Olive oil is perhaps one of the most delightful food staples on the planet.

But unfortunately, it's also one of the most commonly counterfeited foods.

As Larry Olmsted, author of the new book "Real Food/Fake Food: Why You Don't Know What You're Eating and What You Can Do about It," explained to Tech Insider in a recent interview, this is a real problem because people buy olive oil both for its amazing flavor and health benefits.

So if you're not getting the real thing, you're missing out — big time.

There are all kinds of ways that people either pass off lower quality (or even rotten) oils for true extra-virgin olive oil.

In the book, Olmsted writes that it has become less common recently to cut olive oil with sunflower oil or some other form of oil, though this still happens. As he explains, every time the FDA has looked for adulterated oil, they've found it.

That's not the only type of consumer fraud, though.

Often, extra-virgin olive oil might be diluted with low-quality and chemically refined oil. Or, as he explains, some producers will use "older — and often rancid — stocks of oil held over from bumper crops of previous seasons" that might pass inspection on the day they are bottled but will certainly be rotten by the time they reach consumers.

How to find the good stuff

If you're looking for the true high-quality product, here's what Olmsted recommends.

• Know that certain words are meaningless. Words like "light,""natural," or "pure" are all unregulated terms and don't carry any meaning. In the US, terms like "first pressed,""cold pressed," and "first cold pressed" are also unregulated and therefore meaningless— those terms date back to old ways of making oil that are rarely used now.
• Only buy "extra virgin" olive oil. Even if much of that is faked, know that things just labeled "olive oil" or "pure olive oil" are even more likely to be poor quality.
• Olmsted also recommends certain producers, including McEvoy Ranch from California; Cobram Estate from Australia; or Oro Bailen from Spain.
• Certain retailers also stock high-quality oils, including T.J. Robinson's Fresh Pressed Olive Oil Club (available online); Zingerman's, in Ann Arbor, Michigan (available online); Oliviers & Co. (available online); or recommendations on extravirginity.com.
• Certain certifications are excellent signs of quality. For California oils, you can look for "COOC Certified Extra Virgin." The "EVA" label from the Extra Virgin Alliance is a global certification. Italian olive-grower association UNAPROL has a "100% Quality Italiana" certification that's another great sign.
• If you can find a harvest date on a bottle, that's great — you don't want anything older than one year.
• Fresh is key. You don't want to expose the oil to light, which will degrade it, and it starts to go bad as soon as you open it. For that reason, Olmsted recommends small cans or bottles that you use quickly.

As Olmsted tells TI, it's worth seeking out the real thing.

"It's the real foods that are really important," he says. "They're being knocked off because they're good."

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With their eight arms and giant egg-shaped head, octopuses are one of the most alien-looking creatures on the planet. We read Katherine Courage's book "Octopus!" and discovered that the octopus is even weirder than it looks.

A special thanks to NOAA and professor of marine biology at the Alaska Pacific University, David Scheel, for the amazing footage they contributed to this video.

Produced by Jessica Orwig

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Carrots give you night vision. Swimming after eating will give you cramps. You need to drink eight glasses of water a day. Organic food is more nutritious and free of pesticides.

Nope, nope, nope, and nope.

Who hasn't shared these and other amazing-sounding notions about about health and the human body, only to feel embarrassed later on — when you find out the information was inaccurate or flat-out wrong?

It's time to put an end to these alluring myths, misconceptions, and inaccuracies passed down through the ages.

To help the cause we've rounded up and corrected dozens of the most popular health "facts" that we've heard.

Have any favorites we missed? Send them to science@techinsider.io.

Kevin Loria, Lauren Friedman, Kelly Dickerson,Jennifer Welsh, and Sean Kane contributed to this post. Robert Ferris contributed to a previous version.

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MYTH: Milk does a body good!

This is an incredibly successful bit of advertising that has wormed its way into our brains and policies to make milk seem magical.

The US Department of Agriculture tells us that adults should drink three cups of milk a day, mostly for calcium and vitamin D.

However, multiple studies show that there isn't an association between drinking more milk (or taking calcium and vitamin D supplements) and having fewer bone fractures.

Some studies have even shown an association with higher overall mortality, and while that doesn't mean that milk consumption itself was responsible, it's certainly not an endorsement.

Sources: Business Insider, NYTimes, Journal of Bone Mineral Research, JAMA Pediatrics, The Lancet, British Medical Journal

MYTH: Organic food is pesticide-free and more nutritious.

Organic food isn't free of pesticides and it isn't necessarily better for you.

Farmers who grow organic produce are permitted to use chemicals that are naturally derived — and in some cases are actually worse for the environment than their synthetic counterparts. However, pesticide levels on both organic and non-organic foods are so low that they aren't of concern for consumption, according to the USDA.

Eating organic food also doesn't come with any nutritional benefits over non-organic food, according to a review of 98,727 potentially relevant studies.

Sources: University of California - Berkeley, Annals of Internal Medicine, The American Journal of Clinical Nutrition

MYTH: Eating food within 5 seconds of dropping it on the floor is safe.

It's the worst when something you really wanted to eat falls on the floor. But if you grab it in five seconds, it's ok, right?

The five-second-rule isn't a real thing. Bacteria can contaminate a food within milliseconds.

