Preface
Back when I was trying on various
book titles for size, I was temporarily attracted by several that, valued advisors assured me,
were not properly serious for a book on human origins. The Little Brain That Could
rightly emphasized the ape-to-human bootstrapping of brain size. It nicely contrasted with
The Cerebral Symphony, wherein I emphasized how human consciousness now works
(here I consider how it evolved in the context of ice age climate changes -- generation-to-generation
evolution of mind, rather than its minute-to-minute operation). But The Little
Brain That Could might have been shelved in the wrong section of the bookstore -- and
much as I would like to write for young readers, human evolution is a topic that requires the
reader to have considerable experience with the world, a long attention span, and an ability to
keep multiple possibilities in mind simultaneously -- all while retaining the child's intense
curiousity about origins.
Then there was Our Gain in Brain Remains to Be Explained. My advisors
admitted that not many book titles can be sung in the shower, but wondered if that was really
fitting and proper for the "greatest of mysteries." I was particularly attracted by Our
Gain in Brain because, in My Fair Lady, Eliza Doolittle sings her famous line
from the elocution textbook, the one about where it rains in Spain. And then the professor
whispers in an excited aside, "I think she's got it!" Anthropologists and biologists know that,
when attempting to explain what "caused" human evolution, such roles are invariably
reversed. The professor tentatively starts with an excited whisper, "I think I've got it!"
Whereupon a chorus complains, in a mighty refrain, that the matter still remains to be
explained.
That's science for you, though our perfectly normal disagreements are often
misunderstood by journalists and exploited by a certain type of religious fundraiser. There is
total agreement among the experts that evolution happened over millions of years, and that
the apes are the group of animals out of which we evolved. But scientists haven't agreed on
the exact course that prehuman evolution took -- the what, where, and when --
though hard-earned archaeological and fossil finds are sketching in the broad outlines. Nor
can we yet agree on what drove it -- those pesky how and why questions.
Like Darwin, we keep getting into conflict with those who advocate a simplistic view of the
world; not noted for their knowledge of elementary anthropology or evolutionary biology,
they prefer miraculous "explanations." Of course, back when few antecedents were
discernible, the scientists of three centuries ago also relied on the miraculous -- but today, just
saying "God did it" resembles peeking at the last page of a mystery novel, without savoring
the buildup, climax, and explanation of all those incidents along the way. Even religious
scientists tend to agree with the Greek philosopher Polybius who, in the second century B.C.,
said: "Whenever it is possible to find out the cause of what is happening, one should not
recourse to the gods."
WHATEVER THE ULTIMATE CAUSES of ape-to-human evolution, there are surely
multiple proximate causes. The bootstrapping potential of technological problem-solving
(toolmaking, hunting, etc.) is often mentioned as a way of working up from the apes. Other
kinds of cleverness might also work, such as the social problem-solving that affects
reproductive success (the most formidable problem typically faced by a chimpanzee is to
figure out what fellow chimps are going to do next). And climate change, besides biasing
evolution in certain directions, also affects the rate at which other "causes" make progress.
Each proposed cause -- even if true -- seldom convinces other scientists that it is more
important than their own favorite candidate from the multiplicity. Even if you only try to
explain the changes in brain, body, and behavior since we last shared a common ancestor
with the chimpanzees, many things appear potentially important. And because human
evolution only happened once, all of the happenstance of that seven million years can, by
some stretch of the imagination, be held to be essential for the making of modern humans
("We wouldn't be human without it" goes that refrain).
Worse yet, there are some seductively attractive processes that might have sufficed,
given enough time, to do the job of enlarging the brain fourfold. Our gain in brain is
certainly the most central, compelling "fact" of post-ape evolution (though that's largely
because, until recently, it was about all that could be measured from fossil skulls). Size --
even relative size -- may not be the most important aspect (more on that later). But surely
the most commonly noted brain-enlarging process since Darwin's day is "Bigger-than-average
brains are smarter, smarter individuals survive better, therefore a bigger brain will evolve
gradually."
Good old compound interest reasoning, sheer intelligence bootstrapping itself, little by
little. Physicists who make grandiloquent statements regarding life in the universe are
particularly prone to such one-sentence summaries. But such "universal truths," rising above
the messy details, are what science is supposed to be all about, right?
Yet even if true (and I would caution that bigger-than-average brains aren't necessarily
smarter-than-average), such reliable-sounding causes could well have been superseded,
rendered totally irrelevant. Why? A fast-but-chancy track often preempts the slow-but-sure
tracks in the evolutionary race for a new ecological niche. Like patent protection,
the evolutionary inventor may be rewarded with a winner-take-all protected niche, so that
even-better (but late-arriving) candidates are locked out for quite a while. There are also
"windows of opportunity," such as the boom times when competitive rules are suspended.
They are brief intermissions in the grind of ordinary times when interesting things happen. (I
am reminded of them each time that I get bored with a play or concert -- and discover from
the program that there are no intermissions, that I cannot escape gracefully.)
Evolutionary explanations involve a lot of such messy details, threatening the grand
generalities. Since the unique history is important, piecemeal answers are inevitable. Unfort-
unately, a patchwork quilt of little correct explanations does not readily constitute one grand
answer (and so the complaining chorus chants its refrain once more). We keep wishing for a
sturdy framework on which to hang the pieces.
