[akirk]

I think it is a very important detail to understand that new life has to grow in water.

When life moved out of the water, different life-forms discovered a way to take that environment away from the water to have their embryos grow: Birds keep the water in eggs, mammals in their womb.

While egg-laying animals create self-contained environments, mammals need much more energy to develop therefore have to be live-fed. So they feed this separate, new creature. Of course they have to protect themselves from them.

[infinite8s]

If you go even further, our cellular milieu has similar chemical potential as sea water, so we are in effect walking bags of sea water.