Latest / PlanetGeo: The Geology Podcast / 2.5 Billon Tyrannosaurus rex (GeoShort)

Transcript

2.5 Billon Tyrannosaurus rex (GeoShort) · PlanetGeo: The Geology Podcast

• 0:01
  SPEAKER_00: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:14
  SPEAKER_00: Chris, how are we doing today, man?
• 0:16
  SPEAKER_00: Doing awesome.
• 0:16
  SPEAKER_00: How you doing, Jess?
• 0:18
  SPEAKER_00: I'm great.
• 0:18
  SPEAKER_00: I'm super great.
• 0:19
  SPEAKER_00: So before we get into it, you're Chris Bullheis, my former high school teacher, right?
• 0:24
  SPEAKER_00: You live in Huttsville, Michigan.
• 0:26
  SPEAKER_00: You teach a lot of different classes.
• 0:27
  SPEAKER_00: We're good friends.
• 0:29
  SPEAKER_00: We do this podcast together.
• 0:31
  SPEAKER_00: We do.
• 0:33
  SPEAKER_00: Is that short enough?
• 0:34
  SPEAKER_01: We kept it short enough here.
• 0:35
  SPEAKER_01: That's that's good.
• 0:36
  SPEAKER_01: And you are Dr.
• 0:37
  SPEAKER_01: Jess Arabic.
• 0:38
  SPEAKER_01: Uh, like you said, my former student and uh one of the best students I've ever had.
• 0:42
  SPEAKER_01: And you're now a professor.
• 0:43
  SPEAKER_00: Oh, thank you, thank you, thank you.
• 0:45
  SPEAKER_01: Professor of Geoscience at Penn State University.
• 0:47
  SPEAKER_01: So here you go.
• 0:49
  SPEAKER_00: Okay, and today uh this is kind of a fun one.
• 0:51
  SPEAKER_00: This is a recent paper that just came out that really caught, I think, well, my interest and your interest and a lot of other people's interest.
• 0:58
  SPEAKER_00: But what we're gonna highlight here, we'll put a link to this actual paper here.
• 1:01
  SPEAKER_00: But this is a paper by uh Charles Marshall and others, uh came mostly out of the Berkeley lab, and they're talking about the absolute abundance and preservation rate of Tyrannosaurus Rex.
• 1:11
  SPEAKER_00: So we'll put links to these articles in the podcast descriptions if you want a link to the actual scientific article.
• 1:17
  SPEAKER_00: And then they also wrote this very cool like science communication piece that is in this journal called The Conversation.
• 1:23
  SPEAKER_00: So we'll put a link there as well.
• 1:24
  SPEAKER_01: Right on.
• 1:25
  SPEAKER_01: So this was really interesting.
• 1:27
  SPEAKER_01: I think everyone in that has gone into the field of geology is they you have to be in love with T-Rex, right?
• 1:35
  SPEAKER_01: You have to.
• 1:36
  SPEAKER_01: Yes, it's a pre-rec.
• 1:38
  SPEAKER_01: And like I this is something that I've thought about.
• 1:41
  SPEAKER_00: You well, you've thought about a lot of random things.
• 1:43
  SPEAKER_00: So what it's true, in particular about this one, have you thought about Chris?
• 1:48
  SPEAKER_01: I've wondered how many T-Rexes roamed North America, you know, how many how many were there on the land?
• 1:56
  SPEAKER_01: What was the density of these things?
• 1:58
  SPEAKER_01: Uh this is something that I've thought about.
• 2:00
  SPEAKER_01: And so when you when you threw this across my desk, I was like, whoa, that is awesome.
• 2:06
  SPEAKER_01: I uh this is something that I've thought about a lot.
• 2:09
  SPEAKER_00: I uh I agree because I have you know, I I kind of have this preconceived notion, you know, based on Jurassic Park, there's always like one T-Rex, right?
