Learn about how a mutation that evolved to protect us against malaria actually makes us more prone to other diseases; and why astronauts are using old sailing technology (sextants) to navigate through space. Plus: a special update from Cody!
Learn about how a mutation that evolved to protect us against malaria actually makes us more prone to other diseases; and why astronauts are using old sailing technology (sextants) to navigate through space. Plus: a special update from Cody!
A mutation that makes us prone to autoimmune diseases evolved to protect us from malaria by Cameron Duke
Astronauts Are Using Old Sailing Technology in Space by Elizabeth Howell
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Find episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/a-harmful-mutation-evolved-for-good-why-astronauts-are-using-old-sailing-tech-in-space-and-codys-message
CODY: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from curiosity-dot-com. I’m Cody Gough.
ASHLEY: And I’m Ashley Hamer. Today, you’ll learn about how a mutation that evolved to protect us against malaria actually makes us more prone to other diseases; and how old sailing technology is being used by astronauts to navigate through space. Then, stay tuned for a special update from Cody!
CODY: Let’s satisfy some curiosity.
Evolution is how organisms change over time, but it’s not exactly a march toward perfection. Sometimes, those changes have tradeoffs — and humanity is dealing with those tradeoffs today. I’m talking about a genetic mutation that helped protect our ancestors from malaria. That lifesaving adaptation came at a cost: it made us more prone to other illnesses as a result.
Here’s how that works. The cells in our bodies are fringed with proteins and sugar chains. Many of these chains are tipped with special sugars called sialic acids [sigh-AAL-ick, like smart aleck]. Sialic acids help with cell recognition by acting as a sort of ID badge — like “It’s ok, I work here!” They also play a role in immunity: any pathogen that wants to enter the cell has to contend with the net of sialic acids surrounding it.
Just like anything else in our bodies, these sugars are controlled by our genes, and genes mutate over time. Mutated sialic acid genes are the cause of many diseases, though most of these mutations are rare. But there’s one particular sialic acid mutation that all humans share.
See, most of our mammal relatives have a specific sialic acid marker called Neu5Gc [new five G C]. But in humans, the gene for this sialic acid is busted. Instead, we make a different kind, called Neu5Ac [new five A C], and it’s not nearly as good at its job. But it does seem to be good for one important thing: it’s like kryptonite for the malaria-causing Plasmodium parasite. Considering how deadly malaria can be, scientists think that’s the reason we kept the gene for this deficient sialic acid instead of its more competent cousin.
Here’s where it gets really interesting. Remember how sialic acids are like ID badges? Well, if you change the ID badge through a mutation, you’re going to have to update the security protocol, too. In other words, all that extra Neu5Ac led to more mutations in the way the human immune system recognizes its own cells.
And some of those mutations have been linked to conditions like asthma and Alzheimer’s disease. Add that to the fact that our busted version of sialic acid is really friendly to pathogens like cholera, smallpox, influenza, and, yes, coronavirus? You start to realize what a trade-off this mutation really was.
But clearly, it gave us enough of an advantage that we’re still around today. It goes to show that evolution doesn’t strive for perfection. It just settles for good enough.
If you were lost in space, how could you find your way home? It turns out that old sailing technology might be the answer. In 2018, astronauts on the International Space Station wound back to the 1730s and tried navigating with a sextant — a device that sailors once used to make sure they were going in the right direction. Hey, if it ain’t broke, don’t fix it!
On Earth, you can use a sextant to figure out the angle between the horizon and some celestial object: the sun, the moon, or a star, for example. If you know where that object should be at that time of day, you can determine your longitude and latitude. But there’s no horizon in space, so if astronauts are going to use a sextant, they have to take a different approach. Instead of the angle between the horizon and a known star, they could use the angles between two known stars. Obviously, astronauts can normally use high-tech equipment to know where they are, but the hope is that the sextants would come in handy in an emergency.
That might sound weird, but it’s not the first time astronauts have used celestial navigation in space. In 1970, Jim Lovell famously used the sun and Earth's horizon to guide the Apollo 13 mission home after an explosion forced them to shut down their main spacecraft.
So in 2018, NASA researchers decided to see if they should make the sextant technique a regular emergency protocol for astronauts. They had two astronauts test this idea in the International Space Station's wraparound Cupola window. Sextants require a steady hand, and they needed to figure out if that would be possible when the astronauts were floating around. After several months of tests, they concluded that yes, sextants are a totally legit backup tool. They’re simple to use and don’t require much training.
So if the curse of 2020 decides to visit the International Space Station — and, yeah, let’s hope it doesn’t — don’t be surprised if you hear about modern astronauts using old-timey sailing technology to get home.
Before we wrap up, let’s say bye to Cody!
Let’s do a quick recap of what we learned today
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CODY: Today’s stories were written by Cameron Duke and Elizabeth Howell, and edited by Ashley Hamer, who’s the managing editor for Curiosity Daily.
ASHLEY: Scriptwriting was by Cody Gough, Sonja Hodgen, and Natalia Reagan. Curiosity Daily is produced and edited by Cody Gough.
CODY: Join us again tomorrow to learn something new in just a few minutes.
ASHLEY: And until then, stay curious!