Homo Sapiens and the Family Joules
Summary: Being animals, humans are also subject to these absolute laws of energy payoff. In the few remaining hunter- gatherer tribes that are not yet absorbed into modern civilization, anthropologists have measured calories burned vs. calories obtained, breaking them down by people of different sexes and various age groups. They find that males, (who typically do more of the hunting), and especially the strong adult males, generate the majority of the energy surplus to feed all age
groups of the tribe. Children and old people are energy sinks , consuming more energy than they produce, but they provide other critical societal services and benefits: the children provide for continued tribal survival, while the old people provide companionship, wisdom, childcare, health care and cooking. 98 The size of the energy surplus in hunter-gatherer societies is not large. If a long time goes by without a successful hunt, some members might grow weak or even starve. But if there is ample game to be caught and plant food to be foraged, hunter-gatherers don’t spend a lot of time working : most such societies spend just 15 to 20 hours per week per person acquiring their food and spend the rest of their time in leisure and rest. Though this results in a low total energy acquisition, it is matched by an even lower energy input. Calculating the number of calories expended (working 3-4 hours per day) vs. the calories obtained shows hunter-gatherer societies have an ER/EI somewhere between 10:1 and 20:1. (The ‘:1’ represents the energetic investment by the human.) Though a tribe could probably briefly get by for a while on an ER/EI of between 2:1 and 3:1 by working a bit harder (and losing weight), at over 10:1 it has a sufficient energy buffer that allows it to
161
Powered by FlippingBook