Environmental Engineering Reference
In-Depth Information
The predecessor species belonging to our genus—starting with
Homo habilis,
who
appeared nearly 2.5 million years ago—spent all of their evolution as simple het-
erotrophs. Our species,
Homo sapiens
, has spent no less than 95% of its evolution
(assuming it evolved by about 200,000 years ago) in a similarly simple foraging
mode. All of these hominins gathered edible phytomass (tubers, stalks, leaves, fruits,
grains, nuts), collected small heterotrophs (mushrooms, insects, small invertebrates,
mollusks), hunted a variety of animals (mainly herbivorous species), and caught i sh
and aquatic mammals. Given the length of these experiences and the variety of
environments they eventually occupied, it is not surprising that humans developed
a remarkable range of food acquisition strategies, from snaring animals to spear
i shing to elaborate group hunts to using other animals as lures or actual hunters
(cormorants, birds of prey, dogs) as a way to secure a large variety of foods, from
trufl es to i sh.
Small numbers of prehistoric foragers and their low population densities (some
maritime societies were the only exception) would indicate limited harvests of the
biosphere's productivity. Although all prehistoric population estimates are highly
uncertain, the totals may have been no higher than 125,000 people half a million
years ago and as low as 15,000 (or perhaps even less than 10,000) following the
population bottleneck caused by the Toba mega-eruption 74,000 years ago (Ambrose
1998; Harpending et al. 1998; Hawks et al. 2000). Subsequent expansion brought
the global total to no more than a few million people before the emergence of the
i rst sedentary agricultural societies some 10,000 years ago.
Low population densities were the case in most places for most of the time,
though prehistoric hunters have been also credited with being the prime agents of
the late Paleolithic extinction of megaherbivores in North America, Eurasia, and
Australia, a claim I examine in some detail. But it was the hominin use of i re, rather
than foraging for food or the hunting of large herbivores, that was responsible for
the most extensive preagricultural human impact on the biosphere. The epochal shift
from foraging to farming was a complex and protracted process: there was no
Neolithic “agricultural revolution.” In many places the process ceased unfolding in
its earliest stages and for millennia had not progressed beyond the two extensive
food production ways of pastoralism and shifting cultivation.
And, contrary to a common claim, subsistence foraging was not quickly discarded
because of agriculture. The emergence of sedentary farming was characterized by
the prolonged coexistence of cropping and foraging. Foraging on land (ranging from
mushroom picking to the seasonal hunting of mammals and birds) has never disap-
peared, even in the most afl uent societies, and it continues to play an important
