Once upon a time, back when the Human Genome Project threatened to unravel the mystery of human nature – every aspect of individuality would be reduced to a SNIP – the Nature/Nurture debate seemed like the most hotly contested question in science. Are personality traits inherited or learned? To what extent can we rebel against our nature? How free are we?
Those questions now seem rather obsolete. They were rooted, after all, in a false dichotomy. Here is how I summarized this new understanding in my book:
What makes us human, and what makes each of us our own human, is not simply the genes we have buried in our base pairs, but how our cells, in dialogue with our environment, feedback onto our DNA, changing the way we read ourselves. Life is a dialectic. For example, the code sequence GTAAGT can either be translated as instructions for the amino acids valine and serine; or it can be read as a “spacer”, a genetic pause that keeps other protein parts an appropriate distance from each other; or it can be read as a signal to cut the transcript. Our DNA is defined by its multiplicity of possible meanings; it is a code that requires context.
That said, every once in a while you run across a story that reminds you just how powerful Nature really is. A few weeks ago, This American Life devoted its full hour to the powerful tale of two babies from the same Wisconsin town that were switched at birth. (It turns out that one of the mothers knew about the switch after a few weeks, but didn’t say anything for more than forty years.) While the soap opera itself is riveting – how would you feel after learning that your mom isn’t really your mom? – the show is also a testament to the disconcerting reach of genetics. It turns out that the two switched women closely resemble, both in appearance and temperament, their previously unknown biological families. While one family was fun-loving and playful, and gave birth to a daughter that would also grow up to be fun-loving and playful (even though she never knew these parents), the other family was extremely religious, and gave birth to a daughter who also grew up to extremely religious, even though she never knew that her biological father was an evangelical preacher. The list of parallels goes on and on. It’s a rather spooky tale, and although it’s certainly an extreme example of genetics at work, it’s still a useful reminder that who we are is partially beyond our control.