JOHN DANKOSKY: Wildfires have killed dozens of people on the Hawaiian island of Maui this week. The fast-moving fires were driven by strong, dry winds and made worse by ongoing drought conditions there. Recovery could take years and, officials say, billions of dollars after countless homes, businesses, and entire communities burned to the ground. So what do we know about the science behind these wildfires? Here with this story and other science news of the week is Bethany Brookshire, freelance science writer and the author of the book Pests– How Humans Created Animal Villains. Bethany, welcome back to Science Friday.

BETHANY BROOKSHIRE: Hey, thanks for having me.

JOHN DANKOSKY: So what do we know about what caused these fires in Maui?

BETHANY BROOKSHIRE: Yeah, no one really knows the exact cause. What we do know is that they’ve been severely exacerbated by winds from Hurricane Dora. Hurricane Dora is about several hundred miles away, but it’s sent winds of more than 60 miles an hour, which has really driven the burn and the spread into towns and other communities.

JOHN DANKOSKY: Now Hawaii, like a lot of other places, does have wildfires, but not large fires like this. It’s a pretty humid place. Why is this changing now, Bethany?

BETHANY BROOKSHIRE: Yeah, you know, I think a lot of people think, oh, California is the only place with something like a fire season. Everywhere has seasons where fires are more likely than others, but there are some ecosystems that are kind of adapted to burning and benefit from kind of frequent, low-level flames. Hawaii is not one of those. People in Hawaii are not used to dealing with fires like this.

But now Hawaii has pretty much a year-round fire season, and part of that is because of climate change. Climate change has made the islands much drier than before, and that has drastically increased both the number of wildfires and their potential danger. And there are invasive bushes, but most particularly, there’s this tall grass called Guinea grass, which grows really, really fast and really, really tall, and that just provides a crazy amount of tinder for these wildfires.

JOHN DANKOSKY: It’s such a terrible story. And our thoughts are with those in Maui and with all of our colleagues at Hawaii Public Radio who are covering this tragedy this week.

Let’s turn to some other news. The FDA has approved the first pill that treats postpartum depression. Now before we get into how this pill works, Bethany, can you give us a background on postpartum depression and why it’s different from other types of depression?

BETHANY BROOKSHIRE: Yeah, so we know about 1 in 7 people who give birth will suffer from postpartum depression in the weeks and months after giving birth. And postpartum depression is excessive sadness, excessive anhedonia, which is an inability to take pleasure in normal activities. And, in some people, it can be kind of mild. In others, it can be severely debilitating. It can endanger the life of the parent as well as the life of the baby.

And postpartum depression is interesting because we’re still not entirely sure what causes it. Many people theorize that there’s large amounts of hormones going on in the postpartum body. They have been used to large amounts of estrogen and progesterone. And those hormone levels just really take a dive after birth. And there are thoughts that that might be one of the causes behind postpartum depression. And that is why this pill is really interesting.

JOHN DANKOSKY: So how exactly does it differ from antidepressants that are on the market and also prior treatments for postpartum depression?

BETHANY BROOKSHIRE: Yeah, so this pill is unlike any other antidepressant. Most basic antidepressants target specific chemical messengers in the brain, like serotonin or dopamine. This drug, which is unfortunately called zuranolone, and will be marketed as Zurzuvae, because people love to make me pronounce things, is actually a completely different mechanism. It is a derivative of progesterone. And so Zurzuvae is a very different mechanism of action. It’s attacking that method that we think might be causing postpartum depression, those low levels of progesterone, by kind of mimicking some of the breakdown products of progesterone.

And it’s different from previous drugs in that the previous drug that was approved for this has to be administered over 60 hours in a hospital setting– not great.

JOHN DANKOSKY: No, that’s right. It’s not great and not something that a lot of people are going to be able to actually use.

BETHANY BROOKSHIRE: Yeah, and so the new one is a pill, and it’s just once a day for 14 days. And they’re very optimistic because it appears to have very fast-acting effects, much faster than other antidepressants.

