anthropologist at dartmouth college and editor ofof a most rather the editor of a most interesting problem what darwin's dissent of man got right and wrong about human evolution. he is part of the research team that discovered and described to ancient members of the human family tree. he studied wild chimpanzees in western uganda and was in the museums throughout the eastern band south africa from 1998 to 2003 and worked as an educator at the museum of science.

the senior editor of the scientific america has been writing about the evolution of humans and other organisms for the magazine. she's also the co-author with donald johansson of lucy's legacy the quest for human origin. tonight they will be discussing the new book first steps how upright walking made us human. in it, exploring the history of the ability unique to humans and living mammals to walk on two legs and makes the case that it's the crucial change that allowed for the evolution of humans despite the difficulties posed to the gene forever after. publishers weekly praises the love of the discovery and collaborating with colleagues comes through ino examining first-hand. his ability to turn anatomical evidence to be focused detail of human evolution and his

enthusiasm for research both informed and uplifted. i am so pleased to turn things over to the speakers, the digital podium is yours. >> thank you. now i appreciate the introduction. 1 of the things they get excited to write about, so it is a pleasure to be here. and i thought maybe if you are up for it, we could sort of kick off the conversation by having you tell us why. we have primates and language so why focus on this?

>> it's a great question. like you said, we have these differences. we have lots of similarities to our cousins, but we have these differences as well. upright is well. they swim, sprint, leap, walk and climb. a typical moves around all fours. think about a cow, goat, sheep, dog, squirrel move around on all fours but only humans will navigate the world on their extended eye and limbs all the time. when another mammal does it, we kind of lose our minds. we take out our cameras and videotape what is happening and posted to youtube and it gets millions of hits. in researching the book i found examples of bears moving on two legs in new jersey and there had

been almost 500 million views. it ended up on the cbs news and so something tha we do all the time even using the word pedestrian toev describe somethg ordinary when another animal does that it is remarkable. not only that, but the fossil record, i amhi ap legal anthologist. we can tell going back in time the further back we go we start to lose some of these unique characteristics.

on the lineage it is the ability to move on two legs. penot only is it strange but its the most ancient thing to sort of set the lineage off and as i argue in the book, it's the key innovation that led to many of those others that make us human. >> that's a really interesting lens to view the entirety of evolution in a sense. this might sound like a weird question, but we don't really think about what is special it from the standpoint of the biomechanics when you describe the act of walking on two legs and what's unique about

it. it is a balancing act. thinking about what i talked to my students about. imagine if i give an assignment you probably designed it with four legs and they probably make a barstool out of three legs but if you make it out of two legs it's probably not going to work. to move around the world today we can get into the bird locomotion at some point and then in the past we find evidence even in the ancient lineage which is fun to think about. from the bio mechanical biomechl standpoint it is about balance.

1 of the things we can see and identify it's coming from things that are adapted. because of the individual bones that would ally the joints in a way that would prevent us from tipping over or change the action of certain muscles soge they would act in a way to prevent you from tipping over. 1 of the classic examples is the hip joint when you take a step and lift your other leg, you fall over and when a chimpanzee walks on two legs, that is exactly what they do. they wobble from side to side. but humans have evolved. we've evolved with the muscle attachments here down the side of the body and by being on the side, they then will counteract every time you take a step. as you find this part of the body and it looks like this you

can p tell it's something movinm on two legs. and sure enough, she's got the hip joint arranged in a very humanlike way so even if this is the only part of her we found, we wouldt be able to tell that she was able to balance on a single leg and why else do that unless you are moving around on two legs. but, from a biomechanical standpoint, and really connecting it to natural selection it is integrated way. we are incredibly unmistakable. that could be quite dangerous. in addition to that, we are stunningly slow free mammal. usain bolt, the fastest american as far as we know that has

lived, the fastest he ever ran was 28 miles an hour in his 100-meter -- in 2009. his world record —-dash. 28 miles an hour. halfrh the speed of a lion and a leopard. so, evolving this form of locomotion made us slow and so it raises some really interesting questions of in what ways was this beneficial and allow us to overcome.

