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Head to shopify.com/scishow to learn more and for a 14-day free trial. [♪ INTRO] The liver might be the closest thing we humans have to regeneration superpowers. Because it’s one of the main organs responsible for removing toxins from our bodies, it’s evolved the ability to rapidly repair itself if it suffers significant damage.

Last week in the journal Cell Systems, researchers revealed the true power, and true age, of the human liver…with the aid of nuclear fallout. Our livers are so great at regenerating that you can lose well over half of it, depending on who you ask, and the rest will grow back. But does that superpower last for your whole lifetime?

After all, other parts of our body don’t stay completely fresh as we age. To answer that question, one team of researchers studied a certain kind of liver cell, called hepatocytes, from donors between the ages of 20 and 84. This study was a larger one interested in a lot of aspects of liver function, but the part that we’re talking about today involved 33 donors, some living and some deceased.

Hepatocytes are the cells that do most of the heavy lifting in liver repair, both the standard maintenance and in the event of disease. To figure out the age of these cells, the team turned to radiocarbon dating… with a bit of a twist. While all carbon atoms have 6 protons, they can have different numbers of neutrons.

The vast majority have 6 of those as well, so we call them carbon-12 atoms. Carbon-14, meanwhile, has two bonus neutrons. But it’s radioactive, and slowly breaks down.

And above ground nuclear weapons tests in the mid-20th century flooded the atmosphere with carbon-14. But that practice was banned in 1963, so over the years, the ratio of carbon-14 to carbon-12 in the air has dropped. It’s safe to say not a lot of good has come of nuclear testing, but this fact has been exploited to figure out the age of things since those tests took place.

So to figure out how old a given liver cell was, the team calculated the difference between the amount of carbon-14 present in the liver cells, and the amount in the atmosphere. And older and younger donors had pretty much the same ratio, indicating their liver cells were, overall, pretty much the same age. It turns out, liver cells from the oldest donors had basically the same regenerative capabilities as those from the youngest, and everywhere in between.

So finally, we have found the one thing that boomers and millennials have in common. The team also estimated the age of an average liver. On a cell by cell level, there was some variability, including a much older population of cells with extra copies of their DNA.

But on average, the math works out to make your liver about three, whether you are 13 going on 30, or just plain old 30, or pushing triple digits. That’s somewhere in the middle of possible lifespans human cells can have. For comparison, human skin cells last about a month.

And the cells at the center of the eye lens last your entire life. So your body is very nearly a living ship of Theseus. Our second story has less to do with mythological metaphors, except maybe Pompeii.

Last week in the journal Science Advances, researchers reported on how they were able to predict a volcanic eruption, five months before it actually happened. When you live within a stone’s throw of a dormant volcano, it’d be really nice to know if, and especially when, it might erupt. So over the years, scientists have been hard at work trying to develop models that can predict this particular kind of natural disaster.

But that is, of course, easier said than done. Increased seismic activity and ground swelling are usually both signs indicating an imminent eruption, but the problem is that not all volcanoes play by the same rules. Like, sometimes a volcano will erupt with no signs of ground swelling, and sometimes the ground will swell up… but no eruption happens.

Models that can crunch the necessary data in real time need to run on supercomputers, so it makes sense why there’s no volcano forecast app for you to download… yet. But one volcano named Sierra Negra, on the Galápagos island of Isabela, is a model of good volcano behavior. Since 1911, it’s had eruptions every 15 years or so, and consistently provides good seismic and ground swelling data prior to each one.

Back in 2017, a team of researchers had upgraded their volcano forecast tools to incorporate real-time data, modeling how much stress is applied to the rocks holding a volcano’s magma in there, all not erupting and stuff. Observations of Sierra Negra suggested it was going to have another eruption soon, so the team’s supercomputers started crunching those real-time numbers. In January 2018, the simulations put out an estimate for the day that magma would break through to the surface.

Somewhere between June 25th and July 5th, 2018. And Sierra Negra erupted on June 26th. Over the next three months, lava spilled out of five cracks on the northern side of the volcano, and ultimately covered an area of 30 square kilometers.

This is a clear milestone in natural disaster prediction. But it’s worth noting that Sierra Negra basically provided the team’s simulation the best possible conditions for a volcano’s ramp-up to eruption. They literally called it a “lucky accident” in the paper, in part because when they made the prediction, their model used a few assumptions, and the satellite measurements they ran the simulations with were preliminary.

They sort of weren’t even trying, so much as like working up to it. And there was one noticeable difference between prediction and reality. The models said that the magma would break out through the southern side of Sierra Negra, but it actually escaped out the north side.

Follow-up analysis revealed that it was probably a minor earthquake that actually triggered the collapse, as opposed to just a buildup of too much pressure. And that earthquake dictated both where and when the lava started spilling out. It’s still going to take a lot of data, looking at a lot of different volcanic subjects, before scientists can hope to develop an actual volcano forecast tool.

But the ability to forecast natural disasters, and give locals enough time to evacuate when need be, is crucial to save as many lives as possible. And this result is progress… like, more than expected! Still, there’s more work to be done, so best to keep crunching those numbers.

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