Race to speciation:
I recently posted an open letter to Susan Watts about scientific journalism.  She replied promptly with polite interest.  I offered to set up a chat.  She is in England, which is a few hours different in time of day from us, but I am an old doctor and taking call is something I have done a lot of.  Tell me what night to expect to be awakened and I shall be prepared effortlessly. 

As you must know, each time I consult another expert I tailor my description of kinship and fertility to what I take to be the orientation of the person I am tormenting.  So I was going over how I would approach the subject for a scientific journalist.  This time I was following the logic in my mind:
Selection is real.
Selection is a race.
Speciation permits effective selection.
Speciation is a race.
Faster speciation provides a head start in selection.
Faster speciation also puts a limit on the size of a random mating population.
All similar animal species undergo speciation at the same rate.

Hold it right there.

Up until the last step the logic seems iron clad.  And indeed the point is not vital.  It is the next to the last step that is vital.  But I think it’s approximately true.

It is not unheard of in competition for the individual to match the performance of the group as a whole.  In a tropical forest there are many species of tree.  They all tend to reach the same height.  A tree that does not reach the height of the canopy is deprived of vital sunlight.  A tree that grows substantially higher than the canopy is deprived of protection of its excess height.  It is more vulnerable to wind and lightning than a tree that does not stand proud. 

Similarly in a long distance bicycle race, a rider that goes far ahead faces the full resistance of the wind.  (There’s an exception there.  Often the race is led by a police escort.  The police car may give the leader some help in displacing the air.  They like to do it because if the leader sets a world record the police in the car get bragging rights.)  Obviously the rider who trails far behind is going to have difficulty winning.

So I think it is not far fetched to aver that there is a characteristic number of generations to speciation.  From there the idea that the population size limit becomes more persuasive.

And that is all it takes.  Then it’s just a matter of piling up the massive data.

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