Becoming Human by Ian Tattersall, Harcourt Brace, $27, ISBN
0151003408
IAN TATTERSALL has long made it his business to be a thorn in the side of the
body anthropological, prompting professionals and others to view the evolution
of humans as they would the evolution of any other animal. 鈥淢ost people who
accept that mankind has an evolutionary history tend to think of our evolution
as a slow business of perfecting adaptation over the ages,鈥� he says, 鈥渨hich, if
true, imparts in retrospect a certain inevitability to our having become human.鈥�
This is dangerous for several reasons, not least because it encourages a gross
oversimplification of the story of human evolution.
It鈥檚 a story about which Tattersall has strong views. 鈥淭here鈥檚 not a great
deal we can learn about ourselves by contemplating our evolutionary past that we
cannot learn by observing our often bizarre behaviour today,鈥� reads the opening
to the final chapter of Becoming Human.
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This might seem like an example of the above-mentioned bizarre behaviour,
because Tattersall heads the department of palaeoanthropology at the American
Museum of Natural History, New York. He is also a major intellectual presence in
the science of human evolution and has written a couple of highly acclaimed
popular books on human origins. Moreover, much of Becoming Human is
devoted to a wide-ranging鈥攁nd highly readable鈥攖our of the fossil
evidence of how, anatomically, we got to where we are today.
Has Tattersall鈥攁s some of his adversaries have long
contended鈥攆lipped his lid? He acknowledges the tremendous 鈥渢hirst to
explain our place in nature and to know where we come from鈥�. Bumper sales of
magazines sporting concocted images of our ancestors on their covers attest to
that, Tattersall notes. The reason for the above, apparently contrary statement,
he explains, is that 鈥渢he abilities of today鈥檚 Homo sapiens . . .
represent a huge leap away from those of our precursors鈥�. In other words, modern
human behaviour is not a simple extrapolation of earlier trends, but something
entirely new. Evidence of this novel behaviour, such as the rate and degree of
technological innovation and the use of symbolism鈥� implying modern levels
of language and consciousness鈥攆irst appears in the archaeological record,
particularly of Europe, about 40 000 years ago.
These new behaviours are 鈥渕ore akin to an `emergent quality鈥�,鈥� says
Tattersall, 鈥渨hereby for chance reasons, a new combination of features produces
totally unexpected results鈥�. By their nature, emergent qualities cannot be
predicted on the basis of what preceded them.
Becoming Human, as we鈥檝e come to expect of any work from Tattersall,
is wittily and cogently argued, and uncompromising. For instance, in his
discussion of the evolutionary origin of modern humans, there is no mention of
competing hypotheses. For Tattersall, the molecular and fossil evidence
overwhelmingly supports the notion that modern humans evolved in or near Africa
around 150 000 years ago. Period. It is this group that changed so radically 40
000 years ago.
He also neatly balances what some might consider conflicting positions, but
in reality are not. First, as mentioned, Tattersall describes modern human
behaviour as an 鈥渆mergent quality鈥� that, by its nature, can seem beyond
explanation and therefore special. Second, he berates some fellow
palaeoanthropologists for being less than scientific in their evolutionary
scenarios of human origins, and for invoking special processes to explain our
unquestionably special abilities. 鈥淲e did not come by our special features as
the result of a special process,鈥� he states emphatically. The (recent) origin of
fully modern language, perhaps as a result of one or a few small genetic
changes, is the key to the quantum shift in behaviour that is seen in the
archaeological record. 鈥淎lmost all the unique cognitive attributes that so
strongly characterise modern humans . . . are tied up in some way with
language,鈥� argues Tattersall. No mystery. Just something novel and powerful.
In a chapter titled 鈥淓volution鈥攆or what?鈥�, Tattersall traces the
genesis of the teleological view, including his discipline鈥檚 slow but eventually
enthusiastic acceptance of the 鈥淣ew Evolutionary Synthesis鈥� in the 1940s and
1950s. The core of the synthesis鈥攖hat all evolutionary change involves the
continuous, gradual accumulation of small changes 鈥攇ave rise to the
linear, progressive perspective of evolution that dominated palaeoanthropology
for so long. For instance, the increase in the size of the brain over the past
five million years was assumed by many to have been a steady process, a gradual
increase in intelligence culminating in modern Homo sapiens.
Tattersall鈥檚 museum colleague Niles Eldredge helped to dispel this notion in
the 1970s and 1980s, when he and Stephen Jay Gould launched their then
controversial hypothesis of punctuated equilibrium. Much of evolution, including
human evolution, proceeds sporadically, with long periods of stasis and brief
bursts of change. Evolution by jerks, as one wit put it. The archaeological
record, which reveals widely spaced bursts of technological innovation (that is,
until the advent of modern humans), is a clear example in the behavioural
realm.
The 1990s have been a wildly busy time for palaeoanthropology, with the
discovery of several new species of hominid in the earliest part of the human
fossil record, the unearthing of two staggeringly rich fossil caches in
Atapuerca, northern Spain, one 300 000 and the other 800 000 years old, and of
eye-popping Ice Age art in recently found caves in southern France. Becoming
Human is therefore timely in its publication, and Tattersall has done a
fine job of including the new evidence, telling his version of how we came to be
what we are in a way that will delight anyone interested in this most compelling
of stories.
There is plenty of room for debate, of course. For instance, some
archaeologists argue that the advent of symbolic behaviour was not
revolutionary, but gradual, citing examples of putative symbolism as old as 300
000 years. But many of these examples are questionable. Tattersall also argues
that the number of hominid species currently recognised is far too low, in spite
of the richness of recent discoveries.
Becoming Human explores far more than has been covered here. A rich haul, it
includes the meaning of Ice Age art, what studies of chimpanzees tell us about
our common ancestor, the dynamics of stone tool technologies, and the place of
religion in our lives. Tattersall also challenges the popular notions spawned by
evolutionary psychology, which suggest that we are prisoners of our evolutionary
past. If, he argues, important human capacities are an emergent quality, not an
extrapolation of earlier behavioural trends, then this undermines 鈥渢he notion
that our behaviours are programmed in any detail by our genetic heritage鈥�.