Webinar: Evolution of Human Diets
Aired May 22, 2020
Maggy Benson:
Hey, everybody. Welcome to Fossil Friday. We're so happy to have you here with us. I'm Maggy Benson and I'm a museum educator at the Smithsonian's National Museum of Natural History. And while our museum is closed, we're connecting you to the research and scientists from the museum. We've been drawing an international audience for Fossil Friday, and we feel really lucky and thankful to be able to bring everybody together and learn new things during this time. So thank you for joining us. Now, before I begin, I also want to give a special thanks to our generous donors, volunteers, and our other important partners who enable us here at the Natural History Museum to discover, create and share new knowledge with the world, like we're doing today, and every day, free of charge.
So while we wait for some more friends to join us, take a moment to find the Q&A button at either the bottom or the top of your screen. And you're going to use that Q&A for submitting all of your comments today, we do not have a chat. And why don't you go ahead and give it a try now and tell us where you're tuning in from. I'm joining you for my home in Washington, D.C. All right, now, again, for those of you who are just joining us, why don't you find the Q&A and tell us where you're joining in from.
I want to cover a couple more logistics before I introduce our experts. We have a new feature in our video webinars, and that is live captions. We're really excited to have this feature. So to activate your live captions, you can go to the bottom of your screen and click on the CC icon. And from there, you can click on the settings to either turn them on or turn them off. Now because they're live they will be slightly delayed, that's normal.
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We are so happy to have all of you here today with us, thank you for spending Fossil Friday learning about the history of our Earth and all of the living things on it. Now you will notice that when you submit things to our Q&A, you can't see your response, you can't see your other friends' responses, but rest assured that our team here at the Smithsonian can see all of your answers. And so you're going to use this Q&A box throughout our program to answer the questions that we ask you, but also to send in questions that you want our experts to answer. And today we are joined by two additional scientists from the Smithsonian who are going to be in that Q&A answering your questions directly by chat. So I want to take a moment and introduce Dr. Rick Potts and Dr. Advait Jukar.
Rick Potts:
Hi everyone, I'm Rick Potts. I'm a paleoanthropologist, which means that I study early humans, how they lived, how they changed through time. And usually at this time of year, I would be planning my expedition to Kenya, to the Rift Valley, this great gash in the Earth where there's tremendous evidence of early human fossils and stone tools, evidence about how early humans lived. But I can't plan that right now, because I'm not going, but it's okay. I'm in my home in Arlington, Virginia, and I'm really happy to be joining you today to help answer your questions. So thanks very much.
Maggy Benson:
Thank you so much, Rick.
Advait Jukar:
And I'm, Advait Jukar. I'm a vertebrate paleontologist in the Department of Paleobiology at the National Museum of Natural History. And I study the ecology of large animals like elephants and horses and dinosaurs. I like to study how these animals lived and what they may have eaten and how they died.
Maggy Benson:
Wonderful, thank you so much Advait. So Advait and Rick are going to be answering some of your questions directly in the Q&A. So when you send a question, make sure you continue to check on the top. There's a tab that says Answered Questions, and you will see all the questions that Rick and Advait have answered directly by text, so keep an eye on that to get an answer from them. And we will also be taking questions from the Q&A to give to Dr. Briana Pobiner, our featured expert. So now I would like to introduce our experts for today, Dr. Laura Soul is going to be moderating the discussion with our featured paleoanthropologist, Briana. And I will let them introduce themselves now, and I'll be behind the scenes here. So welcome Laura, welcome Briana.
Laura Soul:
Hi. Thanks very much, Maggy. Yeah, so I'm Dr. Laura Soul. I'm a paleontologist, a vertebrate paleontologist at the Smithsonian Natural History. I also am an educator at the museum. And I am here today with Dr. Briana Pobiner who is a paleoanthropologist [inaudible 00:05:51] a slightly different wording. Hopefully we're going to find out some more about that. So Briana, if you want to introduce yourself and what you do?
Briana Pobiner:
So hi, Laura, and hi everybody, I'm really glad to be here with you. As Laura mentioned, my name is Dr. Briana Pobiner, and I'm a paleoanthropologist at the Smithsonian, and I will tell you a little bit more about what that means. Are we set to get started?
Laura Soul:
Yes. If you want to do your screen share, I think you had some photos you wanted to show us.
Briana Pobiner:
I do, let me share my screen. All right, how's that look?
Laura Soul:
Perfect.
