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Why Do Humans Have Chins?

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The chin is one of our most unique human features, unseen in our Neanderthal ancestors. “The presence of a chin is something we use to define modern humans,” Nathan Holton, who studies craniofacial biology at the University of Iowa tells mental_floss. “It’s a diagnostic feature for our species.” And yet, its origins remain a mystery. Why do we have it? Does it serve some evolutionary purpose or was it just a random byproduct of our development over time? 

“Any feature of the modern human skull that’s unique to us becomes very interesting for us to understand why it developed,” Holton says. To get some answers, he and his team studied the facial growth of 40 people as they aged from toddlers to adults, and concluded that our chins developed as our faces evolved to be smaller than those of our ancestors -- about 15 percent smaller, to be precise. Here’s how Holton explains it: 

“If you look at Neanderthal for example, they have big prognathic face. Their mid-face sticks out much farther than ours, as a result what happens is the upper-face and mid-face grow forward. In a sense, it pulls that whole mid-face and the lower teeth forward resulting in more of a sloping chin region. In humans, we have a very short mid-face so the lower part of our mandible (aka the jaw) grows forward more.” 

Sounds complicated, but it really just means that as the upper and middle parts of the human face shrank backwards, the chin became more prominent.

So why did the face shrink in the first place? UI anthropologist Robert Franciscus thinks it has everything to do with human self-domestication. As we transformed from isolated hunter-gatherers to a network of communities, we no longer needed to fight as aggressively over land, and individual relationships flourished. Our hormones shifted. Specifically, testosterone levels dropped and as a result, our bodies (and faces) became smaller. 

"What we're arguing is that modern humans had an advantage at some point to have a well-connected social network, they can exchange information, and mates, more readily, there's innovation," says Franciscus, "and for that to happen, males have to tolerate each other. There had to be more curiosity and inquisitiveness than aggression, and the evidence of that lies in facial architecture."

Dietary changes and the advent of cooking may also have played a role in our small faces and pronounced chins. “We do a lot less chewing and we don’t chew foods that are as tough,” Holton says. “Regardless of why it happened, when we look at things like a chin or the absence of brow ridges or other unique features in modern humans, a lot of it seems to be tied to just a smaller face.”

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Big Questions
Where Does the Phrase '… And the Horse You Rode In On' Come From?
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Horses may no longer be the dominant form of transportation in the U.S., but the legacy of our horseback-riding history lives on in language. When telling people off, we still use the phrase “... and the horse you rode in on.” These days, it’s rare for anyone you're telling to go screw themselves to actually be an equestrian, so where did “and the horse you rode in on” come from, anyway?

Well, let’s start with the basics. The phrase is, essentially, an intensifier, one typically appended to the phrase “F*** you.” As the public radio show "A Way With Words" puts it, it’s usually aimed at “someone who’s full of himself and unwelcome to boot.” As co-host and lexicographer Grant Barrett explains, “instead of just insulting you, they want to insult your whole circumstance.”

The phrase can be traced back to at least the 1950s, but it may be even older than that, since, as Barrett notes, plenty of crude language didn’t make it into print in the early 20th century. He suggests that it could have been in wide use even prior to World War II.

In 1998, William Safire of The New York Times tracked down several novels that employed the term, including The Friends of Eddie Coyle (1972) and No Bugles, No Drums (1976). The literary editor of the latter book, Michael Seidman, told Safire that he heard the term growing up in the Bronx just after the Korean War, leading the journalist to peg the origin of the phrase to at least the late 1950s.

The phrase has had some pretty die-hard fans over the years, too. Donald Regan, who was Secretary of the Treasury under Ronald Reagan from 1981 through 1984, worked it into his official Treasury Department portrait. You can see a title along the spine of a book in the background of the painting. It reads: “And the Horse You Rode In On,” apparently one of Regan’s favorite sayings. (The book in the painting didn't refer to a real book, but there have since been a few published that bear similar names, like Clinton strategist James Carville’s book …and the Horse He Rode In On: The People V. Kenneth Starr and Dakota McFadzean’s 2013 book of comics Other Stories And the Horse You Rode In On.)

It seems that even in a world where almost no one rides in on a horse, insulting a man’s steed is a timeless burn.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
What Could the Repeal of Net Neutrality Mean for Internet Users?
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What could the repeal of net neutrality mean for the average American internet user?

Zouhair Belkoura:

The imminent repeal of net neutrality could have implications for Americans beyond the Internet’s stratification, increased costs to consumers, and hindered access to content for all. Net neutrality’s repeal is a threat to the Internet’s democracy—the greatest information equalizer of our time.

With net neutrality’s repeal, ISPs could be selective about the content and pricing packages they make available. Portugal is a good example of what a country looks like without net neutrality

What people may not realize is that a repeal of net neutrality would also give ISPs the ability to throttle people’s Internet traffic. Customers won’t likely have visibility into what traffic is being throttled, and it could substantially slow down people’s Internet connections.

What happens when this type of friction is introduced to the system? The Internet—the greatest collective trove of information in the world—could gradually be starved. People who experience slower Internet speeds may get frustrated and stop seeking out their favorite sites. People may also lose the ability to make choices about the content they want to see and the knowledge they seek.

Inflated pricing, less access to knowledge, and slower connections aren’t the only impact a net neutrality repeal might have. People’s personal privacy and corporations’ security may suffer, too. Many people use virtual private networks to protect their privacy. VPNs keep people’s Internet browsing activities invisible to their ISPs and others who may track them. They also help them obscure their location and encrypt online transactions to keep personal data secure. When people have the privacy that VPNs afford, they can access information freely without worrying about being watched, judged, or having their browsing activity bought and sold by third-party advertisers.

Virtual private networks are also a vital tool for businesses that want to keep their company data private and secure. Employees are often required by their employers to connect to a VPN whenever they are offsite and working remotely.

Even the best VPNs can slow down individuals' Internet connections, because they create an encrypted tunnel to protect and secure personal data. If people want to protect their personal privacy or company’s security with a VPN [they] also must contend with ISP throttling; it’s conceivable that net neutrality’s repeal could undermine people’s freedom to protect their online safety. It could also render the protection a VPN offers to individuals and companies obsolete.

Speed has always been a defining characteristic of the Internet’s accessibility and its power. Net neutrality’s repeal promises to subvert this trait. It would compromise both people's and companies’ ability to secure their personal data and keep their browsing and purchasing activities private. When people don’t have privacy, they can’t feel safe. When they don’t feel safe, they can’t live freely. That’s not a world anyone, let alone Americans, want to live in.

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

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