In 1961, two biologists named Leonard Hayflick and Paul Moorehead discovered that old age is built into our cells. At the time, many scientists believed that if healthy human cells were put in a flask with a steady supply of nutrients, they would multiply forever. But when Dr. Hayflick and Dr. Moorehead reared fetal human cells, that’s not what they found. Time and again, their cells would divide about 50 times and then simply stop.

Cells that stop growing this way came to be known as senescent.

Continue reading “Signs of Aging, Even in the Embryo” →

Where did dogs come from? That simple question is the subject of a scientific debate right now. In May, a team of scientists published a study pointing to East Asia as the place where dogs evolved from wolves. Now, another group of researchers has announced that dogs evolved several thousand miles to the west, in Europe.

This controversy is intriguing even if you’re not a dog lover. It illuminates the challenges scientists face as they excavate the history of any species from its DNA.

Continue reading “Wolf to Dog: Scientists Agree on How, but Not Where” →

In 1799 the great naturalist Alexander von Humboldt and his companions set out from Caracas, Venezuela, to climb the Andes. They struggled up a mountainside enveloped in mist so thick they had to clamber over rocks by hand. When the fog cleared, von Humboldt was left astonished by the view. Vast grasslands stretched all around him, home to an astonishing number of different trees, shrubs and flowers.

“Nowhere, perhaps, can be found collected together, in so small a space, productions so beautiful and so remarkable in regard to the geography of plants,” he later wrote.

Continue reading “Fast-Paced Evolution in the Andes” →

Multiple Walter Whites will walk the streets on Thursday in search of candy. But some frights endure the fashion cycle and never go out of style.

This week in Proceedings of the National Academy of Sciences, a team of scientists examines one particularly long-lasting source of fear: snakes. The researchers found that certain neurons in the brain only respond to these legless reptiles. These snake-dedicated neurons, they argue, are a legacy of our distant primate past, when the animals posed one of the greatest threats to our survival.

Continue reading “Afraid of Snakes? Your Pulvinar May Be to Blame” →

Around 1.8 million years ago, human evolution passed a milestone. Our ancestors before then were little more than bipedal apes. Those so-called hominids had chimpanzee-size bodies and brains, and they still had adaptations in their limbs for climbing trees. But the fossils of hominids from 1.8 to 1.5 million years ago are different. They had bigger brains, flatter faces and upright bodies better suited to walking.

Their geography changed, too. While earlier hominid fossils have only been found in Africa, the newer ones also turn up at sites stretching across Asia, from the Republic of Georgia all the way to Indonesia.

Continue reading “Christening the Earliest Members of Our Genus” →