Briana Pobiner:
All right. So as mentioned before I am a paleoanthropologist, and as Rick said earlier, a paleoanthropologist is a type of paleontologist who studies human evolution. It's a little bit distinct from a paleontologist in general, who might study any aspect of the past. I'll tell you a little bit about how I became a paleoanthropologist, and you can see a picture of me as a kid on the left-hand side. I don't think I ever had any hopes of becoming a professional tennis player, although I do still play tennis, but I actually wasn't that particularly interested in science when I was a younger kid. It wasn't until I got to Bryn Mawr College, which you can see a picture of in the middle, and I kind of stumbled into an anthropology class. And that class was with Dr. Janet Monge, who's on the right, and then it was the first time that I felt like I really got interested in science as kind of solving mysteries and doing detective work, and I just absolutely got hooked.
So one of the things that I like best about my job is doing field work. I've done field work in Kenya, Tanzania, South Africa, and Indonesia. And one of my favorite things to do is dig up fossils that no one has seen for hundreds of thousands or even millions of years. So in the picture on the left, I'm working at an excavation in Indonesia. In the middle, I'm at a Smithsonian research site called Olorgesailie, and I'm actually sitting in the middle of a fossil hippo footprint that's about a million years old. And another thing that I do, which you can see in the picture on the right, is I actually study bones of modern animals to get a sense of what happens basically right after animals die. I love traveling to different places, working with international teams. And when I'm not doing field work, I also study fossils in museums from previous field expeditions, including in the places that I mentioned, but also in Romania, as well as the U.S.
I want to give you a quick sense of the time periods that I'm interested in. So our evolutionary tree goes back about six million years, you can sort of see a time scale on the left-hand side, which is when we shared a common ancestor with other living apes. I'm really interested in that time period between about a million and three million years ago. And that's because I'm interested in early human meat eating, and that's the part of the diet that I study. And that's when we see kind of an increase in the evidence of meat eating by early humans.
So this tree gives you kind of a sense of one way that different species can be grouped. There have been about 20 species, give or take, of early humans. All of them are now extinct, except for us. We are Homo sapiens, and we're the only ones left. When the museum opens back up, you can come to visit the Hall of Human Origins and you can look into the eyes of your ancestors. So these are eight head reconstructions of different early human species from these different groups, and I'll introduce you to a few of them.
This is Homo neanderthalensis, or Neanderthal, from that Homo group at the top, and they're one of our closest extinct relatives.
This is Paranthropus boisei, and that's from that group on the left of kind of a side branch of human evolution. This is Australopithecus afarensis from the Australopithecus group on the left, and that is the species from which the famous fossil Lucy also comes. And then down here is Sahelanthropus tchadensis, and that's one of the species from the ardipithecus group, and it's a contender for really one of the earliest species on the human family tree.
Laura Soul:
Okay, so let me check that I've got this right. Can you just go back to the tree again?
Briana Pobiner:
Yes.
Laura Soul:
So humans are there in the Homo group in that kind of bush at the top?
Briana Pobiner:
That's right. So we are all, every person on the planet today is a member of Homo sapiens, we are part of that group. And we're the only representative of this entire family tree that is still around, all those other species went extinct. That's right.
Laura Soul:
Wow, who knew there were so many different types of early human relatives? So we've had a couple of people asking questions, and actually [inaudible 00:10:31] really interesting [inaudible 00:10:31] that you gave us of your job. It sounds like there's a ton of different stuff that you do. My favorite, I think, was the hippo footprint, that is so big for a hippo. But yeah, so Mason would like to know, out of all those things that you were talking about, what's your favorite thing about your job?
Briana Pobiner:
My favorite thing is probably getting to travel and do field work because I really like making discoveries and finding new things. And so I think working, I like being with other people, working together on teams to make those discoveries is probably my favorite thing.
Laura Soul:
Okay, and someone has also asked, what is the earliest human? You maybe might have to kind of define what human means for that one?
Briana Pobiner:
Absolutely. That's a great question. If we're talking about our species, Homo sapiens, the fossils of our species go back to about 300,000 years, and the earliest representatives currently are skulls from North Africa. But as far as the earliest humans, if we take our entire family tree, there are fossils dating between about six and seven million years ago from two different places, both from East Africa and West Africa. So we don't have fossils of that common ancestor that we share with living chimpanzees, but we've gotten pretty close. And so the whole tree goes back about six or seven million years, our species goes back about 300,000 years.
