Theory that humans spent part of our recent evolutionary history living by (and largely in) the sea. Hence many adaptions which are odd for land animals, and hard to explain (eg. loss of fur while gaining layers of subcutaneous fat, salt tears, upright walking) are more common in aquatic mammals or easy to understand in the context of a litoral lifestyle.
Amazing how many people I keep bumping into who espouse this theory. I recently met a distant relative-in-law who told me he was writing a book of semi-fictionalised essays highlighting our aquatic nature as it has developed through the ages.
Do you have a view on this Phil?
I really like the theory. I hope its true. For all kinds of reasons. (Not least because I love living by the sea.) I like ElaineMorgan's orginal book "The Descent of Woman" very much. It's a) very radical, and b) very funny. (Having failed to convince the BETON Companhia de Dança to base their La http://paginas.terra.com.br/arte/LaMer/ La Mer on it last year, I'm hoping that a new dance company I know might use the story. )
I'm not bothered by a lot of the criticism that Morgan is "unscientific". As I read it, her way of operating : ie. picking the current "best" theories and criticising them, is almost identical to KarlPopper's presentation of the pre-socratic philosophers (Thales, Anaximander, Anaximenes) which he holds up as the paradigm examples of critical / scientific tradition.
Having said that, I think her critics, linked above, also raise important questions : the predation by crocodiles thing, the degree of difference between human hair-loss patterns and other marine mammals. I don't think they succesfully answer all the questions she raises, but in some cases, they raise counter-issues that are as awkward for her as anything she uses to criticise the "Tarzan" theory.
So basically, I think it's one hell of a bold conjecture. Even if it's wrong, the work done to answer the questions it raises and find what's wrong with it, is very useful work for the reconstruction of early proto-human life. And it should be taken seriously. I'm not knowledgable enough to judge exactly where all the detailed evidence points. But I haven't been persuaded by the anti-story that it can't be true. Though it certainly might not.
The other problem, of course, is that it does resonate with a lot of new-age stuff about the sea, which I have no interest in. I can see that there are plenty of people willing to both praise or damn by association with that. (As I suppose, many political left-wingers want to criticise Tarzanism for the macho, competitive story it tells.)