ia know there's been a lot of scholarship over many decades. with people coming up with all kinds of ideas about why we could come to have this unusual kind of locomotion, and there's some interesting ideas going back as far as darwin and i thought it would be fun to just kind of take a tour through some of those ideas if you wouldn't mind indulging us. >> it's one of those things if there was another mammal that moved on two legs regularly, we would be able to test this more effectively and say what does this other mammal do, what does it eat, what are its mating patterns in which this form of locomotion is beneficial? as a scientist, when you try to figure out something about yourself, you want to look out

into the natural world and say where else do we see examples like this and the fact that we don't have other mammals that habitually walk around on two legs makes us a difficult scientific problem to solve and it's one of the reasons we haven't solved it and you can go right back to 2021. you've got ideas about seeing over tallgrass. very interested in humans being able to stand and see off into the distance. withta that one, if you look off into the distance and see a predator, the worst way to get away from it, you would want to be on all fours because you would be faster so that one never made any sense to me.

there are ideasay about darwin w this connection between our small canine team and tools but it's about freeing the hands-free. we have evidence for this in ad hominem's that are six or 7000000-years-old and we don't have evidence of these tools until about three or three and a half, 3.3 is the oldest reported evidence. the ideas that are a little more reasonable having to do with food sharing and if you can free the hands not to make weapons or

tools butin gather food that hae been promoted. sharing it with potential mates and may be a little more lasting power it's been about energetics and moving on two legs. yes, we are slow but we are energetically very efficient and one of the best ways to explain this is herman and i talked about these ideas and he said that in order to lose a pound of weight, you would have to walk about 70 miles because we are too good at it. we are two energetically efficient. so you don't want to lose weight if you are an early ad hominem

but if you need to get enough food to survive and there's not enough on the landscape, those individuals are moving in a way that is energetically efficient and might survive better. so that is a possible idea. we still have a handle on it and that's okay. there will be plentys of things. to eliminate the ones that are clearly wrong. that's how science works by refuting ideas rather than proving them. we don't know how it evolved but we do have a lot more information than we use to.

maybe we can talk about some of the discoveries that allowed you and your colleagues to start. and what it might have evolved from and where it took us. >> so, a lot of folks listening well probably know about lucy, discovered in the 1970s, just a magnificent partial skeleton. i've got the cast of her. where i do some of my research as well, that pushed it back to the three and a half million years ago.

it existed three and a half million and yet the genetics would point to a common ancestor that we shared at about six or 7 million. the split between the two is complete by 6 million years. that is a big gap. what's going on in that timeframe and in the last 20 years there've been really remarkable and important discoveries that have been made that begin to piece the story together. 1 is a partial skeleton from ethiopia. 4 and a half million-years-old and it has some of the keys of the pelvis and foot that would indicate that at least it was occasionally able to move around on two legs on the ground but

also this is an excellent. when it came down to the ground it appears it didn't. ilif you go further back than that, the evidence becomes much more controversial. so this is a toe bone from a five and a half million-year-old ad hominem from ethiopia and it matches the shape especially the end. this has a curvature to it that's more it has an angulation

like yours and mine meaning it would have been able to push off the ground so this is a cool fossil but it's just the toe. here is a femur that's 6000000-years-old and what's unique about this one as compared to a chimpanzee, here is a chimpanzee, part of the hip joint is very similar but look at how short the neck is and how long on the fossil. by drawing those muscles further from the head, you make them more efficient. wet think that anatomy is evidence for the locomotion. then if we go back even further

than that, 7 million years, there's a remarkable school that was discovered that's very controversial. the researchers that found and interpreted it argued that the base of the spinal cord next to the brain was in a very humanlike position. there is a femur now that has been published by one team and then another has a print and they come to completely different conclusions on whether this is an upright walk or not and to me as yukon burge you're going to get something that isn't quite like any of the

