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Re: Dinosaurs to birds
On Sat, 23 Jan 1999 Dinogeorge@aol.com wrote:
> No, speciation occurs randomly.
_Mutations_ occur randomly. Individuals are _selected_ to reproduce. And
often, if not usually, nature selects not at random but on the basis of
rules (I mean this in the same sense that mathematical rules exist). One
such rule might be: grouping together in flocks makes survival more likely
for the individual. There are probably an unlimited number of such
"rules" to be found--in time. Are you arguing that no such rules exist?
> The directionality comes later, the result of
> differential culling through extinction of less well-adapted individuals.
Directionality certainly does not require extinction. Unless you mean
pseudo-extinction. If a population evolves a longer neck in successive
generations, the ancestor population cannot be said to become extinct. At
least this is my understanding.
I may be wrong, but you seem to be arguing for a sort of Hardy-Weinberg
world (no evolution) for long periods punctuated in a highly stochastic
way by extinction punctuations. This has happened to be sure. But I
don't believe that anyone can claim that evolution doesn't occur outside
punctuations, nor that species don't influence their own evolution.
Eldredge's claim that speciation is _only_ in response to physical events
> If there were no random component to speciation, species diversity would be
> less than it is.
It is true that random _mutations_ are the raw material of speciation.
But all mutations are not equal. And they are not selected randomly.
Indeed, there would be none of the orderliness if they were.