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this evolution in brain size, for it has often been noted
that, on an evolutionary timescale, the rapidity of the
change was practically unprecedented. Since the middle
Pleistocene, about a half-million years ago, the rate of
increase was particularly rapid, so much so that it has even
been suggested that the enlargement might actually have been
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somewhat pathological, leading to a being whose
irrationality and capability for wanton destructiveness
equals or excels his creativity. Certainly, the history of
the Twentieth Century has been a pinnacle of both
tendencies, and also requires an explanation, and a
resulting solution, if we wish to ensure our future
survival. But even though we may have vestigial organs such
as the appendix, and "skeuomorphic instincts" as I have
discussed, blaming our present situation on purported faults
of evolution is neither productive nor scientifically
logical. The mere proposal of a hypothesis that we have too
much brain power for our own good goes a long way to suggest
that we must therefore have the brain power to correct any
such tendency to let foolishness dominate our lives;
scapegoating is seldom a productive hypothesis.
It now appears that the tool-making hypotheses also have
resulted less from a careful analysis of the data than from
superficial concurrence of two tendencies. We have complex
technology, we have large brains, animals have neither.
Seeing that there are facilitations and parallels between
technology and brain power does not, however, provide more
than circumstantial evidence for causation. And recent work
now makes it extremely likely that the ability to produce
technology, it has been called object-intelligence for want
of a better term, has been a development that has "piggy-
backed" upon a much more important development in
intelligence, that which is required for social transaction.
A recent collection of the important papers providing the
foundation for the theory of Machiavellian Intelligence has
been published as a book (2), and I will not present an
extensive argument here for its well-founded conclusions.
One quotation should suffice to illustrate that even
anthropologists such as Thomas Wynn, who might be surmised
to have a "vested interest" in the importance of tool-use
and making in the development of early hominids, has whole-
heartedly agreed with the new view:
Given the evidence of brain evolution and the
archaeological evidence of technological evolution,
I think it fair to eliminate from consideration the
simple scenario in which ability to make better and
better tools selected for human intelligence. At
almost no point in hominid evolution was there even
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a provocative correlation. The earliest known
hominids, Australopithecus afarensis, had a brain
larger than an ape's of equivalent size, but as far
as we know, no greater reliance on tools. Early
Homo at 2 Ma [million years ago] had a much more
'encephalized' brain, but the tools and even the
context of use were not beyond the capacity of
modern apes. Homo erectus did possess technology
that was outside the range of ape behaviour, but by
this time, 1.5 Ma, much of the encephalization of
the Homo line had already occurred. In sum, most of
the evolution of the human brain, the presumed
anatomy of intelligence, had occurred prior to any
evidence for technological sophistication and, as a
consequence, it appears unlikely that technology
itself played a central role in the evolution of
this impressive human ability. (3)
As one of the contributors to the book remarked, Wynn's
paper "is a bombshell to the older 'Tools makyth Man'
view... Wynn throws the question of the cause of human brain
size back into the realm of the invisible: either the social
relationships or the lifestyle which produced technology,
not the technology itself." (4)
The conclusions of the Machiavellian Intelligence
hypothesis fit well with my own theory, and lead to the most
probable evolutionary scenario for the influence of
psychedelic plants in the emergence of modern humans. The
arguments of the hypothesis show that the complexity of
logical operations required for social interaction in large
groups of individuals is far greater than that required for
tool use or making, or for that matter any other activity of
primate species. (5) Studies of societies of monkeys and
apes in both natural and controlled environments strongly
support the theoretical arguments. The brain size of various
species of modern primates, for example, has been closely
correlated with the size and complexity of the social groups
of the various species studied. The complexity of social
interaction would increase geometrically with the number of
possible interrelations between animals in a group
consisting of three or more generations of relatively long-
lived animals. Complex dominance relationships, alliances,
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group undertakings such as efficient foraging and hunting,
lengthy childhood, and relatively constant possibility of
mating activity add to the complexity. The demands of
increasing social complexity was a development requiring far
faster biological evolution of the equipment which
facilitated it than any previous set of demands such as tool
use and manufacture, climate change, interactions with other
species, or other hypothesized evolutionary pressures. Thus
it is reasonable that the rapid increase in brain size among
primates requires no other explanation, despite its
unprecedented speed.
The proposal of early influence of psychedelic plants on
hominid evolution as a factor in brain enlargement (between
one and five million years ago), as suggested by Terence
McKenna, is therefore difficult to support. Criticism of
McKenna's theory as presented in his Food of the Gods has
been sometimes dismissive, (6) and although I find much of
value in the book, I would have to agree that his proposals
that psychedelics were "mutation-causing" agents that
"directly influenced the rapid reorganization of the brain's
information-processing capacities" are unsupported by
evidence, and unnecessary in light of the much more
reasonable Machiavellian Intelligence hypothesis. The
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