[ExI] Armchair Evolutionary Psychology: Larks vs Night Owls

Lee Corbin lcorbin at rawbw.com
Sun Mar 16 18:50:06 UTC 2008


PJ writes

> Lee wrote:
> 
>> I [should] remind everyone that developing a genetic explanation
>> always requires a [discussion of] selective advantage, and since
>> we seem to have here an equilibrium, it's that which needs to be
>> explained too.  E.g., what if there are too many early risers, how
>> does that increase the number of viable offspring of the late risers
>> and vice-versa?
> 
> What about simply, the early birds take the early shift and the night
> owls take the late shift?  Between the two, you cover a larger set of
> hours, get more accomplished and have someone on deck either
> protecting the tribe or getting stuff done.

Yes, there are advantage to that "morning, swing, and late" shift kind
of strategy.  A wise tribal leader might suggest it, or a king might impose
it. (Right now, our market economy evolves it  :-)  but people are at
least free to try to find what suits them.)

No, the problem I'm talking about is the perpetual struggle to keep
*group selection* at bay. Just because some behavior would benefit
the group as a whole hardly means that it will be individually selected
for. (Sorry if this is old hat to you, but, as often, I feel a little responsibility
to the vast unseen audience  :-)

Suppose that in a given tribe there really are genetic differences between
the early risers and late risers. (I don't know if this is the case---I didn't
follow all the URLs, and no one here so far has given me a Y or a N.)
Then the population biologist has to ask, "How can that be? Why didn't 
whichever one that had even the slightest selective advantage come to
predominate?  Why, for example, didn't the early risers take charge 
and create the best opportunities for themselves and leave less for the
late ones?"

But we (I take it) seem to have an equilibrium: that is, there may be
about the same number of each. The best example of this is sex!
Why is the ratio approximately 50/50, with only minor variations
easily explained (or conjectured) by the evolutionary psychologists?

In a number of heavy duty but quite readable books (e.g. "The Red
Queen" by Matt Ridley), the logic is spelled out. Also, Dawkins
explains clearly in his books and essays. The basic idea goes like
this:

Suppose that there is a mutation and some woman begins having
only daughters, and this mutation is passed on to all her (female,
of course) offspring.  Then pretty soon, each *man* is getting a
lot more offspring than before, because each has correspondingly
more women to lay.  Then, you see, women who still have *sons*
start having, ultimately, more offspring than their competitors who
have only daughters. 

(To take the simplest case, suppose that a tribe had one woman
who had sons & daughters equally, or sons exclusively, and all
the other women had all daughters. Then clearly the woman 
making sons gets her genes into subsequent generations at a
far faster rate than any other particular women.)

So an equilibrium exists.  Sorry, I've probably not done such a
hot job explaining this, but probably wikipedia or somewhere
can do much better. 

So it's the same with the early risers vs. late risers.  We'd need
a mechanism for why there is any kind of balance.

Lee




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