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SciShow delivers the latest in science news, including how fist-fighting fueled the evolution of the human face, new insights into the origin of schizophrenic "voices," and new research into the bird flu.
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Have you ever known a guy who just made you think 'Aw he's got a good face for punching'? You may have been on to something. Because it seems that some of our ancestors underwent two very important evolutionary changes that anthropologists now think are probably related.

Four or five million years ago Australopithecus, the common ancestor of Homo sapiens and our extinct relatives the Neanderthals and Homo erectus developed hands that could form fists. And they developed faces that could take a punching.

According to a report this week in the journal Biological Origins this was no coincidence. Instead biologist David Carrier and physician Michael Morgan proposed that the strong, flat facial features that are so distinctive of humans and our nearest relatives developed as a kind of defensive buttressing.

For a long time anthropologists believed that the shape of hominins faces evolved to develop jaw power; specifically for eating hard to chew food like nuts. But recent dental evidence suggests that our early ancestors ate mostly fruit and Carrier and Morgan found that the bones that were most often fractured in fights were the same ones that became thicker and stronger and more robust over time. Especially the bones that formed the jaw, the cheeks, and the orbits of the eyes. They also point out that these changes became more pronounced in males who did more of the fighting than in females.

(1:25) However, you can take my word on all of this, don't go getting into a big bar brawl just to see how your face holds up. In other news, researchers at the St. Jude's Children's Hospital may have uncovered the source of the voices that are one of the most striking and debilitating symptoms of schizophrenia.

Schizophrenia affects 1% of the world's population and it's not very well understood. There are treatments that help many people control their symptoms but we don't know how or why most of them work. For decades anti-psychotic drugs have been known to quiet auditory hallucinations, which often manifest as voices, by binding to a dopamine receptor known as DRD2. Binding to those receptors blocks the activity of the chemical dopamine, but why that helps anything we had no idea. In this weeks issue of Science however researchers say the phenomenon of auditory hallucinations may be linked to a genetic disorder that effects how the brain releases dopamine. 

The disorder basically causes part of the 22nd chromosome to be missing, leaving patients with one instead of two copies of about 25 different genes. And 30% of the people with this genetic condition develop schizophrenia.

By first studying mice with and without those missing genes the team discovered that one of the deleted genes carried instructions for making the molecule that regulates protein production in the auditory thalamus. That's the part of your brain that all auditory information passes through before it's actually processed.

But in patients missing that gene that part of the brain produces weaker neural signals. The brain responds by producing more dopamine to try and amp up that signal. And if you've seen any of our episodes on drugs and addiction you know that when your brain starts drowning in dopamine all kinds of weird things start happening.

The researchers also studied brain tissue samples from 22 human subjects with and without schizophrenia and confirmed that changes to the auditory thalamus happen in people as well as mice. This new understanding of auditory hallucinations will hopefully help doctors find treatments for one of medicine's most frustrating and debilitating conditions.

(3:18) And lastly this week, don't freak out but it turns out that the avian flu is a lot more like the Spanish flu than we thought. Yeah the Spanish flu they killed 50 million people in 1918. The most devastating disease outbreak ever recorded.

In a study published this week in Cell Host & Microbe, University of Wisconsin virologist Yoshihiro Kawaoka showed how modern strains of avian flu differ from the Spanish flu by only a few amino acids.

Viruses are basically just bits of RNA or DNA wrapped up in a protein, and the makeup of that protein is what determines how they function. Current bird flu viruses are unable to efficiently spread between humans which we are all very grateful for.

But Kawaoka and his team created a virus using 8 currently circulating strains of avian flu that was able to spread rapidly among ferrets, whose immune systems, for whatever reason, are very similar to ours. But Kawaoka only had to add 7 amino acids to a few key proteins in order to do it. If viruses in the wild managed to develop those amino acid changes on their own that would be the worst news! And viruses are very good at evolving.

So after creating his own mammal-infecting virus that hopefully he has in a box inside another box that's inside a big building that has a box around it, Kawaoka called for more research into flu vaccines and anti-viral medications which seems like the least he could do.  But in the mean time, you know, if you've got the option of living inside a giant plastic bubble you might want to check that out.

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