• 2:15
  SPEAKER_00: There's not multiple T Rex, uh multiple T-Rexes, T Rex Psi, T Rex.
• 2:20
  SPEAKER_00: I don't know what is plural for T-Rex.
• 2:22
  SPEAKER_00: I don't know.
• 2:23
  SPEAKER_01: There's one T-Rex out to eat everything.
• 2:25
  SPEAKER_00: Yeah, exactly.
• 2:26
  SPEAKER_00: You know, it's a sinister, yeah, exactly.
• 2:28
  SPEAKER_00: And then you, you know, this kept you up at night, I think.
• 2:30
  SPEAKER_01: It did.
• 2:31
  SPEAKER_01: Oh my gosh, yeah.
• 2:32
  SPEAKER_01: So I had a dream last night.
• 2:34
  SPEAKER_01: Crazy.
• 2:34
  SPEAKER_01: I was in a hotel, and so it was really weird because a T-Rex would not fit in a hotel, but I was being chased by T-Rexes, plural through the hotel in a stairwell, okay.
• 2:47
  SPEAKER_01: But it was really weird because I was at at the same time I was scared to death in my dream, but enthralled, you know.
• 2:55
  SPEAKER_01: So what I woke up and I didn't want to wake up.
• 2:58
  SPEAKER_01: I'm like, no, go back to sleep, we'll see if those plays out because there's D-Rexes everywhere.
• 3:02
  SPEAKER_01: I mean, it's amazing.
• 3:03
  SPEAKER_01: It's crazy.
• 3:04
  SPEAKER_01: I just I I did.
• 3:05
  SPEAKER_01: I I even called you during my uh astronomy class today, and we talked about it with them, and we were this is something that I've thought a lot about.
• 3:13
  SPEAKER_01: So I'm really glad to talk about it today.
• 3:15
  SPEAKER_00: Let's go.
• 3:15
  SPEAKER_00: Okay, well, let's get into it.
• 3:17
  SPEAKER_00: I mean, this is a really interesting uh it's an interesting test, and there's a couple of like really interesting take-home points from this paper.
• 3:23
  SPEAKER_00: It was published in in the journal Science, called, you know, the scientific journal called Science, which is one of the premier journals.
• 3:30
  SPEAKER_00: Top tier.
• 3:30
  SPEAKER_00: Yeah, totally.
• 3:31
  SPEAKER_00: You know, their short format and they're potentially, let's say, contentious sometimes.
• 3:35
  SPEAKER_00: The papers published in here.
• 3:36
  SPEAKER_00: I'm not sure if this falls into the category or not, but it's an interesting one.
• 3:40
  SPEAKER_00: So here's what like quote unquote we, the field of science, knew at the time of this paper.
• 3:45
  SPEAKER_00: We knew a couple things.
• 3:46
  SPEAKER_00: This is mostly from the fossil record.
• 3:48
  SPEAKER_00: We knew that T-Rex mated when they were about 15 years old, approximately.
• 3:53
  SPEAKER_01: We have estimates then based on this about how long each dinosaur lived.
• 3:57
  SPEAKER_00: And the total uh time period where T-Rex fossils are found on Earth, the range is about 1.2 or to 3.6 million years.
• 4:05
  SPEAKER_00: So there's not that long of a time when we think in geologic time of actual time when T-Rex existed on Earth.
• 4:11
  SPEAKER_00: So a few million years.
• 4:13
  SPEAKER_01: Right.
• 4:13
  SPEAKER_01: And then and then we also have a rough estimate on their metabolic rate.
• 4:18
  SPEAKER_01: And we take this based on animals that we have living today.
• 4:21
  SPEAKER_01: So it's somewhere between mammals and the Komodo dragon.
• 4:25
  SPEAKER_00: And okay, so this calculation is a really interesting one.
• 4:27
  SPEAKER_00: They figured that, okay, so for each generation of T Rex takes whatever, around about 19 years, which that's sort of similar to humans.
• 4:35
  SPEAKER_01: Our human hold on.
