jevg wrote:On the matter of speciation it is Lenski himself who brings up this point. And my direct quote from the paper shows this.
It is admirable that the authors showed restraint and did not immediately declare the Cit+ population to be a "distinct" species. But it probably is a new species. Since E. coli reproduces asexually, the two populations are effectively isolated. (Even if they weren't, the Cit+ population is isolated from the other 11 cultures.) Unless the entire Cit+ population reverts back to the Cit- genotype, it is a new species. In other words, we now have two kinds of bacteria that differ in both genotype and phenotype and descended from a common ancestor.
It is also clear that historical contingency is a theory that provides the drive towards speciation. So this experiment is about the mechanism of speciation. After all Darwinian theory is about speciation.
I'm not sure what point you are trying to make here. Historical contingency is a proposed mechanism of Darwinian evolution. The LTEE study supports the hypothesis that historical contingency was important in this particular evolutionary change. It does not, however, establish that historical contingency plays an important role in evolution generally. But even if the importance of historical contingency does become established, that would not falsify Darwinian theory; it would reveal in greater detail how Darwinian evolution works.
Therefore the Darwinian mechanism is not a proven theory and I simply argue that it should not be presented as a fact as it so often is.
I would not use the term "proven." Darwinian theory (or more precisely, neo-Darwinian theory) is one of the most well-confirmed theories in science and thus ought ot be taught in science classes. Evolution, on the other hand, is a fact. Even before Darwin, scientists recognized that organisms change over time. They just didn't know how it occurred.
Just to also clarify we are not talking about 30,000 generations. Please remember that there are 12 populations and the experiment has now proceeded past 50,000 generations for each population. That makes 600,000 generations so far.
My take on these numbers is just the opposite of yours. The first bacteria on Earth that could exploit an abundant energy source would have undergone explosive growth, since there would have been no competitors. Within a short time, the numbers of these bacteria would have dwarfed the number in the LTEE's 12 small cultures. If the LTEE shows evolutionary change in 30,000 or 50,000 generations, I would expect such changes to have occurred much more rapidly in the much larger population that probably existed billions of years ago -- or for that matter in the larger natural populations that exist today.
It is also a mistake to generalize from the mutation rate in the LTEE, because mutation rates vary greatly. My evolution textbook has a table showing various mutation rates per 100,000 cells or gametes. These range from 0.00004 for streptomycin resistence in E. coli to 12 for yellow body in fruit flies and 4.2-14.3 for achondroplasia in humans. (Source: Evolution by Douglas J. Futuyma, 2005, Sinauer Associates, p. 171)