Is convergent evolution evidence against common descent?

Hi Randman,If we assume that genetic diversity is generated by random mutations, then we can use simple bayesian theory to calculate the probability that two sequences converged without common ancestry. We could compare this probability to the probability that the two sequences are similar because of common ancestry, and see which hypothesis fits the data best. This is done all the time in molecular evolutionary biology, so your point is basically correct. This kind of convergence is often considered "noise" in the data and the level of noise in each DNA sequence will determine which DNA sequence we use in our analysis.I wasn't really sure what you meant by "the impetus of convergent DNA". Do you mean that sequences might mutate in a particular direction, so that they are more likely to end up similar by convergence that we would expect from random mutation alone? If this is the case, we would just have to work out what the rules of the impetus are, and factor them in to our probability calculations. For example we know that transition mutations (A->G, G->A, T->C, C->T) are more common that transversion mutations (G->C, A->T, etc.) because of the molecular structure of the nucleotides. We can use this information to make our probability models of sequence evolution better.Hope this helps,MickThis message has been edited by mick, 06-06-2005 11:23 AM

Hi randman,your mistake is to think that the differences between kangaroos and humans are the SAME differences as those between mice and humans. They aren't. So you can't say estimate the differences between mice and kangaroos based on this data. You can only calculate the distance from humans to the listed animals.In order to get a pairwise distance between mice and kangaroos you would need a matrix of distances rather than a list.Mick

Hi randman, It's actually caused by shoddy statistics. A single gene that is intended to distinguish between humans and bacteria is obviously going to have trouble distinguishing between humans and kangaroos. The DNA signal will be washed out somewhere between the two extremes by noise. I was actually surprised that the tree was so good.Mick

The Haeckel drawings have been discussed in their own thread. While relevent here they are not close enough to the main topic to be a good idea here. Do not respond here. Hey randman, what precisely is the problem you have with haeckel's drawings? They were fudged to make them look more convincing, sure, but the basic principle still applies.Here are some photomicrographs (not fudged!)fish: chick: pig: human: Care to comment on these photomicrographs? Do they give any succour whatsoever to an anti-evolutionist?Mickadded in edit: by the way, you can see these animated here. amazing stuff.This message has been edited by mick, 06-06-2005 07:18 PMThis message has been edited by AdminNosy, 06-06-2005 08:13 PM