human evolution. It was not a simple march forward, as it once seemed. Instead, our lineage assumed an exuberant burst of strange forms along the way.

Our species, Homo sapiens, now inhabits a comparatively lonely world.

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In 2011, Dr. Dena Dubal was hired by the University of California, San Francisco, as an assistant professor of neurology. She set up a new lab with one chief goal: to understand a mysterious hormone called Klotho.

Dr. Dubal wondered if it might be the key to finding effective treatments for dementia and other disorders of the aging brain. At the time, scientists only knew enough about Klotho to be fascinated by it.

Mice bred to make extra Klotho lived 30 percent longer, for instance. But scientists also had found Klotho in the brain, and so Dr. Dubal launched experiments to see whether it had any effect on how mice learn and remember.

Continue reading “One Day There May Be a Drug to Turbocharge the Brain. Who Should Get It?” →