superchunk said:
For the love of God man, are you really incapable of expanding on the ideas presented in the article? The article says there is ONE species of skinks with TWO dramatically different birthing traits. Southern population lays eggs like other reptiles. It later says that animals that lay eggs (which would by default include these southern skinks) provide calcium to the embryo via the thick shell. The article then clearly says that the northern population give LIVE BIRTH, with a picture even. It later says that animals that give birth use a placenta to provide nutrients like calcium and that without a thick egg they would presume these skinks would potentially have defects. They then realized in these skinks that the mother has traits of an early placenta and give the embryo calcium directly to make up for the lack of a thick shell. How are you missing this relationship in the article? The author assumes that its readers can grasp the bigger connections here between the egg laying and live birth skinks to the general idea of the difference between eggs and placenta. |
You're interpreting it wrong. There is not a dramatical difference between birthing traits. Actually there is no difference at all between traits. The only difference is that the guys in the northern cold retain the eggs longer, because it's cold, not because they're different than the southern guys. They explain the reason why it's possible (in this snake and in others), namely that the uterus is able to secrete calcium to the thin eggs. But the guys in the south can do this too, it's just that there is no cold weather there to trigger the prolonged egg retainment.
