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Chapter 5, Our Hat Size is too Big for Darwin
This
chapter explores the issue that our brain, during evolution, grew so large
compared to our closest relatives, other primates, and what this extraordinary
evolutionary development means in terms of the Darwin theory. The evolutionary
record tells us that our brain grew almost four times larger than it was, in a
period of 2.5 million years, as we developed from hominids to humans. There is
no direct evidence that the trials of nature demanded that growth, but since the
Ice Ages occurred in the same time period, some authors (especially William
Calvin) have suggested a relationship, with more complex thinking and planning
needed to survive the cold when it appeared. The overall changes in our
ancestors, the genetic adaptations of the hominid line, “over the last few
million years has actually been exceptionally rapid when compared to that of
other mammals”. (The Paleolithic Prescription, Eaton, Shostak &
Konner, 1988) Unanswered is the obvious question, if our brain needed to grow to
better survive the cold, why are there no other species that lucky?
We appear to be something very special, or very lucky. “Such marked
brain growth in one branch of a family of animals is quite rare. Usually, the
same evolutionary pressures and constraints affect all the species in a family
in much the same way so that the whole group steadily becomes more intelligent
together.” (The Ape That Spoke, John McCrone, 1991) The
neurophysiologist, William H. Calvin in his book, The River That Flows Uphill
(1986), raises the same point: “Why didn’t some other primate double and
triple its brain size too? Even if no one made it as far as we have, surely
there would be some robust examples in evolution of bigger-is-smarter-is-better,
demonstrating its efficacy for us to see. It doesn’t take other examples of
200 percent. Even a 50 percent increase would help make the point. But none
obliged.” Calvin offers no answers to his rumination. Again why us and us
alone? Actually the Australopithecus branch of our very early family
developed a brain about 50 percent larger than ape brains and within an ounce or
two of the size of the first of our line, Homo habilis;
but the Australopithicus