• 4:38
  SPEAKER_01: That was something that struck me in the article that they don't mate until they're 15 years old, but the life expectancy is 19 years.
• 4:45
  SPEAKER_00: Is that this is the average generational turnover?
• 4:48
  SPEAKER_00: So, like basically the average have kids.
• 4:51
  SPEAKER_00: So gotcha.
• 4:52
  SPEAKER_00: They made it or they started mating around 15 years, that's their adolescent time, but they didn't reproduce until on average about 19 years.
• 4:59
  SPEAKER_01: Yep, makes sense.
• 5:00
  SPEAKER_01: Okay.
• 5:01
  SPEAKER_00: And humans are, depending on where you live and cultural differences, it's between 22 and 33 years.
• 5:07
  SPEAKER_00: And so what they needed to figure out the population density, and I think it's it's a good time to point out, it'd be really fun to talk to these authors.
• 5:14
  SPEAKER_00: So, Charles Marshall or anybody else on this paper, it's really fun to have you on Planet Geo and talk about this.
• 5:19
  SPEAKER_00: But basically, what the calculation requires here is a population sort of density estimate, right, Chris?
• 5:26
  SPEAKER_00: Like how many you're what you've thought about for a while is how many were there in any given area of land, right?
• 5:34
  SPEAKER_01: Right.
• 5:35
  SPEAKER_01: Absolutely.
• 5:35
  SPEAKER_01: I've thought a lot about this, you know, like how many Tyrannosaurus Rex are we talking about per square mile, or how many square miles does a T-Rex exist in?
• 5:45
  SPEAKER_00: Yeah, exactly.
• 5:47
  SPEAKER_00: And so there's this relationship at modern animals between body size and population density, and it's sort of a well-resolved relationship.
• 5:56
  SPEAKER_00: And so they apply this real well-known relationship between body mass or body size and population density.
• 6:03
  SPEAKER_00: And the way to think of this is that for any given square mile or square kilometer of grassland, there are more rabbits in there than there are elephants.
• 6:11
  SPEAKER_00: The big animals need more space to support them.
• 6:15
  SPEAKER_01: Right.
• 6:16
  SPEAKER_01: So let me ask you this though, Jesse.
• 6:18
  SPEAKER_01: Like, just from a scientific standpoint, there are so many variables that go into this.
• 6:24
  SPEAKER_01: Yeah.
• 6:24
  SPEAKER_01: Right?
• 6:24
  SPEAKER_01: I mean, so that's when so when you when I hear you say this and I read the paper, and like, wait a second, now uh elephants, you know, they require this because their body mass, they require this amount of area, but we don't have elephants here.
• 6:40
  SPEAKER_01: So how does that pertain to then tyrannosaurus wrecks living on the globe, right?
• 6:46
  SPEAKER_01: Did they live everywhere?
• 6:47
  SPEAKER_01: You know what I mean?
• 6:48
  SPEAKER_01: Like, that's a question I had.
• 6:50
  SPEAKER_00: I think what you're pointing out is there's a lot of uncertainty in any of these things.
• 6:53
  SPEAKER_00: Well, let's take deer or something.
• 6:55
  SPEAKER_00: You know, a deer in Michigan might require a lot less area or a lot more area than a deer in Africa or a similar animal in Africa, right?
• 7:04
  SPEAKER_00: So there's variability within any one of these one inputs into this calculation, and we'll get to that at the end because the uncertainties in this calculation are pretty large.
• 7:15
  SPEAKER_00: And I think it'd be useful to point out how they arrive at this uncertainty.
• 7:20
  SPEAKER_00: Maybe let's get to the results though, because these are like super cool.
• 7:24
  SPEAKER_00: Yeah, they are cool.
• 7:25
  SPEAKER_00: And they answered your question, right?
• 7:28
  SPEAKER_01: In a way.
• 7:29
  SPEAKER_01: So they get an average of one T-Rex for every 42.4 square miles, which is about 109.9 square kilometers.
