Youâre a med student, so you should understand genetics and inheritance well enough to know that this claim is, at best, inaccurate. If this were true, that would mean, essentially, that everyday environmental factors have no effect, that maternal effects do not exist, and worse of all, that there is a gene for every trait.
One of the parts of the body which is most affected by its environment, including pre-birth, is the brain and brain function. Ambition, tenacity, abilities in retaining and synthesizing data, personality, etc, are all brain functions. Therefore, environment will affect each and every one of them, even without some major event.
Moreover, what would you call a âmajor eventâ? Something that happens over a day?, a month? five years? Would a childhood with food insecurity be considered an âeventâ even though it occurs over 15 years? Is fetal alcohol syndrome the result of a âmajor eventâ?
There are lower-level impacts. Having parents who constantly questioned a kidâs achievements and abilities will have profound effects on the kidâs actions, and capabilities later in life. Yet this in no âmajor eventâ, itâs a low level background environmental factor for the kid.
Even traits with simple inheritance, and relatively simple set of genes, like height, are dependant on a whole range of environmental factors, including emotional effects (not getting enough affection can stunt a childâs growth). It doesnât need a âmajor eventâ for a kid to not follow the height patterns of their parents. A brain has far more complex inheritance patterns, and is affected by far more environmental factors.