Zachriel
Posts: 2723
Joined: Sep. 2006
|
| Quote (dmso74 @ Sep. 15 2009,18:56) | | Quote (Ptaylor @ Sep. 15 2009,18:16) | In the thread about the study showing reptiles' transition from straddled to upright gait PaV once again reminds us that it is not ID's place to match science's pathetic level of detail:
| Quote | Mark Frank:
You’re interested in what I think happened?
I think some act of intelligent design occurred. What do you think happened? You’re the evolutionist, after all. This finding conforms to ID, and refutes Darwinism. Sorry, Mark, but the “ball is in “your side of the court.” You tell me what happened, and how Darwin’s theory explains it.
|
Link. |
PaV's population genetics are a hoot, too:
| Quote | If you have a population size of 100,000, and the population is stable over time, then this would produce 2-3 x 10^12 individuals over a period of 20-30 million years. [I.e., 10^5 'net' offspring would be produced each year]
What would happen in all this time?
This number of offsprings would be enough to (1) produce a “good” mutations[we'll assume the probability to be one in 10^8], and (2) based on the probability of fixation in a population of 1/2N, with N here being 10^5, this would NOT be good enough to bring this ONE mutation to fixation within the population. |
what's missing here? what's that thing called? matural seblection? that wouldn't change the probability of fixation of a beneficial mutation, would it? |
Quite so.
1/2N is the rate of fixation of a single neutral mutation. In a diploid population of size N and a neutral mutation rate of mu, each generation will produce 2Nmu * 1/(2N) = mu new mutations. But for a selection coefficient s, as long as 4Ns is not <<1, then selection may be a predominant factor. Even for weak selection, the relative fixation rate of beneficial vs. neutral mutations > 2s/mu. Taking an example of s=1% and mu=10^-7, the rate of fixation under selection would be many orders of magnitude larger than drift alone.
Another bugaboo is the equivalence drawn between reproductive events and evolutionary potential. A million replications in one generation is not the same as a thousand replications for a thousand generations, even though they have the same number of reproductive events. It's like the difference between a million soldiers each taking one step, and a thousand soldiers each taking a thousand steps. While the former may more carefully reconnoiter the area immediate adjacent to the camp, the latter can explore much farther afield.
Random Walkers
--------------
You never step on the same tard twice—for it's not the same tard and you're not the same person.
|
