“By Darwinian evolution he [Woese] means evolution as Darwin understood it, based on the competition for survival of noninterbreeding species.”
“With rare exceptions, Darwinian evolution requires established species to become extinct so that new species can replace them.”
Dawkins rightly objects. Those are weird claims: the first is, I think, a misreading of Darwin. Darwin says something very different.
In the survival of favoured individuals and races, during the
constantly-recurrent Struggle for Existence, we see a powerful and
ever-acting form of Selection. The struggle for existence inevitably
follows from the high geometrical ratio of increase which is common,
to all organic beings. This high rate of increase is proved by
calculation,- by the rapid increase of many animals and plants
during succession of peculiar seasons, and when naturalised in new
countries. More individuals are born than can possibly survive. A
grain in the balance may determine which individuals shall live and
which shall die,- which variety or species shall increase in number,
and which shall decrease, or finally become extinct. As the
individuals of the same species come in all respects into the
closest competition with each other, the struggle will generally be
most severe between them; it will be almost equally severe between the
varieties of the same species, and next in severity between the
species of the same genus. On the other hand the struggle will often
be severe between beings remote in the scale of nature. The
slightest advantage in certain individuals, at any age or during any
season, over those with which they come into competition, or better
adaptation in however slight a degree to the surrounding physical
conditions, will, in the long run, turn the balance.
That’s plain: Darwin was saying competition between individuals within a species was most important, but that competition to a lesser degree would occur between higher taxonomic categories. The synthesis narrowed and hardened this position; Dawkins reply represents the view that that there is no species selection (which I would disagree with) and that all the action takes place between individuals. Dawkins is closer to Darwin, and much closer to the modern understanding of Darwinian evolution, than Dyson is. (Whether Darwin or the modern understanding are actually right is a different issue, though.)
The second quote is also a little strange — Dyson has phrased it very poorly, as if Darwin was proposing extinctions first, replacement second. Darwin actually proposed replacement first followed by likely extinction (I have to assume that Dyson merely misspoke, because a literal reading would be far too absurd.) Darwin did place a greater importance on selection than I would, and also phrased extinction as a result of competition between species — something that again, the neo-Darwinian synthesis and Dawkins would not support.
The extinction of old forms
is the almost inevitable consequence of the productions of new
forms. We can understand why, when a species has once disappeared,
it never reappears. Groups of species increase in numbers slowly,
and endure for unequal periods of time; for the process of
modification is necessarily slow, and depends on many complex
contingencies. The dominant species belonging to large and dominant
groups tend to leave many modified descendants, which form new
sub-groups and groups. As these are formed, the species of the less
vigorous groups, from their inferiority inherited from a common
progenitor, tend to become extinct together, and to leave no
modified offspring on the face of the earth. But the utter
extinction of a whole group of species has sometimes been a slow
process, from the survival of a few descendants, lingering in
protected and isolated situations. When a group has once wholly
disappeared, it does not reappear; for the link of generation has
Dawkins’ argument is neo-Darwinian, that predators don’t compete with their prey, for instance, they compete with their fellow predators of the same species to see which is better at catching prey. A more relevant situation, though, is to ask what happens when two predatory species are feeding on the same prey species—we can imagine that whichever one was better at catching the available prey would be better able to survive.
Darwin himself was arguing for one species outcompeting a second species, leading to the extinction of the second, so Dyson was sort of closer to being right…but again, Darwin’s vision was a bit more complicated than species A → species B → species C, with extinction separating each succession cleanly; note that he mentions both branching speciation and that extinction can be very slow and prevented by isolation.
I’d say Dawkins better represented the conventional modern view of evolution than Dyson, and as usual, trying to fall back on support from Darwin is a bad idea, except in a historical argument. Darwin was a smart guy, but he’s so 19th century — his ideas are interesting but out of date.
Dyson’s counter-reply is more effective, even though it really doesn’t address his original assertions and makes some new arguable claims. He claims that species once establish evolve very little; instead, I’d say that evolution is still going on at a good pace, but that selection is acting to conserve phenotypic stasis, and that that process is evolution, too. Dawkins and Dyson could probably have a good fight over punctuated equilibrium, and I might well side more with Dyson, but the subject doesn’t really address Dawkins’ argument in any obvious way.
Dyson says it’s absurd to think that group selection is less important than individual selection; I sympathize and agree that evolutionary theory needs to incorporate more higher level mechanisms, but since group selection is categorically rejected by probably the majority of population geneticists, it’s going to be a tougher sell than just dismissing them. Since Dawkins conceded that “the extinction of species is extremely important in the history of life, and there may very well be non-random aspects of it (some species are more likely to go extinct than others)”, we’re really down to arguing relative importance of these events.
There is a real, legitimate debate on this issue, and Dawkins would be an effective advocate for one pole. Dyson is a brilliant fellow, but I get the impression he’s wandering a bit far from his domain of expertise here — I think I’d rather see a Dawkins-Moran head-butting session on this one.