Disclaimer: I am not a geneticist. For those of you who are new here, this is basically a genetics fan blog. I am trying to learn about genetics, and you know what?
Genetics is complicated.
I fully admit that here’s a lot of stuff that I don’t know yet, nor fully understand.
Luckily for me, there are a few genetics basics that are easy enough to understand that even a middle school student can master them:
- “Evolution” is the theory that species change over time due to some individuals within them being better at getting food, reproducing, etc., than other individuals, and thereby passing on their superior traits to their children.
- “Genes,” (or “DNA,”) are the biological code for all life, and the physical mechanism by which traits are passed down from parent to child.
- “Mendel squares” work for modeling the inheritance of simple traits
- More complicated trait are modeled with more complicated math
- Lamarckism doesn’t work.
Lamarck was a naturalist who, in the days before genes were discovered, theorized that creatures could pass on “acquired” characteristics. For example, an animal with a relatively normal neck in an area with tall trees might stretch its neck in order to reach the tastiest leaves, and then pass on this longer-neck to its children, who would also stretch their necks and then pass on the trait to their children, until you get giraffes.
A fellow with similar ideas, Lysenko, was a Soviet Scientist who thought he could make strains of cold-tolerant wheat simply by exposing wheat kernels to the cold.
We have the luxury of thinking that Lysenko’s ideas sound silly. The Soviet peasants had to actually try to grow his wheat, and scientists who pointed out that this was nonsense got sent to the gulag.
The problem with Lamarckism is that it doesn’t work. You can’t make wheat grow in Antarctica by sticking it in your freezer for a few months and animals don’t have taller babies just because you stretch their necks.
So what does this have to do with epigenetics?
Pop science articles talk about epigenetics as if it were Lamarckism. Through the magic of epigenetic markers, acquired traits can supposedly be passed down to one’s children and grandchildren, infinitely.
Actual epigenetics, as scientists actually study it, is a real and interesting field. But the effects of epigenetic changes are not so large and permanent as to substantially change most of the way we model genetic inheritance.
Why?
Epigenetics is, in essence, part of how you learn. Suppose you play a disturbing noise every time a mouse smells cherries. Pretty soon, the mouse would learn to associate “fear” and “cherry smell,” and according to Wikipedia, this gets encoded at the epigenetic level. Great, the mouse has learned to be afraid of cherries.
If these epigenetic traits get passed on to the mouse’s children–I am not convinced this is possible but let’s assume it is–then those children can inherit their mother’s fear of cherries.
This is pretty neat, but people take it too far when they assume that as a result, the mouse’s fear will persist over many generations, and that you have essentially just bred a new, cherry-fearing strain of mice.
You, see, you learn new things all the time. So do mice. Your epigenetics therefore keep changing throughout your life. The older you are, the more your epigenetics have changed since you were born. This is why even identical twins differ in small ways from each other. Sooner or later, the young mice will figure out that there isn’t actually any reason to be afraid of cherries, and they’ll stop being afraid.
If people were actually the multi-generational heirs of their ancestors’ trauma, pretty much everyone in the world would be affected, because we all have at least one ancestor who endured some kind of horrors in their life. The entire continent of Europe should be a PTSD basket case due to WWI, WWII, and the Depression.
Thankfully, this is not what we see.
Epigenetics has some real and very interesting effects, but it’s not Lamarckism 2.0.
evolutionistx 