All living organisms are shaped by their biophysical environment, the world around them. Many creatures have, through the process of natural selection, become adapted to a particular habitat, with traits that aid them in surviving within that habitat. For example, polar bears have white fur that camouflages them in the snowy Arctic. Human beings initially evolved in the grasslands of Africa but have spread to every continent on the planet. We, unlike other animals, have adapted to our various biophysical environments through cultural adaptations and the development of technology, such as agriculture, the mastery of fire, and the making of tools. To this day, despite increased globalization, human populations in different biophysical environments use different customs in order to live well in their unique habitats. "Nurture" consistently continues to affect our "nature."
Though it might often seem that we have mastered our environment, it still affects us in many ways, subtly and unconsciously. For example, studies have shown that our mood fluctuates with the seasons, with warm and pleasant weather leaving us feeling warm and pleasant. But perhaps the most incredible demonstration of how our environment can change us lies in the field of epigenetics, the study of changes in gene activity not caused by changes in the DNA sequence, or how genes are expressed. In 1944, parts of the Netherlands occupied by the Nazis suffered from a famine that killed over 20 thousand people. Since famines rarely happen in affluent countries, scientists were later able to study how this well-documented famine affected the population. Researchers found that—unsurprisingly—the children of pregnant women who had been exposed to famine were smaller, on average, than babies of women who hadn't been exposed to famine. However, when those children grew up and had children of their own, those children were also smaller than average. In other words, the environment of their grandmothers was still affecting them. The changes aren't just physical; neuroscientist Eric Nestler has found, for example, that chronically stressed mice mothers give birth to babies who are more vulnerable to stress.
photo by Alan Wilson