Here's a story from the New York Times about evolution taking place in the lab.
In the corner of a laboratory at Michigan State University, one of the longest-running experiments in evolution is quietly unfolding. A dozen flasks of sugary broth swirl on a gently rocking table. Each is home to hundreds of millions of Escherichia coli, the common gut microbe. These 12 lines of bacteria have been reproducing since 1989, when the biologist Richard E. Lenski bred them from a single E. coli. “I originally thought it might go a couple thousand generations, but it’s kept going and stayed interesting,” Dr. Lenski said. He is up to 40,000 generations now, and counting.
In that time, the bacteria have changed significantly. For one thing, they are bigger — twice as big on average as their common ancestor. They are also far better at reproducing in these flasks, dividing 70 percent faster than their ancestor. These changes have emerged through spontaneous mutations and natural selection, and Dr. Lenski and his colleagues have been able to watch them unfold.
Now 40,000 generations is a lot. It took 18 years to get that many generations in bacteria, which are notorious for reproducing quickly. In human terms, allowing 18 years on average, that's 720,000 years.
In that time, the magnitude of the change would be equivalent to humans growing to a height of 12 feet, and coming into puberty at age 4. This is in addition to other changes that have been observed.
And other scientists are now doing the same sort of research:
Other scientists are watching individual microbes evolve into entire ecosystems. Paul Rainey, a biologist at the New Zealand Institute for Advanced Study at Massey University, has observed this evolution in bacteria, called Pseudomonas fluorescens, that live on plants. When he put a single Pseudomonas in a flask, it produced descendants that floated in the broth, feeding on nutrients. But within a few hundred generations, some of its descendants mutated and took up new ways of life. One strain began to form fuzzy carpets on the bottom of the flask. Another formed a mat of cellulose, where it could take in oxygen from above and food from below.
But Dr. Rainey is only beginning to decipher the complexity that evolves in his flasks. The different types of Pseudomonas interact with one another in intricate ways. The bottom-growers somehow kill off most of the ancestral free-floating microbes. But they in turn are wiped out by the mat-builders, which cut off oxygen to the rest of the flask. In time, however, cheaters appear in the mat. They do not produce their own cellulose, instead depending on other bacteria to hold them up. Eventually the mat collapses. The other types of Pseudomonas recover, and the cycle begins again, with hundreds of other forms appearing over time. “The interactions are everything you’d expect in a rain forest,” Dr. Rainey said.
All of a sudden, the ecosystem seen in The Ringworld Engineers isn't so far-fetched.
Also, see Richard Lenski's web page.
Gregory J. Velicer, a former student of Dr. Lenski’s who is now an associate professor at Indiana University. Dr. Velicer experienced this bafflement firsthand while watching the evolution of a predatory microbe called Myxococcus xanthus. Myxococcus swarms lash their tails together and hunt in a pack, releasing enzymes to kill their prey and feasting on the remains. If the bacteria starve, they come together to form a mound of spores. It is a cooperative effort. Only a few percent of the bacteria end up forming spores, while the rest face almost certain death.
This social behavior costs Myxococcus energy that it could otherwise use to grow, Dr. Velicer discovered. He and his colleagues allowed the bacteria to evolve for 1,000 generations in a rich broth. Most of the lines of bacteria lost the ability to swarm or form spores, or both.
Dr. Velicer discovered that some of the newly evolved bacteria were not just asocial — they were positively antisocial. These mutant cheaters could no longer make mounds of spores on their own. But if they were mixed with ordinary Myxococcus, they could make spores. In fact, they were 10 times as likely to form a spore as normal microbes.
Dr. Velicer set up a new experiment in which the bacteria alternated between a rich broth and a dish with no food. Over the generations, the cheaters became more common because of their advantage at making spores. But if the cheaters became too common, the entire population died out, because there were not enough ordinary Myxococcus left to make the spore mounds in the times of famine.
During this experiment, one of Dr. Velicer’s colleagues, Francesca Fiegna of the Max Planck Institute for Developmental Biology, discovered something strange. She had just transferred a population of cheaters to a dish, expecting them to die out. But the cheaters were making seven times as many spores as their normal ancestors. “It just made no sense,” Dr. Velicer said. “I asked her I don’t know how many times, ‘Are you sure you marked the plates correctly?’ ”
She had. It turned out that a single Myxococcus cheater had mutated into a cooperator. In fact, it had evolved into a cooperator far superior to its cooperative ancestors. Dr. Velicer and his colleagues sequenced the genome of the new cooperator and discovered a single mutation. The new mutation did not simply reverse the mutation that had originally turned the microbe’s ancestors into cheaters. Instead, it struck a new part of the genome.
But Dr. Velicer has no idea at the moment how the mutation brought about the remarkable transformation in behavior. The mutated segment of DNA actually lies near, but not inside, a gene. It is possible that proteins latch on to this region and switch the nearby gene on or off. But no one actually knows what the gene normally does.
Thanks to Clayton Cramer for the pointer.
There are some ironic points, though, in his post.
Intelligent design advocates, for example, and even many Creationists, do not dispute what they call "microevolution," which involves relatively minor changes. Heck, we've been breeding dogs and horses long enough to create distinctive breeds; only a very unimaginative person would deny the possibility that, with enough time, you might get a distinct species.
I fear we have very different definitions of "minor".
Those last two, where a single strain of bacteria is mutating to form entire ecosystems, is hardly "minor".