living apes and is a fabulous combination and maybe a frustrating combination of anatomies that are difficult to interpret. it's kind of what you might expect in a common ancestor. >> do you think that it looks like that? >> i like to talk about fossils i've been able to see. this is not one that i've been able to see myself and however, there are even older fossils now. we don't have much from 8 million, 9 million or 10 million but there is a new discovery from germany and germany might sound surprising to some of the folks listening because we've been talking about bsites in africa but apes

expanded all around the mediterranean and we are living in forests in southern europe so we find that in spain and france and hungary. this new fossil from 11 and a half million looks like it's very upright and to me that's a very interesting find because it could imply, and we are still trying to figure this out it's one of the hot topics right now what is the body form for which it evolved. there are a lot of t-shirts and coffee cups and bumper stickers that would suggest a chimp turned into a human. chimpanzees are not our ancestors. they are our cousins and the common ancestor is an ape that

we branch from the chimps have s have evolved and it isn't a given that the common ancestor was a knuckle walker and some of the ancestors we are finding in those deposits might indicate it was more upright and that could be a more derived form of locomotion. there's plenty of researchers that think it is the form for which it evolved and they have compelling cases for that. we need more fossils to figure this out. >> it's a revolutionary idea and fun to think about. if it is a uniquely holman then trade, is it potentially a

homonym? >> i think the genetic data shows very clearly where these lineages were branching. having i said that, there are bg divergent states. but i think you raised an important point that our field has always operated under the assumption that if you find anything that shows characteristics of the upright locomotion that is automatically by definition a homonym meaning it's in extinct relative of us and would be more closely related to us than any other. i think that assumption is on the table as may be not being 100% correct because if you had apes experimenting with

different forms of locomotion including uprightif in the tree, navigating in the trees, they might have some anatomies that look a little more humanlike for instance it is in some ways, not always but in some ways it looks very muchks like lucy's. and i think that is telling us about the positioning not necessarily weight-bearing on a terrestrial leg about an animal puts in the trees and moving with hand assisted. like orangutans sometimes do. gibbons will do this, spider monkeys will do this. but it would mean finding evidence may not be enough anymore to claim the home and ad hominem status. from five, six, seven, eight,

nine, ten year time period we could see a lot of experiments going on with locomotion. and lots of false starts and places it may have evolved and then that animal died. it just was not a selectively advantageous form of locomotion as a habitat and the habitats changed. a. >> we talk a little bit about the record shows about the origin and you mentioned this very briefly there are other kinds of data that we can look at to study the emergence of this kind of locomotion and you mentioned a place i've always wanted to visit in one of the

most iconic sites even just thinking aboutit it kind of givs meme chills. so there's the very famous set of track waves and what does that track way tell us about the evolution of that point in time which is 3.6 million compared to what you know about it going back? >> it is 2.0. it is those footprints. that place is magical. there are footprints eroding out

of the hillsides. i love fossils and we can squeeze information out of them but footprints are alive and they tell about this moment in time in the life of a living, breathing, thinking individual who was a lot like us and a lot of the recent biomechanical stuff that has been done is telling a story moving a lot like us. it's not hunched over, crouched down like a groucho marx walk or chimpanzee on two legs. this is something that from a distance it would look like you and i walking.

you would pick up some subtle differences probably and that is a fun thing to think about because from the footprints and the bones it looks like they are not pushing off quite as much as we do. the arches are a little flatter, the legs are a little shorter and they are maybe not extending at the hip quite as much as we do when we walk but the walked e differences are subtle. 1 of the amazing discoveries of the last ten years is that we often will think of the evolution in a linear way. i even just did it talking. but what we see instead are different forms evolving in different species. at the same time lucy and her species were around and making

those footprints, there was another that had a divergent big toe that was in ethiopia not far from where lucy was found, climbing trees and walking in biomechanical be a different way. a it was a fabulous discovery made in 2009 and it showed that there were these different forms of walking and coexisting. behind me, this skeleton here was discovered by his 9-year-old son also in 2009 when they were published. i've worked on the foot and the light of this skeleton and when i first started working on it, to me i had just finished my phd. i studied the foot and ankle and leg of the homonyms and to me

