A survey of human evolution
- From: "Lance" <LanceGary@xxxxxxxxxxxxx>
- Date: 13 Feb 2006 05:38:20 -0800
SURVEY: HUMAN EVOLUTION
The proper study of mankind
Dec 20th 2005
From The Economist print edition
New theories and techniques have revolutionised our understanding of
humanity's past and present, says Geoffrey Carr (interviewed here)
SEVEN hundred and forty centuries ago, give or take a few, the skies
darkened and the Earth caught a cold. Toba, a volcano in Sumatra, had
exploded with the sort of eruptive force that convulses the planet only
once every few million years. The skies stayed dark for six years, so
much dust did the eruption throw into the atmosphere. It was a dismal
time to be alive and, if Stanley Ambrose of the University of Illinois
is right, the chances were you would be dead soon. In particular, the
population of one species, known to modern science as Homo sapiens,
plummeted to perhaps 2,000 individuals.
The proverbial Martian, looking at that darkened Earth, would probably
have given long odds against these peculiar apes making much impact on
the future. True, they had mastered the art of tool-making, but so had
several of their contemporaries. True, too, their curious grunts
allowed them to collaborate in surprisingly sophisticated ways. But
those advantages came at a huge price, for their brains were voracious
consumers of energy-a mere 2% of the body's tissue absorbing 20% of
its food intake. An interesting evolutionary experiment, then, but
surely a blind alley.
This survey will attempt to explain why that mythical Martian would
have been wrong. It will ask how these apes not only survived but
prospered, until the time came when one of them could weave together
strands of evidence from fields as disparate as geology and genetics,
and conclude that his ancestors had gone through a genetic bottleneck
caused by a geological catastrophe.
Not all of his contemporaries agree with Dr Ambrose about Toba's effect
on humanity. The eruption certainly happened, but there is less
consensus about his suggestion that it helped form the basis for what
are now known as humanity's racial divisions, by breaking Homo sapiens
into small groups whose random physical quirks were preserved in
different places. The idea is not, however, absurd. It is based on a
piece of evolutionary theory called the founder effect, which shows how
the isolation of small populations from larger ones can accelerate
evolutionary change, because a small population's average
characteristics are likely to differ from those of the larger group
from which it is drawn. Like much evolutionary theory, this is just
applied common sense. But only recently has such common sense been
applied systematically to areas of anthropology that have traditionally
ignored it and sometimes resisted it. The result, when combined with
new techniques of genetic analysis, has been a revolution in the
understanding of humanity's past.
And anthropology is not the only human science to have been infused
with evolutionary theory. Psychology, too, is undergoing a makeover and
the result is a second revolution, this time in the understanding of
humanity's present. Such understanding has been of two types, which
often get confused. One is the realisation that many human activities,
not all of them savoury, happen for exactly the same reasons as in
other species. For example, altruistic behaviour towards relatives,
infidelity, rape and murder are all widespread in the animal kingdom.
All have their own evolutionary logic. No one argues that they are
anything other than evolutionarily driven in species other than man.
Yet it would be extraordinary if they were not so driven in man,
because it would mean that natural selection had somehow contrived to
wipe out their genetic underpinnings, only for them to re-emerge as
culturally determined phenomena.
Understanding this shared evolutionary history with other species is
important; much foolishness has flowed from its denial. But what is far
more intriguing is the progress made in understanding what makes
humanity different from other species: friendship with non-relatives;
the ability to conceive of what others are thinking, and act
accordingly; the creation of an almost unimaginably diverse range of
artefacts, some useful, some merely decorative; and perhaps most
importantly, the use of language, which allows collaboration on a scale
denied to other creatures.
There are, of course, gaps in both sets of explanations. And this field
of research being a self-examination, there are also many
controversies, not all driven by strictly scientific motives. But the
outlines of a science of human evolution that can explain humanity's
success, and also its continuing failings, are now in place. It is just
a question of filling in the canvas-or the cave wall.
http://www.economist.com/opinion/displaystory.cfm?story_id=5299220
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