There’s an old theory that humans went through an aquatic phase in our evolutionary history. I never gave it much credence until a few days ago, when a study came out showing that the wrinkling of fingers and toes in water is likely an adaptation.
This is what the study* showed:
In this study, we show that submerged objects are handled more quickly with wrinkled fingers than with unwrinkled fingers, whereas wrinkles make no difference to manipulating dry objects. These findings support the hypothesis that water-induced finger wrinkles improve handling submerged objects and suggest that they may be an adaptation for handling objects in wet conditions.
Further evidence that it is adaptive includes: the wrinkling is controlled by the autonomic nervous system; other areas of skin do not wrinkle (only fingertips and toes); and it makes it easier to walk on wet surfaces.
What does this imply?
- Looks like the aquatic ape hypothesis may be right. The idea that the human ancestral environment was the African savanna may be wrong (or at least partly wrong: humans may have later spread into the savannah and gained some adaptations there too.)
- Did it boost human brainpower? Seafood is supposedly good for the brain. More seafood may have meant a more intelligent species.
- Did it boost social evolution? Seashores and/or lakeshores are more constrained but also more food-abundant than savannahs. The savannah theory depicts early humans as nomadic wanderers, like today’s desert dwellers in the Kalahari. The seashore theory would depict early humans as more sedentary, living permanently in caves, defending shellfish beds, a bit like the forager but sedentary Northwest Coast Amerindians. This might have been boosted human social cooperation, a key thing that distinguished humans from chimps. Sociability among animals often arises from defending a permanent nest (like an ant colony). Sociability among humans may have arisen from living in a semi-sedentary coastal situation.
All speculative, admittedly, but its another decent theory to add to the pile of explanations of human social and intellectual evolution.
*Kyriacos Kareklas, Daniel Nettle and Tom V. Smulders, Water-induced finger wrinkles improve handling of wet objects Biol. Lett. 2013 9, 20120999, published online 8 January 2013