Mythbusting tests show that moist foods attract more bacteria than dry foods, but there's no "safe duration." Instead, safety depends on how clean the surface you dropped the food on is.

Whether you eat it or not after that is up to you, but if the people that walk on that floor are also walking around New York City, for example, we wouldn't recommend it.

Sources: Business Insider, Discovery.com

Plants are possibly the most fundamental life form on Earth, supplying food and oxygen to ecosystems around the planet.

And yet many aspects of their leafy lives remain mysterious.

Photosynthesis — the process plants use to turn light into energy — is especially something of an enigma. Scientists have puzzled for years about how the process can capture roughly 95% of energy from in sunlight in just one million-billionth of a second.

Compare that to our best solar panels, which work much differently than photosynthesis; they don't even come close, changing just 40% of sunlight into energy.

But a paper published in the journal Nature in 2007, which we learned about from a BBC Earth story and is still making the rounds among scientists, suggests that the key to photosynthesis might work only due to a totally bizarre effect of quantum physics.

Quantum physics governs the universe on incredibly small scales — including at the level of molecules inside chloroplasts, the structures inside plants where photosynthesis happens. At that level, particles don't behave the way that matter we interact with every day does.

For example, the position of particles in quantum physics isn't described by a set location, but by the mathematical probability that will be in any particular location.

When you add these probabilities together, you end up with the spooky principle of superposition — particles existing in several places and states at once.

Photosynthesis takes abundant photons of sunlight and puts it to use with incredible speed and efficiency, losing almost no energy in the process. So what the photons may actually be doing is going through all the pathways in the leaf simultaneously. That includes the most efficient one, which will deliver the maximum amount of energy in the minimal of time.

This means plant chloroplasts somehow "know" how to pick the most optimal path for a photon to harvest its energy.

How plants do this remains unknown, but probing that mind-blowing mystery stands to lead to the next breakthrough in solar power.

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Sharks are the ultimate predators of the aquatic realm thanks to one character in particular – teeth. Not only are shark’s teeth razor sharp but they are also constantly regrown throughout life, gradually replaced like a conveyor belt of rows of teeth, and not just when they are worn down or fall out.

This is in stark contrast to humans, who only develop two sets of teeth in their lives (milk and adult). This was fine when we only lived for a few decades and ate foraged food. But with modern medicine greatly extending our lives and our diets much more abrasive and acidic, these two sets are often not enough meaning we need invasive ceramic implants or impractical dentures. So what if we could find out the genetic basis for shark’s ability to regrow their teeth and use it to develop novel methods of growing new, natural teeth in humans?

Sharks don’t actually regrow teeth one by one but have multiple rows inside their jaw that are constantly regrown. When a tooth on the edge of the jaw drops out, the corresponding tooth in the row behind it moves forward to replace it. The underlying soft tissues anchor and carry each tooth like a conveyor belt.

When juvenile sharks emerge from their egg cases or their mothers' wombs (sharks can be born either way), they have a fully developed conveyor-belt set of teeth (dentition), with rows of sharp teeth ready for feeding.

My colleagues and I recently studied the key genes involved in tooth regeneration in a small species of shark known as the catshark (Scyliorhinus canicula). Its eggs can easily be collected and the embryos inside can be raised to show us the precise set of developmental stages that tooth formation and regeneration goes through.

We found that within the epithelial cells that line sharks' mouths there are special compartments of stem cells that are key to the their continuous tooth regrowth.

Without these stem cells, the sharks would suffer like humans with only a restricted set of teeth, which would in turn affect their success as hunters at the top of the food chain. We analysed the stem cell compartments in shark’s mouths and deciphered all the active genes involved in shark tooth development and regeneration.

Restoring tooth growth

All vertebrate teeth, from sharks to mammals, are incredibly similar. For one thing, their structure is always composed of a hard mineral tissue known as dentine that is covered with even harder enamel or a similar material. But we have also found that the genes that control the process of tooth development are also very similar.

This is important because it suggests that the key genetic information that we discover in sharks could be crucial to understanding how tooth regeneration works and how that process is prevented in humans.

The next phase of the research is to compare the shark tooth genetic signature to the human one to find out if sharks have some genes that are inactive in humans. That might offer clues to the mechanism of our lost regenerative ability and help us work out whether we can regain a way to start forming new teeth within the mouth using stem cells.

We’ve now started a new study to compare human oral tissues that may still retain some ability to regenerate teeth. Specifically, we are comparing active and highly regenerative shark dental stem cells to intriguing cell clusters retained in the adult human jaw that could be the target of a treatment to grow new teeth.

These are early stages of the research, and many labs around the world are focused on various ways to develop new human teeth. But the idea is that if we already retain cells with future regenerative potential, we might be able to culture our own sources of “stem-like” cells to start the process of early tooth development.

We could then implant them into toothless regions of the jaw when new teeth are needed. Of course, many experiments and trials would need to be performed before we get to this stage. So understanding sharks' continuous regrowth could provide vital clues for the production of new teeth for humans.

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Fish.

They seem so innocent and harmless. But secretly, they're subverting scientific law and order.

That's according to a group of scientists nicknamed cladists for their support of a scientific classification system of species based on clades.

A clade is a fancy term for all of and only the modern species descended via evolution from a specific common ancestor.