JOHN DANKOSKY: We should move on. We’re going to go on a journey now into the unknown genes of the human genome. Tell us about this. I thought we knew everything about the human genome at this point, Bethany.

BETHANY BROOKSHIRE: Oh, that’s so cute.

[LAUGHTER]

No, we do not, interestingly. So scientists estimate that the human genome has about 20,000 genes, give or take, that encode proteins. But in many of those cases, we have no idea what those proteins do. And so scientists have developed a database of these proteins that they have called the Unknome, which is a combination of “unknown” plus “genome.”

And this is a massive database of protein-coding genes, with the requirement that at least one gene in the family is in the human genome. And it assigns a score to the different genes, depending on how much we know about them. So a very well-studied gene will have scores above 100, but more than 800 of the known human protein-coding genes have a score of 0, meaning we know nothing about them.

So the group ended up looking at 260 of these low-scoring genes that are shared between humans and fruit flies. And they knocked them down in fruit flies. So they kind of knocked them out, made them not exist. And in 60 of those genes, the result was lethal, meaning that they are definitely necessary for life. We don’t know what they do, but we know they are important.

JOHN DANKOSKY: But we need them.

BETHANY BROOKSHIRE: Yeah, so we know that this database is going to give scientists new avenues to figure out which genes should be studied and potentially how.

JOHN DANKOSKY: Interesting. I want to turn to another story that you actually covered this week for Science News. It’s some new news on a very old moss. What can you tell us about this moss?

BETHANY BROOKSHIRE: Well, it’s really cute. I highly recommend you look up pictures of this very cute moss. The moss genus is Takakia, and it’s extremely old. It is estimated to be 390 million years old, which means this moss saw dinosaurs die to an asteroid and gave a little moss shrug. So this moss is not only old. It’s very rare. There are two species in the genus, and they only occur together on the Tibetan Plateau above 4,000 meters of elevation.

And scientists carried out a 10-year study of these mosses– in the process, three people ended up medevacked for altitude sickness, so it’s a really tough area up there– to find out how these mosses evolved to live in such harsh conditions. And they found that they’re tough little guys, and they have the highest number of fast-evolving genes of any moss. So they’re speed-evolving.

And over the 10 years of the study, they analyzed the ecosystem around these mosses. And they found that the temperature was rising, on average, about 0.43 degrees Celsius per year, and the moss– its range was contracting by 1.6% per year, which means that in another 100 years, a nearly 400 million year old moss might be extinct.

JOHN DANKOSKY: It’s just not evolving fast enough. Oh, what a story. It’s really interesting. And you should go look at pictures of this cute moss. Finally, scientists have found evidence of a version of– I guess it’s hide-and-seek that’s happening in the ocean. Tell us about this.

BETHANY BROOKSHIRE: Yes. So the fish we’re talking about is the trumpet fish. So the trumpet fish lives on coral reefs in the Caribbean, and they’re these long, slender predators, about 20 inches long, and they generally eat things like shrimp and damselfish. And if they were to approach those shrimp and damselfish looking like themselves, the damselfish would come up and check them out and be like, absolutely not. They know danger when they see it.

So the trumpet fish swims up hiding behind a parrotfish, which is a big, friendly boy. We knew there were anecdotal reports of this behavior. To test it scientists, created 3D models of fish and reeled them out over the reef to see how the damselfish would respond. And they showed that the damselfish would flee from a trumpet fish model by itself. They would not react to a parrotfish model by itself. And if a trumpet fish hid behind a parrotfish, the damselfish were slightly less wary, maybe just less wary enough to end up as dinner.

JOHN DANKOSKY: That is so interesting– those sneaky, sneaky trumpet fish. That is all the time we have. I want to thank Bethany Brookshire, freelance science writer and author of the book Pests– How Humans Created Animal Villains. Thanks so much for bringing us these stories, Bethany.

BETHANY BROOKSHIRE: Thank you.

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