SCOTT DETROW, HOST:
It's ALL THINGS CONSIDERED from NPR News. I'm Scott Detrow.
JUANA SUMMERS, HOST:
And I'm Juana Summers. And it's time now for our science news roundup from Short Wave, NPR's science podcast. I'm joined by two members of the team, Angela Zhang and Regina Barber. Hi to both of you.
REGINA BARBER, BYLINE: Hey.
ANGELA ZHANG, BYLINE: Hello.
SUMMERS: So I know that y'all have brought us three science stories that caught your attention this week. Tell us what they are.
ZHANG: The first is the weather on an exoplanet that could also be a failed star.
BARBER: An intriguing find in the social structure of ancient human relatives.
ZHANG: And what we can learn about ourselves from laughing primates.
SUMMERS: OK, Gina (ph), I would love it if we could start in space. Tell me...
BARBER: Yes.
SUMMERS: ...About the weather on another planet.
BARBER: Yeah. This might not even be a planet that we're talking about here. There's a debate over this object, GJ 504 b. It's roughly 25 times larger than Jupiter, and astronomers are uncertain how to define it. Is it a planet like Jupiter, or is it a failed star?
SUMMERS: What do you mean by that? Like, they look the same to us from a telescope, but they're actually different things.
BARBER: Yeah. Huge Jupiter-like planets and a failed star - they do look super similar, but how they get there is different. Stars need a lot of mass to ignite fusion and turn on, and without enough mass, the star doesn't turn on, basically. It failed.
ZHANG: And whichever one this object is, we know that it's really dim and couldn't be fully studied from ground telescopes until a study out this month in The Astronomical Journal about GJ 504 b. Astronomers were finally able to analyze the light using the James Webb Space Telescope, and they got some information on what chemicals are in its atmosphere.
SUMMERS: So what can scientists say about it?
ZHANG: They could say something about the kind of clouds that were in the atmosphere. So this maybe/maybe not planet - it's about 550 degrees Fahrenheit. That's probably how hot your oven gets at home, and that might seem hot to us, but that's actually pretty cool for other worlds like this.
BARBER: Yeah. And that temperature affects what kind of weather it has. Like, there are exoplanets that are so hot the clouds are made up of gemstones. Yeah, and our Jupiter is so cold that the clouds are ammonia ice and beneath that, water vapor.
SUMMERS: So what are these clouds made of? And how does knowing that help our understanding of space?
ZHANG: So the study modeling and this temperature all pointed towards - get this - salt clouds. And there actually aren't a lot of objects in space like this one.
BARBER: Yeah. There's still a lot of questions astronomers, like the lead author Aneesh Baburaj, have. Like...
ANEESH BABURAJ: We still don't know how big planets can get.
BARBER: So uncovering as much as possible can help astronomers make better models for how planets and stars are born.
SUMMERS: All right. Up next, we've got a story about ancient human relatives. What did scientists find out that's so interesting?
BARBER: So in 2013, archaeologists discovered more than a thousand human-like fossils - so, like, bones and teeth - in the Rising Star cave system in South Africa. And one big thing jumped out. All the reconstructed skeletons looked oddly the same size, which surprised scientists because in most primate species, there's a clear difference in size between the sexes.
ZHANG: And this species - called Homo naledi - they lived a few hundred thousand years ago. They walked upright, and they had human-like hands and feet, but their brains were much smaller than those of ancient humans.
BARBER: Yeah. And if you look them up, they look very "Planet Of The Apes"-like.
SUMMERS: OK. OK.
BARBER: Anyway, a study out this week in the journal Cell may have solved this size mystery. An international team of researchers analyzed the teeth of 20 Homo naledi individuals, spanning thousands of years, to determine the sex.
PALESA MADUPE: All of the Homo naledi individuals that we looked at came back missing a male marker.
ZHANG: That's lead author and molecular scientist Palesa Madupe. She says the chances are about one in a million that all 20 would be female. So the team thinks this could have been an intentional, maybe even sex-specific burial practice.
