SCIENCE
ONE of the marvels of evolution has been the egg: a self-contained unit which houses everything the embryo requires for development. But when you think about it, when a bird passes a large, hard mass as big as an egg - big in relation to their body size - it must surely be a painful experience for them. Compare how painful childbirth is for humans. Yet from the bulk of scientific data available on the subject, that does not appear to be the case.
Humans have an uncanny habit of transferringLabour pains are caused by contractions of the muscles of the uterus, accompanied by pressure on the cervix. Birds do not have a cervix in their reproductive system. They do have a uterus, but it is not comparable to that found in mammals, as it is essentially the shell gland, which does not allow ova implantation.
