You may have heard of the “Aquatic Ape” proposal — that humans are the way they are because there was an aquatic period in their evolution. You know: lack of body hair, layer of subcutaneous fat, webbed feet etc. (Doesn’t everybody have webbed feet? I thought I was the odd one out. My last girlfriend had webbed feet.)
It’s an intriguing idea. Unfortunately, when you look into it in even a little detail, the whole theory begins to look very shaky. Here’s a reference to a rather grumpy rebuttal of the main points: http://www.straightdope.com/mailbag/maquaticape.html.
(There’s a link from that page to the equally throught-provoking ‘Pliocene Pussy Cat Theory’ http://www.improb.com/airchives/paperair/volume7/v7i5/pliocene-pussy.html ).
You will note that, for example, seals, otters, platypuses, manatees, beavers and polar bears all have fur. Of all the marine mammals, only the whale and dolphin family are naked. So I think the hairlessness thing is a red herring. Red herrings may or may not have hair.
Anyway, the mainstream view of human evolution is that our ancestors were arboreal apes who adapted to walking on the ground when the climate became drier and jungle gave way to hot savannah. Seems fair enough to me. It explains why I always feel so cold in this distinctly non-African climate.
By the time our ancestors had become fully human, and had started to migrate out and populate the world, they had evolved to exist in a hot, dry climate.
That’s why the popular notion that we need to drink huge amounts of water every day is so obviously bogus. The typical figure quoted in the stories that circulate is “eight glasses of water”. Sometimes, in American sources, it’s spelled out more precisely as “eight 8oz glasses”. That’s about two litres a day. I’ve even seen web sites where the eight glasses have been mysteriously converted to eight litres. But there’s no medical evidence for any of these figures.
What the real doctors say is that the average adult human in a temperate climate needs to replace about a litre of fluid a day. A typical diet contains almost a litre of water per day in the food alone, so any additional liquids at all will ensure that you have enough.
And it can be any source of water, of course. It doesn’t have to be any of the magic hydrating products, or spring water in a stylish plastic bottle. Anything will do: tea, coffee, orange juice, soup, or even Coca bloody Cola. Although that rots your teeth and makes you fat.
(See the invaluable Snopes http://www.snopes.com/medical/myths/8glasses.asp for a detailed analysis.)