Supposedly evolution was very efficient and evolved many human proteins over a few thousand generations. Yet obvious detrimental traits like wisdom teeth remained. Why?
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1$\begingroup$ You're asking about one specific case, but I think the more general question here has good answers for you. $\endgroup$– Bryan Krause ♦Commented Apr 24, 2017 at 1:23
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2$\begingroup$ Not everyone has problems with impacted wisdom teeth, and removing them is a profitable enterprise, so please use caution before you say we should evolve to 'x'. We have always had wisdom teeth, but removing them is a relatively recent affair. $\endgroup$– anongoodnurseCommented Apr 24, 2017 at 1:33
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1$\begingroup$ Please explain why wisdom teeth are "obviously" detrimental, because it's certainly not obvious to me :-) $\endgroup$– jamesqfCommented Apr 24, 2017 at 5:57
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$\begingroup$ I dunno who would describe evolution as "very efficient", it can result in amazing solutions that would be incredibly hard to arrive at by design but making random changes and throwing away the bad ones is not exactly quick or waste-free. $\endgroup$– JCThomasCommented Apr 24, 2017 at 8:37
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$\begingroup$ I would also point out that evolution does not have a will! It just happens. The fact that some traits change faster or slower over time is a matter of chance. $\endgroup$– alec_djinnCommented Apr 24, 2017 at 10:01
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2 Answers
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Reductions in the size of our lower jaw that result in wisdom teeth sometimes becoming impacted result from changes in our diet, and are not the direct result of the evolution of a smaller jaw. This means that natural selection has had at most 8000 years to act on the phenomenon, which occurs in people in their mid to late 20s (who, historically, probably would have already reproduced if they were going to), and so the selective advantage of lacking wisdom teeth has not had enough time or been strong enough to cause the no-wisdom-teeth phenotype to spread throughout the human population.
Before Agriculture, Human Jaws Were a Perfect Fit for Human Teeth - Smithsonian.com (2015)
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$\begingroup$ the real risk with wisdom teeth is splitting the jaw, but as you said that only became a problem after the invention of soft processed food. $\endgroup$– JohnCommented Apr 24, 2017 at 13:56
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$\begingroup$ I would wager that removal of impacted wisdom teeth has resulted in more deaths than infection from said teeth. There is not a single randomized trial proving - or even attempting to prove - that removal of wisdom teeth has a beneficial effect on quality/duration of life. The UK's NHS stopped paying for the standard procedure, and the Cochrane Report advises against it. I have my wisdom teeth; my dentist was peeved because one of them had a small cavity. When I asked why he was upset, he answered that they were hard to fill way back there. He advised me to have it removed. Um, nope. $\endgroup$ Commented Apr 24, 2017 at 14:53
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$\begingroup$ Furthermore, neither of your your citations (one depends on the other) does not deal with wisdom teeth, but with malocclusion. You need better sources. -1 for misinterpretation/misinterpretation of support sources. $\endgroup$ Commented Apr 24, 2017 at 14:55
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$\begingroup$ @anongoodnurse It's possible that wisdom teeth cause problems and also removing wisdom teeth causes problems. I wasn't arguing in favour of surgery, or against it, modern surgery is irrelevant to the discussion. The PLOS One paper discusses jaw size changes as a result of change in lifestyle, I've found another paper that discusses it more explicitly. I've made the assumption that this would be the cause dental crowding and impaction of wisdom teeth problems, I suppose this assumption could be wrong. $\endgroup$– JCThomasCommented Apr 24, 2017 at 15:28
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Wisdom teeth do have a function. If you are missing a molar before the age of 20, a wisdom tooth can easily move in to fill in the gap, by filling in the space or by pushing the molar ahead of it.
This trick has been used by dentist to "fix" the teeth of teenagers who have molars with large cavities but still have wisdom teeth that have not erupted. So rather than go to extremes to save a bad molar, it is just yanked out and the wisdom tooth slips in. Problem solve. ( of course it depend on the actual wisdom tooth as some wisdom teeth are improperly positioned or appears unlikely to erupt to enable this trick to be used) example
Modern dental hygiene is good (but not good enough). So people tend to have all their molars in their early 20s (but not in their mid 30s). The the wisdom comes in too early to be useful to modern people. But i am guessing it had more use in earlier times.
That said... the trait for (third molars) wisdom teeth does not appear to be under positive selection in the human population as not everyone has it. Numbers vary depending on population. 10 to 25 percent of Americans of European ancestry are missing at least one third molar. For African Americans it is 11% and Asian Americans, the figure is 40 percent. The Inuit, a group of people who live in the Arctic regions of Canada, Greenland and Alaska, have the fewest wisdom teeth; about 45 percent of them lack one or more third molar.
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2$\begingroup$ You need a source for your statement that wisdom teeth are being selected against. That is not a credible claim. $\endgroup$ Commented Apr 24, 2017 at 1:32