How Can Owls Rotate Their Heads 270 Degrees Without Dying?

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Thinkstock

For humans, sudden gyrations of the head and neck—whether they’re from car accidents, rollercoaster rides, or chiropracty gone awry—can tear blood vessel linings in the neck, leading to clots that can cause stroke. Not so in owls, which can quickly rotate their heads 270 degrees in either direction without damaging blood vessels or cutting off blood flow to the brain. How do they do it?

To solve the mystery, scientists at Johns Hopkins—led by medical illustrator Fabian de Kok-Mercado and neuroradiologist Philippe Gailloud—used angiography and CT scans to examine the anatomy of a dozen snowy, barred, and great horned owls that died from natural causes. They discovered that the birds are equipped with four biological adaptations that prevent injury from rapid rotational movement; their study appears in the latest issue of Science.

“Until now, brain imaging specialists like me who deal with human injuries caused by trauma to arteries in the head and neck have always been puzzled as to why rapid, twisting head movements did not leave thousands of owls lying dead on the forest floor from stroke," Gailloud said in a press release announcing the results of the study. "The carotid and vertebral arteries in the neck of most animals—including owls and humans—are very fragile and highly susceptible to even minor tears of the vessel lining.”

After x-raying, dissecting and analyzing blood vessels from the dead birds’ necks, the researchers injected dye into the dead owls’ arteries to mimic blood flow and manually turned their heads. What they found was surprising: Unlike in humans, whose arteries shrink as the head turns, the blood vessels just under the jaw at the base of the owls’ heads got increasingly larger as more of the dye entered, but before the fluid pooled into reservoirs. These contractile reservoirs, scientists say, are what allow owls to turn their heads so radically while still having enough blood to feed the eyes and the brain. What's more, a complex supporting vasular network minimizes interruptions in blood flow; the scientists discovered that owls have small vessel connections between the carotid and vertebral arteries that allow blood to flow between the two vessels—so even if one route is blocked by an extreme neck rotation, another can provide an uninterrupted blood flow to the brain.



Click to enlarge.

Bones in owls’ necks also have adaptations designed to facilitate extreme rotation. One of the major arteries feeding the birds' brains passes through holes in the vertebrae, called transverse foramine; the team found that these holes were 10 times larger in diameter than the artery. This extra space creates air pockets that allow the artery to move around when twisted; 12 of the vertebrae in the owls’ necks had this adaptation. "In humans, the vertebral artery really hugs the hollow cavities in the neck. But this is not the case in owls, whose structures are specially adapted to allow for greater arterial flexibility and movement," said de Kok-Mercado. Plus, the owls’ vertebral artery enters the neck higher than it does in other birds’—going in at the 12th cervical vertebrae, rather than the 14th—allowing for more slack.

"Our new study results show precisely what morphological adaptations are needed to handle such head gyrations and why humans are so vulnerable to osteopathic injury from chiropractic therapy," Gailloud said. "Extreme manipulations of the human head are really dangerous because we lack so many of the vessel-protecting features seen in owls." The team created a poster (above) that details their findings, and next plans to study hawk anatomy to see if those birds have similar adaptations for head rotation.

Why Do Babies Learn to Crawl Before They Walk?

iStock/ozgurdonmaz
iStock/ozgurdonmaz

Fabian van den Berg:

Babies walk or dance before they crawl actually, well sort of, you’ll see.

Babies are amazing little creatures. They are very different from adults and should be treated as such. They aren’t born as blank slates, though; a lot of things are innate, and a lot of things are learned. And boy can they learn—not just by watching others do things, but also by experimenting. There’s a reason why early developmental psychologists called them "little scientists." They will form strategies on their own, test them out, and choose the best one.

We’ll focus on walking for now.

Newborns come fully equipped with a stepping reflex. If you happen to have a newborn at your disposal you can try it out (but support the head). By dragging them a bit over a surface, the feeling of their feet/soles touching will initiate a stepping reflex, it looks like they’re walking. (Don’t let go though, they are definitely not ready to stand on their own yet and will fall down.)

The reflex tends to be present for the first two months, sometimes returning right before they start to walk. It’s thought that the reflex helps to train the muscles and motor nerves. The reason why it disappears is thought to be because the legs become too heavy, the muscles grow faster than their strength. Basically, they become too chubby and the reflex doesn’t work anymore.

In a way, they are born with the ability to walk or dance (it differs a bit from baby to baby), but then lose it again because they grow so fast.

There are a lot more interesting and fun baby reflexes, like swimming and grasping, but that’s for another answer.