To make that a little easier to understand, picture your own family tree: Your maternal grandmother, your mom and all of her siblings, and you, all of your siblings, and all of your mom's siblings' children — they're a kind of clade. Take away your siblings or add your father, though, and it's no longer a clade.

This is where fish get into trouble. A lot of trouble. Trouble the size of an elephant, a whale, and an emperor penguin all put together.

That's because all life evolved out of the water. Reptiles, mammals, birds — even dinosaurs — allcame from something that we would say looked pretty much like a fish. And there's so much more diversity among what we call "fish" in every day conversation that they spread far around the outskirts of these subgroups.

Here's a simplified depiction of the problem at hand:

As you can see, there's no way to draw a clade that will encompass everything we call a fish without snagging a mouse or a manatee along the way.

So for the cladists, either there is no such thing as fish — or we're fish too.

Of course, the cladists' approach to species is useful for asking certain questions. When evolution has literally built everything you are thinking about, classifying all those things based on how evolution works makes a lot of sense.

But it's hard not to find the proclaimed death of the idea of a fish a little absurd.

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On August 25, 2016, the U.S. National Park Service will celebrate its 100th birthday.

From the founding of the first park — Yellowstone— to today, the park service has protected and preserved large swaths of wilderness, from shorelines to mountain ranges, as well as myriad of historic sites and monuments. And today, the park system expands across 84 million acres, covering 412 sites.  

Over the last century, these parks are, and have always been, vital to science by providing living laboratories for research in some of the most intact natural landscapes in the world. In addition, because these natural sites have been managed and studied for nearly a century, there is a huge wealth of archival scientific data available to researchers working in the parks today.

To find out more about the role that national parks have played in the history of science, Business Insider spoke to Timothy Watkins, a climate change science and education coordinator at the National Park Service who is working with the US Geological Survey to draw attention to the scientific value of parks. Here are just a few national sites that have been instrumental.

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Yellowstone National Park

Renown for being America’s first National Park, Yellowstone is also the site where microbiologist Thomas Brock discovered an interesting bacterium living in the park’s hot springs. This bacterium, which Brock named Thermus aquaticus, was able to survive in waters that were 80 degree Celsius (176 degrees Fahrenheit).

“That was just absolutely astonishing because nobody thought that anything could live at that temperature,” Watkins told Business Insider. “It revolutionized our understanding of the way life had evolved [to] survive in extreme environments.”

After Brock made his discovery, other scientists studying this bacteria found that it is an important, stable source of the enzyme DNA polymerase, which allows DNA strands to replicate. “They realized that you could use that thermally stable DNA polymerase to do some very important engineering and chemistry in the lab,” Watkins said, and researchers, who later won the Nobel Prize in 1983, developed a technique using this enzyme, called the polymerase chain reaction (PCR), which is used in medical and biological research to amplify copies of a segment of DNA.

“But it all started with a bacterium that was found in Yellowstone National Park,” Watkins said.

Isle Royale National Park

Isolated in the middle of Lake Superior, Isle Royale National Park is a rugged, small island, and it was also here that, in 1958, wildlife biologist Durward Allen began doing some some incredibly important research on the predator-prey relationship of wolves and moose. This project has continued ever since, with scientists returning every year to count the populations of these two animals, and today, this research project is the longest continuous study of any predator-prey system in the world.

“It’s really important field ecological data on real live populations out in the wild that has produced a data set that is just incomparable,” Watkins said. “[It] has informed and confirmed certain models of populations of predators and prey relationships in ecology that were derived from mathematical models or studies of bacteria or very small organisms in the lab … and a lot has been learnt from the predator-prey relationships, as well as the influence of disease and climate change.”

Durward Allen is largely considered a pioneer among ecologists for initiating the Isle Royale wolf-moose project and having the insight to understand the value of continuing to observe a site long after others would have moved on to study something different. “That work really became canonized and is in every introductory textbook on the market now,” Watkins added.

Tule Springs Fossil Beds National Monument

Located just north of Las Vegas, Nevada, Tule Springs Fossil Beds National Monument is the site where nuclear physicist Willard Libby field-tested his technique of Carbon-14 dating.

Libby, who had been a part of the Manhattan Project, developed this technique of Carbon-14 dating, also called radiocarbon dating, after World War II. Carbon-14 is an isotope of carbon that decays naturally, so Libby realized that it is possible to measure its concentration in an object and compare it to other isotopes of carbon in order to calculate the object’s age.

He had developed the method of carbon-14 dating in the lab and tested it on some museum specimens, but the first time Libby actually used the technique in the field was on Pleistocene-era mammal fossils in Tule Springs, and his results showed that these mammal fossils were 30,000 years older than any human presence in the area.

“He provided evidence that falsified the hypothesis that humans were killing and cooking those mammals,” Watkins explained.

Libby’s work on Carbon-14 dating won him the Nobel Prize in 1960, and today the site of his research is protected by the National Park Service as a national monument.

The Rio Summer Olympics are finally here, and it's once again time to watch your favorite top athletes compete at the international level.

Olympic athletes are some of the best in the world, and the road to becoming one of these athletes is incredibly difficult. For example, men have only a 1 in 19,552 chance of becoming an Olympic wrestler, and women have a 1 in 45,487 chance of playing basketball in the Olympics.

Years of hard work and training go into becoming an Olympic athlete. But is there any ideal body type that helps give these athletes that special edge? 

