Look at humans: I think it goes like this homo-halibus->homo-erectus->homo-sapien. That is not a smooth transition. I will use a car analogy. The three human species are like the '55,'56 and '57 Chevy. These are distinct models. There are no 55 1/2 Chevys with a blended design incorporating some features of the '56 model year. Now the cars may share the same sealed beam headlight assembly, the eye equivalent in humans, but that does not mean they are not distinct and different designs. You cannot swap a fender from a '56 Chevy with a '57.
To my knowledge there are no homo-erectus/homo sapien cross breed transitional fossils. Same with every species in the chain of human development.
This is my observation a trained engineer.
I don’t see much of an analogy between biological procreation and 1950s model Chevys. Unless it procreation done in the back seats of 1950-ish Chevys.
That’s my observation also as a trained but “not-overly-interested-these-’ How Many Angels Can Dance On The Head Of A Pin’- arguments” engineer!