• 7:39
  SPEAKER_01: So your fiance lives in Washington, D.C., right?
• 7:41
  SPEAKER_01: So this would be two T-Rex individuals living in Washington, D.C.
• 7:46
  SPEAKER_00: Um seems like a reign of terror.
• 7:48
  SPEAKER_00: Washington, D.C.
• 7:49
  SPEAKER_00: is not a big place.
• 7:49
  SPEAKER_00: It's kind of amazing, actually.
• 7:52
  SPEAKER_01: Taking a hard pass on that.
• 7:53
  SPEAKER_00: So you you and I are from Ottawa County.
• 7:56
  SPEAKER_00: Which interestingly is about the average county size in the United States.
• 8:00
  SPEAKER_00: Oh, is it really?
• 8:01
  SPEAKER_00: I didn't know that.
• 8:01
  SPEAKER_00: Okay, yeah, it's yeah, it's about 600 square square miles, is roughly the average county size.
• 8:06
  SPEAKER_00: So that's a really good stat.
• 8:08
  SPEAKER_00: Yeah, that's a big yeah, like that.
• 8:10
  SPEAKER_00: Good on you.
• 8:11
  SPEAKER_00: Ottawa county, or the average county in America, would support about 14 T-Rex.
• 8:18
  SPEAKER_01: No way.
• 8:19
  SPEAKER_01: That's a lot.
• 8:20
  SPEAKER_01: That's a lot of T-Rexes.
• 8:21
  SPEAKER_01: So this answers my question, and it's horrifying, but yet very, very um, I don't know, interesting.
• 8:30
  SPEAKER_01: I would be enthralled.
• 8:34
  SPEAKER_01: How about that?
• 8:35
  SPEAKER_00: You you you would both want to wake up for your dream and only back to it.
• 8:39
  SPEAKER_01: I know.
• 8:40
  SPEAKER_01: Yes, I would, I would, I would.
• 8:42
  SPEAKER_01: So this calculation though then can go back one stage further, and it estimates that about 20,000 individual T-Rexes were alive at any one time.
• 8:53
  SPEAKER_01: About twenty thousand T-Rexes were alive at any one time, which means about two and a half billion T-Rexes roamed the planet during their reign.
• 9:06
  SPEAKER_00: That's a really cool number.
• 9:07
  SPEAKER_00: Two and a half billion.
• 9:08
  SPEAKER_00: It really is.
• 9:08
  SPEAKER_01: Yeah.
• 9:09
  SPEAKER_00: That's a very, that's a very cool number.
• 9:11
  SPEAKER_00: So this is where we're gonna get into the take-home points here, right?
• 9:14
  SPEAKER_00: There's I think there's two take home points we want to derive from this.
• 9:16
  SPEAKER_00: But the first one, that 2.5 billion number and all of the numbers we've listed so far, there's a significant amount of uncertainty around those actual numbers.
• 9:25
  SPEAKER_00: So that 2.5 billion number, if you take the really upper end or actually conservative estimate for the upper end of this uncertainty range, it's like 42 billion individual T-Rex ever existed on Earth throughout Earth history.
• 9:39
  SPEAKER_00: If you take the lower estimate, it's about 130 million.
• 9:43
  SPEAKER_00: So the average is two and a half billion, but there's a big range of potential values out there, right?
• 9:50
  SPEAKER_00: Of potential number of T-Rex.
• 9:52
  SPEAKER_01: I'm just uh that is a huge range of uncertainty.
• 9:56
  SPEAKER_01: Side note, I'd really love to talk to these authors, so let's try to get them on this podcast.
• 10:00
  SPEAKER_01: Let's go.
• 10:01
  SPEAKER_01: All right, seriously, that'd be awesome.
• 10:03
  SPEAKER_00: Let's go.
• 10:04
  SPEAKER_00: Absolutely.
• 10:05
  SPEAKER_00: I think this is a really important take-home point here.