Laura Soul:
Wow, that's quite a long time. I'm just going to remind everybody, you might have noticed we're answering questions. So anyone who's viewing, remember that you can submit questions to us in the Q&A, which you will be able to find at the bottom or top of your screen, little speech bubbles. And you can submit any questions that you have for Briana or for Rick and Advait to answer there. And then I think we'll do one more before we go onto the rest of the stuff that you wanted to talk to us about. Ena has asked about updates about the origins of Homo floresiensis. What do we know about them and their small stature and what they evolved from?
Briana Pobiner:
That's a great question. So you can see a reconstruction of Homo floresiensis on the bottom left, that really small face. So this is a species that's found only on the island of Flores in Indonesia, between about a 100,000 and 50,000 years ago. It's unusual and surprising because for being so late in evolutionary time, it's incredibly small, and so the adults only stood about three feet tall.
The origin of the species or its predecessors, or where it came from is still a little bit of a mystery. There are tools nearby in Indonesia that date back to about a million years, so there were some early human species in the area at least by then, and there are fossils of a species called Homo erectus. You can see her reconstruction on the top middle of those heads. And so we have Homo erectus fossils in Indonesia dating back to about 1.8 million years ago. So it's likely that Homo floresiensis either evolved from Homo erectus that made it to Indonesia and then evolved that small stature in response to having not a lot of food to eat and resource stress, so evolving small size is something that sometimes happens on islands. Or it could have evolved from an even earlier species that we haven't found remains of in Indonesia yet.
Laura Soul:
Okay, so kind of a slightly unanswered question, but we've got lots of good ideas, all right.
Briana Pobiner:
Exactly, exactly.
Laura Soul:
Several people have asked about food that early humans ate, and I think this might be a great time to carry on with the rest of the presentation.
Briana Pobiner:
Wonderful. So yes, I am basically ... I'm a dietary detective. I want to figure out what early humans ate in the past. So before I tell you how I do that, I want to ask you all a question, let me know in the Q&A what kind of evidence you think I would look for, or a paleoanthropologist would look for to figure out what you ate for dinner yesterday.
Laura Soul:
Okay, everybody tell us your answers in the Q&A, what do you think you could use as evidence to find out what someone ate last night for dinner? All right, we've got lots of answers, poop, feces, poop, everybody's saying poop, DNA, stomach contents, look in the garbage, look at what's in their mouth, what's in their stomach, food scrapes. Lots of people saying poop, general consensus about poop, I think. Someone said tooth enamel, that's an interesting suggestion. All right. Okay, Briana, what should we start looking for if we want to figure this out and be a detective like you?
Briana Pobiner:
Excellent. So those are really good answers, and I will definitely talk about some of those lines of evidence. The first one is one that nobody mentioned though. I might want to know what your family generally eats on a regular basis. If we think about our evolutionary family, our closest living relatives are chimpanzees and bonobos. So we know that they usually eat plants like fruits and leaves and seeds and nuts. They eat insects, they eat birds and eggs. They like honey. And occasionally they eat small animals. So if I was studying early human fossils I might expect early humans to have eaten kind of like this just based on their family or their evolutionary history.
So somebody mentioned teeth, that's a really good answer. So if I was to figure out what you ate for dinner last night I might want to look at your teeth and I might want to look at your head, in particular, your skull. So I might to look at your teeth to figure out, do you have sharp teeth like dogs and cats who are carnivores? Maybe you ate meat for dinner. Do you have big teeth with big chewing surfaces like horses and cows who are herbivores? Maybe you ate plants. Or do you have teeth that are sort of in between like pigs who are omnivores? Maybe you ate lots of different kinds of foods. So paleoanthropologists can even look really closely at early human teeth, and we can even do this with your teeth, to look at patterns of pits and scratches on your teeth to get a sense of some of the characteristics of the food that you ate. Was it hard? Was it soft? Was it tough? They can even look at the chemistry of fossil teeth.
But let's get back to that size and shape, and so that's called morphology. So that arrow is pointing to a picture of a modern human skull, and that arrow is pointing to a picture of an early human skull. Some early humans, and that skull happens to be from the genus Paranthropus, had molar teeth that were three times the size of ours today, so that can give us a sense that they were chewing more often than we were. And here's another thing that we can do, we can just look at the size and shape of your skull. So I want everybody to do this with me. So put your hands up here on your head and chew. Do you feel chewing muscles?
Laura Soul:
I do.
Briana Pobiner:
Okay, so put your hands up here now and chew, do you feel muscles?
Laura Soul:
Everyone who's watching, are you finding that you can feel any muscles moving up here? Is it the same or different as below?
