If a troop of baboons encounters another troop on the savanna, they may keep a respectful distance or they may get into a fight. But human groups often do something else: They cooperate.

Tribes of hunter-gatherers regularly come together for communal hunts or to form large-scale alliances. Villages and towns give rise to nations. Networks of trade span the planet.

Human cooperation is so striking that anthropologists have long considered it a hallmark of our species. They have speculated that it emerged thanks to the evolution of our powerful brains, which enable us to use language, establish cultural traditions and perform other complex behaviors.

Continue reading “Scientists Find First Evidence That Groups of Apes Cooperate” →

Along our evolutionary journey from monkey-like primates to bipedal apes to big-brained humans, we have had the company of an extraordinarily loyal companion: Pediculus humanus, otherwise known as the human louse.

And all the while, the lice have recorded this journey in their genes. A new study, for example, found that some lice in the Americas are hybrids of those carried there by Native Americans and others ferried across the Atlantic by European colonists.

Continue reading “Lice Genes Offer Clues to Ancient Human History” →

For biologists, menopause is baffling. If natural selection favors genes that produce more descendants, why don’t women remain fertile their entire lives? What’s the evolutionary benefit of living for so many years without having more babies?

The mystery has only deepened as scientists have looked for menopause in mammals in the wild and found clear evidence of it only in a few species of whales. “It is very, very rare,” said Kevin Langergraber, a primatologist at Arizona State University.

Continue reading “Chimpanzees Go Through Menopause, Too” →

An international team of scientists has mapped the human brain in much finer resolution than ever before. The brain atlas, a $375 million effort started in 2017, has identified more than 3,300 types of brain cells, an order of magnitude more than was previously reported. The researchers have only a dim notion of what the newly discovered cells do.

The results were described in 21 papers published on Thursday in Science and several other journals.

Ed Lein, a neuroscientist at the Allen Institute for Brain Science in Seattle who led five of the studies, said that the findings were made possible by new technologies that allowed the researchers to probe millions of human brain cells collected from biopsied tissue or cadavers.

In more than 1,500 animal species, from crickets and sea urchins to bottlenose dolphins and bonobos, scientists have observed sexual encounters between members of the same sex.

Some researchers have proposed that this behavior has existed since the dawn of the animal kingdom. But the authors of a new study of thousands of mammalian species paint a different picture, arguing that same-sex sexual behavior evolved when mammals started living in social groups. Although the behavior does not produce offspring to carry on the animals’ genes, it could offer other evolutionary advantages, such as smoothing over conflicts, the researchers proposed.