Hmm... This one I'm kind of hesitant to bring up...

Infant Mortality.

It's a major issue in primitive cultures. For a culture at the VS level, we could expect an infant mortality rate of between 25 and 50%. Diseases, accidents, wild animals, drownings, you name it. Even an idyllic island life can be hard. If we're really going to simulate a village, a portion of the babies born need to die. It's an accepted fact of life in primitive cultures.
Having high Science, Medical, and Fertility tech levels should help the rate, as should having lots of well-trained doctors available. The Breeding skill of both parents should also effect a child's chances of survival.
But the mortality rate probably shouldn't go below about 5%.

Hang on, let me put on my asbestos underwear. OK. Flame away.

-=P. T. Murphy.