Some MGH content/quotes, often paraphrased, that were presented during the sessions, with comments:

“In the aftermath of highly stressful or traumatic situations, our soul nerve [vagus] and lizard brain may embed a reflexive trauma response in our bodies.” (“lizard brain” is no longer an accepted concept)

“… form of racialized trauma lives in the bodies of most white Americans.”

BTW, blanket statements about “Americans” are inappropriate (especially in today’s polarized US) as North America can be seen as composed of eleven historically rooted peoples, each with differing sets of values and moral foundations (Colin Woodard, American Nations, 2011).

The following observation is reasonable: “…intergenerational transmission” [of trauma originally inflicted on enslaved persons occurs via] “..  families in which one family member abuses or mistreats another, [or].. unsafe or abusive systems, structures, institutions, and/or cultural norms.” [systemic racism, oppression of the disadvantaged]. But MGH boldly claims that “trauma is passed on in our DNA expression, through the biochemistry of the human egg, sperm, and womb.” [and therefore] “This is why white-body supremacy continues to persist in America, …”

Based on numerous lab experiments with rodents, results from the field of “epigenetics” have conjectured that transgenerational transmission of anxiety and elevated stress can occur in humans via mechanisms involving chromosomes modified by molecular decorations that are transmissible for one to several generations. Any substantial contribution by such mechanisms to the well-being of even a single subsequent human generation is now doubted by many in the field, and convincing interpretations of seemingly relevant evidence have yet to appear.

Yet in MGH we find:
“This trauma goes back centuries—at least as far back as the Middle Ages—and has been passed down from one white body to another for dozens of generations. White bodies traumatized each other in Europe for centuries before they encountered Black and red bodies. This carnage and trauma profoundly affected white bodies and the expressions of their DNA. As we’ll see, this historical trauma is closely linked to the development of white-body supremacy in America.”

With respect to events affecting the womb: Yes, chemical toxins or maternal psychological stress can negatively affect a newborn, and lead to chronic persistent afflictions, involving changes in the sets of genes that are expressed, but there is little support that this is primarily rooted in epigenetic changes on chromosomes, and more importantly, little support that such effects would affect a following third generation, if parents were spared toxins and stresses.

Some references:

https://www.nytimes.com/2018/12/10/health/mind-epigenetics-genes.html
http://www.wiringthebrain.com/2018/05/grandmas-trauma-critical-appraisal-of.html
https://whyevolutionistrue.com/category/epigenetics/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4020004/
https://www.nature.com/articles/s42003-021-02316-6

Quote from Kevin Mitchell podcast The Dissenter 486 June 2021 :
“People like their sciencing terms. Somehow these are used to give an aura of authority. ….. Certainly there are really long lasting serious transgenerational effects through cultural  and psychological means. There’s no need to bring in epigenetics to explain this, or in some way to give it a more sciency feel. It doesn’t need a molecular explanation when there are perfectly good cultural explanations. Epigenetic explanations actually trivializes the real societal and cultural consequences of things like slavery. Those consequences are still felt through viral memes and cultural transmission. You don’t need to reach for epigenetics to justify in some way the idea, or validate the idea that those things are happening.”

Cultural transmission and persistent systemic problems, less prominent in MGH, would more likely be the principal explanations when trauma is documented over many generations. In practice, stress from the systemic problems does not require transmission from a previous generation. Persistence of these problems leads to individuals in each generation becoming traumatized. The book does describe scoring adverse childhood experiences (ACE). Kids in challenged neighborhoods typically have high ACE scores. Attitudes and discrimination due to ACEism are pervasive, but do not always map directly to racism.