The Discovery of Ardi, The Oldest Human Ancestor

We should fill people in on exactly what we're talking about. So we're talking about a skeleton that was discovered that is 1.2 million years older than Lucy? Yeah, the skeleton is 4.4 million years old. The oldest known human relative? Well, it's the oldest known skeleton. And actually this is an important distinction I should make. Like I said before, skeletons are rare. This is the oldest skeleton. There are three other members of the human family that are older. But the thing is they're much more fragmentary. They're not anywhere near as complete. Like there's one, another one from Ethiopia found by the same team that found the skeleton we're talking about. That's some teeth, like a toe bone, a few other broken elements of the skeleton. There's another thing, another species called aurorin from Kenya, which is about 6 million years old. Again, much more fragmentary, some teeth. I think they got a couple thigh bones, partial thigh bones. And then there's a skull from Chad called Salanthropus that's about 6 million, maybe 7 years old, depending on who's dating, you believe. And that's a very nice skull, but it's a head without body. So anyway, people sometimes get confused by this. So Arty is indeed the oldest skeleton. It's by far more complete than this other stuff. But there are some fragmentary things that are older. And they all become part of the story too. And what is the scientific controversy? Do you think it's... is it based on real skepticism? Or is ego involved in this? You're laughing. Ego? In science? What are you talking about? It's unfortunate, man. These are scientists. There's a lot of egos involved in science, unfortunately, right? Yeah, there's a lot of egos. There's a lot of disbelief because the skeleton was so surprising in a lot of ways and so contrary to the predictions that many people in science had made that there was a kind of like a head explode for a lot of people. So we should break down those particular things that are different than what was expected, right? First of all, it walked upright. Yeah, so it walked upright. So it's primitive. I mean, if you saw... if we could go back in the time machine and look at it, you know, this thing, the species name is Ardipithecus ramidus. That's kind of a mouthful. But Ardipithecus ramidus is the individual skeleton that they found. That's the individual... like your joke. You're the individual and your species is Homo sapiens. That's how you think about this. Ardipithecus ramidus species, Ardipithecus ramidus, species, the individual skeleton. So the interesting revelations with it is it has upright posture. So it's standing upright, but it's still got the opposable toe. So this is a creature that was in the trees. Clearly climbing, but it also appears to be upright, walking with the supposed toe. So it seems... Everyone knows that sometime deep in the human past, there was some kind of a boreal ancestor, some kind of ape. But the question has always been, well, what kind of ape? Does it look like a modern ape or does it look like something we've never seen before? And so the surprising thing about Arty is it's actually quite different than the living apes. So yeah, so it's got the supposed toe, walks upright. Are their proportions... Chimps have shorter legs than they have arms. Is Arty's proportions similar to that? No, Arty... I mean, it's certainly more ape-like than any of us. But there's a couple of interesting things about its proportions. So all the other living apes have longer arms than they do legs. They spend a lot of time climbing. Long arms, long... And they have different proportions, but they all have that in common. They got longer forelimbs than hind limbs. Arty was a big surprise because it actually had longer legs than forelimbs. I mean, it definitely has bigger hands, has longer arms than we do. But that was a surprise, at least to me, and I think to some of the researchers. And I was talking before about these kind of surprises that appear after the fact. Well, that was one because the bones are broken. These guys on this research team, it's called the Middle Outwash Research Project. They spent a lot of time reconstructing this and then estimating how well the lengths of the pieces that are not there. And then run all kinds of regressions and a lot of calculations and stuff. But so that revelation was sort of a delayed bombshell, if you will, that it actually had these limb proportions that were more like a biped. And so ours, our legs are longer. Chimps have longer arms. So does it have almost equal length arms and legs? Jamie actually just put a photo of it up here and I'm getting a chance to take a look at it. Oh, it's fascinating. So it has long legs, almost like a person, but longer arms than we do. Yeah, longer arms than we do for sure. I don't remember the exact name, but I think the calculation they did was that legs are... Oh, I think the arms... Yeah, I want to say it's like 90 something percent. So it's pretty close to one to one length, but indeed the arms are a bit shorter. So the surprising part was that it didn't walk at all on its knuckles, being that it was that old? Yeah. So humans are... We come from the African apes. That's pretty clear from genetics. That's been clear for a long time. There are two main groups of African apes. There's gorillas and there's chimps. Now within those... And chimps also includes this other species you might have heard of called bonobos. And within those, there's like debate about, should we divide them into some subspecies and stuff? But don't worry about that for now. But anyway, what they all have in common is they knock a walk. So they got these long fingers and when they walk, they do this. If you look at a video sometime, you'll see it. And because our two closest cousins both do that, there was a perfectly plausible theory that human ancestors did it well. So we evolved from a knuckle walking ancestor. I mean, there was even a cover story in Nature that the headline was almost that. Humans evolved from a knuckle walking ancestor. So yeah, so that was the theory. And then so here with Artie, we have a creature that's... It's not the last common ancestor with the African apes, but it's certainly getting closer. It's getting a big step closer. And the people, the anatomists who specialize in these things, say that there's like no hint of knuckle walking. Not only was it not knuckle walking to get around, but also it has no vestige of a knuckle walking ancestry. So in other words, there's no like residual anatomy that would suggest that... That it ever knuckle walks. Yeah. So it was bipedal from the very early days? Very, very early days of... Of its evolution. Yeah, of the species evolution. Well, it's bipedal. All you know is what you find at that 4.4 million year old window. And that what comes before that is... Speculation. Yeah, I mean, it's these people that do this. It's intelligent speculation, obviously, but you don't know what you haven't found. And so now the... I mean, there's a debate about just how long ago the last common ancestor of humans and chimps lived. It's probably at least anywhere from 1.5 million years before ARDI to... Some estimates put it even further back than that. So yeah, there's another school thought that's kind of emerged that says, well, it still could be a knuckle walking ancestor that gave rise to humans and ARDI, but it just... All the stuff had disappeared by the time you got to ARDI. Anyway, that's kind of a counter argument that we can get more into that later. I don't want to get too esoteric on you, but... But it seems so fascinating that it has these really long arms, but that there's no evidence whatsoever of not only knuckle walking in that species, but knuckle walking as an ancestry. Episodes of the Joe Rogan Experience are now free on Spotify. That's right. They're free from September 1st to December 1st. They're going to be available everywhere, but after December 1st, they will only be available on Spotify, but they will be free. That includes the video. The video will also be there. It'll also be free. That's all we're asking. Go download Spotify. Much love. Bye-bye.