We’ve compiled a list of the nation’s top athletes who are competing in Rio or have dominated their sports at the Olympic Games in the past. While some wingspans for older athletes are not readily available, we estimated that they were 1 to 2 inches greater than height. Here are the ideal body types that allow athletes in a variety of sports to compete at the world level:

Here are the Olympic superstars lined up together.

Join the conversation about this story »

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Science can't say whether people in your life are good or evil, per se. But it's getting better at figuring out whether they enjoy hurting you.

A fairly new field in personality research studies "misanthropic" traits: characteristics that lead people to hurt those around them for their own benefit. And psychologists have established a "dark triad" of harmful personality traits: narcissism, psychopathy (or a lack of empathy), and Machiavellianism (or a tendency to manipulate others.)

Any one of these traits makes a person stressful to those around them. Taken together they add up to an "antagonistic and selfish" strategy for getting ahead at other people's expense.

Now, some researchers suggest a fourth trait should join the triad: sadism, or joy in inflicting pain on others.

Why sadism matters

Sadism is a term with a long history. Sadists take pleasure in hurting other people. They're our most fearsome and evil villains — whether real or imagined, like Ramsay Bolton of "Game of Thrones."

But the idea of sadism is fairly new to clinical settings. That's in part because the whole study of personality, and specifically of "dark" personality traits, is fairly recent and underdeveloped. But it's also because traits like sadism, along with the rest of the dark triad, are difficult to tease apart with clinical precision.

Even papers that support the idea of sadism as part of a larger "dark tetrad"acknowledge that its effects can be difficult to distinguish from the three existing triad traits.

But a growing body of work in just the last few years has shown that sadism correlates specifically and strongly with cruel behavior — for example, trolling and cyberbullying.

The sadism test

In order to develop a rigorous test for sadism, researchers assembled a list of questions designed to poke right at the heart of a sadistic personality.

The first version was 20 questions long. Subjects were asked to say how strongly they agreed or disagreed with a list of (rather chilling) statements, using a scale from one to five. (One meant completely disagree and five completely agree.)

1. I have made fun of people so that they know I am in control.
2. People do what I want them to because they are afraid of me.
3. When I tell people what to do, they know to do it.
4. I never get tired of pushing people around.
5. I would hurt somebody if it meant I would be in control.
6. I control my friends through intimidation.
7. When I mock someone, it is funny to see them get upset.
8. Being mean to others can be exciting.
9. When I get annoyed, tormenting people makes me feel better.
10. I have hurt people close to me for enjoyment.
11. I enjoy humiliating others.
12. I get pleasure from mocking people in front of their friends.
13. I think about harassing others for enjoyment.
14. I have cheated others because I enjoy it.
15. I think about hurting people who irritate me.
16. I'd lie to someone to make them upset.
17. I have stolen from others without regard for the consequences.
18. Making people feel bad about themselves makes me feel good.
19. I am quick to humiliate others.
20. I have tormented others without feeling remorse.

When 199 undergraduate students took the test, the results were promising but inconclusive.

The test, researchers found, was good at measuring sadism and dark triad traits. And it suggested that there were specific and interpretable patterns in people's misanthropic personalities. But it didn't as good a job as they'd hoped in identifying sadism as separate from psychopathy and the rest of the dark tried.

So they weeded out questions that might have caused too much overlap and tried again with a nine-question version of the test:

1. I have made fun of people so that they know I am in control.
2. I never get tired of pushing people around.
3. I would hurt somebody if it meant I would be in control.
4. When I mock someone, it's funny to see them get upset.
5. Being mean to others can be exciting.
6. I get pleasure from mocking people in front of their friends.
7. Watching people get into fights excites me.
8. I think about hurting people who irritate me.
9. I would not purposely hurt anybody, even if I didn't like them.

This time, when 202 students took the test, the results were stronger. It still correlated with other dark triad traits like psychopathy as expected, but did a better job of showing that sadism is a separate category. In both tests, men scored much more highly than women for the negative traits. These results were published the journal Personality and Individual Differences.

The researchers note that there's a lot more work to do on what they're calling the Assessment of Sadistic Personality (ASP), including finding subjects who aren't college undergrads taking questionnaires for course credit (not the most diverse or representative sample). But they expect it will play a significant role as they come to understand sadism in clinical terms.

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Michael Phelps is the most decorated Olympian ever, and his medal count at the Rio Olympics has continued to climb.

The swimmer has long been the modern Olympian with the most individual records. Now, he's even coming up against records set 2,168 years ago. As of August 10, Phelps had tied the ancient record set by Leonidas of Rhodes for the most individual wins (12). And he still has a couple more events to go.

So what makes Phelps such an incredible swimmer?

Many have pointed out that he has a perfect physique for swimming, and they're not wrong:

In sports in general, there has been a sort of a "size sort" over recent decades, where athletes have started to focus on sports that they have an ideal body type for, Dr. Michael Joyner, a physician and Mayo Clinic researcher who is one of the world's top experts on fitness and human performance, told Business Insider.

Interestingly, said Joyner, elite performers in certain sports tend to be about the same size, as you can see if you look at rowers, gymnasts, and of course, swimmers.

Phelps certainly fits the bill.

