Sunday SciKu: Friendly Finches

Photo by David Clode

Past studies have shown that humans can recognize the voice of a friend after hearing just two words with 90% accuracy, and that babies recognize their mother’s voice at birth. I’ve never found an answer to the question of how many voices we have stored this way, and I wonder if it might be up to Dunbar’s Number—the number of social contacts we’re able to store and keep track of without external support systems. That number, around 150, is thought to govern the tribe sizes in hunter-gatherers, among other things, and thus has a large influence human cognition and history.

I always think of this when I notice a celebrity voiceover. If I recognize John Krasinski in an Esurance commercial, does that mean he’s in my tribe psychologically, even though I don’t actually know him? What a strange world we live in.

Anyway, this week’s SciKu was inspired by research out of U.C.-Berkeley showing that zebra finches are also able to recognize the voices of their friends in this way, right up to their own “tribe” size of 50. The thought of finches twittering to their friends made my day.


all these years
your voice on the phone
still birdsong


Sunday SciKu | Radiocarbon Record

Photo by Denis Agati via Unsplash

Here’s some potentially great news, the significance of which will probably go entirely unnoticed. It requires some explanation, so hold on tight. First here’s the primer on radiocarbon and coronal mass ejections:

99% of the elemental carbon on earth is the C-12 isotope and 1% is C-13, both of which are stable. Occasionally, though, a nitrogen atom in the atmosphere gets whacked by a high-energy cosmic ray from space, knocking off a proton and turning it into the radioactive C-14. This is a continuous process, as the earth is always being showered with galactic cosmic rays, so new C-14 atoms are always being created even as they decay over time, and the amount in the atmosphere remains relatively constant.

When plants take in CO2 for photosynthesis, a trace amount of it is always C-14. Because the C-14 decays but the C-12 doesn’t, we can use the ratio between the two to determine how long ago the plant was alive. The half-life of C-14 is 5,730 years, so if only half is left, that’s how old the sample is. Carbon dating: as simple as it is amazing!

The only problem is that it turns out the atmospheric concentration of C-14 isn’t as steady as we first thought. Tree rings and stalactites show that some years in the past have seen huge anomalous spikes in C-14 production. There are only two natural phenomena we know of that could create enough high-energy particles to explain these spikes: enormous coronal mass ejections from our own sun or supernovae from distant stars.

We really want it to be the latter. My biggest worry for the future of humanity isn’t nuclear war or pandemics or climate change—it’s coronal mass ejections. Due to solar flares and magnetic field instabilities, the sun regularly flings chunks of itself out into space as superheated plasma. Usually they’re small blobs. During the solar maximum every 11 years, there are a few CMEs every day. But sometimes they’re not small at all.

If something like the 1859 Carrington Event happened today, it would wipe out not just the power grid, but many of the electrical circuits on whatever continent was sun-facing when it arrived. It would be a catastrophic disaster and take years to rebuild—but we would, with the help of the night side of the Earth, which would be spared. These happen every 150 years or so, and the last was 1921. In July 2012, one of these missed us by 9 days.

The C-14 spikes, though, are much larger, and happen every 800 years, on average. The last was the Charlemagne event of 774 AD. C-14 production was 20 times the background rate that year. And we’re overdue for one of these.

If they’re caused by distant supernovae, we just get the cosmic rays. Cancer rates might go up, air travel might be impacted, there’d be more cloud formation and more lightning for a year—but civilization would be fine.

If it came from our own sun, though, a year’s worth of this energy is compressed into a few hours of hot plasma, and all of our technology is toast. For Charlemagne’s world, with no circuits to fry, this was only a magical global aurora, and maybe a bad hair day from static electricity. For us, it would be 400 Fukushimas simultaneously. No trucks, no trains, no water pumps. No phones, no radios, no refrigerators. All gone, overnight. No factories to rebuild any of it. If you can’t imagine how that would turn out, read The Road. Humanity would survive deep in the Amazon and for clusters of doomsday preppers, and that’s about it.

But I said this was good news! And here it is:

In a paper published this week, CU Boulder geoscientist Robert Brakenridge was able to date supernova remnants to many of these C-14 spikes in the tree ring record. It really could just be option A! Carrington could be the biggest CME our sun is capable of. And the next supernova candidate, Betelgeuse, is hundreds of years off and far enough away that it wouldn’t matter much at all.

