Zachriel
Posts: 2723 Joined: Sep. 2006
|
Quote (Utunumsint @ Jan. 28 2010,11:14) | Quote (Zachriel @ Jan. 28 2010,10:10) | Behe's argument is that evolution can't go beyond a certain point, the Edge of Evolution. That means only one or two mutations. He claims that Lenski's Experiment supports this because it took a long time for trillions of bacteria to discover this pathway, and many lines didn't discover it at all. (It's funny when they talk about trillions as a lot when it comes to bacteria.) |
So anything that requires more than one or two mutations, e.g. three at a time, is beyong the reach of evolution, according to Behe. |
That's Behe's confusion. The odds of mutations are fairly well known. Multiple rare events are rare, of course. But if each successive mutation confers a benefit, then it will become fixed in the population much faster than chance. Quote (Utunumsint @ Jan. 28 2010,11:14) | Quote | In Lenski's Experiment, there was a potentiating mutation that was probably neutral, so it wasn't selected. It became dominant in the population by chance. This sets up the second mutation which is selectable in a citrate-rich environment. Theoretically, this is non-controversial. Fixation has been part of population genetics for generations. What is interesting is actually observing it. Without actual observation, it isn't possible to know how often such events occur. | So they knew that such mutations could happen, but they didn't know how rare they would be. It, therefore takes trillions of e-coli to produce one such mutation. Of course, as one critique observed, there are 10 to the power of 16 e-coli in one ton of dirt. So such mutation, given this large population size, should be common....??? |
Sorry. That wasn't clearly expressed. Mutations rates are well-established. The rate a neutral mutation will fix is a matter of analysis. What isn't known is how often a neutral mutation will potentiate a beneficial mutation. And therefore, whether evolution is primarily contingent on happenstance or adaptation. In this case, it appears happenstance was important because the other lineages never discovered the adaptation. Generally, it seems there is more neutral evolution on the molecular level than with macroscopic structures, but even that is not known with certainty.
Quote (Utunumsint @ Jan. 28 2010,11:14) | But was it Behe's argument that the citrate utilizing capacity was not possible without the two mutiations? Therefore there is a whole class of functional developments that are not reachable by incrementatal adaptation? |
That was the result. It took two mutations, the first of which was neutral and fixed by chance. His argument then is that this is the most evolution could accomplish. Of course, if a third mutation comes along that improves the mechanism, then there is no reason it can't be selected and fixed in the population. Or a fourth. Then a potentiating mutation, then a selectable one. As long as there is a selectable pathway, there is no Edge of Evolution.
By the way, there is no doubt that there are whole classes of functional developments beyond the reach of incremental adaptation. The vast majority of genomic sequences will never be searched by evolution.
--------------
You never step on the same tard twice—for it's not the same tard and you're not the same person.
|