Neurobiologically, a fetus becomes a person at about 9 months
post-natal, or 18 months after conception. This is because the need
for the woman to be capable of efficient locomotion precludes
enlargement of the cervix to a large enough diameter to permit
complete maturation of the child's brain in the uterus; among
placental mammals this species-wide premature birth situation is
unique, I believe.
-Daniel Pouzzner
