Okay, aside from being mammals, and all the mammal qualities like hair, being warm blooded, etc., what do rabbits, beavers, and horses have in common? Their adult teeth never stop growing! These animals have to grind them down to keep them from becoming too large to fit in their mouths!
Imagine if humans were like this. You know when you get a shitty haircut, and it’s painful to leave the house, but you know, in a month or six weeks, it’ll just be a bad memory? Now picture that with your teeth. You catch a handlebar in the grill, break three teeth and feel like the rest are going to fall out, and you know you don’t have to go to the dentist! They’ll be growing out here pretty soon!
Alright, for ‘Long in the Tooth’, I have to reference another phrase here to give you the entire picture. You’ve heard the phrase ‘Never Look a Gift Horse in the Mouth’, right? That’s because it’s difficult to gauge a horses age without looking at its teeth. You see, when horses are young, their teeth come in nearly straight up and down from their gums, meeting where they can wear each other down as the animal ages. But, as the horse gets older, its teeth start to angle outward, still meeting to wear properly, but protruding farther and farther from the gums. So, someone who knows what they’re looking for can pretty much make a semi-accurate estimate of a horses age by the angle at which the teeth protrude. This makes ‘Looking a Gift Horse in the Mouth’ like getting a really nice gift, then pointing out the problems with it.
Another way to explain this is, if you think of two lines, coming at each other from two different points and meeting, you get the shortest distance, or for a young horse, the shortest teeth. But if you take those same lines from the same points and, while keeping them meeting in the middle, slide that meeting point farther away from center, the lines get longer the farther that meeting point is moved away, like the teeth of an elderly horse.
So, while researching this phrase, my childhood conclusions about its meaning was shattered. But, we know that ‘Long in the Tooth’ comes from horses’ teeth protruding farther and farther from the gums as they get older!