Evolutionary biologists have long puzzled over this because natural selection is expected to have selected for organisms that try to maximize their reproduction. But in industrialized societies around the world, increasing wealth coincides with people deliberately limiting their family size -- the so-called 'demographic transition'. In a new study, researchers reject a popular theory put forward to explain the phenomenon. This 'adaptive' hypothesis proposes that low fertility may boost evolutionary success in the long term by increasing offspring wealth, which in turn eventually increases the number of long-term descendants because richer offspring end up having more children.
