All of Your Teeth Evolved From a Single Ancestral Tooth in the Age of the Dinosaurs

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iStock

Anyone who's received a root canal or a lecture from their dentist about flossing probably doesn't appreciate their teeth like they should. But our pearly whites are unlike any other structures in the body, and for that, they deserve some recognition.

In their new video, TED-Ed explains what exactly makes teeth unique. Unlike regular bones, teeth are made of two layers: a hard enamel coating and a strong dentin core. The combination of these two components makes teeth both hard and strong enough to endure a lifetime of wear and tear.

The tooth's tough composition isn't exclusive to humans. All mammals, whether they're meat-tearing cats or grass-munching cows, grow their teeth the same way, and they owe their teeth's existence to a common ancestor.

In the 19th century, paleontologist Edward Drinker Cope hypothesized that the tribosphenic molar, a tooth type that evolved during the dinosaur age, is the root of all modern mammalian teeth. With just a few genetic tweaks made over millennia, the tribosphenic molar has given way to the teeth used by carnivores, herbivores, and omnivores to process their food.

To learn more about the evolution and biology of teeth, check out the video from TED-Ed below.

[h/t TED-Ed]

A Low-Carb Diet Could Shorten Your Lifespan

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iStock

The Atkins, Paleo, and Keto diets may have different gimmicks, but they all share a common message: Carbs are bad and meat is good. Yet a new analysis reported by New Scientist suggests that anyone who buys into this belief may later come to regret it. According to the paper, published in The Lancet Public Health, people who eat a moderate amount of carbs actually live longer than those who avoid them.

For their study, researchers analyzed data previously collected from 15,400 participants in the U.S. They found that people who received about 50 to 55 percent of their calories from carbohydrates had the longest lifespans, roughly four years longer than those who got 30 percent or less of their energy from carbs.

This doesn't necessarily mean that the key to a healthy diet is to stock your pantry with pasta and croissants. The study also showed that people who got up to 70 percent or more of their energy from carbs died one year earlier on average than subjects in the 50 to 55 percent group. A closer examination at the eating of habits of people who ate fewer carbs revealed another layer to the phenomenon: When people avoided carbohydrates in favor of meat, their chances of early death rose, but the opposite was true for people who replaced carb-heavy foods with plant-based fats and proteins, such as nuts, beans, and vegetables.

These numbers point to something dietitians have long been aware of: Eating a diet that's based around animal products isn't ideal. Getting more of your protein from plant-based sources, on the other hand, can lower your blood pressure and reduce your risks of type 2 diabetes, heart disease, and certain cancers. Nonetheless, fad diets that forbid people from eating carbs while letting them eat as much steak as they want are still popular because they're an easy way to lose weight in a short amount of time. But as the research shows, the short-term results are rarely worth the long-term effects on your health.

[h/t New Scientist]

Why Is Pee Yellow?

Chloe Effron
Chloe Effron

WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

Your body is kind of like a house. You bring things into your body by eating, drinking, and breathing. But just like the things we bring home to real houses, we don’t need every part of what we take in. So there are leftovers, or garbage. And if you let garbage sit around in your house or your body for too long, it gets gross and can make you sick. Your body takes out the garbage by peeing and pooping. These two things are part of your body’s excretory system (ECKS-krih-tore-eee SISS-tem), which is just a fancy way of saying “trash removal.” If your body is healthy, when you look in the toilet you should see brown poop and yellow pee.

Clear, light yellow pee is a sign that your excretory system and the rest of your body are working right. If your pee, or urine (YER-inn), is not see-through, that might mean you are sick. Dark yellow urine usually means that you aren’t drinking enough water. On the other hand, really pale or colorless pee can mean you might be drinking too much water! 

Your blood is filtered through two small organs called kidneys (KID-knees). Remember the garbage we talked about earlier? The chemicals called toxins (TOCK-sins) are like garbage in your blood. Your kidneys act like a net, catching the toxins and other leftovers and turning them into pee.

One part of your blood is called hemoglobin (HEE-moh-gloh-bin). This is what makes your blood red. Hemoglobin goes through a lot of changes as it passes through your body. When it reaches your kidneys, it turns yellow thanks to a chemical called urobilin (yer-ah-BY-lin). Urobilin is kind of like food coloring. The more water you add, the lighter it will be. That's why, if you see dark yellow pee in the toilet, it's time to ask your mom or dad for a cup of water. 

To learn more about pee, check out this article from Kids Health. 

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