00:00Where you're from can shape your life in some pretty unexpected ways, including how likely you are to deal with
00:06earwax clogging up your ears.
00:09If you are East Asian, your earwax will almost definitely be dry and white.
00:14And if you come from Europe, Africa, or the Americas, let me guess, yours is yellow and sticky, right?
00:21If that's your case, I have some not-so-pleasant news for you.
00:25You're more likely to get blocked ears than your East Asian friends.
00:30Sticky wax clumps together easily and picks up some dust and debris on its way down the ear canal.
00:36And bam, you've got a plug in there.
00:38Pushing it down with a cotton swab or earbuds only makes things worse.
00:43Dry earwax is flaky and brittle, so it finds its way out of the ears more easily.
00:48Scientists figured out that this difference in earwax quality comes down to one gene called ABCC11.
00:56If you inherit two copies of the A version of this gene, your cells don't release certain oily molecules, and
01:03you've got dry earwax.
01:05If you inherit at least one G version, those molecules get released, and you get wet earwax.
01:13That same gene doesn't stop at your ears.
01:16It also controls what happens in a specific kind of sweat gland called apple cream glands.
01:22These glands don't cool you down like normal sweat glands.
01:26Instead, they release a thicker fluid loaded with proteins and fats.
01:30On their own, these fluids don't smell, but bacteria treat them like an all-you-can-eat buffet, and the
01:36waste products from the feast are what we recognize as body odor.
01:40If your ABCC11 gene doesn't release those compounds, bacteria have nothing to work with, and your sweat barely smells at
01:49all.
01:50This explains why many people with dry earwax don't really need deodorant.
01:55They still sweat, but the sweat doesn't turn into odor the same way.
01:58That's why deodorant culture exploded in some regions and barely existed in others.
02:04First of all, East Asia, until global marketing stepped in.
02:08Dry earwax isn't just common in East Asia.
02:11It's dominant.
02:13In countries like Korea, China, and Japan, the majority of people carry the A variant.
02:18Genetic mapping shows this mutation likely appeared in Northeast Asia, tens of thousands of years ago,
02:25then slowly spread outward as humans migrated.
02:29Genes don't spread for fun.
02:31Evolution only keeps things that help you survive or reproduce.
02:35So, what was the advantage?
02:38One theory points straight at climate.
02:41Ancient Northeast Asia was cold, brutally cold.
02:45Sweat that doesn't evaporate easily becomes a liability in freezing temperatures.
02:50Less oily secretion means sweat dries faster, reduces heat loss, and lowers the risk of hypothermia.
02:58Another theory says smell equals danger.
03:02Strong body odor makes you easier to track.
03:05Not just by other humans, but by predators.
03:08If you're living in dense forests or snowy terrain where sound carries poorly,
03:13scent becomes a neon sign saying,
03:16Food! Over here!
03:18Less odor could mean fewer unwanted encounters.
03:22What makes this story so cool is how rare it is.
03:26Most visible human traits don't come from one gene.
03:30Height, skin tone, and intelligence all involve hundreds or thousands of genes working together like an orchestra.
03:37But earwax type is just one typo in your DNA instruction manual.
03:42Change one letter, and your body runs a different program.
03:47Before this turns into an internet myth factory, let's make certain things clear.
03:52Dry earwax does not mean someone is cleaner.
03:55Wet earwax does not mean poor hygiene.
03:58Producing odor is one thing.
04:00Detecting it is another.
04:02Some populations carry genetic variations that make them more sensitive to certain smells,
04:07and others barely register them.
04:09That's why one person says,
04:11This smells strong, and another smells nothing at all.
04:15Some people have something called hyperosmia,
04:18which means an unusually strong sense of smell.
04:22This trait is pretty rare, and researchers are still figuring it out.
04:26But genetics clearly play a role.
04:28Certain gene changes affect how smell-processing nerve cells grow,
04:32and how odor molecules reach receptors in the nose.
04:36Some super-smellers even associate certain smells,
04:40such as sweat, with negative consequences and unpleasant memories.
04:45In the case of smells, culture builds on top of biology.
04:50If fewer people smell strong body odor,
04:52societies develop different hygiene norms,
04:55perfume use, and even social expectations around scent.
