Prefatory reading: http://en.wikipedia.org/wiki/Demographic-economic_paradox
Prosperous people generally have less babies than poorer people. This seems contrary to what I would expect, from an evolutionary perspective.
Western places have great prosperity and thus great caloric abundance. Typically, when animals experience caloric abundance, they increase their population size.. historically humans seem to have fit this pattern just fine even with the advent of agriculture (i.e. the human population size exploded into the billions after agriculture). Now however, after grasping the extent of influence diet can hold over general health and behavior, it seems like a decline in dietary quality might be a good explanation for the decreased fecundity seen in prosperous peoples.
the general idea being:
1) Increases in wealth seem also to bring increases in the westernization of a group's diet. i.e., Chinese start becoming more wealthy, and suddenly you see more Coke and McDonals popping up around China. If a we believe this to be true, and if we believe a Western diet is poor in quality, then we can say generally wealth brings a decline in dietary quality.
2) A western diet, despite caloric abundance, could reduce fertility, directly via infertility and indirectly via something like a general drop in libido or desire to reproduce and such? i'm talking something like this http://en.wikipedia.org/wiki/Francis_M._Pottenger,_Jr.#Meat_study , with the cats receiving adequate calories and continuing to reproduce, but having fertility progressively decline and disease progressively increase over the generations due presumably to the cats being metabolically messed up from inadequate diet.
Basically the question is, to what extent, if any, can dietary factors explain the inverse relationship between wealth and fertility currently observed across the world?
Some sub-questions include:
-are Western diet eaters currently in the middle of walking down a path like Pottenger's cats (see above), with evidence for this being how kids today are expressing diseases that were once thought specific to adults?
-if animals are in an abundant calorie environment, but are metabolically messed up somehow either from dietary deficiencies or damage, do they have less babies? If so, is this because of increasing infertility, or are the animals fertile but unwilling to pursue mating rituals/sex as often?
-If western nutrition were 'fixed' (made more in line with that which yields health), would fertility rates in the west then rise to rates similar to those currently seen in more undeveloped nations/places? Or is (western) culture responsible for the decline in fertility, and thus improvements in everyone's health would not yield increases in fertility/birth rates.
any relevant evidence or reasoning for or against any of the above ideas would be awesome.