Early developmental biology (by “early” I mean early pregnancy) is the shit you Do Not Touch. Each step of development is highly dependent on the previous steps (assuming this bit’s here, that bit’s there, etc.). If you make a change it’s extremely likely to be fatal or have negative consequences like birth defects, and the likelihood of a bad outcome climbs steeply as you move the change earlier and earlier in the process. That’s why pretty much every animal - humans, tigers, whales, lizards - looks the same when they’re a teeny tiny little fetus.
My example is testicles! Testicles begin in the same place as ovaries, which made a lot of sense back when we were coldblooded! Having a pair of balls dangling in a soft pouch between your legs isn’t a strategy you adopt if you can help it. In the alternate timeline where lizard people rose to dominate the earth instead of humans they don’t have “Ouch, I’ve been hit in the balls!” humor.
But the testicles form next to the kidneys early on in the developmental process (and as we’ve established, you don’t fuck with those stages), so they have to migrate south VERY late in the development! Because they SCHLOOP on down after everything else is pretty much in place, it weakens the abdominal wall, which is why men are more prone to certain types of hernias than women are.