there was variation but not functionally meaningful. it was so different from any that i had seen with its heels and ankles and knees and aspects of s the hip and lower back that we hypothesized that walked in a very different kind of way. what's neat is that this carries right up until the place is seen and even on the doorstep you have neanderthals in europe and asia and then a ride in south africa there is a new species. there were all these different species and populations

coexisting. some of them we interbred with and some of them i don't think we did. from the foot bones and leg bones it looks to me like many of them walked in these biomechanical he different ways and different flavors. so i like to think about jumping in a time machine and going to any of these time periods to see these different kinds of our ancestors. theye not only look a little different and begin different things, but they would be walking in slightly different ways. >> it's really wild to think about that degree of experimentation for the majority. right up until virtually yesterday in geological terms.

>> when i was at the university of michigan, the story very much was right up to homo sapiens and what do we do with neanderthals and that is what wee argued about. were they different or part of our heritage and now so to me it wasn't that interesting. we had evolved so lets go back. now it's interesting there is a lot going on. >> if we go back to walking more or less like we do, it's interesting the oldest known are just a few hundred thousand years younger than those footprints.

so we are getting a little bit closer to what darwin was talking about potentially. and i'm just wondering how you see things aligning. could it be this is what freeze to the hands? >> i think that possibility is back and the idea of these origins also included brain the size and enlargement which we know now is not part of the story but that does indeed happen later. but you are absolutely right. if you go back to the 1970s, 1980s, we have 3.6 and the oldest at 1.8.

and it looked like darwin was wrong, like the two were chronologically not aligning and then there were those at the set with 2.6, 3.6. we are getting closer. it did get pushed back thanks to the tibia about 4.2 million-years-old and it's in very humanlike. i would like to see what the rest of that looks like. honestly i was going to say my hopes but my expectations given how remarkable my colleagues are at finding these fossils. i think about who's made extraordinary discoveries in eastern africa in the last decade or so, the last two decades.

so, knowing more about that is going to be important but back to your point, we now have at least the reports of 3.2 million and they are controversial but at the same time, 3.3 million, to me i don't see any reason why theyno wouldn't be making stone tools. they are walking like us, there is slight brain enlargement, about a 20% increase in size and there is that new discovery on the basis of the juvenile skeleton that shows they had slowed down brain growth. ..

>> but it also is a story of cultural buffering and social buffering that how do you ward off any of that how do you survive in a landscape like that? how do you avoid being picked off by the leopard all the time is that you look out for each other. you have each other's back. so our society is built by a bp olds locomotion simply it will not be an evolutionary success elicit happens and something that is either superfast like an ostrich or

super social. and even in compassionate and empathetic like we are. >> that was a fascinating point that you made in the book when you start off early ideas a bipedal is him to now you making the argument that actually it could never have worked if our ancestors did not have the empathy and cooperation. >> a i think that idea of uprightness to bring the man on —- the tools just for weapons is still part of the popular culture. we've all seen 2001 a space odyssey where in the beginning the wielding of the weapons.

that has its intellectual roots where they discover the first cone child over my shoulder here. but later in his career in the 19 forties, post-world war ii he worked at a site where he discovered bones that had been smashed and he formulated a hypothesis that we where the blood thirsty killer eights. that idea had roots and is filtered again as partt of the culture even though we know now at that site those bones were smashed because of hyenas. science has refuted that idea is still how we think about ourselves and instead i draw attention to a fossil like this but with this fossil the

amazing thing with this fossil is it has a heal fracture. so this bolt of bone sticking out the inside of the femur is a heal fracture. think about breaking your femur 2 million euros years ago. no fire or shelter and no doctors that you break your leg and you heal and survive? that can't happen unless other individuals help you out. as much as 2 million going back to lucy's species there is a second skeleton he is three.5 million years old we think he is a large male and