Briana Pobiner:
So [crosstalk 00:17:54]-
Laura Soul:
They're saying no, no, we've got lots of nos.
Briana Pobiner:
Lots of nos. I'm glad, because if you did feel chewing muscles up there, you would have a skull that had this kind of crest up there where that arrow just came up. And so that's another Paranthropus skull, and the chewing muscles on Paranthropus were so big that their skulls evolved this ridge or this crest on the top of their skull to make extra attachment area for those chewing muscles. So that's another way that we can just look at the size and shape of your skull and teeth to get a sense of what you eat on a regular basis.
Laura Soul:
Okay, so we don't have that big sagittal crest-
Briana Pobiner:
We do not have that.
Laura Soul:
And we [crosstalk 00:18:31]-
Briana Pobiner:
Yes, exactly. That's called a sagittal crest, and we do not have those. Another thing we can do ... Thank goodness there were no toothbrushes a million years ago, because actually sometimes we get bits of plant microfossils stuck in our teeth. We brush them away, but early humans didn't. And so plants can take up silica in the soil and that silica can also be redeposited as something called phytoliths, they're basically rigid microscopic structures that have different sizes and shapes depending on what kind of plants there were. Sometimes those plants actually got stuck in the dental calculus, or the plaque that gets hardened, on early human teeth. And so these are images of actual plant microfossils removed from Neanderthal teeth, and so they can give us a clue of exactly what kinds of plants those Neanderthals ate, and even if they were cooking those plants. So microfossils, tiny things, can be their useful.
Another clue, so this was a really popular answer, poop. So we absolutely can look at coprolites, or fossil feces, or fossil poop, to get a sense of what you ate last night. So this happens to be a very large fossil poop that's called the Lloyds Bank coprolite. It dates to about the 9th century and likely came from a Viking.
Laura Soul:
A Viking poop.
Briana Pobiner:
Correct.
Laura Soul:
Wow.
Briana Pobiner:
So scientists can actually analyze what's in this poop and get a sense of what this person ate, and so apparently the person who made this poop ate a lot of meat and bread. And we actually have evidence of coprolites or fossil poop going back to about 50,000 years ago that are associated with Neanderthals in Spain.
Laura Soul:
Oh, that's really cool. Now we have coprolites from lots of other types of animals as well. How big was that poop? Because it looked, not to put too fine a point, but it looked massive.
Briana Pobiner:
So it's apparently one of the biggest ... Fossil poop is not that common, but it's one of the biggest fossil human poops that have been found. I think I read that it was 20 centimeters long, eight inches long, about that.
Laura Soul:
Okay, that's pretty impressive.
Briana Pobiner:
It is impressive. So another line of evidence, somebody said garbage, that was a great answer. So if I wanted to figure out what you ate last night, I might look in your garbage, or I might look in a compost heap to see what's left. And so a lot of what paleoanthropologists do is we dig up the things that were left that people sort of threw away. But okay, if I was look at this garbage pile a million years later, what kinds of things do you think might preserve? So let us know in the Q&A.
Laura Soul:
All right, everyone, it's time to tell us what you think in the Q&A. Again, if you were to look at this compost heap, which parts of it do you think actually might still be around in a million years time? Maggots, and dirt, seeds, food, seeds, plants, stems, wood, husks. Someone says bones and old plants, bones, bone fragments, mango. Someone says nothing. The dirt, plants and bones. So we're kind of having ... Lots of people are saying maybe the harder things, so plant stems and bones and seeds.
Briana Pobiner:
Excellent, so those are really good answers. And so what I study in particular are bones. So those of you who replied bones, I know sometimes we don't put bones in a compost heap, but we do throw them in the garbage. So this is a one-and-a-half-million-year-old antelope leg bone, and so an antelope is sort of similar to a deer. And this is from an excavation in an area called Koobi Fora in Northern Kenya where I did research for many years. So I might find a bone and I might be able to say, "Well, I think an early human ate this." But how would I know whether an early human ate this, or whether it died naturally? I would have to actually look a little bit closer with a magnifying lens, and here's a clue. So what do you think made those marks that are circled in red?
Laura Soul:
Okay, so this is the next question for you all, what do you think might have made those marks that are circled in red on the picture? Teeth, lots of people saying teeth, and now we've got Meghan and Rupert saying, knife, teeth, knife or teeth, they haven't quite made up their mind. Cut marks, oh, someone says flint tools, animal butcher marks, teeth and/or knives. A weapon, knife and maybe a stone one, predators, arrows or spears. So we've got a lot of different answers, but lots of people are saying stone tools or knives or teeth.
