I bought a copy of BBC's 'Knowledge
' magazine the last time I made it to a big bookstore, and I've been carrying it around in my purse and reading it at lunch breaks and the doctor's office and that sort of thing. This magazine is seriously awesome. Like a less tongue in cheek Mental Floss.
The April issue highlights Darwin and Evolution and has a seriously excellent article called "Evolution in Action" about Richard Lenski's experiments with E. Coli bacteria, which he's been working on since 1988. He teaches at Michigan State! How did I not know about him then so I could fangirl him!?
There's a lot of information at the wikipedia article.
But in short, Lenski started with 12 identical lines of E.Coli bacteria in their own petri dishes. He set about starving the bacteria by giving them very minimal amounts of glucose. To quote the article, "Lenski wanted to see if the bacteria would be altered by natural selection. In each generation, some of the bacteria would mutate. A few of those mutations might make them grow and reproduce faster in their flask and they'd out-compete the other bacteria. Over time, natural selection might transform the bacteria in measurable ways...If evolution was at all repeatable, he hoped to get similar results in many of them."
Every day he takes some of the bacteria and freezes it, creating a fossil record. Any changes can be checked by thawing a previous generation of bacteria out and examining them.
After 5000 generations of bacteria all 12 lines grew faster and were about twice the size of their 'ancestors.' And more and more changes occurred. The same genes mutated in most lines, but not the same way. So while more than one line evolved to use the glucose more efficiently, when they had to feed on maltose instead some lines adapted well, and others starved. By 2001 one of the lines had developed the ability to eat citrate, and the population in the dish exploded.
The whole experiment is just incredibly exciting...and so well planned, researched and maintained.