he has resealed ankle fracture. so again he stepped in a hole or fell out of a tree or something and he broke his ankle. now if you are a zebra and you break your ankle, that's not a good situation but you can still get from point a to point b. if you are a biped and you break your ankle you're already so you hop around your landscape and see how you survive so this is healed so they did survive so it is connected to bipedalism so as biped the fact that we have injuries that make us particularly feeble as a biped is again explainable only if we were and continue to be

empathetic and social with one another. >> fascinating. no have questions from the audience. >> i had not heard that about the healed ankle that is amazing i had no idea that was that far back. >> that was a discovery in 2010 now it is 11 years ago but still it is an indication of just how rapidly my colleagues are finding these and putting them out there and each of these fossils has this amazing story to tell about why we are the way we are today so they can be

overlooked and that's a cool fossil and didn't get the attention that it deserved. >> i feel that the memory that i have is that the last i heard there wasn't evidence of that so anyway. that's awesome and nice to know we can be nicer than we think it's very reassuring. >> if you are able to change human anatomy to make bipedalism easier what would you adjust? >> the foot. the foot is a disaster. i study feet it is evolution's

example of aam good tribe. you did your best but what happens is you converted and grasping 8-foot into something that needs to be rigid and have moments of flexibility but then to be pushed off the ground in a rigid way. we have the same 26 bones in our foot that chimpanzees do so if you try to create something from scratch and it needs to contact the ground, absorb elastic energy then kick off for your next step in you make it out of 26 parts? you fail that engineering course. look at this. there you go. so what has happened over avian evolution is the bones that make up the ankle and

foot have fused together into a single rigid structure that is composed of 26 bones it is about eight in the foot of an ostrich. this ends up looking a lot like the prospect on —- prosthetic power olympians use with great effect and can run very fast so yes i would change the foot. the back is a mess as well but i work on the foot so that's the first placeil i would go then he t is a disaster as well but we will stick with the flat. [laughter] >> we have another question so is it possible for bipedalism

and humans or anywhere else to evolve and improve anymore? do we represent the zenith of what this will be? is that even possible to speculate? >> it's a great question i love to speculate about i don't think so if you look at the pleistocene and all the body forms that existed i don't see the human body today homo sapiens having some advantage over some of those others. it looks like the joints were smaller but i certainly don't think we have reached a pinnacle of bipedal locomotion and i would much rather have the skeleton of an ostrich if i wanted to get from point a to point b on two legs or a t

rex for that matter. and if you look back in the past one of the fun things i get to research writing this book was bipedal animals long gone next it. for instance there is a crocodile discovered in north carolina it was a vertebrate paleontologist at north carolina state and at the museum i'm sorry. she reconstructed the gate of this ancient crockett alien on two legs occasionally imagine if it would jump on two legs and spread 9-foot long. [laughter] but it didn't have evolutionary legs what happened to crocodiles? they are onn all fours they are ambush and self hunters so

being bipedalei was not necessary to be successful ultimately even with dinosaurs the earliest dinosaurs were bipedal and then upon a stories and break your saurus and stegosaurus and triceratops those are quadrupeds that evolved from bipeds. so bipedal is seems to pop up and honestly fail and then will convert to quadra pedal is him or be dead in the lineage. >> you brought this up in the conversation as a reminder but bipedalism was gradually is so what is the time span? how many millions of years? >> we don't know it depends

entirely on the body form of that common ancestor because if that is the ancestral tray and chimpanzees in the node on —- gorillas retained it, then you have to have intense rapid natural selection to go from a knuckle walking common ancestor do something that is not just getting picked off by leopards because it is hunched over and cannot move quickly or efficiently. so in that circumstance it is happening incredibly fast. or it happens incredibly slowly if the common ancestor is something that is imagined more with shorter arms up in the trees and moving on two legs and then if there is environmental change and you

get a forest it has to move across the landscape but it already has a body form to do that. so it is an old locomotion just in a new setting. in that case it would be very gradual so what we would be looking for are the anatomies something as a terrestrial biped. we have not even thought what that would be as a field. how would you distinguish between something walking on two legs on the ground or moving on two legs and a system in the trees where the branches are moree compliant? you wouldn't need the hit mechanics because you hold your body with your hands so you don't have that pelvic tilt problem. that is something we as a field having grappled with.

