For millions of years, North America was home to a zoo of giants: mammoths and mastodons, camels and dire wolves, sloths the size of elephants and beavers as big as bears. And then, at the end of the Pleistocene Epoch about 12,000 years ago, most of them vanished.

Scientists have argued for decades about the cause of their extinction. Now, a study analyzing the ancient bones of a young child who lived in Montana suggests that early Americans hunted mammoths and other giant mammals to oblivion.

Continue reading “Mammoth: It’s What Was for Dinner” →

Shortly after conception, a fertilized egg divides, becoming two. Then each of those cells splits, becoming four, and on and on. Over time, those lineages of cells grow distinct, giving rise to all the different organs and tissues in the human body and comprising as many as 36 trillion cells.

Scientists would love to understand the trajectory of each of those cells over time. “It’s something that developmental biologists like me have dreamed of for over 100 years,” said Alex Schier of the University of Basel in Switzerland. But the best they have managed has been taking snapshots of cells at different stages.

Continue reading “‘DNA Typewriters’ Can Record a Cell’s History” →

As soon as you put starch in your mouth — whether in the form of a dumpling, a forkful of mashed potatoes or a saltine — you start breaking it down with an enzyme in your saliva.

That enzyme, known as amylase, was critically important for the evolution of our species as we adapted to a changing food supply. Two new studies revealed that our ancestors began carrying more amylase genes in two major waves: the first one several hundred thousand years ago, possibly as a result of humans starting to cook with fire, and the second after the agricultural revolution 12,000 years ago.

Continue reading “How Early Humans Evolved to Eat Starch” →

Comb jellies, the delicate bells that pulse their iridescent bodies through the ocean, are some of the strangest creatures on earth. “They are the aliens of the sea,” said Leonid Moroz, a neuroscientist at the Whitney Laboratory for Marine Bioscience in St. Augustine, Fla.

The aliens belong to the oldest branch of the animal family tree. They split from the ancestors of all other living animals about 700 million years ago and have traveled down their own odd evolutionary path ever since. Studies by Dr. Moroz and others suggest that comb jellies evolved their own nervous system, as well as their own muscles and digestive tract — complete with two anuses.

Continue reading “When Two Sea Aliens Become One” →

A fruit fly’s brain is smaller than a poppy seed, but it packs tremendous complexity into that tiny space. Over 140,000 neurons are joined together by more than 490 feet of wiring, as long as four blue whales placed end to end.

Hundreds of scientists mapped out those connections in stunning detail in a series of papers published on Wednesday in the journal Nature. The wiring diagram will be a boon to researchers who have studied the nervous system of the fly species, Drosophila melanogaster, for generations.

Continue reading “After a Decade, Scientists Unveil Fly Brain in Stunning Detail” →