IRA FLATOW: This is “Science Friday.” I’m Ira Flatow. Coming up, the endangered fossil treasures of Utah’s newly slimmed down national monuments. We’ll talk about the potential loss of important fossils at the Grand Staircase and Bears Ears.

But first, there are around 100 named ages in geology. If you’re a geologist, my heart goes out to you to remember all of these. And now, a recent proposal wants to add a new one dating around 4,200 years ago. It has set off a debate between geologists and archaeologists about what the ancient world really was like back then.

Joining me now to talk about that and other selected short subjects in science is Annalee Newitz. She’s a science journalist and book author based in San Francisco. She joins us from KQED. Welcome back.

ANNALEE NEWITZ: Hey, thanks for having me.

IRA FLATOW: I know this is one of your favorite subjects, Annalee.

ANNALEE NEWITZ: [LAUGHING]

IRA FLATOW: Right, right?

ANNALEE NEWITZ: Yes, it is.

IRA FLATOW: So what is this debate about? Who is saying we need a new geological age and why– fill us in on this.

ANNALEE NEWITZ: So we actually do have a new geological age. It’s called the Meghalayan Age. It’s named after a state in India. And as you said, it starts about 4,200 years ago and it goes up into the present. And it’s been the source of incredibly bitter debates between geologists and archaeologists because the way that geologists decide that there is a new age on Earth is that they have to identify some kind of huge event that’s changed the ecosystems of Earth, to kind of justify, like all right, now we’re in a new age here.

And so some of these events are things like ice ages or a meteorite hitting the earth, things that we recognize as kind of catastrophic. So for the Meghalayan Age, what geologists argue is that there was a global drought that affected the course of human civilization. Because remember, this is a period when we actually have human cities and writing, and people are kind of doing their thing. And what archaeologists are saying is, no, actually we don’t really have evidence that there was a drought that was altering civilization.

IRA FLATOW: Wow. So it’s like the farmers and the cowboys should be friends.

ANNALEE NEWITZ: [LAUGHING]

IRA FLATOW: I mean, so what evidence do they advance that there was a global drought?

ANNALEE NEWITZ: So most of the evidence really does come from archaeological sources. And so in some ways, the debates around this– and there are many debates that I won’t even get into here– really boil down to, how did the physical sciences and the social sciences talk to each other about data? And so what we see are– there’s evidence in the written record that cities were abandoned in the Middle East and in North Africa during this time. We have evidence for a lot of political instability in a lot of these places.

And so geologists look at that and they combine it with evidence from the sort of– from Earth science records. And they say, look, this was obviously a civilization-changing event. But archeologists say no. They say actually a lot of these written records are poems that were written in the form of lamentations that were just typical of the time. These aren’t really people going through a catastrophe. They’re just sort of writing poems in ancient Egypt, like in the style of emo music today. They’re just sort of feeling sad.

And a lot of these urban abandonments that we see, for example, in the Middle East, weren’t really people abandoning civilization. They were just moving. They were migrating. And so we see civilization transforming, but was it really enough of a catastrophe for us to say that we’re living in the Meghalayan Age now? That’s going to continue to be a huge debate, especially when you add in questions about whether we should be in the Anthropocene, which is a different age where human civilization has changed enough of the Earth that we can say, all right, maybe we’re in a new age. So that’s a whole other debate and that kind of gets into this as well.

IRA FLATOW: But they’re saying that they’re– across the whole globe, Egypt, other places were all in this transition at the same time.

ANNALEE NEWITZ: So that’s what geologists want to argue. And the International Commission on Stratigraphy, which is the group of geologists that controls time by making these names. They’re saying that this was all sort of at the same time.

Archeologists are saying, actually no. Even the written records show that this was really a period of about 200 years. So we can’t really find a causal link between drought and civilizational collapse. It may have just been one of those correlation doesn’t equal causation moments that we love in science, where just because you have political instability doesn’t mean it’s caused by drought or the environment.

IRA FLATOW: Something new besides the planet Pluto to argue about.

ANNALEE NEWITZ: [LAUGHING]

Exactly. Nothing better than names for our geological time unit.

IRA FLATOW: Speaking of names, in other ancient history news, I know there’s new work on Mayan societies that’s kind of interesting.

ANNALEE NEWITZ: Yes. This is something that I’m super excited about. It’s one of the biggest discoveries around Maya civilization in the past decade. There was just a LiDAR survey done in one of the areas of sort of the greatest extent of Maya civilization in northern Guatemala. And so what that means is that scientists flew over the top of the trees in that area and used LiDAR, beaming lasers down onto the planet, to look through the tree cover and see the remains of things like ancient structures, ancient roads. So they found over 6,000 new structures attributed to the Maya during this Late Classical period, which is about between the 600s and the 900s CE.

And so what that means is that the Maya weren’t just building fabulous sites like Tikal, which was actually in this LiDAR survey. These sort of isolated cities that we’ve heard about from Maya history, they actually were spending a lot of time living in what amounted to suburbs. They were living outside the cities. And they were engaging in incredibly sophisticated intensive agriculture outside the cities, which were linked by a massive network of roads that were also uncovered through this LiDAR survey. So now, we have a picture of the Maya as not these people who kind of hunkered down in these walled cities, but actually a lot of them lived out in the suburbs and were farming, and were not necessarily part of these intensive city-states in the way that we once thought.

IRA FLATOW: So is this like a megalopolis like Baltimore, Washington? Maybe they had their own beltway.

ANNALEE NEWITZ: Yes, they may have. It was basically a big sprawl.

IRA FLATOW: Wow.

[LAUGHTER]

We’ve seen novels and we’ve seen people– the City of Z, that kind of stuff where they went looking for giant civilizations because of rumors. Maybe they really existed.

ANNALEE NEWITZ: Yeah. Or maybe they really should have been thinking about where to find the suburbs and where to find these farms. Instead of looking for lost cities, look for lost suburbs in northern Guatemala and you learn a lot more about the Maya civilization.

IRA FLATOW: I’m going to quote you on that, OK? Let’s look for lost suburbs.

[LAUGHTER]

Thank you, Annalee.

ANNALEE NEWITZ: Yes, thank you so much.

IRA FLATOW: Annalee Newitz, science journalist and book author based in San Francisco. She was joining us from KQED.

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