But there has also been unproven speculation out there that Phelps has extreme qualities that make him such a good swimmer, such as the myth that he has double the lung capacity of the average human. (There's no actual evidence for this, and Dr. H. Richard Weiner, a swimmer and former team physician who practiced sports medicine at the University of Wisconsin-Milwaukee, previously told Scientific American that some of the claims about Phelps border on the ridiculous.)

While Phelps is certainly built for swimming, most of his competitors are too. They're tall, strong, long-armed, and frequently have longer-than-average torsos and relatively shorter legs. As "The Sports Gene" author David Epstein pointed out in a TED talk, even star water polo players share physiology that's different from the average person.

But it takes more than just build to get to where Phelps is.

As Weiner explained to Scientific American, physical advantages aren't sufficient on their own. You also have to have talent and technique, like Phelps' excellent stroke mechanics.

If you've watched Phelps during the Rio Olympics, you'll see that he has intense focus, drive, and a competitive nature too. All of those seem to be pretty important characteristics of a top Olympian.

It's the combination of all these factors that makes Phelps such an amazing athlete. Yes, his body is partly responsible, but that's not all.

SEE ALSO: Here's what Michael Phelps eats every day for the Rio Olympics

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The Olympic athletes competing in the Rio Games are the elite of their sports. You see the best cyclists, runners, and swimmers in the world, battling to see who can take home the gold.

A ton of factors are part of getting there: Talent, technique, training, and physique all play a role.

And as far as physique goes, over the past few decades there's been a "bit of a size sort" in different sports, Dr. Michael Joyner, a physician and Mayo Clinic researcher who is one of the world's top experts on fitness and human performance, told Business Insider. Some athletes have started to focus on the sports they may be suited for based on their body type.

There are always exceptions, and in some cases, skill can be more important than a physical trait. But in general, Joyner says (and has written), elite competitors in each sport tend to share similar physiology.

Those ideal body types are well represented in Rio, and it's fascinating to see how much top athletes differ from one another.

Check out how four Rio contenders epitomize the build needed for their sports:

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Swimming: Michael Phelps

Gymnastics: Simone Biles

Cycling: Chris Froome

It's no shock that everyone gets hyped up when music starts blasting out of the speakers at a major athletic event. The crowd goes wild, energy flows across the venue, and athletes feel an extra surge of preparedness when the sound hits them. 

This became so noticeable that in 2007, USA Track and Field banned athletes from using headphones during competition in order "to prevent runners from having a competitive edge." 

But, exactly how does music help athletes get psyched up for their event?

Researchers from Georgia Southern University set out to answer this question. First, they looked at previous studies, noting that music has been shown to divert attention away from feelings of fatigue, stimulate enhanced performance, lower feelings of anger and depression, and quicken movements (when there's a speedy beat). Athletes who competed in sports like figure skating, meanwhile, could reach optimal performance by listening to music with a slower tempo. 

The researchers measured how music affected seven Division I collegiate athletes participating in soccer, football, and tennis. They watched the athletes perform with and without music, and noticed that music controlled arousal levels before and after competition and helped athletes mentally prepare before competing. It also seemed to helped them control their moods and create a sense of camaraderie during athletic competition.

These observations were based on just seven athletes, but other studies have come to similar conclusions.

One small study by researchers at Brunel University revealed that music can enhance endurance by 15%. When competing at any level, but especially at the pinnacle of a sport, even a 15% increase in performance can be the difference between victory and loss. 

So it turns out that what just seems like a fun crowd-pleaser can actually make a difference in how the athletes competing at an event perform.

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Scientists believe they have discovered the oldest vertebrate animal on Earth: a female Greenland shark that lived to be nearly 400 years old.

The shark, which measures over 16 feet in length, lived for an estimated 392 years, but could have an age range between 272 to 512 years, according to research recently published in the journal Science.

The centuries old shark takes the title of longest-living vertebrate from a bowhead whale that was estimated to be 211 years old. Though the shark was probably born in the 17th century, she could have been born some time between 1501 and 1744, the BBC points out.

But that doesn't make the shark the oldest animal to have lived — that record is held by a clam named Ming, which lived to turn 507, The Guardian reports.

"Even with the lowest part of this uncertainty, 272 years, even if that is the maximum age, it should still be considered the longest-living vertebrate," said Mr Nielsen.

The study, led by biologists from the University of Copenhagen, used radiocarbon dating to find the ages of 28 deceased Greenland sharks, studying their lenses to determine their age. The species of shark is now the world’s longest-living vertebrate.

Here's what a Greenland shark looks like in action:

When they’re born, Greenland sharks measure 42 centimetres and grow at a rate of 1 centimetre each year. The largest sharks end up measuring over 16 feet long, while female sharks reach sexual maturity on their 150th birthday, the study found.

To find the sharks’ ages, scientists measured the carbon levels in the lenses of their eyes, and looked for carbon-14 — which entered the ocean in the 1960s in the wake of nuclear bomb testing from the mid-1950s — to figure out which sharks were born before and after that time, a Science article explains.

Then, the researchers compared their radiocarbon dating findings with the sharks' estimated growth patterns, to determine how long the sharks born before the 1960s lived.

"We had our expectations that we were dealing with an unusual animal, but I think everyone doing this research was very surprised to learn the sharks were as old as they were,” Julius Nielsen, the marine biologist from the University of Copenhagen who led the study, told the BBC.

Business Insider has contacted the Marine Biological Association for comment.