Briana Pobiner:
Very nice. So those answers are really good answers. And one of the things that I do is study marks like this to figure out who made them. And I can give you a little clue about the difference between tool marks, which you can see on the left, and so those of you who answered flint tools or butchery marks or something like that, you're correct.
You can see a picture on the right of tooth marks, and those happen to be tooth marks left by lions on a leg bone, the bottom of a femur, of a zebra. And so the studies that I do in a modern wildlife conservancy in Kenya called Ol Pejeta Conservancy, are basically looking at the chewing patterns left by different predators. So one of the differences you can see is that the tool marks tend to be narrow, they to be deeper, and they tend to be more linear. The tooth marks on the right tend to be a little more irregular shape, sometimes they're round, they're usually wider and so not every mark necessarily we can tell the difference between, but a lot of them we can. But I think both tool marks and tooth marks are really good guesses, the ones that I showed before are definitely tool marks.
Laura Soul:
Okay, so because they have that really kind of straight, narrow cut, then you can probably say there was an early human using a tool?
Briana Pobiner:
Exactly, that's right. And that's the kind of evidence that I look for. So the last thing that I might do is I might look in your dishwasher to see what kind of silverware, like knives and spoons and forks you used when you ate dinner. So can we do this for early humans? We can. A few people mentioned stone or flint tools before. So while there wasn't metal a million or two million years ago, we can look at tools that early humans made from stone and get a sense of what those tools were used for.
So these tools include stone knives to cut meat, you can see some of those on the bottom left, and also rounded rocks called hammer stones that were used to break open leg bones to eat marrow. And later in time, even stone tools were made for very specific activities like fish hooks and spear points. Sometimes we can even look at the wear on the edges of tools to get a sense of what they were used for. And occasionally, we can even see traces of plants or even animal blood on the edges of tools. So those tools can also give us a really good sense of what those early humans were eating.
Laura Soul:
All right, great. So we've talked about teeth and muscles and the shape of your head and looking in your garbage pile and silverware and poop, are there more things?
Briana Pobiner:
So what I want to do next, I can pause for questions, but then I'm going to sort of put everything together to give you a sense of what a paleoanthropologist does at a fossil site to figure out what happened.
Laura Soul:
Okay, all right. So yeah, we have had lots of good questions come in, so we'll ask a few now that we have found out all of those different things you're looking for. So let's have a look. So Ezra and Levi would like to know, did they cook their food or eat it raw?
Briana Pobiner:
That's an awesome question, Ezra and Levi. So the answer is not until about a million years ago do we have good evidence for early humans cooking their food. So there's a few sites that are dated to earlier than a million years ago that might have evidence for cooking. Interestingly, we have evidence for human meat eating going back to somewhere between two-and-a-half and three-and-a-half million years ago, so it seems like people were eating raw food for quite a while.
Laura Soul:
Okay, that's interesting. So some questions that people had kind of based on that earlier stuff that you talked to us about, the different species of our relatives, Veronica would like to know, how do you tell the difference between different species of humans?
Briana Pobiner:
That's a great question, Veronica. So what we do is usually we can look at the skeletal remains, we look at the fossils, and scientists determine basically sort of what the boundary of a species is, how much variation is in a species. And then we look at the size and shape of things like skulls and teeth and the rest of the skeleton, and when new fossils are found, we say, "Well, they look most similar to this species." And if they look different than other fossils that have been found before, then that's when scientists would name a new species.
Laura Soul:
Okay. And then just one more before we take a look at the bigger picture. All of those beautiful facial reconstructions that you showed us at the beginning, how do you or the artists that make them know how to make them look? How do we know about their skin color or their hair or anything like that just from the bones?
Briana Pobiner:
That's a great question. So the artist that did all of those facial reconstructions is named John Gurche, and he's written a few books about his work, including one about the work that he did for our Hall of Human Origins at the Smithsonian. And he has, and paleoartists like him have deep knowledge of human and ape and other animal anatomy. They can tell from fossils where muscles would be thick and thin, where they would put different fat pads and things like that. For things like skin color and hair texture, it's a little bit more of an inference. The skin color that was used on all of those reconstructions is based on modern human skin color in the areas where those fossils are found today, so that gives us a sense of how light or dark the skin color might be.
