All humans at sometime before birth have webbing between the fingers and toes. Use internet to find pictures of the human fetus before birth, and observe this. As the fetus ages before birth this webbing disappears. Sometimes this webbing has to be surgically removed by a doctor. Could a prolonged environment of water favor the genes to help us get oxygen from water, or swim faster.
Alleles are different forms of genes for one trait.
We have 4 alleles for any, one major or minor trait. Please look at the picture and identify the 4 alleles. You may have alleles for traits that you don't express. Would this have anything to do with that pink color. They have no other dark pigments to mask the pink.