How many fingers do you have? Hopefully, 5. Do you think that’s the normal condition for all animals? Do you think that’s air you’re breathing right now? … OK, so I watched the Matrix last night, but still, do you think all tetrapods (dudes with 4 feet, including you, and anything else with four flippers, wings, or feet) have 5 digits on each limb? Actually, there’s a pattern within tetrapods of limb reduction in various lineages – our earliest ancestors seemed to experiment with digit numbers and went a bit berserk by growing extra fingers from their fishy flippers.
Some early tetrapod limb bone patterns