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The dinosaurs may be long gone, but plenty of truly giant things are still living on this planet — including the largest animal ever known to exist.

And the No. 1 largest living thing, according to scientists, is a pretty surprising contender.

There's always a chance we could stumble on something even bigger, but that would be quite a feat.

We've gathered a handful of superlatively large organisms below so you can guess what's largest and see if you're right.

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Largest virus: Pithovirus sibericum

The largest known virus was thawed out of 35,000-year-old permafrost and is 1.5 micrometers long. That's too small to see without a microscope, but for a virus — it's huge.

Source: Smithsonian Magazine

Largest spider: the Goliath bird-eating spider.

Source: London's Natural History Museum

Largest fruit: jackfruit.

The average human brain is about three pounds. This makes it a much bigger proportion of our bodies than what is seen in other animals. Especially notable is our large cerebral cortex, which is responsible for memory, communication, and thinking.

So how did we get these big brains?

A team of researchers in the UK have proposed one possible answer: Over the past 2 million years, we worked our brains extra-hard in evaluating complex social situations and deciding who to cooperate with, they write in their paper, published August 12 in the journal Scientific Reports. 

Robin Dunbar, an evolutionary psychologist at Oxford who was a coauthor of the study, previously proposed something called the "social brain hypothesis," which is the idea that"the disproportionately large brain size in humans exists as a consequence of humans evolving in large and complex social groups."

This is just an idea, of course, and it's difficult to prove. By using computer models, however, the researchers hoped to show how this might have played out in the distant past.

The new study, Dunbar said in a press release, "reinforces this hypothesis and offers an insight into the way cooperation and reward may have been instrumental in driving brain evolution ... [This suggests] that the challenge of assessing others could have contributed to the large brain size in humans."

Evolution works in favor of those who try to help people just as successful, or more successful, than themselves, the authors note. The catch here is that one is forced to do a lot of mental judging when trying to figure out exactly how successful another person really is. And that's a colossal, and pretty much never-ending, cognitive task.

The scientists bolstered support for the hypothesis by running computer models that simulated how people make decisions when coming into contact with others. They were able to see how these model humans judged their counterparts, and this was used to determine which behaviors become stronger over time, as this process is carried out. 

These judging behaviors have been very strong in humans, as they are used (and were even more so in the past) to ensure survival. Over time, the brains of the human population have expanded, and the models suggest that this phenomenon could be part of the reason why.

And this new information could be used to help us in the future, too. The researchers think what they learned could be applied to engineering intelligent, autonomous machines to act out appropriately when coming into contact with one another. For example, driverless cars of the future will need to manage themselves, but also know how to cooperate with other driverless cars.

So, while this information provides some interesting theories about human evolution in the past, it could be even more influential as we figure out how technology will evolve in the future.

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Dogs have long been man's best friend, living as our domesticated companions for as long as 32,000 years.

Today, they are one of the most popular pets in the US, found in over 54 million American homes, or about 44% of all households.

And every one of us thinks that our dog is uniquely special and smart. But how much do we actually know about our furry buddies and what's going on inside their heads?

To find out more about our four-legged friends, we spoke to Dr. Brian Hare, professor of cognitive neuroscience at Duke University, author of the book "The Genius of Dogs," and host of the new DogSmarts podcast.

"What really has happened in the last 10 years is that we've learned more about how dogs think than in the previous 100 years," Hare told Business Insider. "There have been a lot of big discoveries … Dogs are very distinctly different from us genetically, but psychologically, they are more like us than some of our more closely related, more genetically related primate relatives."

Here are a few of the recent discoveries that Hare and other scientists have made about dogs:

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1. Dogs empathize with us.

When you look at your dog and yawn, chances are your dog might yawn, too, because dogs can "catch" your yawn, according to a 2008 study published in Biology Letters. This is called "emotional contagion," and it's a basic form of empathy.

Previous research has shown that primates could "catch" yawning, but this was the first study to show that human yawns are possibly contagious to domestic dogs as well.

Dogs are believed to empathize with us in other ways as well. Research suggests that they are sensitive to their guardians' emotions and that their behavior is influenced by the expression of these emotions. A study from the University of Helsinki found that dogs can sense when their owners are angry and have even evolved to respond accordingly. Another study found that dogs respond in a similar way, physiologically and behaviorally, to humans when they hear a human baby crying— another example of emotional contagion.

2. Dogs want eye contact with us.

Dogs are the only nonprimate animal to look people in the eyes without misinterpreting what it means, Mic reports.

Wolves, meanwhile, interpret eye contact as a sign of hostility, according to Science Magazine.

3. With eye contact, they grow attached to us.

Eye contact has an important effect on both human and dog brains.

"Just by making eye contact with dogs," said Hare, "we have an increase in oxytocin." Oxytocin, sometimes referred to as the "love hormone," plays an important role in attachment-forming, bonding, and trust.

Usually, this kind of response — an increase in the hormone to facilitate bonding — occurs only between parents and their children, or maybe romantic partners, Hare said. This "is the first time that it has been shown that different species, dog and human, can interact and affect the oxytocin loop."

Chances are good you think you're more or less the same person you were last week. But the lining of your gut is totally different, and the hairs on your head are 2.5 millimeters longer.

