A continuum of societies may be constructed, ranging from tiny, simple bands of hunter-gatherers in poor environments to large, dense populations of irrigation agriculturalists that is, from the entirely nomadic to the fully sedentary.
Others have suggested that the legalization of abortion in the 1970s has reduced crime, by reducing the number of youngsters growing up in poor environments.
Children who grow up in poor environments were found to have slower brain development than their middle-income and high-income peers, a study published this week found by comparing images of children's brains as they aged. .
Moreover, inbreeding depression worsens in poor environments that strongly affect overall fitness.
In contrast, we would predict consistently larger inbreeding depression in poor environments the closer the environmental axis was related to fitness.
We predicted that inbreeding depression would be greatest in poor environments of those environmental axes that have the greatest influence on fitness.
Increasing resource uptake rate might be efficient for fast growth and reproduction in a rich environment, but can lead to fast resource exhaustion in poor environments and hence in increased mortality before reproduction and/or expansion.
A recent study on Soay sheep suggests that in poor environments, selection, for example, on survival may be stronger, but the amount of heritable genetic variation respectively smaller [35].
In line with this expectation, we found that inbreeding depression in poor environments (relative to good environments) was larger the more closely the environmental axis was related to fitness (Spearman rank correlation: rS −0.699, t approximation = 2.93, d.f. = 9, n = 11, p = 0.017; Figure 2).
More importantly, there is ample evidence that appropriate infant feeding practices result in better growth for infants and young children in poor environments.
