When these get too long, they are prone to breaking and causing hangnails etc., and in extreme cases you see people with these really unweildy hands due to nails that are too long. So I assume that primitive people, i.e. those who didn’t have scissors or nailclippers or the equivalent, had some way of cutting them. But how? (biting them?)
FTM, what about the fingernails of apes and monkeys? Are they stronger than our or what?