33,000 generations

This is an interesting piece on evolution research by Michigan State University.

EAST LANSING, Mich. — A team of researchers at Michigan State University has documented the step-by-step process in which organisms evolve new functions.

The results, published in the current issue of Nature, are revealed through an in-depth, genomics-based analysis that decodes how E. coli bacteria figured out how to supplement a traditional diet of glucose with an extra course of citrate.

The researchers are working on cultures of E Coli bacteria, which grow rapidly in a glucose medium so that thousands of generations of bacteria can be studied over a matter of a few decades.

Lenski’s long-term experiment, cultivating cultures of fast-growing E. coli, was launched in 1988 and has allowed him and his teammates to study more than more than 56,000 generations of bacterial evolution.

56,000 generations turns out to be more than enough for significant changes to evolve in the E Coli organism given the right environmental pressures. In this case, the pressure was the replacement of glucose, which the organism easily metabolizes, with citrate which it can't metabolize.

The experiment demonstrates natural selection at work. And because samples are frozen and available for later study, when something new emerges scientists can go back to earlier generations to look for the steps that happened along the way.

“We first saw the citrate-using bacteria around 33,000 generations,” Lenski explained. “But Zack was able to show that some of the important mutations had already occurred before then by replaying evolution from different intermediate stages. He showed you could re-evolve the citrate-eaters, but only after some of the other pieces of the puzzle were in place.”

I suppose in human terms, 33,000 generations would be well over half a million years. Not that we can scale up findings like this - it just gives a certain perspective to the thing. Leads one to wonder how long humans could take to evolve a stronger dose of common sense.  

I'm also reminded of something my mate KF told me a few months ago, about the reason coal formed during Carboniferous. As this piece says, coal was formed because there were no fungi capable of breaking down the lignin in wood. Once a fungus evolved with this capability, further coal formation was impossible because fallen trees would rot away due to the action of the fungus.

Presumably, before that fungus evolved, everywhere was chock full of dead trees which wouldn't rot properly, which is why we have so much coal.