The human body's ability to replace worn out cells with shiny new ones is key to the long lifespans we're so used to. There are a couple things we keep all our lives, like the visual cortex, but almost everything wears out and gets replaced, at least for part of our lives. And some things, like our hair and nails, just grow and grow and grow.

We've gathered together scientists' estimates scientists of how quickly we go through different types of cells. Many of these ages have been established using a technique called bomb-pulse dating, which uses the traces of atomic radiation we each carry to determine how old cells are. 

Keep in mind: All of these are average numbers.

For everything that's regularly replaced, you'll be carrying a cells that are slightly older — and a lot that are younger, since cells are replaced on rotation not all at once. And these numbers represent total ages, so for example, an individual cell doesn't stay on the surface of your skin for over a month — its lifespan includes the time it takes to rise through all the skin layers.

But it's incredible to think an individual heart cell will spend decades powering your whole body.

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I want you to do something for me. Ready? Okay.

Forget about your arms for a second.

Go on. You can do it. Now fold them up against your body, and stick out your hands so your fingers seem to stick straight out from your shoulders.

Flap them a little. (I'll know if you don't.)

Isn't this a treat? You make a beautiful fish, really.

Now look at your fingers. See how they splay out, hanging a bit limp from your knuckles? Your hand could almost be the fin of an honest-to-god fish.

It turns out that's not a total coincidence.

Science has long known that humans — along with crows, capybaras, crocodiles, and other vertebrates  — inherit their basic body plans from our fishy ancestors. In fact, as my colleague Meghan Bartels has written, from an evolutionary perspective we're basically all fish anyway. At a certain point a group of four-limbed fish called tetrapods just wandered up onto land and gave rise to...everything else.

A new paper in the journal Nature reveals some surprising new details about how that transition likely happened.

As Carl Zimmer points out in the New York Times, naturalists have known for a long time that tetrapods share similar bone patterns in their limbs. Charles Darwin wrote: 

What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include similar bones, in the same relative positions?

But those obvious analogies in bone structure don't transfer outside the tretrapod group. Fish fins are constructed of nubs of bone out of which erupt "dermal rays," a kind of tough tissue that lattices the skin and doesn't exist in our hands.

The paper suggests that those rays actually develop through a similar process to human fingers. Researchers found that when when they disabled a group of "Hox" genes in mouse and zebrafish embryos using CRISPR gene editing, the mice failed to develop toes and the fish didn't develop dermal rays.

In other words, the same genes are involved in constructing the fingers on your hands and the rigid frets of a fish's fins. CRISPR is a new tool that allows biologists to make fine line-edits to the genetic code of living things.

So, even though the results are very different, the same group of genes tells fin and finger tissues to move to the ends of limbs and do their thing.

You can stop flapping your fingers now.

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The pitter-patter of tiny feet is one of my favorite sounds to come home to at the end of a long day. 

And I'm convinced that my dog, Izzie, is just as elated to see me as I am to see her.

But what's she really thinking when I open the front door and our eyes meet? Is she simply excited for the dinner I'm about to feed her, or do we have a real bond?

To find out more, we spoke to canine behavioral researcher Julie Hecht and Duke University professor of cognitive neuroscienceBrian Hare, who wrote the book "The Genius of Dogs," and hosts a new podcast called DogSmarts.

Here are a few of the recent discoveries that Hecht, Hare, and other scientists have made about dogs:

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1. Why does my dog get so excited whenever I say the word 'walk'?

Dogs, like dolphins, apes, and parrots, can learn a series of vocal commands or words. One dog, a border collie named Chaser, learned more than 1,000!

Researchers say Chaser used a process called “fast-mapping,” or inference, which is pretty similar to how human children learn language skills. Basically, it involves guessing the meaning of a word based on the object that is being used in conjunction with that word. So if you're constantly saying "walk" and then fetching your dog's leash and taking him outside, he may be able to infer that the word "walk" has something to do with the action of going for a walk.

2. Why does my dog yawn everytime I do?

Just like people, dogs can "catch" yawns. A study in the journal Biology Letters says this "emotional contagion" is completely normal. More importantly, the researchers write, your dog catching your yawn is a sign of basic empathy.

Dogs are believed to empathize with us in other ways as well. A University of Helsinki study suggested that dogs can sense when their owners are angry and have even evolved to respond accordingly. Another study found that dogs respond in a similar way, physiologically and behaviorally, to people when they hear a human baby crying.

3. Why do dogs turn away from us when we try to hug them?

A psychologist who studies canine behavior found a disturbing trend in 250 photos of people hugging dogs— the dogs were not happy. How do we know? According to animal behavior researcher Julie Hecht, there are three common signs of stress in dogs: 1) Turning their heads away from the thing that's bothering them; 2) Showing the whites of their eyes; and 3) Lowering or pinning back their ears. Most of the dogs in these photos were showing these signs.

Still, some dogs might tolerate a hug, especially if it comes from someone familiar. In other words, dogs have myriad ways of showing affection, but hugs may not be one of them. If your pup tends to shrug away from your embrace, try patting her head or scratching her tummy instead, advises Hecht.

When you're a scientist trying to understand a disease, it's common to experiment on rodents, slice up their tissues for glass slides, and pop those specimens under a microscope.

This basic approach has barely changed in a century, and it's not hard to see why: It's relatively simple, cheap, and keeps leading to powerful drugs and treatments for humans.

