Why is it that we go through life with only two sets of teeth (prostheses being excluded for the purposes of this discussion :))? Evolution being what it is, wouldn’t it have been biologically natural for Early Man to grow a couple of extra sets given that personal hygiene (and diet?) were not exactly conducive to optimal maintenance of the pearly whites?
Why are tooth brushes available with hard bristles? Doesn’t it somewhat defeat the purpose by scraping away the enamel over time?
There was no evolutionary pressure to develop a third or fourth set of teeth in adulthood. The teeth our ancestors were provided with lasted them for a lifetime, which in those days was about 35 years.
The bristles, being a polymer, are simply not abrasive enough to wear down enamel, which is very hard.
I think.
Maybe.
I think wisdom teeth might be the third set of teeth. Incomplete, to be sure, but they replaced the teeth which would be worn down or busted most quickly. (I would have thunk that something nearer the mouth would be busted quicker by chewing, but I suppose a race of “grazing” humans would use their molars a lot for grinding up hard stuff.) Anyway, so the hunter gatherers would presumably lose some of their molars by age 20 or so, and the wisdom teeth would fill in the gaps, while their old incisors managed the lighter work of snipping food just fine.
Also, and here’s another thought, maybe if you did lose all your adult teeth, but got a new set of wisdoms, you could survive. Not having incisors and cuspids just meant that you had to cut up food real small; not having molars/wisdoms would mean you couldn’t chew anything. Which would be a real drag until Campbell’s soup came around.
Wisdom teeth are the last of the second set of teeth. But since our skull shape has changed (larger cranium but smaller jaw), there isn’t room for the last four teeth in most of us.
I have two of my 4 wisdom teeth (does that make me a half-wit? :)) I had my upper 12-year molars extracted for braces, so my upper wisdom teeth just grew in their place.
I’ve heard of some people who do grow a 3rd set of teeth. I guess they’re more highly evolved. 
I looked in the mirror today/My eyes just didn’t seem so bright
I’ve lost a few more hairs/I think I’m going bald - Rush
My dentist tells me not to use hard-bristle brushes, if that helps.
In early hominids teeth did get quite the workout due to the diet. You can see teeth in fossils that have been quite worn down. That said, as time move on and species evolved there were two disinct homonid types, Robustus and Gracile. [i}Robustus* generally were bigger boned and had larger jaws and teeth, Gracile types, to which modern humans belong, were not as thick boned and have smaller jaws and teeth. The main difference is due to diet, but there was a general trend in hominid evolution towards smaller jaws and teeth over time. This doesn’t really answer why we only have two sets of teeth but I think that it shows that there no evolutionary pressures for it to develop.
As far as hard bristled toothbrushes, I’m not sure since every dentist has told me to aoid them, I think they maybe for dentures.
Only 2 sets of teeth is bad enough. Why did we only get one heart via evolution?
Ich weiss nicht was solles bedeuten das Ich so traurig bin.
if we take wisdom teeth as the final part of the second set, and the fact that early man reproduced in the teens and died in the 20’s, maby 30, then we see no reason for more sets .: no evolutionary pressure for them.
The hard bristel question is a good one. A quick informal poll around the office has everyone telling me that their dentist specifically tells them to avoid using a hard bristel toothbrush.
So is this a toothbrush conspiracy, or does the dentist sit there going “Boy, is this patient an asshole. I think I’ll recommend the HARD bristel brush for him”. Who exactly is the person out there who is being told (or chooses) to buy these hard bristel toothbrushes? Or are they reserved exclusively for cleaning silver, and for new recruits in the military to clean toilets?
I used to always use hard bristled toothbrushes. I liked the feel of them. But then my dentist told me not to, so now I use soft. If I recall, his reason was that it would wear away the enamel in time. Of course, this is the same guy who wants me to have my still-under-the-gums wisdom teeth surgically removed despite the fact that in all my 33 years they have not caused me any problems whatsoever. Voluntary oral surgery thats not covered by insurance? Great! Sign me up!
Not in this lifetime.
“I should not take bribes and Minister Bal Bahadur KC should not do so either. But if clerks take a bribe of Rs 50-60 after a hard day’s work, it is not an issue.” ----Krishna Prasad Bhattarai, Current Prime Minister of Nepal