Februari 09, 2017
there's a certain set of humans in the worldthat hears the "why do i have to brush my teeth?" question pretty much every evening.right around, say 8 o'clock. almost always posed by the offspring of that person. usuallyunder the age of 10. and in those instances, the answer almost always is "because yourmother and i told you to!" but one of our followers on tumblr asked a more thoughtfulversion of this same question: "why do i have to brush my teeth from an evolutionary perspective?" the answer is still because your mother andi told you to! okay, actually, it is a pretty cool question. cause our primate ancestorsdidn't brush their teeth, and surely they didn't have their teeth falling out all overthe place, and they weren't dying of gingivitis.
right? right. well some of them did, but notall of them. i mean all animals that have teeth likelyhave to deal with tooth decay to some extent. veterinarians will tell you that they seecats and dogs all the time that have cavities or caries, as scientists call them. and biologistshave reported finding wild animals as diverse as lions, and bears, and orcas with huge painfulabscesses. but part of why we have to brush our teeth has to do with longevity. most wildprimates just don't live long enough for things like tooth and gum disease to catch up withthem. we do. for example, the life expectancy of our nearestevolutionary relative the chimpanzee is just 40 years in the wild. in captivity, though,it's around 60. and tooth decay can become
a problem with captive apes and monkeys, whichis why keepers have to regularly brush their teeth. which i imagine is not super fun. our life expectancy, meanwhile, is around80 in most industrialized countries, which means we're living twice as long as our closestgenetic relatives. so we gotta keep our parts working for a lot longer than they were probablysupposed to work. and this means brushing your teeth a couple times a day. considerit a small price to pay for having benefited so much from evolution. but beyond that, by far the most importantfactor that effects our dental health, as opposed to that of our genetic predecessors,is our diet. most primates live quite nicely
on diets of fruits, and seeds, and nuts, andleaves. and in the case of chimps, the occasional insect or piece of meat. but since we startedcultivating grain some 12,000 years ago, our diets have become totally dominated by starchesand the simple sugars that they contain. the bacteria that form cavities really love thesesugars, and for the same reason that we do:they are a very readily accessible form of energy.so the more sugar you eat, the more susceptible you are to tooth decay. and this is true notjust for leftover halloween candy and coca-colas, but any kind of cereal grain you can thinkof like wheat, or oats, or corn. the evolutionary connection between tooth decay and agricultureis so distinct in fact that anthropologists can actually determine whether a culture startedfarming in part by studying when they started
to get cavities. again, it's just part ofthe cost of being such an awesomely successful species. now seriously, brush your teeth!go to bed! it's late; you've got school in the morning! thanks for watching this scishow quick question.if you have a question that you would like us to answer, you can ask us on our tumblr,or our facebook, or our twitter, or in the comments of this video. and if you want tokeep getting smarter with us, you can go to youtube.com/scishow and subscribe.
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