0:00:07.123,0:00:09.763 When a team of archaeologists[br]recently came across 0:00:09.763,0:00:13.003 some 15,000 year-old human remains, 0:00:13.003,0:00:15.293 they made an interesting discovery. 0:00:15.293,0:00:19.122 The teeth of those ancient humans[br]were riddled with holes. 0:00:19.122,0:00:23.942 Their cavities were caused by the same[br]thing that still plagues us today, 0:00:23.942,0:00:28.124 specific tiny microbes [br]that live in our mouths. 0:00:28.124,0:00:30.512 These microbes are with us[br]soon after birth. 0:00:30.512,0:00:34.313 We typically pick them up as babies[br]from our mothers' mouths. 0:00:34.313,0:00:35.924 And as our teeth erupt, 0:00:35.924,0:00:39.943 they naturally begin to accumulate[br]communities of bacteria. 0:00:39.943,0:00:41.194 Depending on what we eat, 0:00:41.194,0:00:43.621 and specifically how much sugar[br]we consume, 0:00:43.621,0:00:48.493 certain microbes can overpopulate[br]and cause cavities. 0:00:48.493,0:00:52.343 Diets high in sugary foods cause[br]an explosion of bacteria 0:00:52.343,0:00:55.994 called mutans streptococci[br]in our mouths. 0:00:55.994,0:00:58.874 Like humans, these microorganisms[br]love sugar, 0:00:58.874,0:01:03.306 using it as a molecular building block[br]and energy source. 0:01:03.306,0:01:04.653 As they consume it, 0:01:04.653,0:01:07.944 the bacteria generate byproducts[br]in the form of acids, 0:01:07.944,0:01:09.894 such as lactic acid. 0:01:09.894,0:01:13.144 Mutans streptococci are resistant[br]to this acid, 0:01:13.144,0:01:16.314 but unfortunately, our teeth aren't. 0:01:16.314,0:01:20.404 While each human tooth is coated[br]in a hardy, protective layer of enamel, 0:01:20.404,0:01:22.803 it's no match for acid. 0:01:22.803,0:01:28.154 That degrades the armor over time,[br]leaching away its calcium minerals. 0:01:28.154,0:01:31.575 Gradually, acid wears down a pathway[br]for bacteria 0:01:31.575,0:01:35.576 into the tooth's secondary layer[br]called the dentin. 0:01:35.576,0:01:40.195 Since blood vessels and nerves[br]in our teeth are enclosed deep within, 0:01:40.195,0:01:43.875 at this stage, the expanding cavity[br]doesn't hurt. 0:01:43.875,0:01:46.045 But if the damage extends [br]beyond the dentin, 0:01:46.045,0:01:48.376 the bacterial invasion progresses 0:01:48.376,0:01:52.856 causing excruciating pain[br]as the nerves become exposed. 0:01:52.856,0:01:55.665 Without treatment, the whole tooth[br]may become infected 0:01:55.665,0:01:57.346 and require removal 0:01:57.346,0:02:00.586 all due to those sugar-loving bacteria. 0:02:00.586,0:02:02.505 The more sugar our food contains, 0:02:02.505,0:02:04.895 the more our teeth are put at risk. 0:02:04.895,0:02:09.826 Those cavemen would hardly[br]have indulged in sugary treats, however, 0:02:09.826,0:02:11.977 so what caused their cavities? 0:02:11.977,0:02:16.135 In meat-heavy diets, there would have[br]been a low-risk of cavities developing 0:02:16.135,0:02:19.256 because lean meat [br]contains very little sugar, 0:02:19.256,0:02:22.285 but that's not all our early human[br]ancestors ate. 0:02:22.285,0:02:27.285 Cavemen would also have consumed[br]root vegetables, nuts, and grains, 0:02:27.285,0:02:29.830 all of which contain carbohydrates. 0:02:29.830,0:02:32.027 When exposed to enzymes in the saliva, 0:02:32.027,0:02:35.645 carbohydrates get broken down[br]into simpler sugars, 0:02:35.645,0:02:40.105 which can become the fodder[br]for those ravenous mouth bacteria. 0:02:40.105,0:02:44.376 So while ancient humans did eat[br]less sugar compared to us, 0:02:44.376,0:02:47.392 their teeth were still exposed to sugars. 0:02:47.392,0:02:50.666 That doesn't mean they were unable[br]to treat their cavities, though. 0:02:50.666,0:02:54.638 Archaeological remains show that[br]about 14,000 years ago, 0:02:54.638,0:03:00.549 humans were already using sharpened flint[br]to remove bits of rotten teeth. 0:03:00.549,0:03:02.917 Ancient humans even made[br]rudimentary drills 0:03:02.917,0:03:06.018 to smooth out the rough holes left behind 0:03:06.018,0:03:10.369 and beeswax to plug cavities,[br]like modern-day fillings. 0:03:10.369,0:03:13.387 Today, we have much more sophisticated[br]techniques and tools, 0:03:13.387,0:03:17.877 which is fortunate because we also need[br]to contend with our more damaging, 0:03:17.877,0:03:20.180 sugar-guzzling ways. 0:03:20.180,0:03:24.559 After the Industrial Revolution,[br]the human incidence of cavities surged 0:03:24.559,0:03:27.308 because suddenly [br]we had technological advances 0:03:27.308,0:03:31.209 that made refined sugar cheaper[br]and accessible. 0:03:31.209,0:03:37.058 Today, an incredible 92% of American [br]adults have had cavities in their teeth. 0:03:37.058,0:03:39.947 Some people are more susceptible [br]to cavities due to genes 0:03:39.947,0:03:42.998 that may cause certain weaknesses,[br]like softer enamel, 0:03:42.998,0:03:46.928 but for most, high sugar consumption[br]is to blame. 0:03:46.928,0:03:50.218 However, we have developed other ways[br]of minimizing cavities 0:03:50.218,0:03:53.750 besides reducing our intake of sugar[br]and starch. 0:03:53.750,0:03:56.630 In most toothpastes [br]and many water supplies, 0:03:56.630,0:03:59.328 we use tiny amounts of fluoride. 0:03:59.328,0:04:03.109 That strengthens teeth and encourages[br]the growth of enamel crystals 0:04:03.109,0:04:06.470 that build up a tooth's defenses[br]against acid. 0:04:06.470,0:04:08.020 When cavities do develop, 0:04:08.020,0:04:11.909 we use tooth fillings to fill [br]and close off the infected area, 0:04:11.909,0:04:13.989 preventing them from getting worse. 0:04:13.989,0:04:18.120 The best way to avoid a cavity[br]is still cutting down on sugar intake 0:04:18.120,0:04:20.151 and practicing good oral hygiene 0:04:20.151,0:04:23.051 to get rid of the bacteria [br]and their food sources. 0:04:23.051,0:04:24.900 That includes regular tooth brushing, 0:04:24.900,0:04:25.909 flossing, 0:04:25.909,0:04:27.160 and avoiding sugary, 0:04:27.160,0:04:28.003 starchy, 0:04:28.003,0:04:31.671 and sticky foods that cling to your teeth[br]between meals. 0:04:31.671,0:04:36.050 Gradually, the population of sugar-loving[br]microbes in your mouth will decline. 0:04:36.050,0:04:38.102 Unlike the cavemen of yesteryear, 0:04:38.102,0:04:41.950 today we have the knowledge required[br]to avert a cavity calamity. 0:04:41.950,0:04:43.700 We just need to use it.