What parents really pass down: genes, epigenetics and learned adaptation
Geneticists and trauma experts differ on how much experience can cross generations biologically, versus being passed on through genes or through how children adapt to their environment. Knowing where the evidence stands keeps parents from both fatalism and unfounded fears about inherited trauma.
Through what three channels do parents pass things to their children? Show answer
The DNA sequence itself, chemical and RNA marks that sit on top of genes, and the environment children grow up in and adapt to.
What is the Weismann barrier? Show answer
The separation of the body's cells from the germ cells. What happens in body cells, including the brain, should not contribute to sperm or egg.
What is epigenetic reprogramming? Show answer
The erasing of about 90% of chemical marks in sperm, eggs and the early embryo, so development starts from a blank slate.
How does Oded Rechavi define epigenetic inheritance? Show answer
As the environment of the parents somehow changing the children through something other than the DNA sequence, passed on through the germline.
Why does Rechavi say famine during pregnancy is not an inherited effect? Show answer
The baby is already in the womb and exposed directly, so it is a direct effect that needs no new biology to explain.
What would prove a true transgenerational effect in mammals? Show answer
It would need to show up in grandchildren through the father's line and great-grandchildren through the mother's line.
What has Rechavi proven in worms? Show answer
That acquired traits are inherited through small RNAs, including virus immunity and behaviour changes, lasting roughly three to five generations.
Why can't arbitrary memories be inherited, according to Rechavi? Show answer
The brain stores memories as synaptic connections, but anything heritable must pass through a single fertilized cell with no connections.
How does Gabor Maté define trauma? Show answer
Not what happened to you, but what happened inside you as a result of what happened to you.
What does Maté's rat example show? Show answer
Early maternal handling shapes the adult's capacity to handle stress, and pups moved to more attentive mothers develop normally, so it is the environment acting on genes.
Why do siblings turn out differently, in Maté's view? Show answer
No siblings have the same childhood. Birth order, circumstances and temperament change how a parent shows up and how each child experiences it.
How heritable is autism, according to Karen Parker? Show answer
About 40 to 80 percent genetic, largely an inherited polygenic condition, with environmental risk factors that matter differently for different children.