SUMMERS: Oh, interesting. So how big of a deal would that be if it's true?
BARBER: It could be a big deal because Homo naledi isn't in our direct lineage, and burial practices are largely ascribed to humans. Although other animals do it, like elephants and naked mole-rats.
SUMMERS: Interesting. So how are others in the field reacting to these findings?
ZHANG: They're pretty excited. Researchers have been puzzling over this for more than a decade, actually. We talked to Charles Musiba. He's an evolutionary anthropologist at Duke University who wasn't a part of the study. Though, even with his excitement, he was also a little cautious.
CHARLES MUSIBA: Could this be an intentional sort of disposal of the bodies? The answer, probably, is yes. I'd like to see a little bit more evidence, but it sort of strongly suggests that way. And the biggest question is, where are the males?
SUMMERS: Where are the males, indeed.
(LAUGHTER)
SUMMERS: Hopefully, we'll have you on later for an answer to this next mystery. So let's move on here. For our last story, let's stay with these distant relatives. There's new research that could tell us more about how humans evolved to communicate. And you said it's from studying primates.
BARBER: Yeah. So how humans evolved to communicate is not totally clear. I mean, we don't have recordings of our hominid ancestors, you know, talking. But we can study some distant relatives - the great apes. There are orangutans, gorillas, chimpanzees and bonobos. And so how they communicate and vocalize could give us clues about our own evolution.
ZHANG: And what do we have in common? We play, and we laugh.
CHIARA DE GREGORIO: Many non-human primates love being tickled, especially when they are, like, babies.
ZHANG: That's primatologist Chiara De Gregorio from the University of Warwick. Her team measured the tempo of laughter in great apes and human children, and they just published their results in Communications Biology. They found that great apes, like us, laugh in a steady rhythm, almost like a metronome. And they found that the laughter actually changed over time.
DE GREGORIO: We go from orangutans that are solitary animals...
(SOUNDBITE OF ORANGUTAN LAUGHING)
DE GREGORIO: And then you have gorillas, which have more a family kind of group...
(SOUNDBITE OF GORILLA LAUGHING)
DE GREGORIO: Then you have chimpanzees and bonobo, which start to have a really, like, complex social life...
(SOUNDBITE OF CHIMPANZEE AND BONOBO LAUGHING)
DE GREGORIO: ...Going towards more complex society, then a laughter becomes more variable and more flexible.
SUMMERS: It's so cool hearing all of those together. I mean, you can really hear how the chimpanzees and bonobos - the last two that we heard - do sort of sound like human laughter.
BARBER: Yeah. They basically made us laugh, right?
SUMMERS: (Laughter).
BARBER: And we're actually more closely related to bonobos and chimpanzees out of all the great apes, and our laughter is the most similar to theirs, like you said. So this study shows us that as a species becomes more social, maybe laughter gradually evolves, as well.
SUMMERS: And what can that tell us about humans?
ZHANG: Well, as you heard, the great apes have a pretty cute laugh.
SUMMERS: They do.
ZHANG: But it's also pretty regular, like that metronome. And they can't really change it, as you also heard. But humans can. The human children in the study were the only ones who could actually modulate or change how they laughed.
BARBER: And that laughter conveys really important information.
DE GREGORIO: We can have a polite, small laugh in front of a - I don't know - an important person. But then maybe you are at the pub with friends, and we laugh in a total different way.
BARBER: You can totally imagine those scenarios, right?
SUMMERS: Oh, yeah, for sure.
BARBER: Totally. And laughing like this requires a lot of vocal control, which is also how you learn to speak, which, of course, also sets us apart from the great apes.
SUMMERS: Angela and Regina, thanks to both of you.
BARBER: Thank you.
ZHANG: Thanks.
SUMMERS: Angela Zhang and Regina Barber work for NPR's science podcast Short Wave, which you can follow for new discoveries and answer to everyday mysteries just like these.
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