While doing research for my post on the mammalian dive reflex, I stumbled across an interesting TED video. It discusses the idea that humans evolved as "aquatic apes" somewhere between the common ancestor between chimps (~6,500,000 years ago) and the first know Homo sapiens (~200,000 years ago). If you look at a timeline of paleolithic fossils, it's hard to see where this would fit in.
From a speciation standpoint, this wouldn't be unprecedented. Whales evolved to their current iterations from land mammals. Though not a direct evolutionary ancestor, think about the modern hippo. They spend the bulk of their time in the water... even for mating. Interesting evolutionary side-note: Did you know whales have vestigial hips and legs embedded in their bodies... similar to our tailbones? Did you also know that whales are sometimes born with external legs through peculiar gene expressions?
As you watch the video, keep in mind that the hypothesis doesn't say that we evolved from apes who had moved into aquatic areas and became fully adapted to aquatic life. It merely suggests that our ancestors spent a significant amount of time in the water for hundreds of thousands of years (guessing)... or just long enough to begin to develop adaptations for "a life aquatic". Compelling evidence is our slightly webbed fingers and toes, and our ability to consciously override our breath control. The latter is key for diving and isn't found in the majority of mammalian species. It's also related to our ability to speak, a la voice control.
However, the mammalian dive reflex doesn't really fit with the hypothesis. Since it's found in nearly all mammals, there's no reason to believe that the hominin line evolved it during the Paleolithic.
Did I mention this theory is almost universally ignored? Did I mention I don't think there's currently any compelling reason to believe it? Oh well, it's interesting. It also attempts to explain some things that aren't necessarily 100% explained by the strict African savanna hunter-gatherer hypothesis. As such, I think it's an interesting exercise in testing our assumptions...
Edit: I was sent the following video via a friend on Twitter:
<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/0kVbW_ZoC_8?fs=1&hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/0kVbW_ZoC_8?fs=1&hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>