Back, then back again.

[Darwinian]

We all know that whales and dolphins etc. returned to the sea as land mammals but, are there any animals out there that have not only returned to the sea but then returned to the land again?

[leo-rcc]

I don't know, good question.

[DD_8630]

The 'Aquatic Ape' hypothesis states that our ancestors returned to the oceans at some point. Evidence for this includes the way our hair grows on our bodies.

Of course, our ancestors didn't evolve to be as aquatic as our cetacean cousins, but still :p.

[lukec]

Interesting. The point made about the sub-cutaneous fat catches my eye. About the controlled breathing- can other apes not do this as well? Very odd, first I've heard of this, I'll have to look into it.

[Demonaura]

First I have heard as well. It's not impossible I suppose but, unlikely.

we would only evolve to live on land if it was the better environment for us. I think once we got here natural selection and our own desire to stay in the newer, more commfortable environment would at least keep enough of us on land to keep a species going.

Though two seperate subspecies is more likely too, or one simply getting killed off. But I still have not heard of any examples of creatures evolving and moving as a species onto land, and then back. My understanding of such matters is that the species would only make such a move if it were the better option, and afterwards theres almost no chance they would move back as long as land remained the better option.

[Kyuuketsuki]

The 'Aquatic Ape' hypothesis states that our ancestors returned to the oceans at some point. Evidence for this includes the way our hair grows on our bodies.

Of course, our ancestors didn't evolve to be as aquatic as our cetacean cousins, but still :p.

The Aquatic Ape theory (as PJ Myers of the Pharyngula blog says it doesn't actually deserve being called a "theory") is pretty much rubbish and you can read more here: Aquatic Ape: Sink Or Swim

Myers sums it up as follows:

This "theory" (really, it doesn't deserve the promotion) is often taken as quite reasonable at first glance — hey, whales have reduced body hair and are aquatic, humans have reduced body hair so maybe they also went through an aquatic stage in their evolution — but once you dig just a tiny bit deeper, the inconsistencies within the hypothesis and the contradictions with reality loom larger and larger, and you really should realize that it's utter nonsense. But weirdly, there are a number of people who have gotten quite obsessed with the idea and who have written reams of papers to rationalize the baloney. Back in the 20th century wrangles over the Aquatic Ape nonsense would spontaneously emerge on usenet all the time (here's one example) because its proponents had to be completely refractory to contradicting evidence. Good times.

One interesting twist to it all is that it's an odd variant of denialism. These people aren't rejecting an established scientific conclusion, such as that HIV causes AIDS or that human activities contribute to global warming — they are pushing beyond reason for a conclusion that science denies. I suppose you could say they're denying the evidence that shoots down their favored beliefs, but at least they actually have a positive (but bogus!) hypothesis that they aren't afraid to recite at you, which puts them several notches above the Intelligent Design creationists.

Anyway, Moore has a tremendous amount of useful information rebutting the Aquatic Ape Speculation — it's well worth a browse, and also amusing to read some of the crackpot defenses (one of my favorites is the claim that Neandertals had large noses that they used as snorkels). And I'm not just saying that because he was nice enough to stop by Morris!

Kyu