Guiness World Records writes about 2 persons that have maximum quantities of extra extremities.
Pranamya Menaria (India; born August 10, 2005) has 25 in total (12 fingers and 13 toes). This is as a result of the condition Polydactyly and Syndactyly.
Devendra Harne, pictured above, (India; born January 9, 1995) also has 25 in total (12 fingers and 13 toes) as a result of the condition polydactylism.
Maybe it's not very comfortable. Too much fingers... Or better as others. I don't know. But the nature makes these experiments not only with humans. Look at this photo. Incredibly but "Pink Tentacle" writes about different octopuses that have an incredibly quantity of extremities. 85, 88 and even 96! Imagin poor octopi what a difficult life it has. Specially after some glasses of beer...
