Recently, biologist Richard Lenski of Michigan State University discovered that one of the populations of E. coli bacteria which he has been cultivating for 20 years developed a rare and unexpected new trait. His 12 populations have been reproducing for more than 44,000 generations now and every 500 generations, he saves a sample so he can "replay" their development to see what happened.
But sometime around the 31,500th generation, something dramatic happened in just one of the populations – the bacteria suddenly acquired the ability to metabolise citrate, a second nutrient in their culture medium that E. coli normally cannot use. Indeed, the inability to use citrate is one of the traits by which bacteriologists distinguish E. coli from other species. The citrate-using mutants increased in population size and diversity.
"It's the most profound change we have seen during the experiment. This was clearly something quite different for them, and it's outside what was normally considered the bounds of E. coli as a species, which makes it especially interesting," says Lenski. ...
Lenski's experiment is also yet another poke in the eye for anti-evolutionists, notes Jerry Coyne, an evolutionary biologist at the University of Chicago. "The thing I like most is it says you can get these complex traits evolving by a combination of unlikely events," he says. "That's just what creationists say can't happen."
Source: New Scientist
Previously, most of the evolutionary developments had been relatively minor and predictable — like evolving larger cells and faster growth rates. The evolution of the ability to metabolize citrate, however, wouldn't have been predicted because it's so unusual. It's just such improbable developments, though, which Evolution Deniers insist aren't possible through a completely natural, materialistic process. What can they argue here, though? Can they really argue that their god decided to intervene and alter the genetics of one population in one biologist's laboratory experiment? That strikes me as even more improbable.
In addition to demonstrating that new traits can evolve naturally, this also demonstrates just how contingent evolution can be:
...the experiment stands as proof that evolution does not always lead to the best possible outcome. Instead, a chance event can sometimes open evolutionary doors for one population that remain forever closed to other populations with different histories.
Evolving the ability to metabolize citrate is arguably a nice improvement because it allows the E. coli to take advantage of even more nutrition, but it only happened in one of twelve populations. If it's so advantageous, why didn't more evolve this ability by now? The answer is because the best advantages and the best solutions to environmental problems don't always evolve. These twelve populations are like twelve sets of the same population run twelve different times, and in only one of them did this important benefit develop. In the history of life on our planet, there are many missed opportunities and many evolutionary developments which might not have otherwise happened — if you rewind the tape of life and play it again, natural history might turn out radically different for no apparent reasons.