Remember how we used to laugh at people who thought that giraffes developed longer necks because mommy giraffe stretched to reach stuff and that made her babies have longer necks? That was silly: you can't change genes through behaviors, right?

Time to think this through.

The topic of epigenetics is fascinating. Could environment change one's DNA - or more accurately how your DNA is expressed? Could this be part of why the nature/nurture dichotomy is so unsatisfying?


  1. See - the issue is that there is no Nature/Nurture DICHOTOMY, its an interaction, a dance, an interplay of the past, present, and future.

    Our genes are adapted to where our species has been. We have them because our ancestors who were best able to reproduce had them, and passed them on. Our genes also carry around a lot of "just in case" sorts of mutations - traits that may not be adaptive now, but may come in handy in the future if the environment changes. And, the environment can be counted on to change: droughts, famines, floods, meteors, etc. And of course, there are lots of spontaneous mutations that just don't seem to work out.

    So the idea is definitely that environment will have a role in how ones genes are expressed: this is your phenotype. Over time, differences in phenotype will start to change a population's genotype. A great example of this is Sickle-cell trait. If you have the Sc trait, your red cells break easily. This can cause problems if you live at high altitudes where oxygen is lower. You can imagine that tired, weaker people living on a mountain are at somewhat of a disadvantage, and may not be chosen as spouses, or have more problems having and feeding their kids, and over time, Sc trait stays rare, b/c it just doesn't work.
    Now, if you live in a warm place, and are using intensive irrigation and agriculture practices, you're creating a larger, steady food supply. But you're also becoming a resource to mosquitos that now have lots of deforested area with standing water in which to breed and lots of people to suck blood from. The disease malaria starts to take a toll on the people. Yet if you have Sc trait, you don't get as sick, and you get over you're sickness more quickly. This is because your red cells burst before the malaria parasite can really build up numbers. So the number of people carrying the Sc gene goes up. Unfortunately, if you get 2 copies of the gene, you get a disease that leads to dying as a child. Yet on balance, more people are living better with Sickle cell trait than are succumbing to either malaria or Sickle cell anemia, so the gene persists at a fairly steady rate.

    What humans are really good at is using our behavior to overcome and/or augment our genes. These are our cultural adaptations that allow us to live in the arctic even though we have sparse fur, to hunt animals that are bigger and stronger than we are, to carry food back to our sick, so we don't have to leave them to their chances.

    Some people have argued that this means more "weak genes" are around - an ugly and inaccurate idea which has lead to eugenics and genocide and other atrocities.
    A better understanding is that we have many more "just in case" genes hanging around, because you never know what the future will bring!

  2. IU, have you read "Survival of the Sickest?" It's FASCINATING and I think it would be right up your alley.

    And the whole epigenetics thing just adds a wonderful new wrinkle to our thinking.

  3. No - sounds juicy! Thanks for the tip Laura. Here's hoping I get to catch up on reading things for fun this summer!


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