Hair texture is definitely a little bit different, you might notice that Neanderthal had a man bun, that's a bit of an artist reconstruction, but we know that Neanderthals had some artistic ability. And there are certain parts that we have really difficult, that are almost impossible to figure out what they looked like, like ears, your ears don't have any bone on the outside. But we can tell things like your nose. So your nose is mostly soft, but we can tell from this little part of where the nose sticks out, whether there would've been an outward projecting nose or a flat nose.
Laura Soul:
So there's some kind of artistic reconstruction, but a lot of it is based on things that we understand from looking at humans now. All right, [crosstalk 00:29:49].
Briana Pobiner:
Absolutely.
Laura Soul:
So actually somebody has asked, "Do you find," we're looking at the silverware slide still, "lots of tools left by early people?" And I think maybe you've got another photo that can tell us about that?
Briana Pobiner:
I do. So why don't we move on to the next slide because we can sort of put all of this together at that point. So the last thing I want to talk about is how did paleoanthropologists use evidence that they find in an excavation to figure out what happened at a fossil site? So this picture is of an excavation called Site 15 at a place called Olorgesailie in Southern Kenya. And this is a Smithsonian research site that Dr. Rick Potts, who was introduced earlier, has been working at for more than 30 years. This particular excavation is in a layer of sediment that's almost a million years old. And I want to ask you, what kind of evidence do you see and what do you think that evidence can tell us?
Laura Soul:
All right, so I think last question for you all to reply to you in the Q&A, what evidence can you see in this picture there, and what do you think that might tell us? Someone saying bones, bones, lots of bones, bones, bones, bones. Can anyone see anything else in there? I'm not sure if I can, I'm kind of squinting at this. It's quite small on my screen. Someone else, "Is that a bowl, a stone bowl?" Lots of people saying bones and fossils though.
Briana Pobiner:
Excellent. So, yeah, so there are bones and fossils in there, or fossil bones, but what you may not be able to see are there are lots of stone tools. And this excavation, this is part of a giant extinct elephant skeleton surrounded by more than 2,000 stone tools.
Laura Soul:
Wow.
Briana Pobiner:
So this evidence tells us, along with evidence of early human fossils from nearby, we can paint this kind of picture of the past, putting all that evidence together. We have a sense that early humans were around. I've been with Rick studying the fossils from that elephant skeleton, some of them have butchery marks on them, like those cut marks you saw before on that fossil. So we can get a sense that early humans were around, they were using those stone tools that were there with the elephant and they were butchering the elephant to get off meat presumably to eat. So that's the sort of dietary detective work that we do to get to kind of flesh out and paint a picture of what happened at prehistoric sites.
Laura Soul:
Wow, that's amazing. And that's a really huge animal, so it probably took quite a while.
Briana Pobiner:
It probably did. And that's an extinct kind of elephant that's bigger than modern African elephants today.
Laura Soul:
That's huge. All right. So that's really interesting. I mean, I hope everyone's enjoyed learning about all the different types of evidence we can use that actually allow paleoanthropologists like Briana to reconstruct these beautiful pictures. These are all based on evidence, we don't just make them look nice, so that's really interesting. We do actually have lots more questions from people who are watching, so we'll check through a few of these. Julia would like to know, what kind of predators did early humans face?
Briana Pobiner:
Oh, that's a good and one I'm really interested in. And because my work is in Africa that's where I'm mostly going to answer from. So lions, leopards, cheetahs, and hyenas and jackals and other large predators that were in Africa, their relatives, or even the modern species were around for the last few million years. But there was another kind of predator that's extinct now that was around in Africa when early humans were eating meat, and that's saber-tooth cats. There were a few different species of saber-tooths around that early humans would've had to contend with.
Laura Soul:
I'm pretty glad they're not around anymore.
Briana Pobiner:
So am I. So I would say, because I'm also interested in the tooth marks left by those predators that help us understand how early humans interacted with the predators, and if they scavenged from predator kills, I would love to actually have a saber-tooth around just so I can see what their tooth marks looked like. But I do have a study going on on that, so you'll have to stay tuned about that.
Laura Soul:
Okay. I think it's probably pretty common among paleontologists, we'd all like an extinct animal. I would love a dinosaur, just so I knew what they were really like, that would be great. All right, so we've got a question about human evolution. Isabel asks, "What is a common misconception that you feel many people have about human evolution?"
Briana Pobiner:
Oh, that's a great question, Isabel. So I would say probably the most common misconception is the idea that human evolution proceeded in a linear process. That one species evolved into another, and that evolution was progressive and that we are the pinnacle. So as you saw from one of my earlier slides, human evolution, like the evolution of other organisms, really proceeded in a branching pattern. A lot of those branches led to extinct species, most of them certainly on the human family tree. I would say the idea that there's some kind of missing link, which implies a chain, that if you could just find all of those missing links, you'd have this kind of one line. So I think that's the biggest misconception.