• 10:07
  SPEAKER_00: And this calculation range is huge, right?
• 10:09
  SPEAKER_00: Like it almost feels like it doesn't matter.
• 10:11
  SPEAKER_00: Oh, you say 2.5 billion T-Rex.
• 10:13
  SPEAKER_00: But if if you don't know between 130 million and 42 billion, like what's the point in the number, right?
• 10:19
  SPEAKER_00: That it kind of feels like that in a way.
• 10:21
  SPEAKER_00: It does.
• 10:22
  SPEAKER_00: It does.
• 10:23
  SPEAKER_00: But it's an important exercise in how do we calculate the uncertainties there?
• 10:28
  SPEAKER_00: Because, first of all, it's an interesting calculation they've done, and they've tried to get an estimate of the range of possible answers here, which takes a lot of effort and which is a really good thing.
• 10:38
  SPEAKER_00: But the other thing is what they do is this uncertainty, what's called uncertainty propagation calculation, that's called the Monte Carlo method.
• 10:47
  SPEAKER_00: And as we pointed out earlier, there's a whole bunch of parameters that go into this calculation.
• 10:52
  SPEAKER_00: And basically, what this is is you just randomly test all the potential variables in there.
• 10:59
  SPEAKER_00: And the analogy that I like for this one is that it's basically like imagine you live in the middle of a subdivision where there's like a whole bunch of little small winding roads, the speed limit's really low, it's hard to go fast anywhere, there's not a lot of traffic, right?
• 11:11
  SPEAKER_00: And you want to decide, I want to get to some highway on the other side of this subdivision.
• 11:15
  SPEAKER_00: Like, what's the best way to get there?
• 11:17
  SPEAKER_00: Well, imagine an era like I grew up in the era before Google Maps.
• 11:22
  SPEAKER_00: So in high school, I kind of did this all the time.
• 11:24
  SPEAKER_00: You just basically turn left and then right and then left and right randomly, like randomly try this, right?
• 11:29
  SPEAKER_00: So a Monte Carlo simulation is basically you go to one intersection, you flip a coin, you randomly turn right or left, and then you get to the next intersection, you randomly turn right or left, flip the coin again, decide right or left, and you do that over and over.
• 11:41
  SPEAKER_00: When you get to the highway, you record your time.
• 11:44
  SPEAKER_00: All right, so hold on a second.
• 11:46
  SPEAKER_01: So this has to be tested based on what we see today.
• 11:50
  SPEAKER_01: What do you know about how accurate that is?
• 11:53
  SPEAKER_00: Yeah, so basically, so the way this calculation goes is if you do this over and over and over, right?
• 11:58
  SPEAKER_00: You make this drive every day for your entire life, whatever, you do it 10,000 times or something, you'll get sort of an estimate of the average time, and you'll get a really high upper end, like the most circuitous route you could possibly make, and the fastest route possible, but you'll get an average with like a big range in between there.
• 12:17
  SPEAKER_00: And so this is actually a really reliable way to test all of the potential outcomes, all of the potential variables here.
• 12:25
  SPEAKER_00: And so it's a great question, Chris.
• 12:27
  SPEAKER_00: Like basically, this is one of the most reliable ways we have to figure out the uncertainty in a very complicated calculation.
• 12:35
  SPEAKER_01: Okay, but this has a huge uncertainty.
• 12:38
  SPEAKER_00: It does, and it means that there's a big uncertainty in the calculation.
• 12:41
  SPEAKER_00: And the other benefit of this Monte Carlo simulation technique is you can isolate which values.
• 12:46
  SPEAKER_00: So we're plugging in five or ten different variables into this calculation.
• 12:51
  SPEAKER_00: We can test and figure out which one impacts our uncertainty the most.
• 12:55
  SPEAKER_00: So which one is the biggest problem?
• 12:57
  SPEAKER_01: So, Jesse, can you summarize where do we need to know more information?
