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Greetings,

Im new to the forum. I have dropped in on Rans website, and particularly his Langblog section, once in a blue moon. Since I have only briefly navigated the forum, I am rather unfamiliar with what topics already have been covered. So I hope you will forgive me if I am repeating something that already has been stated.

People can adopt conscious measures to avoid conception, as indicated by the Wikipedia article that silverspringwoman cited. In addition to that, I believe that the bodies of many animals including humans have built in mechanisms that automatically keep reproduction to sustainable levels.

Hunter-gatherers are very fit people. They routinely walk long distances. They eat natural foods. They do not eat refined sugars, a high proportion of concentrated starches, and other foods that pack fat onto their bodies. Honey, for example, is a rare treat for a person whose nutrition comes from gathering and hunting activities.

As a consequence of the above, hunter-gatherers have body fat ratios similar to those of Olympic athletes. When the fat in a womans body drops below a certain percentage of her total body mass, she stops menstruating. This apparently is a relatively common phenomenon amongst competitive women athletes. It also occurs in women who suffer from anorexia nervosa.

Another factor that suppresses ovulation is breast feeding. In hunting-gathering tribes, it is common for mothers to nurse their children until they are four or five years old. It is not just breast feeding on its own that suppresses ovulation. It is the way in which so called primitive mothers breast feed that suppresses ovulation. Mothers in hunting-gathering tribes do not have watches or clocks. They have never heard that they are supposed to feed their babies every four hours. In fact they feed their babies at the slightest squeak. Hence their babies snack throughout the day, taking sips of mothers milk as often as every fifteen minutes. Every time the baby suckles, even if its just for a couple of minutes, the suckling action stimulates the mothers body to secrete the hormone that suppresses ovulation. Since the mothers body receives that stimulus frequently throughout the day, the mechanism that suppresses her ovulation operates more effectively than it operates in so called civilized women who breast feed their infants less frequently. Of course, breast feeding on its own becomes less and less effective in suppressing ovulation as the child grows and starts to supplement his/her diet with other foods.

When anthropologists studied the !Kung (also known as the Bushman) people of the Kalahari Dessert in Southern Africa, while those people still were leading their traditional hunting-gathering lifestyle, they found that the average !Kung woman menstruated only 48 times in her life. Infrequent menstruation amongst !Kung women, in turn, was attributed to their low fat to muscle ratio, resulting from the long distances they walked, as well as their habit of offering their babies frequent snacks of breast milk.

During that phase of the tribes existence, the average !Kung woman had five children. Apparently that rate of reproduction kept the !Kung population stable. People died of accidental causes (snake bites and so forth), so the average birth rate of five children per woman was just enough to replace the folks who died.

Unfortunately I cannot cite a reference to that information about !Kung women. I read it in a newsletter about breast feeding when I was nursing my own babies over twenty years ago.

As an aside, other species that are in close contact with crop growing humans lose the mechanism that suppresses THEIR ovulation as well. For example, rats that live in the wild ovulate only when their bodies acquire a certain percentage of fat. That, in turn, happens when their sources of wild food are plentiful. When wild food sources are scarce, wild rats do not ovulate. Rats that live in close proximity to grain growing humans, however, have a steady supply of grain to eat. Hence they are fat. Hence they ovulate regularly.

When rat life cycles are not interrupted, parasitic germs that use rats as hosts and that can transfer from rats to humans, also flourish. So the agrarian revolution that enabled humans to have a steady supply of concentrated starch in the form of grain also enabled rats to have a steady supply of grain and also continually exposed humans to diseases that rats carried. If memory serves me correctly, I read about the relationship between human crop growing and rat reproduction rates in one of Daniel Quinns books.

Hmmm, this may be somewhat interesting to some people, but what relevance does it have to the question posed in the original post? Well I suppose if humans encountered a Doomsday scenario, its possible that the surviving humans might be forced to be leaner and fitter than most civilized people currently are. Presumably that would help women to ovulate less frequently. If, on top of that, mothers breast fed their babies on demand rather than according to schedules, it would further help to suppress ovulation.

Well at least that would be my guess.