I have been listening to a really interesting (and somewhat confusing) lecture series on human behavioral biology and have really enjoyed it so far. Out of all the interesting and unbelievable things I am now becoming acquainted with, there was one that I thought I'd share here. In a lecture called "Behavioral Genetics I" I learned about the pre-natal environment, and the lasting effects that things like stress and diet (of the mother) can have on a fetus while still in utero. Even though both stress and metabolic problems (or whatever you want to call them) are often passed from generation to generation (for about 3-4 generations being the average) neither is a genetic trait, i.e. they are not transferred to the offspring through DNA. These are examples of non-Mendelian inheritance, or non-genetic inheritance. They are circumstantially transferred from mother to fetus (and through subsequent generations) through some specific situation or as a result of some outside influence. I find that totally fascinating!
The following paragraph comes from a study on people who lived through the Dutch Hunger Winter in 1944.
For example, I guess it's during the third trimester that a fetus develops its metabolic pace, I guess you could say. That is to say it is during the last trimester when the fetus sort of (metaphorically) takes stock of how often and how much nutrition they are getting from mom and they adjust their metabolism, (which remains fixed ever after for the rest of their life) to most efficiently absorb calories. The staggering affect of this is that if the mother is starving, or otherwise not eating properly, or overexercising (so her body needs more calories than she is giving to her baby) then the fetus develops a very thrifty metabolism that can eek every last drop out of its caloric intake. If the mother eats normally, then the fetus develops a metabolism that is more normal, i.e. doesn't try to hold on to every calorie that enters the body. What that translates to down the road (in western society mostly) is that in the first case, there is a very high chance that the fetus will be obese, and will develop diabetes later in life, because it's body is tuned to absorb every last calorie, and once they are introduced to a western diet McDonald's and ice cream, their body can't process it normally. In developing nations this is actually adaptive because starving mothers there are more likely to raise their kids in an environment where there is little food and they need that frugal metabolism to survive.
It's just really incredible to think that during that 3 month window, way back when, inside mom, the amount of nutrients she consumed while the fetus was developing, could have lasting effects like her offspring having a lifetime battle against obesity.
Likewise, stress in the mother during pregnancy can alter the amount of stress hormones produced by her fetus and lead to things like depression and increased susceptibility to stress later in life. It basically works like this; mom gets stressed, she releases glucocorticoids into her blood stream. The fetus then absorbs them and as a result, develops a smaller than average brain, thinner cortex, which in turn makes it harder for the fetus to produce the hormones that block glucocorticoids (i.e. they can't turn off the stress response, after the stressful situation has ended). This leads to depression, anxiety, etc, And when the offspring get pregnant (years later) the cycle continues through the next generation.
So I guess the moral of the story is if you get pregnant, eat a lot of (healthy) food and whatever you do DON'T FREAK OUT!
I guess I should note that there are some scientists out there who disagree with the conclusions reached above. There were other studies conducted that produced different results. However from what I've read, it seems the differences are due to inconsistent controls from experiment to experiment. (For example, a similar study was done on Russian babies, and the results showed no correlation between mothers starving and obesity of fetus later in life, but in the Russian case the study covered the average of all babies (not just the ones in the last trimester), and the fluctuation in food supply was much more gradual than in the Dutch Hunger Winter study.)
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