• 13:04
  SPEAKER_01: I mean, there's a huge variability, you know.
• 13:07
  SPEAKER_01: We have, you know, millions of di of T-Rexes, or we have billions of them, which is a huge range.
• 13:13
  SPEAKER_01: So what do we need to know more about?
• 13:14
  SPEAKER_00: Yeah, it's a good question.
• 13:16
  SPEAKER_00: What they point out in their paper is that this it where the uncertainty lies here is this relationship between body mass and population density.
• 13:25
  SPEAKER_00: So basically, we need to know more about how T-Rex lived in order to make this calculation.
• 13:30
  SPEAKER_00: So studying more T-Rex fossils and understanding what the landscape looked like while they were alive would help us a lot.
• 13:37
  SPEAKER_00: So that was really the main source of uncertainty in their calculation.
• 13:41
  SPEAKER_00: And it might be a reason why you know this calculation has not been done before because it's fairly difficult to pin that down.
• 13:48
  SPEAKER_00: So that's where they that's where they land, at least from reading the paper, but I'd love to talk to them about this.
• 13:52
  SPEAKER_01: Yeah, so very cool.
• 13:53
  SPEAKER_01: So the takeaway for me is there were a ton of T-Rexes uh roaming the earth, and that's awesome.
• 14:00
  SPEAKER_01: Like I've always wondered about this.
• 14:03
  SPEAKER_01: Were they extremely rare?
• 14:05
  SPEAKER_01: And the answer to this is no, right?
• 14:07
  SPEAKER_01: They were not extremely rare, which is exceedingly cool.
• 14:12
  SPEAKER_00: Yeah, and it relates to the fossils, right?
• 14:14
  SPEAKER_01: So so yeah, that was really cool.
• 14:17
  SPEAKER_01: They expect one in 80 million organisms to be preserved as fossils, and so that's crazy.
• 14:25
  SPEAKER_00: That's crazy.
• 14:27
  SPEAKER_00: So when you go to like the Chicago Field Museum, and is it Sue?
• 14:30
  SPEAKER_00: Is that the dialogue for T Rack?
• 14:32
  SPEAKER_01: Yeah, yeah, yeah.
• 14:32
  SPEAKER_01: It is, it is Sue, yeah.
• 14:34
  SPEAKER_00: Yeah, so when you see that, it's like, look at that and think this is one in 80 million chance of actually being found, being preserved, being found, and then I'm looking at this amazing thing that's one in 80 million.
• 14:48
  SPEAKER_00: That's unbelievable.
• 14:50
  SPEAKER_01: Yeah, the story of Sue is amazing to go to the Chicago Museum or wherever she happens to be, because she travels all over the place.
• 14:57
  SPEAKER_01: Yeah, wherever she happens to be is such a cool story.
• 15:01
  SPEAKER_01: It's emotional.
• 15:02
  SPEAKER_00: It's another podcast episode, man.
• 15:04
  SPEAKER_01: It is, it really is.
• 15:06
  SPEAKER_00: All right, well, I think that's probably a wrap.
• 15:08
  SPEAKER_00: This is longer than a normal Geo short, but it's a super cool paper.
• 15:12
  SPEAKER_01: So Yeah, whatever.
• 15:13
  SPEAKER_01: It is what it is.
• 15:14
  SPEAKER_01: It's science, and that's cool.
• 15:15
  SPEAKER_01: Science is freaking cool.
• 15:16
  SPEAKER_00: So that's right, that's right.
• 15:18
  SPEAKER_00: We're done.
• 15:18
  SPEAKER_00: All right, man.
• 15:19
  SPEAKER_00: Good stuff.
• 15:20
  SPEAKER_00: All right, talk about it.
• 15:20
  SPEAKER_01: Good stuff next week.
• 15:24
  SPEAKER_00: All right, thanks for listening to Planet Geo.
• 15:26
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• 15:29
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• 15:31
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• 15:35
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• 15:36
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• 15:38
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