Why in the world would they do that?
Beats me. According to the evolutionist anything is possible. Not only did we lay eggs once, we laid them while swinging from trees. There's nothing to validate this as anything but someone's over-active imagination. I look at my little cocker spaniel and don't think of her as a 115th cousin once removed. Yes we have a few things in common as mammals, air breathing lungs for one, live birth for two, but other than that I can't see some critter crawling out of a cess pool and deciding to be a dog or a human. IF we were dependent upon water/drought conditions then yes, maybe I could see us becoming fish or amphibious. That would leave us two, possibly three, animal forms on earth that could survive under water/air/both conditions. But a fish crawling upon land and thinking "hmmm, do I want to be a cocker spaniel or a human....decisions decisions."
We have walked on the moon, explored Mars, measured light from distant galaxies, broken much of the human genetic code and still nobody can say how we went from fish to human or provide definitive proof thereof. I'm keeping an open mind, just saying there IS no proof that evolution, a/k/a Darwinism, is nothing more than junk science.