Complete source list – Link #122: Humans Are the Only Primates Without Palm Pigmentation
http://www.clinuvel.com/en/blog/lightandhealth/the-skin-on-your-palms-and-soles/
http://unrealfacts.com/only-one-primate-has-no-pigment-on-the-palms-of-their-hands/
http://uselessfacts.net/animal-facts/
http://informationcentral0.tripod.com/id19.html
http://www.angelfire.com/wv/stephsplace/know.html
http://www.begent.org/funfact.htm