That's not to say there aren't steep costs, though.

About 25 million lab animals are sacrificed each year, and a few thin-tissue slides are hard to reuse for other research. Experts also say it's difficult (and sometimes impossible) to build up a 3D model of a whole animal by scanning individual tissue slides.

But Ali Erturk, a neurobiologist at Ludwig-Maximilians-Universität München, hopes to solve these and other problems with a new lab process called "ultimate 3D imaging of solvent-cleared organs" (uDISCO) — which some scientists say will be "transformative" for studying brain diseases like Alzheimer's and schizophrenia.

uDISCO, as Erturk and his team describe in study published Monday in the journal Nature Methods, can turn mice, rats, and other mammals almost entirely clear.

Skin, muscle, bone, brain tissue — nothing stays entirely opaque.

"I love it," Dr. Ingo Bechmann, a neuroscientist at the University of Leipzig who wasn't involved in Erturk's study, told Business Insider in an email. "It will revolutionize anatomy in countless ways, in particular neuroanatomy."

What's more, uDISCO doesn't damage fluorescent proteins that scientists use to "light up" certain tissues in transgenic animals. It can also shrink a whole mouse to fit into laser-powered microscopes designed to 3D-scan small specimens like organs.

In effect, Erturk and his team have created "whole boy atlases" of an animal that can be flown through down to a cellular level, like this nervous system of a mouse:

These high-resolution digital maps, says Erturk, will make more out of an animal's sacrifice by letting other scientists study it down to a cellular level.

"One would just need to go to [the] website, choose the organ of their interest, and visualize various cellular systems within the individual organ or in the entire organism if desired," Erturk said in a statement given to Business Insider.

Reinventing a bag of old lab tricks

All the tricks that make uDISCO work have been around for awhile. However, this is the first method to make use of them all — and without destroying important bits of an organism.

Clearing up animal tissue, for example, was pioneered by German anatomist Werner Spalteholz at the turn of the 19th century. (He made parts of human cadavers translucent.)

Whole-body scanning of animals that produce fluorescent proteins also isn't that new. The process is called "ultramicroscopy," and it was shown to work on fruit flies in the early 2010s.

And while see-through glowing rodents are also at least a couple years old, no one has rendered any this clear without damaging fluorescent proteins locked away in their cells, says Erturk — everything becomes roughly 85% to 90% transparent after uDISCO.

"It's really the most potent, highest transparency you could achieve with a large specimen," he told Business Insider.

"[I]f we want to know how water pipes are organized within a wall without any prior knowledge, the easiest way would be to be able see-through the wall. [Imagine] that the concrete wall becomes glass without any destruction," Erturk said in the statement. "Now we can see every pipe connection, and easily identify if one is disconnected."

The process begins with a mammal that's born to produce fluorescent jellyfish proteins in certain cells, like nerves or heart muscle tissue. Under special lighting conditions, those proteins glow brightly to illuminate that body system while leaving other tissues dark. The animal is eventually sacrificed for use as a lab specimen.

Erturk and his team's innovation is amping up tissue clarity in such specimens (so proteins glow more brightly) while shrinking everything down by as much as 65% (so the whole creature can fit in a laser-scanning microscope).

The secret ingredients? Tert-butyl alcohol, which gently pushes water out of animal cells and replaces it, and diphenyl ether (DPE), which dissolves fats. Both chemicals are flushed through sacrificed animals over the course of a few days, rendering them transparent.

"The clarity is quite complete," Erturk says. "You see a yellowish hue, but that is coming from residual tissue."

'Transformative discoveries' on the horizon

But the real development is what these animals look like after being scanned my a laser-powered "ultramicroscope."

The machine builds up the animal in 3D, allowing a researcher to fly through it and zoom in on individual cells.

In an email to Business Insider, Dr. Matthias H. Tschoep, a molecular biologist at the German Research Center for Environmental Health, said uDISCO will lead to "transformative discoveries," including ones that researchers can't yet predict.

The reason, Dr. Tschoep noted, is that uDISCO will accelerate the work of scanning an animal's entire body by 10 to 100 times — now done tediously done by slicing up a lab animal and scanning individual microscope slides — and with improved resolution.

"Obviously, mice aren't humans and these methods will not be applicable to human physiology or clinical medicine," Dr. Tschoep cautioned. "However, these methods may in the future offer highly detailed three dimensional analysis of human post-mortem organs or ... surgically removed tumors, with a speed that was previously unimaginable."

One human organ that Erturk is especially focused on is in your head.

"Governments are putting in billions of dollars to map the human brain. But it's like going out of the solar system — it's impossible with current technology," Erturk said, noting a complete brain map — similar to a human genome map — could lead to radical medical advancements.

"It'd be important to see connectivity in a schizophrenia or Alzheimer's brain," Erturk said, explaining that brain-scanning machines, like fMRI, only show large-scale anatomy. Microscopes, meanwhile, don't reveal all of the mind's neuron-to-neuron connections.

"I believe we have a tool that's a good compromise," Erturk said. "I don't think we're far away from mapping the brain in this way."

In the meantime, he hopes fewer mice, rats, and other lab animals will meet their demise.

"It's hard to predict how many" uDISCO could save, Erturk said. "Even if it's 5% or 10% or 20%, it would mean hundreds of thousands of animals worldwide every year."

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