THERE ARE SEVERAL THINGS that I hope to contribute to the debate about human
evolution through this book. Individually, each may seem a little mundane, hardly an obvious
"antecedent to consciousness." But they do hang together in a way that helps explain how the
more elegant human abilities might have emerged.
The first is that where the rain falls is surprisingly important (and in Spain, it
falls mainly in the mountains, not the plains). As droughts demonstrate, climate is fickle;
"sudden death playoffs" can happen within a matter of a decade or so. Abrupt climate change
makes versatility, often a virtue, a necessity. There were many abrupt shifts during the last
2.5 million years of fluctuating climate known as the Ice Ages, quite in addition to the slow
advance and retreat of the continental ice sheets. That 2.5 million year period is exactly
when our brains enlarged and reorganized beyond the ape standard, exactly when toolmaking
became prolific. Given the greenhouse problems coming up, one might almost call those
several dozen ice ages "the qualifying rounds."
A second involves how hominids might have discovered hunting. I have
touched on this in earlier books (and, in The Cerebral Symphony: Seashore Reflections
on the Structure of Consciousness, elaborated on the spare-time uses of throwing's mental
machinery, which is quite handy for augmenting insight, foresight, and language abilities).
But here I emphasize how the projectile predator niche might have been invented and
bootstrapped with the aid of toolmaking (I will even touch on something which an early
reader nicknamed "the killer Frisbee").
Third, I suggest that there is a three-part cycle of evolutionary alterations in
body proportions. This cycle can be rerun, something like a college course that can be
repeated for additional credit; it involves several different sets of genes that regulate fetal and
childhood growth. One likely result of the selection cycle I propose is a bigger and bigger
adult brain; another predicted result is a considerable fluctuation in adult height during ape-to-human evolution.
That cyclical subscenario also illustrates that any explanation, to use a baseball
metaphor, has to touch a lot of bases along the way. Any adequate explanation must propose
a framework whereby we could have evolved from an upright-walking hominid with an ape-sized brain
to the fully-human cave painters of the last ice age. My modest attempt at this is
in the form of a multimillion-year scenario, paced by the cyclical subscenario and (during the
last 2.5 million years) by the ice age rhythms. The bases one should touch are, of course,
part of the explanatory problem. My selections overlap with those of modern anthropology
while adding some nudges and constraints from climate and brain.
While I naturally hope that my scenario will turn out to be correct in both outline and
details, the more realistic aspiration is that it might demonstrate the breadth of
explanatory power that theories need. The anthropologists' favorites of the last few decades
are rather narrow. They are known via static images, like tableau in a museum: seed-eating,
"Man the Hunter," home-base, "Woman the Gatherer," and scavenging. Not unreasonably,
they tend to emphasize either animal behavior or "stones and bones."
But R.G. Collingwood noted in 1939 that history "is concerned not with events but
with processes. Processes are things which do not begin and end but which turn into one
another." Each is a continuing development involving many changes; the drying climate that
changed forests into savannah in East Africa is probably the anthropologist's favorite process.
I hope to demonstrate that the harder-to-depict re-entrant process is particularly
important (what goes out the front door is eligible to re-enter the back door, and take another
pass through the transformation). Indeed, an adequate explanation of human evolution will
need a wide range of processes (both re-entrant and one-shot) from ecology, climatology,
developmental biology, evolutionary biology, immunology, and from my own fields,
physiology and neurobiology. The people piecing the story together will probably come from
ethology, primatology, developmental psychology, the cognitive sciences, philosophy,
linguistics, systems modelers -- as well as anthropology. The correct portrayal of the
prehuman path (if we ever agree on one) will probably be too multifaceted to state in one
sentence, and so we will yearn for the good old days of "Bigger-is-smarter-is-better gradual
Darwinian improvements." The story surely won't sound as elegant as "The Rain in Spain."
IT IS WINTERTIME IN SEATTLE as I finish this book. The relentless sound of rain on
the roof reminds me of the incorrigible leak that again imperils my collection of Current
Anthropology; the downhill path to disorder is threatening my view of the uphill record.
But then the typically snowy nature of wintertime elsewhere in these middle latitudes is the
fourth important "cause" of our brain boom that I have found so fascinating. "Think
Snow" is a bumper sticker (much favored by waterlogged would-be skiers) which I would
commend to those paleoanthropologists fixated on the tropics, as a slogan emphasizing a
golden opportunity.
I suppose that we could have quadrupled our brains without the virtues of winter, but
I'll bet that it would have taken forever. So much brain enlargement in a mere 2.5 million
years is awfully quick by the standards of evolutionary biology. Yet winter once a year, an
abrupt climate change every few millennia, and an ice age every hundred thousand years will
speed up things ever so nicely -- at least if you've got our kind of brain, rather than a bear's.
Or so my story goes.
W.H.C.
Seattle, Washington
The Ascent of Mind
(Bantam 1990) is my book on the
ice ages and how human intelligence evolved; the
"throwing theory" is one aspect.