“Small families are not a new invention. For most of human history, from about one million years ago until as recently as ten to fifteen thousand years ago, all people lived as hunter-gatherers. Men hunted animals and women foraged for fruit and vegetables. Societies were made up of small, scattered bands of people. They had a good, protein-rich diet and most deaths were due to accident, predation and inter-group warfare rather than disease. The children of hunter-gatherers had an excellent chance of survival. Using nothing but the natural, stress-related methods we have discussed, women gave birth to only three or four children in their lifetime. Of these, two or three survived.
Large families did not appear until about ten thousand years or so ago, when agriculture brought a change of lifestyle. In the most fertile areas, large and concentrated communities developed, living on a carbohydrate-rich diet. Disease and infant mortality were rife. The average number of children was about seven or eight, but double figures were commonplace. Even so, whole families could be wiped out in days by virulent disease. As with the hunter-gatherers, on average, only two or three in each survived.”
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Robin Baker,
Sperm Wars: Infidelity, Sexual Conflict, and Other Bedroom Battles