There is a highly complex biochemical relationship between the embryo and the mother. The mother actively tries to kill anything that might be in her uterus, s

There is a highly complex biochemical relationship between the embryo and the mother. The mother actively tries to kill anything that might be in her uterus, she even periodically cleans her uterus radically by ejecting a layer of it. The embryo needs to produce hormones that manipulate the mother to stop that, and deliver them into the mother. If the embryo fails, it dies. Source: http://aeon.co/magazine/science/pregnancy-is-a-battleground-between-mother-father-and-baby/ http://aeon.co/magazine/science/pregnancy-is-a-battleground-... We do something similar in software development. If our program experiences a segfault, we usually let it die, instead of figuring out at runtime what went wrong and trying to do what we still can do. Then we change something and try again. Making it hard for the embryo in the beginning and starting over if it didn't make it, is the biological equivalent to that strategy. It might result in a heuristic whether it's worth investing more resources in it. Saving resources gives an evolutionary advantage. On the other hand, it makes evolutionary progress harder since more conformity of the embryo is a condition to survive.