Laura Soul:
Okay, so that tree that was in the slide at the beginning is actually a great representation of what it was probably more like.
Briana Pobiner:
I think so. I mean, we haven't drawn the lines between the ancestors and descendant species because some of those are still debated, but it gives you a sense that there was definitely this branching pattern. Yeah.
Laura Soul:
Okay. And then one of the species that was in that was Neanderthals. And Drew would like to know why did the Neanderthals go extinct, and what was responsible for their extinction?
Briana Pobiner:
I would like to know that too. So we don't know the answer to ... Paleoanthropologists don't know the answer to that question, we have some ideas. And honestly, it's even difficult to tell sometimes with modern species why species are going extinct. If we look at what's happening with species that are in danger to going extinct today, it's often changes in climate, competition with other species, occasionally something like diseases. And so there have been questions about whether Neanderthals, because Neanderthals and modern humans overlapped in time and space in some places, we know that they interacted because genetics tell us that they interbred. So there's a question sometimes of, did our species Homo sapiens drive Neanderthals to extinction? We don't know the answer to that question, but there doesn't seem to be any kind of widespread battles or any evidence of that kind of warfare or things that we have more in modern times. So the bottom line is, we don't know. It was probably a combination of things that led to Neanderthal extinctions.
Laura Soul:
Okay, maybe Drew could become a paleoanthropologist and find out the answer to the question himself.
Briana Pobiner:
Absolutely, test some of the hypotheses out there, that would be great.
Laura Soul:
Yeah, that was a great scientific question. All right, so another question about early humans, was the digestive track of ancient humans different from ours?
Briana Pobiner:
That's a really good question. And so we have indirect evidence for that, we don't have a preserved digestive tract, that would be really cool, except in a very rare instances in much more modern times. But we can tell from the shape of the rib cage, that particularly before the evolution of the genus Homo, that digestive tracts were bigger, more like living chimpanzees and bonobos, they were more intricate. So probably with the evolution of Homo, of the genus Homo, is when we saw a change in digestive tracts more similar to modern humans today. But presumably because we have the same digestive organs that other primates and many other mammals have, that, that wouldn't have changed over time, it would've been the proportion and the shape and the size of those organs.
Laura Soul:
Okay. I've got some questions about teeth. So how much smaller were Homo erectus teeth than afarensis teeth?
Briana Pobiner:
Yeah, so Homo erectus teeth were significantly smaller than Australopithecus afarensis teeth, and we think that's probably because of a shift in diet, potentially with an increase in meat eating. Also it's during the time that Homo erectus was around, and so that's between about two million years ago, all the way up to maybe even as late as 143,000 years ago, so Homo erectus is the longest lived species on our family tree. We do see an increase in meat eating, we see the origin of the controlled use of fire, so these things would've potentially, and also a real increase in tool use. And so all those things would've led to more processing food outside of the heads of Homo erectus, and so that probably led to a decrease in the size of the teeth, because there wasn't selection pressure for those big teeth to do lots of chewing and processing.
Laura Soul:
Okay, and did farming change how human teeth evolved?
Briana Pobiner:
Ooh, that's a great question. So farming in the last several thousand years didn't change how human teeth evolved as much as in earlier times, but farming had much more of an effect on other parts of our bodies. We can see that when farming started actually stature got smaller, so people got shorter for a time. And then once kind of our diet breadth increased again and we started eating more kinds of food, we got taller again. So farming probably didn't have a really strong influence on the size and shape of human teeth, of modern human teeth, in the last several thousand years.
Laura Soul:
Okay. And then a question, I'd be really interested to know if we can tell this actually, Clara wants to know, did ancient humans speak a language?
Briana Pobiner:
That's a really good question. And if words fossilized, we could know that for sure. So we assume because lots of other primates are really good communicators that early humans also had some form of pretty sophisticated communication. We don't really know when language evolved, but we can look to the archaeological record for evidence of symbolism, like the use of color, of trade networks starting, somewhere around the time of the origin of our species, or potentially even with Neanderthals, and maybe a species called Homo heidelbergensis, which is the common ancestor that we share with Neanderthals. So written language comes much later than we think probably spoken language, but the timing of when spoken language evolved is tough to know.
