I have a tough time believing that millions of years of mammalian evolution left a flaw of lack of blood clotting after birth. I understand that a tiny percentage of babies have health complications from bleeding at birth, but I have to imagine that there was an evolutionary advantage to this too, or it wouldn't have developed that way. I would be interested in seeing some well-controlles studies showing the differences between health of babies (in the same population, of course) that did and didn't receive vitamin K shots.