Evolution of live birth: Provided we ignore the placenta
|August 30, 2010||Posted by O'Leary under Darwinism|
Here’s an article on the supposed evolution of live birth:
… even the live-bearers have not got rid of the shell entirely. Baby skinks that are born live come out encased in a membrane – all that is left of the eggshell. With a bit of help from their mothers, most of them break out of the membrane within 36 hours.
How did live birth evolve? One group of the egg-laying skinks retain their eggs inside their bodies for longer than the others, and it seems that the live-bearers evolved from these “intermediate” skinks.
Reptiles are more likely to develop live birth if they live in cold climates, where it is a good idea to protect their offspring in their bodies, rather than exposing them to the rigours of the environment too soon. Sarah Smith of Stony Brook University, New York, points out that this explains why it is the skinks who live in the chilly highlands that give birth to live young.
Journal reference: Journal of Morphology, DOI: 10.1002/jmor.10877
I don’t get how this shows that live birth is evolving.
Animals that produce their young in eggs have way different systems from those that produce them via placentas, as do mammals.
With eggs, live birth is just a technicality.
In other words, the eggs hatch indoors instead of outdoors.
Maybe some snakes or skinks are in between, but so?
To me, a more significant interest is the reptiles that protect their eggs or young, like crocodiles, alligators and cobras. that suggests that the theory of the unfeeling reptilian brain is not true.