Score one for a future!


fate of the world
in a child counting
tree rings


Sunday SciKu | Glowing Platypuses

Photo: Figure 1 from “Biofluorescence in the platypus,” Mammalia, 15 Oct 2020

This Sunday’s #sciku is about the recent accidental discovery that platypuses have fluorescent fur, joining a surprisingly wide phylogenetic range of mammals to feature the trait. Opossums, flying squirrels, and platypuses diverged from each other over 20 million years ago, and yet they all glow in UV light. What’s interesting is that we had no idea they were fluorescent, and still don’t know why it’s adaptive. It seems to be a feature of nocturnal mammals, so likely involves either intra-species signaling—perhaps a sexual fitness display?—or a kind of camouflage to hide from UV-sensitive predators. None of the articles make much of it, but notice in the photo how the coloring is completely different on the dorsal (back) side compared to the ventral (stomach) side. That reminds me of the coloring patterns on sharks and military aircraft, that camouflage themselves differently for those looking from below than those above. Flying squirrels are the same, only glowing on their bellies. Makes me think it’s more about hunting than being hunted. Platypuses eat things like shellfish and aquatic worms, which also bioluminesce. My hunch is that they’re fooling their food.

Anyway, we only discovered glowing squirrels a few years ago, and platypuses this week! So much of nature leaves us in the dark.


fluorescent fur!
the neighbors throw a party
without us


Sunday SciKu | Body Temperature

Photo by Denny Müller

Apparently, the average human body temperature has been decreasing since the beginning of the Industrial Revolution, when Carl Wunderlich’s records established 37 C (98.6 F) as the norm. In the U.S., it’s declined by 0.03 C per decade, and is now as low as 36.4 C (97.5 F).

The theory has been that increasing access to modern vaccines, antibiotics, and clean drinking water has decreased the body’s background inflammatory response—but it wasn’t proven. This study out of U.C.-Santa Barbara does that, using health data from a group of farmer-gatherers in the Bolivian Amazon, who have been undergoing rapid changes in their access to healthcare over the last two decades because of new social programs in Bolivia. The team found that, indeed, the average body temperature of the Tsimane began at 37.0 C and has decreased by a full degree after these government interventions.

This is all new to me, and made me think about how everything is economics. There’s an energy cost to maintaining a higher basal temperature, and being able to use that energy elsewhere is a bio-economic transaction. And where is that extra capital we’re given by modern medicine spent? Could this be why other studies show that general intelligence has been increasing over the last two centuries, as well? Or do we just store it for the future as fat, which is also increasing?

And then the fact that we’re becoming more cold-blooded as a consequence of that bio-economics reminded me of the studies suggesting that wealth decreases empathy—a psycho-economic transaction, where decreased vulnerability leads to a decrease in reciprocal altruistic reward. The famous study shows that more expensive cars are less likely to stop for pedestrians at a crosswalk.

So everything is economics, on every level, including the prosperous but cold math of the global economy expanding its reach into the Amazon. As always, it was fun trying to cram all of these thoughts into a tiny Sunday sciku.


we find it healthy to grow


Sunday SciKu | Word Form Area

For a long time I’ve been interested the Snake Detection Hypothesis, which says that it was primates’ co-evolution with snakes that allowed for the rapid development of our excellent vision—we had to be able to quickly recognize camouflaged snakes so they wouldn’t kill us as we coexisted for millions of years in the same habitat. My hunch has been, though I’ve never found any research on this topic, that it’s this same high-contrast pattern detection that allows us to read text, and that the “visual word form area” of the brain is an adaptive overlay on top of the snake detection area. If you look at the pattern on a snake, it kind of looks like text. Which has cool implications for the Eden myth, where it was the snake that taught us knowledge. I have no idea whether or not this is true, but it would be interesting if it is.

Anyway, this paper points toward that hypothesis, showing that the visual word form area is pre-wired into the brains of infants. They put 40 newborns into an fMRI machine and showed that they already have the VWFA. Which begs the question—how could this module have already evolved when majority literacy (let alone universal literacy) is only 75 years old? In 1820, only 12% of the global population could read—yet we already have a pre-wired VWFA just 200 years later? How is that possible? My answer: snakes.


your first words
snaking across the page
parting the grass