Environmental Engineering Reference
In-Depth Information
productive cores of several ancient civilizations. In other environments, however,
particularly those with mixtures of forested and cultivated areas, the seasonal
pursuit of animals and plant collecting coexisted for millennia with annual cropping,
and some of these practices are still alive (if on a scale that makes only a marginal
contribution to the overall food supply) even in some of the world's most afl uent
postindustrial societies.
Plants, Meat, and Fire
Our evolutionary heritage is clear: all extant large primates (chimpanzees, gorillas,
and orangutans) are omnivores whose diet is dominated by a variety of phytomass
tissues but also contains some heterotrophic biomass, ranging from ants and ter-
mites (sometime cleverly collected by sticks or blade tools) to small invertebrates
and mammals. Archaeological records and food choices observed among those
foraging societies that survived into the twentieth century indicate a very large range
of collected plant tissues, from dwarf willow leaves and the contents of caribou
stomachs in the Arctic to a profusion of roots, tubers, leaves, stalks, seeds, nuts,
fruits, and berries in the tropics.
Tropical gatherers collected commonly as many as 50-100 different species
(Scudder 1976), and similarly large inventories of wild plants are still exploited by
many African societies today. In Uganda's Bulamogi county, the list contains 105
species belonging to 77 genera (Tabuti, Dhillion, and Lye 2004), while the Luo of
western Kenya gather 72 different vegetables (Ogoye-Ndegwa and Aagaard-Hansen
2003). Such diversii cation of plant food sources is to be expected given the com-
bination of a relatively low energy density of most plant tissues (particularly leaves),
difi cult accessibility (whether tubers or fruits in high tree canopies), the seasonal
occurrence of fruits, seeds, and nuts, and short- and long-term l uctuations in plant
productivity.
But equally unsurprising is the fact that a much smaller number of species, often
less than a handful, usually accounted for most of the food energy derived from plant
collection: nuts and seeds (plant tissues with the highest energy density, commonly
above 20 MJ/kg and as much as 25 MJ/kg) and starchy tubers (with moderately high
energy density, up to about 4 MJ/kg, but bulky and easy to collect) were usually
dominant. Prehistoric foraging for plants could, at worst, damage the exploited
species in a very limited and temporary way: population densities were too low to
have more extensive impact, and human foraging was of secondary importance when
compared to the pressure exerted by large numbers of herbivores and seasonally
