I've also considered the cliche "Neurons that fire together wire together!" If you've got a FiSe mom, your brain is constantly receiving FiSe signals and literally playing them on your mirror neurons. I wonder if that could tip the balance.
It would be really interesting to do some family trees. ^  O ^ O....
teatime - Regarding type changing over time, or the influence of nurture on type, there's some videos I can show you:
Identical vultology, identical mannerisms; separated at birth.
And this study:
Which shows identical vultology, while also studying similarities in tastes. Also separated at birth.
And these two were also separated, growing up with different languages:
I believe this is a testable question; and from what I've seen type is not only innate, it's also rather unchanging with time. Even while being separated for decades, and going through different upbringings, the vultological signals remain identical.
One could expect that identical twins might look identical but not gesticulate identically. Yet the inverse is true. They not only look like, they also gesticulate identically even without exposure to any specific type of gesticulation style. And the vultological similarities span down to even the same kind of laugh and energy.
This is a very important discovery/confirmation for CT. It means that whatever CT is tracking is almost certainly genetic, and not nurture-dependent or epigenetic.
I've literally been thinking about this forever. I clearly remember what gt me started. I was a toddler (I only know this because it was my mom's birthday), and friend of my mom's showed up at another friend's house. She had a twin, and it took me a minute to sort out which twin she was. I began wondering how I knew and paying attention to the exact differences. I also wondered if the differences in animation would be telling (though those thoughts came way later) and eventually I figured those differences would result in long term facial changes.
I think a lot of us on this forum naturally pay attention to that kind of thing. A few others here are familiar with Mew and Weston Price. I think all humans unconsciously notice these things, but then there are those of us who like to make it explicit knowledge.