Environmental Engineering Reference
In-Depth Information
pursuit and, in the case of large seasonal migrations, also
in careful monitoring of herd movements in order not
to miss a unique opportunity for a relatively large meat
gain. Dependence on fishing was another key density-
determining factor: in the Pacific Northwest, with its
massive runs of salmon, fishing allowed the establishment
of permanent settlements and sharp reduction of mobil-
ity needed for food acquisition.
Energetic imperatives also determined the minimum
group sizes for successful hunting. An individual hunter's
daily success rate in pursuing small mammals was rarely
higher than 15%-30%, so at least three to six hunters
were needed to ensure daily meat supply for their fami-
lies. With an average of six or seven people per family,
this translated to minimum group sizes of 18 to 40 peo-
ple, an estimate well supported by archaeological and
ethnographic evidence. The benefits of group hunting
were clearly illustrated in Harako's (1981) studies of
two Mbuti bands in the Ituri tropical rain forest. Solitary
archers shooting monkeys had a daily success rate of a
mere 10% and averaged daily just 110-170 g of meat
per capita. Spear hunters averaged about 220 g, but net
hunting yielded 370 g for every band member. This
gain is even more impressive given that spear hunting
was highly dependent on the superior experience of the
oldest hunters (93% success rate for 40-50-year-olds, 2%
for hunters under 20), and hence the yield was vulnera-
ble to incapacity or death. A minimum number of adults
was also required to butcher a large mammal and trans-
port pieces or just stripped meat to a camp; this all added
up to energy input beyond the capability of one or two
families.
In common with chimpanzees, all foragers were om-
nivorous, eating dwarf willow leaves and the contents of
caribou stomachs mixed with seal oil in the Arctic, and
termites and roasted and ground ungulate hinds in Afri-
ca's savannas. Many gatherers ate parts of many plants.
Gwembe Tonga (Zambezi Valley) collected 58 varieties
of leaves and stalks, 53 kinds of seeds, nuts, fruits, and
berries, and 17 bulbs, roots, or tubers (Scudder 1976).
Basarwa foragers exploited 34-126 plant species. But
only a few species were usually dominant. Nine out of
85 plants gathered by !Kung accounted for 75% of all
edible phytomass, and mongongo nuts alone provided
more than 50% of plant food energy. Australia's Anbarra
collected 29 mollusc species, but 95% of their food en-
ergy came from just five bivalves and 60% of the gross
weight was from a single species (Meehan 1977). A pref-
erence for energy-dense seeds is not surprising. Many
groups on all continents collected grass seeds (typically
around 15 MJ/kg); South Africa's si bean (Bauhinia
petersiana) provided 17.7 MJ/kg and mongongo nuts
(Ricinodendron rautanenii) as much as 25 MJ/kg, and
pi˜on nuts gathered and stored by Californian foragers
contained 26.5 MJ/kg.
The high value of meat in foraging societies is well
documented by the hunters' willingness to spend much
energy on its acquisition and on its sharing with other
members of the group (Kelly 1995; Stanford and Bunn
2001). Mbuti women spent only a few hours a day gath-
ering, but spear hunters pursuing larger game averaged
about 11 h away from the camp, completing round-trips
of over 20 km (Harako 1981). Some energy expendi-
tures were extraordinarily high. A reliable report has the
Kalahari hunters running at an easy trot for up to 30 km
without pause and catching up with a wounded animal
with an all-out spurt (van der Post and Taylor 1984).
Basarwa hunting forays ranged between 13 km and
