Diet restricted size of hunter-gatherer societies
Seasonal bottlenecks in available food determined overall limit on
population size

Date:
November 8, 2021
Source:
McGill University
Summary:
Short growing seasons limited the possible size of hunter-gatherer
societies by forcing people to rely on meat, according to a
recent study.

After looking at population size for the roughly 300 hunter-gatherer
societies which existed until quite recently, the researchers
found that many of these groups were much smaller than might have
been expected from the local ecosystem productivity. In regions
with short growing seasons, hunter-gatherer groups had smaller
populations per square kilometre than groups who depended on
abundant plant foods throughout the year.



FULL STORY ========================================================================== Short growing seasons limited the possible size of hunter-gatherer
societies by forcing people to rely on meat, according to a recent
study by a team of international reseachers including McGill University professor Eric Galbraith.


========================================================================== After looking at population size for the roughly 300 hunter-gatherer
societies which existed until quite recently, the researchers found that
many of these groups were much smaller than might have been expected from
the local ecosystem productivity. In regions with short growing seasons, hunter-gatherer groups had smaller populations per square kilometre than
groups who depended on abundant plant foods throughout the year.

Need for meat limited population size "Basically, if people had to live
through long dry or cold seasons when plant food was scarce, in order to survive they had to depend on hunting a very limited number of animals," explains Galbraith, a professor in McGill's Department of Earth and
Planetary Sciences and at the ICTA-UAB (Institut de Cie`ncia i Tecnologia Ambientals of the Autonomous University of Barcelona), and a senior author
on the paper published recently in the journal Nature Ecology & Evolution.

"This led to a seasonal bottleneck in the amount of food available, which
then set the overall limit on the population size, no matter how much food there was during the plentiful times." The team developed a mathematical
model that simulates daily human foraging activities (gathering and
hunting) and the resultant carbon (energy) flows between vegetation,
animals, and hunter-gatherers in a realistic global environment.

"We were struck by the fact that -- despite a long list of unknowns
-- a very strong result emerged from the model equations," says
Galbraith. "Wherever growing seasons were short, hunter gatherers
required meat to make up a high percentage of their diets. And -- just
as in the modern world -- it took much more land to produce the same
amount of meat as plant-based food." The researchers then went back to
look at the detailed ethnographic observations and found that, although
its significance had not been noticed, this finding was well supported by records of hunter-gatherers including the Ache in the tropical forest, the
Hiwi in the savannah, and the Bushmen groups in the Kalahari Desert. Due
to similarities between the lifestyles of contemporary hunter gatherers
and those of our foraging ancestors, it is likely that strong seasonality limited population sizes throughout our species' past.

========================================================================== Story Source: Materials provided by McGill_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Dan Zhu, Eric D. Galbraith, Victoria Reyes-Garci'a, Philippe Ciais.

Global hunter-gatherer population densities constrained by influence
of seasonality on diet composition. Nature Ecology & Evolution,
2021; 5 (11): 1536 DOI: 10.1038/s41559-021-01548-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211108162208.htm

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