Science Magazine: Evolution in Action (2005)

Breakthrough of the Year Equipped with genome data and field observations of organisms from microbes to mammals, biologists made huge strides toward understanding the mechanisms by which living creatures evolve Evolution in Action The big breakthrough, of course, was the basic facts of evolution. With all this in of noncoding material is either inserted or one Charles Darwin made a century and a mind, Science has decided to put Darwin in deleted in the chimp as compared to the half ago. By recognizing how natural selec- the spotlight by saluting several dramatic human, bringing the total difference in DNA tion shapes the diversity of life, he trans- discoveries, each of which reveals the laws between our two species to about 4%. formed how biologists view the world. But of evolution in action. Somewhere in this catalog of difference like all pivotal discoveries, Darwin’s was a lies the genetic blueprint for the traits that beginning. In the years since the 1859 publi- All in the family make us human: sparse body hair, upright cation of The Origin of Species, thousands One of the most dramatic results came in gait, the big and creative brain. We’re a long of researchers have September, when an international team pub- way from pinpointing the genetic underpin- BREAKTHROUGH sketched life’s transi- lished the genome of our closest relative, the nings of such traits, but researchers are ONLINE tions and explored chimpanzee. With the human genome already zeroing in on a few genes that may For an expanded aspects of evolution already in hand, researchers could begin to affect brain and behavior. This year, several version of this section, Darwin never knew. line up chimp and human DNA and examine, groups published evidence that natural selec- with references Today evolution is one by one, the 40 million evolutionary tion has recently favored a handful of uniquely and links, see the foundation of all events that separate them from us. human genes expressed in the brain, including www.sciencemag.org/ biology, so basic and The genome data confirm our close kin- those for endorphins and a sialic acid receptor, sciext/btoy2005 all-pervasive that sci- ship with chimps: We differ by only about and genes involved in microcephaly. entists sometimes 1% in the nucleotide bases that can be The hunt for human genes favored by take its importance for granted. At some level aligned between our two species, and the natural selection will be sped by newly pub- every discovery in biology and medicine rests average protein differs by less than two lished databases from both private and public on it, in much the same way that all terrestrial amino acids. But a surprisingly large chunk teams, which catalog the genetic variability vertebrates can trace their ancestry back to among living people. For example, the first bold fishes to explore land. Each this year an international team year, researchers worldwide discover enough cataloged and arranged more than extraordinary findings tied to evolutionary a million single-nucleotide poly- thinking to fill a book many times as thick as morphisms from four populations all of Darwin’s works put together. This year’s into the human haplotype map, or volume might start with a proposed HapMap. These genetic variations rearrangement of the microbes at the base of are the raw material of evolution the tree of life and end with the discovery of and will help reveal recent human 190-million-year-old dinosaur embryos. evolutionary history. Amid this outpouring of results, 2005 stands out as a banner year for uncovering Probing how species split the intricacies of how evolution actually pro- 2005 was also a standout year for ceeds. Concrete genome data allowed researchers studying the emer- researchers to start pinning down the molec- gence of new species, or specia- ular modifications that drive evolutionary tion. A new species can form RESEARCH CENTER PRIMATE ;YERKES NATIONAL (CHIMPANZEE) change in organisms from viruses to pri- when populations of an existing mates. Painstaking field observations shed species begin to adapt in different SCIENCE new light on how populations diverge to ways and eventually stop inter- form new species—the mystery of mysteries breeding. It’s easy to see how that that baffled Darwin himself. Ironically, also can happen when populations this year some segments of American soci- Chimp champ. Clint, the chimpanzee whose genome wind up on opposite sides of ety fought to dilute the teaching of even the sequence researchers published this year. oceans or mountain ranges, for CREDITS: (DNA) C. BICKEL/ 1878 23 DECEMBER 2005 VOL 310 SCIENCE www.sciencemag.org Published by AAAS B REAKTHROUGH OF THE YEAR example. But sometimes a single, lake to lake. Instead, they found that each species will help pin contiguous population splits into two. group of stranded sticklebacks had lost its down the genetic aspects Evolutionary theory predicts that this armor by the same mechanism: a rare DNA of many such diseases. As for the splitting begins when