what does evolution theory teach about how mammels came to lactate,and giv birth to live young rather than?

Question

eggs?

cathy, i actually heard that the mother gets the germs by kissing the baby´s skin, but yeah, its amazing

Answer 1

It's not clear, but there are various theories.

Regarding the mechanism, it's thought that mammary glands arose from apocrine sweat glands (hair oil glands). One theory proposes that early mammary glands were for supplying nutrients to permeable eggs, as well as keeping them moist.

As for live young and mammary glands in general, there are various advantages that apply (not necessarily all at the same time). Caring for young, post-birth development (rather than womb development), mobility (eggs aren't very mobile) are some examples.

Answer 2

there are oviparous mammals, you do know that, right? Start there. The duckbilled platypus comes to mind. They also have toxin glands.

An intermediary form would be marsupials who birth a fetus that finishes development in an enclosed pouch.

Evolution theory, as you call it, supports these observations as intermediate forms of development of mammalian traits.

Answer 3

Well, the rules of evolution cause us to look for animals that lay eggs but still lactate to maintain their young as precursors to mammals and we find the monotremes, including the platypus and akidna (sp?) which do exactly that.

Answer 4

I would love to know this one - lactation is amazing and breastmilk (or whatever species milk) is so perfectly tailored to provide the exact nutrition that an infant of that species requires. Personally I can't believe that such an elegant system arose by a series of unfortunate events. Did you know that if a baby gets sick, while nursing it "injects" some of the germs into the mother's breast, and then she makes antibodies against that disease in her milk? Incredible!