That brings us to toddlers and locomotion: Many parents will attest they looked forward to their baby being able to move on their own, and as soon as they did they missed the times the little bugger would stay put.

Infants can be very motivated, which is where the little scientist pops up. Having toys or anything interesting looking sitting around is very tempting. Kids love touching things, they explore, and they really want to go there… But how…

Should they wait for the big person to either bring them there or bring the shiny to them? No, of course not. They can move now—so off they go!

They will experiment and explore a lot of different ways of getting around. A very popular one is scooting. They are laying there (they’re good at that), but they want to be elsewhere. Almost all children will solve this conundrum by pulling or pushing themselves using their hands [and] scooting or shuffling across the floor. A popular and funny variation is scooting on their bums. If they can sit, they’ll prefer to sit and just use their arms and legs to push themselves around.

It’s not uncommon for children to be in this stage until they learn how to walk. It really is a matter of what works best for them.

Crawling is merely a more advanced version of scooting. Their legs become stronger and they are able to control them better. They will happen upon crawling by trial and error, and find that it can bring them from Point A to Point B faster than scooting.

The logic is simple to follow: I want to go over there, crawling works best, so crawling it is.

Strategy use is very common in children, you see it in many aspects. They will try out new things, compare it to old things, and decide on whatever works best. In the case of crawling it’s mostly about speed. But as I said before, not all kids crawl. For some scooting works best, and they’ll use it until they learn how to walk.

It’s also not strange to see them use different strategies, sometimes crawling, sometimes scooting. Usually this occurs when they are learning and experimenting with new strategies.

Children don’t need examples to learn, they are very capable on their own. They will try and discover things like the small scientists they are.

Crawling is one of those things. They don’t need to see it, they discover it, realize it works better than what they had before, and start using it more and more until something better (like walking) comes along.

This post originally appeared on Quora. Click here to view.

Why Do Hangovers Get Worse As You Get Older?

iStock/OcusFocus
iStock/OcusFocus

“I just can’t drink like I used to” is a common refrain among people pushing 30 and beyond. This is roughly the age when it starts getting harder to bounce back from a night of partying, and unfortunately, it keeps getting harder from there on out.

Even if you were the keg flip king or queen in college, consuming the same amount of beer at 29 that you consumed at 21 will likely have you guzzling Gatorade in bed the next day. It’s true that hangovers tend to worsen with age, and it’s not just because you have a lower alcohol tolerance from going out less. Age affects your body in various ways, and the way you process alcohol is one of them.

Because your body interprets alcohol as poison, your liver steps in to convert it into different chemicals that are easier to break down and eliminate from your body. As you get older, though, your liver produces less of the enzymes and antioxidants that help metabolize alcohol, according to a study from South Korea. One of these enzymes—called alcohol dehydrogenase (ADH)— has been called the “primary defense” against alcohol. It kicks off the multi-step process of alcohol metabolization by turning the beer or booze—or whatever you imbibed—into a chemical compound called acetaldehyde. Ironically, this substance is even more toxic than your tipple of choice, and a build-up of acetaldehyde can cause nausea, palpitations, and face flushing. It usually isn’t left in this state for long, though.

Another enzyme called aldehyde dehydrogenase (ALDH) helps convert the bad toxin into a new substance called acetate, which is a little like vinegar. Lastly, it’s converted into carbon dioxide or water and expelled from your body. You’ve probably heard the one-drink-per-hour recommendation, which is roughly how long it takes for your liver to complete this whole process.

So what does this mean for occasional drinkers whose mid-20s have come and gone? To summarize: As your liver enzymes diminish with age, your body becomes less efficient at metabolizing alcohol. The alcohol lingers longer in your body, leading to prolonged hangover symptoms like headaches and nausea.

This phenomenon can also partly be explained by the fact that our bodies tend to lose muscle and water over time. People with more body fat don’t break down alcohol as well, and less water in your body means that the booze stays concentrated in your system longer, The Cut reports. This is one of the reasons why women, who tend to have a higher body fat percentage than men, often suffer worse hangovers than their male counterparts. (Additionally, women have fewer ADH enzymes.)

More depressingly, as you get older, your immune system deteriorates through a process called immunosenescence. This means that recovering from anything—hangovers included—is more challenging with age. "When we get older, our whole recovery process for everything we do is harder, longer, and slower," gastroenterologist Mark Welton told Men’s Health.

This may seem like a buzzkill, but we're not telling you to put down the pint. However, if you're going to drink, just be aware of your body’s limitations. Shots of cotton candy-flavored vodka were a bad idea in college, and they’re an especially bad idea now. Trust us.

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