[extropy-chat] HISTORY: Solved & Unsolved Riddles

[Spike]

...
> Could be something as simple as walking upright
> offered a mating advantage... spike

To expand on this thought just a bit, I 
might conjecture about two muscle systems
in the human body that appear out of scale:
the gluteus maximus and the pectorals.  

What I mean by  this is that those two muscle 
systems forming the upper chest and rear,
seem oversized for what they are required to do,
from a mechanical point of view.  Yet both
may have mating advantages, for they make
the human with large pecs and fanny appear
more attractive to potential mates, both
in clothing and out.

Consider the pecs and their task, to adduce
the arm.  If I recall from my high school anatomy, 
the chest muscles are actually a set of muscles.
The back has a similar arrangement, but these
are in general smaller and weaker than the pecs.  
Yet their task, from a mechanical point of view should
require about the same amount of force.  All else
being equal, one might expect the opposing muscle
systems to be approximately equal in size and
power, yet in humans they are clearly out of
balance.  

Conclusion: humans have exaggerated pecs, not
because we need them for any real survival 
advantage, but rather we evolved them because
they look good.

Same or perhaps moreso with butts, since the
selection effect works in both genders.  We all
like protruding fannies.  These too, one could
argue, are larger and stronger than they need to
be.  Consider when you run or walk a very long
distance, especially with a load or backpack.  
Your leg muscles may get very sore, but your
butt muscles almost *never* do.  Do they?  Mine don't.

You almost need to devise some oddball exercise 
machine to even challenge those powerful muscles 
to any real degree.  Of course, such
exercise devices have come into existence, 
specifically for that reason, again primarily 
to attract potential mates.  It is conceivable
that exaggerated glutes may not only be physically
attractive but may also be an asset during
the actual mating process itself.

My speculation then is that pre-upright walking
protohumans began to mate-select for larger 
stronger buns, which were then nicely pre-adapted 
for the transition to upright walking.  This nicely
solves the puzzle of what survival advantage was
conferred by upright walking: there may be none.  
We are erect because of sex.

spike