I have a friend who is always fanatic about something. Last year it was the evils of Islam. This year it’s Intelligent Design (and, apparently semi-fundie Christianity). He loves to drink beer and debate, and so do I, so I indulge his whims. Besides, he’s a great guy, fanatic beliefs aside.
So, I’ve got him reading “Your Inner Fish” (which I enjoyed immensely) and he has me reading "“The Edge of Evolution” by Michael J. Behe. Behe is making me itch, since it’s clear he’s choosing his data to make his point rather than letting the data lead where it will. I need some assistance, however, finding counter-examples, since I know computers and a bit of music, but nothing about biology.
I’m only into chapter 3, but so far:
He maintains that random mutations are always destructive, never an improvement (he doesn’t define improvement–one of my beefs).
He claims that the numbers don’t support evolution (which he always calls “Darwinian evolution”–another irritation). That there couldn’t be enough mutation over the given time periods to produce the species differentiation that we observe in the modern world.
Can anyone point me to sources that will help me debunk these claims?
Rather then refuting that, ask him to prove it. How does one prove that something random is always destructive? Impossible.
I believe this is refuted quite well in your book, which I read recently, too. In particular, the discussion of how small changes in regulatory genes can lead to big changes in phenotype.
One point to remember and press home is that while individual changes to the genome might be “random” (in the sense of occuring as a statistically distributed error in gene replication), the cumulation of such changes into a new and beneficial phenotype are not. Mutations are either beneficial, harmful, or neutral, in terms of their effect upon the ultimate reproductive success of the carrier; most, in fact, are demonstratably neutral, as much of the genome is not directly involved in coding for expressed phenotypes and structures. What all that extra material does do is an active area of debate and contention among molecular biologists and zoological researchers–some argue that it’s just stuff that is harmlessly carried around, while others have proposed hypotheses with various levels of support that suggest that such spare material provides significant benefit to the carrier, as either a buffer against damage or as part of the unexpressed mechanics of replication. And then the hardcore gene-centrist faction argues that it is actually part of an extended phenotype; that the benefit is to the genes themselves, stochastically hitching a ride with an organism in order to expand their raw numbers and the possibility of wider replication. Anyway, the argument that “random” mutations are always harmful is clearly bunk. As to what constitutes “improvement”, this can only be seen in retrospect; improvement in the selective sense is a phenotype that is “selected for” by environmental pressures.
I don’t understand the second argument at all. Successful mutations are distributed and proliferated per exponential functions in the same way that money that is invested increases via periodic compounding. This isn’t just a hypothetical; you can actually run the experiment on a lab bench, watching a species of photosynthetic bacteria adapt to a new peak wavelength of light that you impose. Not only is the variation in species entirely plausible by the rate of mutation, but in fact what we see today is but one very small fragment of genetic and phenotypic variation in history, which itself is a virtually infinitesmal sliver to total possible variations. As a practical example, look at the domestic canine, which despite being one genetically-compatible species varies from pocket-size to the scale of a small pony, with a vast array of different characteristics; and almost all of this variation (from selective breeding) has occured over the last five thousand years (and for “show” dogs, in no more than a few hundred). Admittedly, this is due to artificial selection (and has resulted in neotenic and otherwise extreme characteristics which would not render the animal successful in nature) but given the even more extreme if nonteleological winnowing effects of life in the wild, it is easy to see that, in fact, small variations in the genome resulting from the diploidal combination of chromosomes can result in dramatic changes in expressed form in just a few generations.
I recommend reading Richard Dawkins’ Climbing Mount Improbable and (with some reservations regarding arguments for excessive gene centricism and extended phenotypes) The Blind Watchmaker. He refutes the claims of Intelligent Design–particuarly arguments of insufficient variation and the inability of “random” variation to explain working and seemingly “designed” biological organisms–quite rigorously.
Take two almost-identical creatures, who differ in some small way genetically. One of these will be slightly more “fit” for its environment. If a random genetic change could explain A changing to B, why couldn’t a random change explain B going to A? It can just as easily go either way. The environment will then put selection pressure towards the one that’s more fit.
Bacteria mutate. Some of them mutate and acquire an “immunity” to antibiotics. That is an “improvement” to the organism that is mutating as it allows it to infect more carriers and to replicate itself. This is not a destructive mutation to anyone but the carriers of the bacteria. The fact that all bacteria (or even all the bacteria of a particular type) haven’t mutated in this way indicates that the mutation is random. Therefore, this disproves the above.
Utter nonsense. It is, in fact, trivial to demonstrate this. Consider the RNA codon table. As seen therein, it is often the case that a given nucleotide slot can vary between 2 or more of the 4 available nucleotides with no adverse effect on the amino acid thus produced. Thus, a mutation in coding for the amino acid Alanine in which the third base is transcribed during replication as G instead of the (for example) original C will not effect the resulting amino acid - it will still be Alanine, and the final protein function will not be altered. Thus, it is incorrect to state that “mutations are always destructive”. An alleged biochemist like Michael Behe ought to be sufficiently aware of how gene transcription works to know that such a statement is without merit.
As noted above, small changes in regulatory genes can have dramatic effects on phenotype. It has been said that evolution happens during development; turn off a gene here, turn on another gene there, and the resulting phenotype can be markedly different. Consider, for example, the differences between a caterpillar and a butterfly. Both are generated from the same genotype; it is the developmental switching on and off of genes within that genotype that produces the marked differences in phenotype.
The fact that small changes can have profound effects means that the time needed for the observed differences between species to occur need not be infinite, or even particularly vast.
What exactly does he call a “non-random” mutation? I don’t think even Behe says that every modification was intelligently designed, so I’m fairly sure that even Behe (when addressing his non-creationist audience) would agree that there are favorable random mutations.
As for your point 2, I beileve Dawkins references mathematical and simulation studies showing the speed of evolution.