| Humans have a few biological advantages compared to other species. The most obvious is our big brains, which have empowered us to become the dominant species on Earth. But another feature that is often overlooked is our chins — yes, we're the only animals on Earth with true chins. You might be thinking, "Wait a minute, I give my cat chin scratches all the time," or "Surely chimpanzees, our closest animal cousin, sport some kind of chimp chin," and the answer is nope and nope (respectively). When you're scratching the "chin" of your feline companion, what you're really doing is scratching the mandible, i.e., the lower part of the jaw — not the chin, which is the bony part that juts out at the bottom of your face. Elephants and manatees also have chinlike protrusions in their lower jaws, but they don't quite qualify as true chins. The mystery of why no other animal has a real chin gets even more interesting because past human species, such as Homo erectus and Homo neanderthalensis, didn't have chins either — instead, their faces simply ended in a flat plane. So why did evolution find the need for human chins? Scientists aren't exactly sure. The most prominent theory is that chins help humans chew, but scientists from Duke University and the University of Florida found that chins aren't actually much help there; they technically make chewing more difficult, as they reinforce the wrong part of the face for aiding mastication. Chins also don't help much with human speech, which is another theory that's been suggested, and researchers say it's unlikely they're a mere product of sexual selection or a protection against violence, such as punching. Some scientists think the chin might be a spandrel, a byproduct of other evolutionary changes that on its own serves no real purpose — basically, a happy accident. We may never truly know exactly why humans have these extra bony bits on the ends of our faces, but keep your chin up. After all, you're the only species that can. | 
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