Page 37 - Deep Learning

20 Introduction

the valley. The latter decisions might be unprecedented in the experience of
the current members of the band.
Although climate shifts most often occur over a long period of time com-
pared to a human lifetime, they occasionally happen abruptly. “dramatic
alterations between cold and warm, steppe and forest, glacial and interglacial,
occurred time and again in the late phases of humanity’s descent, and when
they happened, the change was measured on a scale from decades up to a
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few centuries.” Also, migration can move a hunter-gatherer band from one
climate zone to another, perhaps in a decade of migration. Within the living
memory of its members, a hunter-gatherer band might experience a shift from
a wet-dry, two-season climate to a temperate, four-season climate. Such a shift
requires a response that goes beyond past experience. Whereas the response to
a wet season might be to move temporarily to higher altitudes, the appropriate
response to autumn is to stockpile food; to move to higher ground will only
increase the hardship of winter.
In a period of plenty the children in a hunter-gatherer band might sur-
vive more often than normal. The result might be an unprecedented popula-
tion explosion, a strain on the band’s resources and a subsequent splitting of
the band. Each of the descendant bands now operates in an environment that
includes another and potentially competing band, perhaps an unprecedented
situation. competition might lead to warfare, and then as now, inventions in
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military technology might create novel situations. The first hunter-gatherer
band to go into battle carrying shields must have bewildered their opponents;
how do you fight an enemy you cannot reach?
We do not know that these hypothetical vignettes ever occurred in exactly
this way, but they are plausible. My purpose in presenting them is not to claim
that they happened at some specific time or place but to give concretion to
the idea that the historical and experience-defying character of the environ-
ment was a living day-to-day reality for proto-humans and archaic humans,
as opposed to an intellectual curiosity of interest primarily to philosophically
disposed scientists at the end of the 20th century. over the hundreds of thou-
sands of years of human evolution, perturbations in the material, biological
and social environments that changed the rules of survival must have occurred
over and over again; if not these exact perturbations, then others. The turbu-
lent and unpredictable character of reality was always directly experienced; it
was the clockwork character of some material systems that required systematic
investigations to be seen.
We arrive at a paradox: Prior experience is our only guide to the future.
There is no other source of expectations. But in a world characterized by