I really enjoyed this talk by Karen B. Michels on epigenetic inheritance (see video below):
Michels is a Radcliffe fellow (one of the top 50 artists/scholars as chosen by Harvard each year) and she begins the talk by explaining how when she first got the email informing her of her acceptance, she started screaming on a bus in rural Vietnam, and the other passengers may have thought “these foreigners are soooooooo weird”
I thought it was a funny story; her audience didn’t, but she was adaptable enough to quickly switch gears and dive right into epigenetic inheritance.
Epigenetics literally means “on top of genetics”, and the epigenome refers to the chemical tags placed on the DNA sequence to either silence or activate certain genes. Unlike our genome, which remains stable throughout our life unless we get rare mutations, the epigenome is much more sensitive to environmental effects like smoking and diet etc.
The question is, does this environmental damage to your epigenome get passed on to your kids? Many studies claim it can, including a very famous study in which the children of mice taught to fear a certain smell, also feared that smell.
However Michels explains that if you have kids, these epigenetic tags are removed not once, but twice, during fertalization, which should protect your kids from the environmental damage you did to your epigenome.
So how does Michels explain what looks like cases of environmental damage to the epigenome being passed on? A common example is a grandmother smoking during pregnancy causing obesity in grandkids. While this is commonly interpreted as a case of epigenetic inheritance (since smoking damages your epigenome), Michels explains that the grandkid didn’t nessecarily inherit her damaged epigenome from grandma, but rather smoking damaged the unborn female fetus (including its reproductive cells, thus damaging the future grandchild to boot).
Study after study proclaims “epigenetic inheritance” even though they don’t even come close to proving it (which would require four generations on the female line and three on the male line). Michels got so frustrated by the misleading use of the term “epigenetic inheritance” that she complained to Nature Genetics and their response was NOT INTERESTED.
The audience gasped.
Michels explained that the way you get published, tenure, and grants is to use epigenetics in your titles.
Michels does not deny epigenetic inheritance, she just feels there’s no evidence for it in humans (and presumably other complex animals) with the exception of genomic imprinting.
Overall I loved the talk, but what I really wanted to know was how an epigenetic inheritance skeptic like Michels explains how mice can be born to fear smells their parents were taught to fear.