Evolutionary Biology: The History of Life
When Charles Darwin published The Origin of Species in 1859, biology had a new lens through which to look at the world. Researchers soon set about to test his theory of evolution. They scrutinized species' adaptation, studied the phenotypes (physical makeup) of organisms and, when technology permitted, studied the genotypes (genetic makeup) of the same organisms.
After more than a century of close examination, the fact of evolution is not in dispute. "It's the tempo and mode of evolution that are being studied," says NSF Population Biology Program Director Mark Courtney. Understanding how evolution works may become increasingly important as humans continue to discover methods that bypass natural selection, such as the genetic alteration of crops and cloning. For evolutionary biologists, the real excitement is learning how individual species -- including humans -- evolve as environmental conditions on Earth change.
In its most elementary definition, biological evolution means changes in heritable traits within populations of organisms across generations. The result is not necessarily inherently better organisms, but rather organisms that are more likely to be adapted to the prevailing set of environmental conditions. Organisms with traits suited to the environment are more likely to survive and reproduce, thus increasing the probability of transmitting their genes to the next generation.
Within the millions of groups of organisms -- animals, plants, bacteria, etc. -- there are many ways of adapting to the environment and thus increasing the chances of passing on genes. One of the things scientists don't understand yet, says evolutionary biologist Douglas Futuyma, is the limit to adaptation.
Futuyma, of the State University of New York at Stony Brook, studies beetles and their host plants. He moves the insects off the host plants and gives them a new species of plant to call home. The beetles either adapt to the new environment or die. What he really wants to know, he says, is "do they have the potential to adapt to any plants, or only one kind?" Some of the beetles can move with little stress. Others are such specialists that they die. "The ragweed-feeding species will not take more than one or two bites out of goldenrod," he says, even when goldenrod is the only food available. Futuyma's findings have important implications for agriculture. "If we understood what the criteria are that allow adaptation, we could predict how much damage insects will do to new crops and potentially advise what kind of new crops will be appropriate."