Certainly an epigenetic contribution. It turns out that the mother's body during pregnancy can have a huge and heritable impact on the baby. E.g., studies have

Certainly an epigenetic contribution. It turns out that the mother's body during pregnancy can have a huge and heritable impact on the baby. E.g., studies have shown that nutritional problems (like famine) during pregnancy can cause the baby to have obesity problems later in life. These have been shown to be the result not of direct genetics (the fetus's DNA has already been selected), but by causing a different mix of genes to be expressed. That shouldn't be too surprising. It seems logical that evolution would find a way to prepare a baby to be born into an highly-food-constrained environment so their metabolism will be more conserving of resources. What really is surprising (at least to me) is that the child's propensity has been observed to be passed down even to the grandchild.