Yes, all valid points to some extent.

> don't they?

dolphins, whales?

That was my first reaction, eta - doubtless influenced by the fact I've just been reading Elaine Morgan's The Aquatic Ape, in which she synthesises the scientific evidence and theories suggesting an important period of human evolution that would place us in a directly analagous state to other water-based mammals, not least in terms of brain development and language and social organisation.

Does anyone know what more up-to-date thinking is on these theories? (meanwhile, keep on eating those omega-3 fatty acids!)