ok slimebeast (if that is your real name) here are direct quotes without all the other hubbub to help you see it more clearly.
Starts off with...
"Along the warm coastal lowlands of New South Wales (map), the yellow-bellied three-toed skink lays eggs to reproduce. But individuals of the same species living in the state's higher, colder mountains are almost all giving birth to live young."
Then the article continues with other reptile species and some history notes.
Then...
"One of the mysteries of how reptiles switch from eggs to live babies is how the young get their nourishment before birth."
Generalization, but still distict to each population; those that have eggs and those that have live babies. Then it discusses how a placenta helps mammals and how eggs give calcium.
"In mammals a highly specialized placenta connects the fetus to the ovary wall, allowing the baby to take up oxygen and nutrients from the mother's blood and pass back waste.
In egg-laying species, the embryo gets nourishment from the yolk, but calcium absorbed from the porous shell is also an important nutrient source."
Then it discusses in general terms how a thin shell (or no shell with live birthing skinks) could have a nourishment issue. Then it moves on to the scientists studying these northern skinks...
"Stewart and colleagues, who have studied skinks for years, decided to look for clues to the nutrient problem in the structure and chemistry of the yellow-bellied three-toed skink's uterus."
The conclusion for these specific southern skinks is....
" 'Now we can see that the uterus secretes calcium that becomes incorporated into the embryo—it's basically the early stages of the evolution of a placenta in reptiles,' Stewart explained."
Then it concludes with the answer to 'why' would this transition happen, thus why would they evolve to an entirely different birthing platform.
