SSS 2008-08-07

（单词翻译）

This is Scientific American's 60-Second Science. I'm Steve Mirsky, got a minute?

Neandertals were our closest relatives. And now we know a lot more about them. Because researchers have for the first time sequenced a complete Neandertal genome—that of their mitochondrial DNA¹. The study appears in the August 8th issue of the journal Cell. We all have a large genome in our cell nuclei². Then there’s a separate genome only in mitochondria, those organelles forever immortalized in textbooks as the powerhouse of the cell. The Neandertal DNA sequence falls outside the variation range found in humans today. It also confirms that the last common ancestor of us and Neandertals lived some time between 800,000 and 520,000 years ago. The new info shows that a disproportionate number of Neandertal sequence differences change the amino acid sequences in proteins. One explanation would be that Neandertals had a smaller population size. Which would give natural selection fewer options to choose from. So, did Neandertals mix with our direct ancestors? The sequence finds no evidence for such mixing. But we’ll have to wait for a full nuclear genome sequence to be sure.

Thanks for the minute, for Scientific American's 60-Second Science, I’m Steve Mirsky.