29 December 2010 pm

I just got back from a fun early evening with my running buddy Tracy. I am enjoying the Baylor-Illinois football game; for now. Illinois is up 24-7 toward the end of the third quarter and the defense is playing well.

Jerry Coyne talks about a new mathematical model for evolution. Roughly speaking: the new model talks about evolution occurring “in parallel” rather than sequentially:

If you want to change 20,000 genes, for example, with only 1/40 of all segregating mutational variants being advantageous, then it would take 1034,040 “trials” (roughly the time it takes for a new adaptive mutation to become fixed) to effect this change. This could never occur, since even with an organism having 100 generations per year and with a “trial” equivalent to one generation, this would take a number of years equal to 10 followed by 34,038 zeroes. (Since life began there’s only been about 3 followed by nine zeroes years.) That’s not long enough!

As you’ve probably already guessed, evolution doesn’t work this way. As evolutionary change is occurring at one gene, it’s simultaneously occurring at other genes, affecting other traits, if there are adaptive mutations in the populations for those traits too. A “trial” doesn’t involve producing variants at every gene, with evolution occurring only if all of the genes have adaptive variants. Rather, in each trial the new adaptive mutations arise and begin their march toward fixation in some genes, leaving the rest to change during subsequent trials. In other words, evolution occurs in parallel rather than in series.

I’ll borrow one of his analogies (used in the New Republic article The Great Mutator). The ID-Creationist scheme has it this way: suppose you need 20 genes to change to effect a beneficial mutation and that the probabilities are independent and are, say, 1/6 (like rolling a 1 on a die). The probability of getting this in one change would be (1/6)^{20} and the expected time for this to happen would be 6^{20} generations. On the other hand, if we just need all 20 to eventually change and the changes can occur 1 gene at a time (e.g., one beneficial change in the first trial; maybe one in a subsequent trail) we then need the time for the 20′th change to occur. That is, you start, get a 1 in one slot; keep that, keep rolling, then perhaps get another 1/6, keep going until you have 20 slots with 1′s. The expected number of runs is r(q/p) which is 20 (5/6)/(1/6) which is 100; far less than the previous example.

Biology Colds annoy us. Our bodies react to these viruses and cause us misery. But elimination of the cold viruses might well cause other problems.

Human evolution The Neanderthals ate cooked vegetables! Evidently they were more evolved than I am. (I know…that is a low bar).

A new record for a solar powered aircraft has been set.

Climate Change

Rep. Bachmann is either a liar or an idiot.

Atheism: some atheists try so hard to be liked; in fact they try so hard that they say stupid things. Evidently, this person doesn’t get it. It is more about “I reject this due to a lack of evidence” rather than “I know that no “whatever” of any kind exists.” PZ Myers has some fun with her.

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December 30, 2010 - Posted by | atheism, environment, evolution, Friends, mathematics, science, statistics, superstition

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