some individuals in a defect affecting a signaling molecule HapMap, its aims are explicitly population stop mating with others, but involved in the development of dermal bones biomedical: to speed the search for empirical evidence has been scanty. and teeth. That single preexisting variant— genes involved in complex diseases This year field biologists rare in the open ocean—allowed the fish such as diabetes. Researchers have recorded compelling examples to adapt rapidly to a new environment. already used it to home in on a gene for age- of that process, some of which Biologists have often focused on related macular degeneration. featured surprisingly rapid coding genes and protein changes, but And in 2005, researchers stepped up to evolution in organisms’ shape more evidence of the importance of help defend against one of the world’s most and behavior. DNA outside genes came in 2005. A urgent biomedical threats: avian influenza. For example, birds called study of two species of fruit flies found In October, molecular biologists used tissue European blackcaps sharing breed- that 40% to 70% of noncoding from a body that had been frozen in the ing grounds in southern Germany and DNA evolves more slowly Alaskan permafrost for almost a century to Austria are going their own ways—literally than the genes them- sequence the three unknown genes from the and figuratively. Sightings over the selves. That implies that 1918 flu virus—the cause of the epidemic decades have shown that ever more of these regions are so that killed 20 million to 50 million people. these warblers migrate to northerly important for the Most deadly flu strains emerge when an ani- grounds in the winter rather than heading organism that their mal virus combines with an existing human south. Isotopic data revealed that northerly DNA sequences are virus. After studying the genetic data, how- migrants reach the common breeding ground maintained by positive ever, virologists concluded that the 1918 virus earlier and mate with one another selection. These noncoding started out as a pure avian strain. A handful before southerly migrants bases, which include regulatory of mutations had enabled it to easily infect arrive. This difference in regions, were static within a species human hosts. The possible evolution of such timing may one day drive but varied between the two species, an infectious ability in the bird flu now wing- the two populations to suggesting that noncoding regions ing its way around the world is why officials become two species. can be key to speciation. worry about a pandemic today. Two races of Euro- That conclusion was bolstered by A second group reconstructed the com- pean corn borers sharing several other studies this year. One plete 1918 virus based on the genome the same field may also experimental paper examined a gene sequence information and studied its behavior. be splitting up. The cater- called yellow, which causes a dark, They found that the 1918 strain had lost its pillars have come to prefer likely sexually attractive, spot in dependence on trypsin, an enzyme that viruses different plants as they grow— one fruit fly species. A sepa- typically borrow from their hosts as they infect one sticks to corn, and the other eats hops rate species has the same cells. Instead, the 1918 strain depended on an ); BLACKCAP) BRIGHT (EUROPEAN ANDY and mugwort—and they emit different yellow gene but no in-house enzyme. As a result, the recon- pheromones, ensuring that they spot. Researchers structed bug was able to reach exceptionally attract only their own kind. swapped the non- high concentrations in the lung tissue of mice DROSOPHILA Biologists have also predicted coding, regulatory tested, helping explain its virulence in humans. that these kinds of behavioral traits region of the spot- The finding could point to new ways to prevent may keep incipient species separate ted species’ yellow similar deadly infections in the future. even when geographically isolated gene into the other Darwin focused on the existence of evolu- populations somehow wind up back in species and pro- tion by natural selection; the mechanisms that the same place. Again, examples have duced dark spots, per- drive the process were a complete mystery to been few. But this year, researchers found haps retracing the evolu- him. But today his intellectual descendants that simple differences in male wing color, tionary events that sepa- include all the biologists—whether they study plus rapid changes in the numbers of chromo- rated the two. Such a genetic morphology, behavior, or genetics—whose somes, were enough to maintain separate iden- experiment might have astonished and research is helping reveal how evolution works. tities in reunited species of butterflies, and that delighted Darwin, who lamented in The Origin –ELIZABETH CULOTTA AND ELIZABETH PENNISI Hawaiian crickets needed only unique songs to that “The laws governing inheritance are quite , 6050 (2004) (STICKLEBACK);ARNOLD ( SCHARF/PETER DAVID stay separate.

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