05:00Body odor has nothing to do with how much you sweat.
05:03It's about bacteria, not liquid.
05:06And deodorant doesn't stop sweat,
05:09but mainly messes with bacteria so they can't throw their little stink party.
05:14If this story feels oddly familiar,
05:16that's because it's part of a bigger pattern.
05:20Your body constantly runs background code
05:23written thousands of years ago by ancestors,
05:25who had no idea what DNA even was.
05:28You're basically walking around with ancient software,
05:32quietly deciding how you experience modern life.
05:35For example,
05:36did you ever wonder why some people bite into cilantro
05:39and think it tastes exactly like soap?
05:41It's not in your head.
05:42It also has to do with your genes.
05:45Cilantro contains natural chemicals, called aldehydes,
05:48which give it that fresh, citrusy smell and flavor most people enjoy.
05:53But for some folks,
05:54those same aldehydes turn on smell receptors in the nose
05:57that makes the herb taste overwhelmingly soapy or even foul.
06:03Studies suggest that between about 3% and 21% of people
06:07detect a soapy flavor,
06:09depending on ancestry and genetic background.
06:12That's why you might have family members who love cilantro
06:15and others who absolutely detest it.
06:19Genetics isn't the only factor.
06:21Cultural exposure and how frequently you've eaten cilantro
06:24can also influence your taste perception.
06:27But your DNA provides the baseline sensitivity.
06:31Interestingly,
06:32the soapy sensation doesn't seem to appear with seeds of coriander,
06:36which are the dried fruit of the same plant.
06:38They lack the same mix of aldehydes.
06:42Lactose intolerance is also a result of just a few genetic tweaks.
06:46Our world used to be a place where almost every adult
06:50got stomach cramps from milk
06:52because that was once normal.
06:55After the last ice age,
06:57humans could only digest lactose as babies.
07:00As soon as we stopped breastfeeding,
07:02our body shut down the enzyme that breaks lactose down,
07:06called lactase.
07:07This meant most adults were lactose intolerant,
07:10even if they loved cheese or yogurt.
07:12Then around 10,000 years ago,
07:15when farming was in its early stages,
07:18humans started domesticating animals like cows,
07:21sheep,
07:21and goats,
07:23which offered a steady supply of milk.
07:25But here's the twist.
07:27Ancient Europeans were chugging milk
07:29long before their bodies evolved the ability
07:31to digest it as adults.
07:33They drank it without the lactase enzyme,
07:36and many didn't complain as much as you'd expect.
07:38Some of that was probably because
07:41fermented dairy like cheese and yogurt
07:43has far less lactose than fresh milk.
07:47So why did lactose intolerance actually become common?
07:52New research suggests it wasn't simply
07:55because dairy was tasty or nutritious.
07:57When crops failed or sickness ravaged communities,
08:01people who could digest lactose had an edge.
08:04Undigested lactose can pull water into your intestines
08:07and cause severe trouble in times of famine or illness,
08:10which makes survival even harder.
08:14Those who could handle milk sugar
08:15were more likely to make it through.
08:18This genetic shift where lactase production
08:20doesn't shut off after childhood
08:22is called lactase persistence.
08:24It turned milk from a risky experiment
08:26into a reliable calorie source for many populations.
08:30Today, it's super common in Northern Europeans
08:33and certain African groups
08:35with long histories of dairy farming,
08:37but much rarer in East Asians
08:39and many indigenous peoples.
08:41As you see, the ability to drink milk as adults
08:44didn't just show up
08:45because someone liked their cereal with milk.
08:48It spread because of survival pressure,
08:51changing how humans evolved
08:53alongside the animals they lived with.
08:56So next time someone jokes about earwax or body odor,
08:59remember what's really happening.
09:01You're seeing evolution in action,
09:03not fossils, not bones,
09:05but living biology shaped by climate,
09:08survival, migration, and chance.
09:11One tiny genetic letter
09:12quietly rewired daily life for millions of people,
09:16and most of us never even noticed.
09:20That's it for today.
09:21So hey, if you pacified your curiosity,
09:23then give the video a like
09:25and share it with your friends.
09:26Or if you want more,
09:27just click on these videos
09:28and stay on the bright side.
09:30Let's do it for today's news play.
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