"to prepare for what is likely to be a life of hardship" But then we had boom times a mere 15 years later. Human society causes mass changes at short time scal

"to prepare for what is likely to be a life of hardship" But then we had boom times a mere 15 years later. Human society causes mass changes at short time scales. Biological mechanisms we may have facilitating adaptation to more long-term changes are likely to be counterproductive when the socioeconomic environment changes. Maybe in the past times of hardship would tend to be either quick (a year or two) or slow (a generation of so), but as expected lifespans increase and as technology causes more intermediate length boom-bust cycles, epigenetic changes could be maladaptive over the lifetime of the individual. This is moreso true when the adaptations needed are not those of a hunter-gather (such as earlier onset puberty), but of an industrialized society (where early puberty can impact lifetime employment). And with anything biological weird side-effects, or even mistakes can happen. Looking at the wikipedia article "Epigenetic effects of smoking" has this blurb: " CYP1A1 was found to be hypomethylated in the placentas of fetuses prenatally exposed to cigarette smoke, along with the transposable element AluYB8.[4] Methylation of transposable elements is one of the primary ways they are prevented from replicating or moving within the genome." So you've got increased mutation rates (from the transposable elements and other effects) in infants exposed to cigarette smoke. Increasing mutation is a literal gamble for a genome to do, as only a few mutations will be beneficial. Sometimes the situation is bad enough the body needs to gamble. But this doesn't mean the effects will be net beneficial, just that the body not making changes is also a bad idea. TL;DR: This is something we need to pay attention to as a side-effect of geopolitical and economic policies.