A team of scientists reported on Thursday that it had recovered the genome from a 4,500-year-old human skeleton in Ethiopia — the first time a complete assemblage of DNA has been retrieved from an ancient human in Africa.

The DNA of the Ethiopian fossil is strikingly different from that of living Africans. Writing in the journal Science, the researchers conclude that people from the Near East spread into Africa 3,000 years ago. In later generations, their DNA ended up scattered across the continent.

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In 1977, a University of Oxford statistician named Richard Peto pointed out a simple yet puzzling biological fact: We humans should have a lot more cancer than mice, but we don’t.

Dr. Peto’s argument was beguilingly simple. Every time a cell divides, there’s a small chance it will gain a mutation that speeds its growth. Cells that accumulate several of these mutations may become cancerous. The bigger an animal is, the more cells it has, and the longer an animal lives, the more times its cells divide. We humans undergo about 10,000 times as many cell divisions as mice — and thus should be far more likely to get cancer.

Continue reading “Elephants: Large, Long-Living and Less Prone to Cancer” →

In recent years, a peculiar sort of public performance has taken place periodically on the sidewalks of Seattle.

It begins with a woman named Kaeli N. Swift sprinkling peanuts and cheese puffs on the ground. Crows swoop in to feed on the snacks. While Ms. Swift observes the birds from a distance, notebook in hand, another person walks up to the birds, wearing a latex mask and a sign that reads “UW CROW STUDY.” In the accomplice’s hands is a taxidermied crow, presented like a tray of hors d’oeuvres.

This performance is not surreal street theater, but an experiment designed to explore a deep biological question: What do crows understand about death?

Continue reading “Crows May Learn Lessons From Death” →