In which my inner nerd comes out to play

Science alert! If you are utterly disinterested in the world around you, don’t bother to read this post as it will undoubtedly bore you.

I love evolutionary biology and genetics. The intricacies of life never cease to fascinate me, so when I read of studies like this I am so filled with wonder and excitement that I want to share it with everyone. To sum up this link for those of you not inclined to read it themselves (tsk tsk), this experiment, conducted over the course of 20 years, provided supporting evidence to Gould’s hypothesis of evolutionary contingency, in which he puts forth the idea that

…if the tape of life were rewound to the time of the organisms found in the Canadian outcrop known as the Burgess Shale, dated to about 530 million years ago, and replayed with a few contingencies tweaked here and there, humans would most likely never have evolved (source link here).

In other words, Gould suggested that you cannot re-evolve the same end result from the same starting point.

This particular experiment took 12 colonies of identical E. coli bacteria and let them flourish in identical environments for 20 years, or 40,000 generations. Every 500 generations a sample from each of the 12 colonies was frozen, to be thawed out and to resume growth at a later date, for comparison.

At around generation 31,500, something interesting happened. From the article:

After about 31,500 generations, one colony of bacteria evolved the novel ability to use a nutrient that E. coli normally can’t absorb from its environment. Thawed-out samples from after the 20,000-generation mark were much more likely to re-evolve this trait than earlier samples, which suggests that an unnoticed mutation that occurred around the 20,000th generation enabled the microbes to later evolve the nutrient-absorption ability through a second mutation…In the 11 other colonies, this earlier mutation didn’t occur, so the evolution of this novel ability never happened.

“I would argue that this is a direct empirical demonstration of Gould-like contingency in evolution,” Lenski [the lead researcher] says. “You can’t do an exact replay in nature, but we were able to literally put all these populations in virtually identical environments and show that contingency is really what had occurred.”

The next step will be to determine what that earlier mutation was and how it made the later change possible, Lenski says. If the first mutation didn’t offer any survival advantage to the microbes on its own, it would make the case airtight that Gould was right. That’s because a mutation that doesn’t improve an organism’s ability to survive and reproduce can’t be favored by evolution, so whether the microbe happens to have that necessary mutation when the second evolutionary change occurs becomes purely a matter of chance.

“I don’t think they’ve necessarily shown” that the first mutation gave the microbes no survival advantage, comments Christopher Dascher, a microbiologist at Mount Sinai School of Medicine in New York. “But they certainly point very strongly in that direction.”

Lenski notes that the growth rate and the density of bacteria in the colony jumped up after the second mutation, but not after the first one.


This is the statement that gets me excited:
“a mutation that doesn’t improve an organism’s ability to survive and reproduce can’t be favored by evolution, so whether the microbe happens to have that necessary mutation when the second evolutionary change occurs becomes purely a matter of chance.”

I know its completely nerdy and geeky of me, but I find this to be totally awesome. And a definite rejection of the creationist assertion that there is no proof of evolution in science. So to those individuals, I say “take that!”

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21 thoughts on “In which my inner nerd comes out to play

  1. My inner nerd spent all afternoon digging a hole in the front yard, so I’m totally into this after picking up earthworms and such…

    I kinda of like the notion that humanity was happenstance.

  2. Much of evolution seems to be happy (an sometimes not so happy) accidents. Which is intriguing – organisms nvolve becuase they are imperfect and mutate. Doesn’t leave any room for the creationist yahoos.

  3. Chica and Citizen. yes. Exactly!

    I should modify my last line…to the creationists, I say

    “take that and stick it!”

    I cant express how annoyed I am at creatonists.

  4. Take that indeed! HA!

    Of course, creationists will say it doesn’t apply because you’re talking bacteria and not the perfect human god created in a week, or somesuch nonsense.

  5. first, i’m an evolutionary creationist (not sure if that’s a term, but i’m calling myself that). i believe God said, and therefore it was. but i also believe in evolution and that the “seven days” thing was just the story to frame the and share that fact.

    second, you can say “take that” all you want… but just as you’ll never consider or take seriously what i believe, those creationists out there could care less what “take thats” you throw at them.

    just sayin’ 🙂

  6. I agree with Puss: fascinating! Part of me would love to go back to school to be a zoologist. But I get all hung up and chemistry and such. Good post.

  7. I agree with Puss: fascinating! Part of me would love to go back to school to be a zoologist. But I get all hung up and chemistry and such. Good post.

  8. I watched a Discovery channel show that had geneticists activated sleeping dna in chickens just to prove that yes, they did still have the original Dinosaur dna. As in not needed. It was seriously cool how they put it all together with the experiments and low and behold, it was mutating back to prehistoric looks. Super cool stuff. We are nerdy here too. Glad to be in good company!!!

  9. I’m with Kara…although I am intrigued with nature and the inner workings of life, this gets a little too over my head. =\

  10. I’ve always thought of our species as it is now as simply “one of the best expressions of life” in our world.

    It’s interesting to imagine how intelligent creatures of our life form would appear were a couple contingencies tweaked in our past. How interesting it would be to be thrust among such a group, if only the imagination of Madeleine L’Engle could become a reality for me.

  11. Sorry about that Rachel!

    Transcript:

    Ludacris: You see this chain? I recycled it off of some old rims I had.

    Tommy Lee: You call that eco? This tattoo right here? Made outta soy ink.

    Ludacris: That’s nuthin. you know the hotel we stayin at? You remember the hot tub right?

    Tommy Lee: Oh yeah.

    Ludacris: I filled it with all women instead of water. Saved 150 gallons.

    Tommy Lee: Seven days with no shower! 226 gallons. BLAM!

    Ludacris: That’s impressive. (pause) That’s nasty, man. For real.

    Introducing Planet Green, the first all green TV network.

  12. I love genetics, been hooked for years since my 8th grade teacher introduced us to Punnett Squares.

    I find particularly intriguing the fact that a microbe may or may not have a mutation that doesn’t improve its ability to survive and wonder if this applies to at least half of popular culture.

    This is indeed fascinating stuff. Nerds make the world go ’round.

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