New experiments push evolution in ways Darwin never expected
Column: Advances in DNA research enhance basic concepts of evolution.
Carl de Souza/AFP
As scientists celebrate Charles Darwin’s 200th birthday this month, it’s worth considering what Darwin did not know. He hadn’t a clue about genetics or DNA. That knowledge has extended Darwin’s evolution research to include the fundamental information that underlies our planet’s organic life. He also knew nothing of combinatorial chemistry in which robots carry out thousands of simultaneous experiments. This modern technique has enabled scientists to explore the formation and evolution of the first living cells.
David Deamer at the University of California in Santa Cruz is one of those scientists. At the annual meeting of the American Association for the Advancement of Science (AAAS) that ended Monday in Chicago, he explained why he thinks the origin of life on Earth is the result of combinatorial chemistry – millions of simultaneous “experiments” operating on a global scale. He described how his laboratory mimics that era in an array of thousands of individual compartments in which different molecule mixtures undergo reactions. He noted that critics doubt that the right molecules would randomly come together to jump-start life. But, he added, the possibility that combinatorial chemistry provided millions of opportunities for this to happen on primitive Earth “gives us a better way to think about the probability of life emerging from this process.”
While Darwin knew nothing of DNA, modern geneticists readily admit that they have a lot to learn, too. Research published in the journal Nature on Feb. 12 (Darwin’s birthday) illustrates this point. Evan Eichler at the University of Washington in Seattle and colleagues have taken a fresh look at genetic changes that shaped the emergence of humans and modern apes from their common ancestors 8 to 12 million years ago. It turns out that change due to mutations in individual genes, which drives much evolution, had slowed down. Instead, those ancient ancestors were undergoing a burst of duplication of whole swatches of their genomes. This resulted in mix and match rearrangements of DNA that led to significant structural changes in the animals themselves.
This research gives a new perspective on the question of why humans differ strikingly from close ape relatives with whom they share so much of the same genome. The difference at the level of genetic information now appears to lie in the mix and match rearrangements of genetic duplication. The researchers say they discovered “striking examples of gene-containing duplications within the gorilla and chimpanzee that are absent in the human lineage.”
Meanwhile, Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany shared the latest results from Neanderthal DNA research at the AAAS meeting. Neanderthals appeared about 300,000 years ago. Yet their DNA shows common roots with humans reaching back at least 880,000 years. Also Neanderthals and humans share a gene called FOXP2 that is related to speech, suggesting that Neanderthals may have been able to speak. Other genetic differences suggest that humans and Neanderthals did not interbreed.
Darwin’s concept of evolution through natural selection of inheritable changes is the overarching theme of biology today. Yet modern researchers, who know so much more than Darwin did about the history and mechanism of those changes, have only begun to explore the theme’s full implications.