Word: dna
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Dates: during 2000-2009
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...change so that it could produce two-legged primates? One part of the answer is that mutations over time altered genes that encode proteins, and some of those changes have been favored by natural selection. But that does not mean that our genome - the sum total of our human DNA - is a finely tuned collection of protein-coding genes. In fact, a lot of mutations that all humans carry neither helped nor harmed our ancestors. They spread just by chance. And a lot of our genome is not made up of protein-coding genes. In fact...
...natural selection in action. They've documented that beaks of finches on the Galápagos Islands have gotten thicker when droughts forced the birds to crack tough seeds to survive. They've observed bacteria develop resistance to drugs that were believed to be invincible. Now biologists are applying DNA-sequencing technology to natural selection, which lets them identify the individual genetic changes that boost reproductive success...
...Darwin's other major claim: that different species share a common ancestry. Over the past 15 years, for example, paleontologists have found several fossils of whales with legs, linking modern whales to their terrestrial ancestors. Besides studying fossils, biologists can discover the genealogy of species by looking at their DNA. The fossil record points to hippos and other hoofed mammals as being the closest living relatives of whales. So does their DNA. Our own DNA contains clues to the bonds we share with the rest of life - it turns out, for instance, that we are closer kin to mushrooms than...
Paleontologists can track some of life's transformations in fossils - observing how fins gradually evolved into feet, for example. But fins and feet and other complex structures are also encoded in DNA, and until the 1980s, biologists had almost no knowledge of the genes that built them. Over the past 25 years, biologists have identified many of the genes that help build embryos. A number of them help lay out the embryo's blueprint by letting cells know where they are. The cells absorb proteins floating around them, and the signals trigger the cells to make other proteins, which...
Darwin had no way of knowing this, since he had no way of examining DNA. If he did, he might well have rethought one of his most potent metaphors for evolution: the tree of life. It's not that the metaphor is wrong. Scientists regularly reconstruct evolutionary branches today. When a new disease breaks out, for example, the fastest way to figure out what to do is to determine what the pathogen is related...