Laura Soul:
Okay. And then another one, because you'd spoken about having lots of fossils of early humans from Africa, but Drew would like to know, how did humans come to the Americas?
Briana Pobiner:
That's a great question. So there's a couple different competing ideas about how modern humans migrated to the Americas. And so we see all of the fossil remains of humans in North and South America, or of our species of Homo sapiens, and I would say probably the most well accepted idea is that while sea levels were lower, there was basically an ice bridge across from Asia to North America, and that either with boats or potentially just by walking, that early humans migrated into North America.
Laura Soul:
So it would be from nowadays Siberia to Alaska, between there?
Briana Pobiner:
Exactly, so probably ... And there are some archeological sites from that area that give us a sense of how that might have happened.
Laura Soul:
Okay. All right, and then something that lots of people have asked, but I know that Abby and Rowan and Saoirse have, they would like to know, what would you recommend that kids do if they want to be a paleoanthropologist, or what's your general advice for anyone who wants to become one?
Briana Pobiner:
So my general advice is to see if you can. So first of all, figure out what aspect of paleoanthropology you might be interested in. Is it the tools aspect, the human fossils aspect, the genetic aspect? And then one of my biggest pieces of advice is to try to get experience in the field, particularly as a college student to seek out maybe be a field school or an internship or a volunteer opportunity to try out kind of the day-to-day experience working with a paleoantropologist and getting a sense of what that's like to see if you like it or not.
Laura Soul:
Okay, so it sounds like when you're younger you figure out what you're interested in and find out as much as you can, and then maybe as you get a bit older and get to college, that's when you start trying to get some experience.
Briana Pobiner:
Yeah, I think that's good advice. Yeah.
Laura Soul:
Okay. All right. Thanks so much, Briana, it's been really interesting finding out all of this stuff about the evolution of our species and our early ancestors, and especially about all those different types of evidence that we can use to try and paint a picture of ancient human lives. So now I'll probably hand back over to Maggy. But I'd just like to say that everybody did a really great job today asking us questions in the Q&A and answering all of those things that we asked you. I think you all did a really great job as diet detectives yourselves, so thank you.
Maggy Benson:
Yeah, well done everybody. Your questions were amazing. And Briana, it was so fascinating to learn more about your work. Now I just screen shared a website, the Human Origins website, humanorigins.si.edu. And I wonder, Briana, if you could just say something about how people can find the answers to their own questions about paleoanthropology and early human diets here.
Briana Pobiner:
Absolutely. So thank you for sharing that, Maggy. So this is the website of the Human Origins program here at the Smithsonian. And there is lots of different information, lines of information on this website. You can look up the research projects that we do on the Human Evolution Research tab, all the different kinds of evidence in the Human Evolution Evidence tab across the top, the different characteristics that make us human, our large brains, our body size and shape and the tools and the food that we eat. And particularly for students, if you're interested, the Education tab has some information about field schools for college students, which will be going on, hopefully starting again next summer.
And then also some information for teachers about some curriculum materials that I led a project to help develop for high school classes that use human examples to teach about evolutionary principles. The Multimedia tab has videos, and the Exhibit tab has a map of the Hall of Human Origins at the Natural History Museum. And it also has, for teachers, a field trip guide, if you're interested, once the museum opens back up, in bringing your students. And finally, the About Us tab has a part about all of the members of the Human Origins program team, including the staff at the Natural History Museum and all of our research associates. So have fun exploring.
Maggy Benson:
Yeah, wonderful. And that website again is humanorigins.si.edu. So thank you again for everybody for joining us today, this has been a fabulous Fossil Friday. And thank you to Rick Potts and Advait Jukar who have been answering questions in our Q&A. I did want to share with our friends who are still here, that we will be back tomorrow at 11:00 a.m. for another drawing webinar, where we will be drawing a T. rex. And so this is a drawing that I drew in the first week, this was a ceratosaurus. So artists Bob Walters and Tess Kissinger will teach us how to draw a T. rex, so join us at 11:00 a.m. tomorrow morning. You can get that information at the Natural History Museum's website, naturalhistory.si.edu, if you want to draw one yourself.
All right, and when you leave this program your Zoom window will have a link that pops up in the browser to our survey. We would love to hear what you think, so please fill that out and give us your feedback so we can continue making programs that meet your needs. So thank you so much, Briana. Thank you, Laura. Thank you, Rick. Thank you, Advait. And thank you to all of our viewers who tuned in today. We'll see you next time on Fossil Friday.
Briana Pobiner:
Thanks, bye.
Laura Soul:
Bye.
