The science of the biological effects of the stresses of poverty is in its early stages. Still, it has presented us with multiple mechanisms through which such effects could happen, and many of these admit an inheritable component. If a pregnant woman, for example, is exposed to the stresses of poverty, her fetus and that fetus’ gametes can both be affected, extending the effects of poverty to at least her grandchildren. And it could go further.
Studies of mice and fruit flies have shown that epigenetic traits similar to the ones Meaney proposed can be passed down, and last for dozens of generations. The effects of things like diet and prenatal parental stress have been observed to be inherited, not just through histone modifications, but also through DNA methylation and non-coding RNAs.7 In one 2014 study, the offspring of a mouse trained to fear a particular smell were observed to also fear that smell, even with no previous exposure to it. The effect lasted for two generations.8 In humans, inheritable effects of stress have been observed through at least three generations from parents who survived mass starvation (Dutch Hunger Winter),9 a fluctuating food supply (the Överkalix cohort)10 and the Holocaust. The effects of early paternal smoking and paternal betel quid chewing have been observed to be transmitted to children in a sex-specific manner, supporting biological epigenetic transmission in humans.11 According to a 2014 survey of the field, “the few human observational studies to date suggest (male line) transgenerational effects exist that cannot easily be attributed to cultural and/or genetic inheritance.”10
Even at this stage, then, we can take a few things away from the science. First, that the stresses of being poor have a biological effect that can last a lifetime. Second, that there is evidence suggesting that these effects may be inheritable, whether it is through impact on the fetus, epigenetic effects, cell subtype effects, or something else.
This science challenges us to re-evaluate a cornerstone of American mythology, and of our social policies for the poor: the bootstrap. The story of the self-made, inspirational individual transcending his or her circumstances by sweat and hard work. A pillar of the framework of meritocracy, where rewards are supposedly justly distributed to those who deserve them most.