The Spirit in Human Evolution - Waldorf Research Institute

expansion of brain size, especially the cortex. How this extremely valuable adaptation in
the blood supply to the brain evolved is unclear. But if the impulse to go beyond normal
physical limits created this selectionary pressure, then presumably early hominids were
regularly dropping like flies from heat stroke. Those with the fortuitous mutation that
reversed blood flow out of the brain by way of a new network of veins had an immediate
advantage. This adaptation belongs to a suite of thermoregulatory adaptations that
Homo erectus possessed, including the “human” nose that cools inhaled breath whilst
retaining precious moisture; tall, slim stature which increases surface area over against
body volume (peoples in cold climates tend to be short and stocky to conserve body
warmth); and probably sweating from a mostly hairless body. Of course, naked skin in
a tropical climate would of necessity have been darkly pigmented.
Brain-Size Peaked Already?
The human brain has not actually continued getting progressively larger. It would
be more accurate to say that brains increased in size until recently. Curiously over the past
20–30,000 years brains have actually been getting smaller. According to Robert Martin,
from an average of 1569 cc for male Cro-Magnons (early European Moderns), brain
volume has fallen to an average of 1436 cubic centimeters. 33 This has certainly not been
due to a decrease in social complexity, technical demands or loss of cognitive abilities,
or poorer nutrition.
Martin suggests that the reason may be that Neanderthals and Cro-Magnons
weaned their offspring at a later age, thus leading to larger brains. Perhaps having
reached an optimum size for the effort involved, mankind, or at least womankind, took
a small step to emancipating itself from its demanding offspring. As we know, there
is no correlation between brain size and intelligence among present human races or
individuals, despite racist attempts to prove them. The London Underground recently
did its bit to counter this prejudice with a cartoon poster showing a series of identical
brains labelled Negro, Asian, and Caucasian. The last brain was half the size and was
labelled Racist.
Feet before heads in a general evolutionary sense, increased brain size has gone
hand in hand with a progressive increase in the elaboration of the central nervous system.
The more sensory information that was being processed and the greater the complexity
of representational systems, the greater became brain size by volume. Bifocal vision
in primates and in particular in hominids would, for example have vastly increased
the amount of sensory data being simultaneously processed. While it is true that other
animals have far more sensitive sense organs (one need only think of the dog’s sense of
smell and so on), and that apes and humans have lost much of their senses of smell and
taste, bifocal color vision, with the capacity to resolve focus of great clarity and depth,
delivers probably more sense data simultaneously than any other sense organ in all of
nature.
This kind of vision requires considerable processing capacity in the brain and thus
high levels of representational ability. Added to this the manipulation of prehensile hands
co-ordinating with visual perspective also requires large networks of neural connections.
If we correlate all this with the factors discussed above we have an extraordinarily
complex development resulting in larger brains and more importantly, since brain size
within very broad parameters is no measure of cognitive capacity, brain organization
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33
Martin, R., 1995, p54.
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