I will comment on these later, but first, I just want to take a look at Crevo's blog post regarding this paper.
These two sentences:
For instance, the basic cost is the cost of replacement. In order for the next generation to have the same population as the current one, the minimum cost is for each member of the previous generation to have exactly one offspring.
demonstrate nicely why this whole issue is a non-issue. The sentences again, with emphasis:
For instance, the basic cost is the cost of replacement. In order for the next generation to have the same population as the current one, the minimum cost is for each member of the previous generation to have exactly one offspring.
Why would the next generation have to have the 'same population' (i.e., same population size) as the previous? Is this a requirement of evolution?
Answer: There is no reason that subsequent populations need to have the same nubers as the previous. And there is no such requirement in evolution.
Haldane's original formulations, which are the basis for ReMine's "one big thing", utilized the concept of a constant population size, primarily for mathematical purposes. In real life, population sizes fluctuate, and are not set at some predetermined optimum. They can grow and shrink as warranted by any number of external (or internal) influences, such as food supply, predator/prey relationships, etc. (all of which ReMine purposefully* and conveniently ignores in his paper), and essentially by definition, after a speciation event, a population will almost certainly get larger. Yet this growth will only incur a "cost" if, and only if, getting back to some predetermined population size is a goal.
Crevo goes on:
In this model, substitution to fixity can occur in a single generatiton, provided all of the original-type members die off in one she-bang. But that leaves a new problem -- the population size is now very small, so the chances of a beneficial mutation occurring are much, much less.
Interesting. As written, it comes across as though all critters lacking the beneficial allele are suddenly struck down. Could not the non-beneficial allele possessers die off gradually? And why would the occurrance of a new beneficial allele be relevant at all?
Well, it wouldn't, but creationists like to toss in as many 'anti-evolution' buzzwords as they can.
For example, let's say that you have a population of a million. One of them comes in with a novel mutation. Let's consider a scenario. Let's say that all of the original population dies off, and only a few organisms remain, one of which is the one carrying the novel trait. That trait can reach fixity very quickly. However, it is now a million times less likely for a given new novel trait to emerge (beneficial or otherwise). Therefore, while this particular trait was able to come to fixity quickly, it slows down the ability for another novel trait to enter the population. If on the other hand you keep most of your original-type, you have a better chance of getting new traits, but it requires a much larger cost to achieve fixity.
Non-sequitur upon red herring. Why the impetus for a "new novel trait"? Besides the double positive ('novel' means 'new'), what is the relevance? There is none. If there were a reason that most of a million-member population died off leaving only those with an allele that allows them to survive, those survivors HAVE the 'new novel trait' that allowed them to survive and reproduce, making them the most fit individuals. ANY offspring they have will add to the population. Is that a 'cost'? Or is 'cost', as used here, just a buzzword with a negative connotation?
Further, there seems to be an unwritten assumption in Crevo's essay that a particular number, or at least a particular rate, of 'new novel traits' must be produced if evolution is to be accepted. I see no reason whatsoever that such a tenet be inferred, much less required, of evolution. As best I can tell, evolution is not predicated on some particular rate of 'new novel trait' production, or beneficial mutation production. These are just confabulations.
I will be discussing ReMine's paper in a subsequent posting.
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*From the abstract, emphases mine:
"Many factors that traditionally caused confusion are identified and dismissed, including genetic death, genetic load, the environment, and extinction, which are not essential to the cost of substitution."
He does, however, discuss population size fluctuation, but 'dismisses' it.
Such things can impact population dynamics, so "dismissing" them is at the very least curious, since population size can certainly affect the rates of 'replacement' on the way to reaching that 'goal' of maintaining the population size as required in ReMine's model.
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