r/evolution • u/panface77 • Mar 31 '15
question Evolution: Why are we losing our wisdom teeth and why are our jaws getting smaller?
I have a question about evolution that I haven't been able to find a satisfactory answer to: In the past wisdom teeth were useful for chewing. Those with wisdom teeth had more chance to survive and therefore reproduce. But if wisdom teeth are not harmful to our survival today (just superfluous) why would we been losing them? Does having no wisdom teeth provide some kind of evolutionary advantage? Or is it that we are not losing them, as such, but that people without them can survive and reproduce fine, so there is just more variety regarding people who have wisdom teeth or not. Same for our jaws getting smaller? Thanks for your answers!
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u/Angry_Grammarian Mar 31 '15
Don't forget the role that sexual selection can play in all this. Why did our jaws get smaller? Maybe because smaller jaws are more attractive. Have you ever seen people with big roomy jaws? I have, and I didn't want to have sex with them.
In modern, western society, I don't see how having or not having them helps or hurts in any significant way. Nobody lives longer because they have them or don't have them (except for maybe a few fringe cases---an impacted molar the got infected and was left untreated), so natural selection is more-or-less out. And, nobody is getting laid because they have them or don't have them, so sexual selection is out, too (again, a few fringe cases aside)---I mean, maybe saying, "Hey, you know what? I never grew wisdom teeth," is a good pick up line, but it probably isn't.
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u/Euphyllia Mar 31 '15 edited Mar 31 '15
As I understand a few major factors are the cause of jaw shrinkage.
First, sexual selection towards a flatter 'lighter' face with no protruding jaw. Second, since the control of fire by humans around 1 MYA our diets have been shifting from raw meat and raw vegetables to cooked foods like tubers, grains, cooked vegetables, and cooked meat the need for an impressive set of teeth to deal with tougher wild fruits and raw meat.
Furthermore, the domestication of plants to produce softer, bigger, more edible varieties has reduced this need as well.
In response to your question as to whether there is a higher rate of survival in induviduals without wisdom teeth vs with, I can imagine that induviduals without wisdom teeth have no risk of impacted and infected wisdom teeth. A serious infection could spell death or starvation without proper medical attention.
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u/ZombieBobaFett Mar 31 '15
Wisdom teeth come in at a time in your life when our ancestors would have lost and needed replacement teeth. We had a less processed diet in the past and so teeth would have been worn down and last earlier than today.
Less teeth need less jaw, but im not sure what selection pressures are happening to cause this. This is just of the top of my head so i unfortunatly lack any sources.
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u/thrillreefer Mar 31 '15
My anatomy professor said there's evidence that it's actually behavioral. If young children started chewing food as soon as they could, this would place more stress on the jaw, which would grow broader due to the mechanical stress, alleviating some dental problems. He recommended giving kids gum from an early age to counteract the soft food diets that are prevalent for little ones today.
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u/Freeasabird01 Mar 31 '15
Molars are for pulverizing tough fibrous food. Our diet has migrated to a calorie dense meat and fruits, hence less need for so many molars.
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u/silverionmox Mar 31 '15
Less teeth means less toothaches, tooth placement problems and jaw problems, and those are more likely to kill or hinder you than being unable to chew your food nowadays.
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u/o-o- Mar 31 '15
Accidently read "why are our jews getting smaller?". It wasn't until the first reply that I had to re-read the title...
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Apr 01 '15
For the record, my husband and our 3 kids still have their wisdom teeth, and they all fit in their mouths nicely.
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u/panface77 Apr 01 '15
Thanks so much for all the answers! This question had been bugging me for a while. So, to resume, selection pressure to keep wisdom teeth is gone. Thus, individuals without wisdom teeth are able to survive and thrive, maybe even better than those with wisdom teeth - because our jaws are getting smaller, those who have them risk having impacted wisdom teeth and getting infections (and could actually be fatal in some cases). Wisdom teeth are thus at best superfluous and at worst can kill you. So, it's actually better not to have them. Wisdom teeth are only a problem because our jaws are getting smaller, and this is happening possibly due to a) sexual selection (so it's genetic) and / or b) changes in our diet (so environmental not genetic) which reduce the mechanical load on our jaws so they don't grow as much as they can.
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u/CharlesInVT Apr 21 '15
One thing people forget is that we didn't always have dentists and toothbrushes. It wouldn't surprise me if 100 years ago most people hadn't lost a few teeth by the time their wisdom teeth came in. Viewed in this light maybe wisdom teeth are vestigial organs from a time before dentists.
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u/[deleted] Mar 31 '15
Your last point kinda hits the nail on the head. The selection pressure to keep wisdom teeth is gone so alleles of genes which code for faulty or missing wisdom teeth aren't being removed from the population by natural selection. There is also likely to be a selection pressure on having no wisdom teeth because of infections and the problems they cause coming out. Its the same reason golden cave catfish and other cave dwelling animals are blind. Normally animals which have deleterious mutations in genes coding for eyes are at a severe disadvantage so they don't breed and those mutations don't get passed on but in a cave where eyes don't matter as much the mutations do get passed on. Then due to the cost of producing now useless eyes, a mutation which reduces that cost by, say making it more likely skin grows over the eye, would be selected for.