>>8999381that's harder to pin down because more or less fingers actually does show up even in complex organisms sometimes, so it's something that evolution still has something to play with rather than being rigid (evolution is limited by what is viable, and once something has its niche it is hard to change, especially one more fundamental - it's why ribosome genes hardly evolve at all). it's worth pointing out that not just mammals have 5 digits but so do birds, reptiles, and amphibians, meaning it was also something that developed a long time ago. what it seems is that 5 allows for a good spread and versatility (things like grip, balance and combat) while any more would be redundant, offering fewer benefits for higher costs, and less would be easier to develop but offer less to the organism
some organisms have gotten around the 5 digit thing though: hooves develop as a fusion of digits, as well as flippers. wings also are kinda unique in birds, you can barely make out the 5 digit part of it
so basically, it just so happened that 5 won out in evolution a long time ago, and all the tetrapods (mammals, birds, amphibians, reptiles) have evolved slight differences on those 5 digits, in some cases fusing them back together to in the end form less. this is what i mean by evolution is a tinkerer, it just makes small changes to what's already there instead of drastic big ones. and if something lands at the local extrema, where a small change in any direction is worse even if a large change in a direction is better, evolution will keep it the way it is
