🚀 go-pugleaf

w.p.coyne@newcastle.ac.uk writes:

>darice@yoyo.cc.monash.edu.au (Fred Rice) writes:
>
>>I was wondering, is there an evolutionary explanation for the great
>>capacities humans have to think?  I'm thinking about things like our
>>ability to do advanced mathematics, for instance.  There is no
>>evolutionary survival advantage in being able to solve differential
>>equations, for instance.  If this is the case, then *why*, in
>>evolutionary terms, can we do such things?
>
>Maybe you should rephrase the question "What are the forces which have
>pushed/pulled human intelligence up to the level where it has given
>humans the ability to do such abstract things as differential 
>equations?"

Human evolution is a complex process that includes the development of
also other weird characteristics than the big brain, for instance upward
gait and nakedness. To me it seems that by far the most coherent
explanation is that during the time their brain started to evolve larger,
our ancestors were living at the seashore. It is rather typical for sea
mammals that the size of their brains is larger in relation to body size
than with terrestrial mammals of the same weight. I doubt that dolphins
could solve differentials, but they are the only animals that have as big
brains as we do, and they are also known to be rather smart.
There are at least two reasons why a mammal that turns (partly) aquatic
would develop a large brain. First, neoteny is a typical characteristic
of aquatic mammals, and this results kind of automatically in larger
brains, because the foetus always has relatively larger brains than the
adult. Second, seafood is rich in some fatty substances that are
essential as building blocks of the brain, while these substances are
rather scarce in the food available in terrestrial environments. In
savannah or forest, therefore, an exessively big brain is an
energetically expensive luxury that would be selected against, while in a
marine environment it would not be such a burden and could grow beyond
the limits of immediate need.
The climate changes have certainly played their part in initiating the
process by driving the future humans away from the shrinking rain
forests. But it was the life at sea that caused the radical anatomical
and physiological changes that make us so different from the rest of the
primates. The evidence for this hypothesis is summarized in two books by
E. Morgan: The Aquatic Ape (1982 or thereabouts) and The Scars of
Evolution (1990).
I have been wondering why this theory is so seldom mentioned in
speculations about our evolution. If any of the experts who have been
contributing to this discussion could give me an answer, I would be very
pleased indeed.

Hanna Tuomisto
hantuo@utu.fi