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November 27, 2003

Ahistorical evolution

Missed this story, An apparent order to evolution slowly emerges: New evidence seems to show that evolution repeats itself and is not as random as first thought, in The New York Times a few weeks ago (I got this from the Taipei Times). Funny thing, the central crux of the article seems to be showing that the evidence is disproving Stephen Jay Gould's ideas (big surprise!):


Stephen Jay Gould, the late Harvard paleontologist, crystallized the question in his book Wonderful Life. What would happen, he asked, if the tape of the history of life were rewound and replayed? For many, including Gould, the answer was clear. He wrote that "any replay of the tape would lead evolution down a pathway radically different from the road actually taken."

OK, what does the science say?


...In 1988, Lenski and his colleagues set up a dozen genetically identical populations of E. coli bacteria in bottles of broth and have followed their evolutionary fates.

Now, more than 30,000 bacterial generations later, Lenski and colleagues have what is becoming one of the most striking examples of repeatability yet. All 12 populations show the same patterns of improvement in their ability to compete in a bottle and increases in cell size. All 12 have also lost their ability to break down and use a sugar, called ribose.

You can go to Richard Lenski's website to get more information on this topic. Of course, a standard Creationist response would be that this is "microevolution." But you don't have to look at bacterial studies to see that Gould was exaggerating.

Here is an image of the extinct Tasmanian Tiger



Here is an image of the "Dingo" that replaced them on the Australian continent:


My point is not that evolution can't take another path from the ones that we know, after all, the kangaroo doesn't quite look like herbivores on other continents[1], but common physical motifs reappear many times in any survey of the history of macroevolution. Gould knew this, he was a paleontologist, but he chose to give the masses a different impression by shading the emphasis in another direction.

In any case, nice to see evolutionary biology being presented as a science where people actually do experiments in a lab, rather than just a montage of artists sketches of reconstructions of extinct creatures that we only know from fossils (of course, also a fan of theoretical evolutionary biology that uses some maths)....

fn1. Note the similarity in appearence of the Icthyosaur, bottle nosed dolphin and swordfish, obviously these were creatures of various phylogenetic origins who were constrained by functional necessity into a certain body plan. In contrast, there has been no reprisal of the Plesiosaur body plan. Perhaps its particular niche disappeared? Well, there is some evidence that ammonites were the main food of this creature. Ammonites were very large cephalopods, bigger cousins of the nautilus, and, they became extinct during the late Cretaceous (concurrent with most big animals like the dinosaurs, flying and marine reptiles). That string of conjectures and suppositions took me 5 minutes, a combination of logical thinking, google and a few basic facts regarding how evolution works. I am probably wrong on the details, but it seems a much more frutifull way to go than encapsulating the idea that "evolution is random and without constraint" in flowery literary prose....

Posted by razib at 02:10 AM