>> suggesting contemplating these different scenarios it would be easy to fall into the trap about some of these maybe not in your position but i don't know. it seems like it would be a present on —- pretty easy trap to fall into i think this happens gradually there probably isn't one nationwide bipedalism was evan tatian but a host of things to search for the answer is probably pretty wrongheaded. however there's population and variation in certain that move more than others in the end of having more food and

reproductive opportunities and off you go we just try to figure out whatwe it is to allow those individuals to have more food and opportunities there are other scholars that think this was more low market richard dockins wrote about this that bipedalism emerge because it was a cool thing to do and chimpanzees and gorillas occasionally move on two legs so that became the fat in that population then you could havewa more and more individuals because bone is plastic you to get some of those anatomies that are key to a bipedal locomotion not because you inherited them genetically but acquired them through your life so the best example is that when you are

born your fingers are perfectly straight but as you start to toddle around your femur begins to angle and and you become not need but we are not born that way. so if you find the femur that has an t angle to it, tells us this individual had to have walked on two legs because there is no other way to get the angle so there is a cool combination of anatomies you are born with and what you acquire to blend together in the musculoskeletal system that allow you to move on two legs. >> thank you may have matthew asking what circumstances are making it easier to find more fossils today? >> great question.

like any scienceou you build on the work of previous generations and there are lots of false starts that happened and mistakes made and you learn from the mistakes of your predecessors but having said thatha there's a lot of technological advances. for instance in south africa one of the reasons my colleague has been able to find as many fossil sites is by using satellite imagery and looking at the clusters of trees. when you are on the landscape walking and it'soo really hard to see that from the top down you can see them much better. so that's one of the things that happening but the decolonization especially in eastern africa has played a huge role and instead of doing. shooting science dropping in and spending a couple weeks

and then going back to the united states or western europe is incredible fossil discovery is done by individuals that are from those countries. and so many others so what do you think about that kate? why do you think we get this? >> i wonder if there is the wild affect into the cradle of what was explored and found these amazing things so maybe we all need to look at those phases that didn't have any

more fossils for us that we did not look at yet to go in with a fresh eye and a fresh outlook. >> and that assumption of the great discoveries that have been made the last ten years i have just been astounded by the fossils were getting more of what we already know about that has happened to some degree but we are also finding things that any of us could have predicted. i certainly were not have predicted any of them and has been a wonderful awakening in our field. and a dose of humility there is a lot out there for us to

discover and a lot of ideas will be wrong. that is okay. as long as we are following the evidence then it is okay to have an idea based on the evidence that you have in and look at this new fossil shows i was wrong. >> i think we can leave it there. we are out of time thank you so much this is fantastic and thank youou to you for joining us. please learn more of this incredible book. i for the link in the chat is also a link to donate thank you for tuning in and stay safe. have a lovely night.

>> the whole thing is based on the series of facts and claims and narrative the overarching that it says america was founded and it began because of and the sake of to defend slavery that is the central idea for all of american history. that is factually incorrect but also the overarching historically incorrect and it is intended to get around the actual facts and history for this argument to go after the very claims like the american

founding and american history for reasons that have to do with establishing at right now and fighting current politics this country is systemically racist with certain policy outcomes that is the overarching factual problem. with the whole 1618 project. >> as entirely on point. but in with that slave ship and but then had passengers in the caribbean and then brought north by a pirate ship so to

say that the beginning of slavery is america because he recognized slavery assimilated those to the category of indentured servant within a few years they were set free and then became full landowners and citizens of this country. so the very basic idea in the beginning of slavery in america, that is false that growing up into the giant bush that we call it that every significant event is part of the scheme by which black people were oppressed and treated as chattel. of course there is history for americans slavery even to get

the most basic part of this wrong. >> after obtaining a phd that the most scientific challenge of