Carl%20Sagan%20-%20The%20Demon%20Haunted%20World

The Wind Makes Dust
This more or less typical hunting vignette comes from the !Kung
San people of the Kalahari Desert, in the Republics of Botswana
and Namibia, who are now, tragically, on the verge of extinction.
But for decades they and their way of life were studied by
anthropologists. The !Kung San may be typical of the huntergatherer
mode of existence in which we humans spent most of our
time, until ten thousand years ago, when plants and animals were
domesticated and the human condition began to change, perhaps
forever. They were trackers of such legendary prowess that they
were enlisted by the apartheid South African army to hunt down
human prey in the wars against the 'front-line states'. This
encounter with the white South African military in several different
ways accelerated the destruction of the !Kung San way of life.
It had, in any case, been deteriorating bit by bit over the centuries
from every contact with European civilization.
How did they do it? How could they tell so much from barely
more than a glance? Saying they're keen observers explains
nothing. What actually did they do? According to anthropologist
Richard Lee:
They scrutinized the shape of the depressions. The footprints of
a fast-moving animal display a more elongated symmetry. A
slightly lame animal favours the afflicted foot, puts less weight on
it, and leaves a fainter imprint. A heavier animal leaves a deeper
and broader hollow. The correlation functions are in the heads of
the hunters.
In the course of the day, the footprints erode a little. The walls
of the depression tend to crumble. Windblown sand accumulates
on the floor of the hollow. Perhaps bits of leaf, twigs or grass are
blown into it. The longer you wait, the more erosion there is.
This method is essentially identical to what planetary astronomers
use in analysing craters left by impacting worldlets: other
things being equal, the shallower the crater, the older it is. Craters
with slumped walls, with modest depth-to-diameter ratios, with
fine particles accumulated in their interiors tend to be more
ancient, because they had to be around long enough for these
erosive processes to come into play.
The sources of degradation may differ from world to world, or
desert to desert, or epoch to epoch. But if you know what they are
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