Segment 7 of Learning Module 11. Okay, so we will continue with looking at the fossil evidence of Australopithecus. We now move to South Africa, where considerable evidence of Australopithecines also exists. Probably the most unusual specimen comes from a site called Tong in South Africa, where a very small cranium was found.
It's also labeled as Australopithecus. this time Australopithecus africanus, it's nicknamed the Tong child. So it's nicknamed a child because it was about three to four years of age when it died. And of course, they could look at this sort of thing and evaluate age based on teeth and the eruption of the teeth. So that's a good indicator of age.
Now, I do want to emphasize that child, three or four years of age, that seems like a young child to us. But of course, if their growth rate is similar to, let's say, a chimpanzee, then three to four age is probably approximating early adolescence for us. So still a juvenile, but maybe not as young as we might expect.
All right. So we're looking at the Tong child has a forehead, a little bit of a forehead. If you recall that chimpanzees, it goes straight. back from the eye orbits from the brow ridge there's no forehead expansion at all the tongue child seems to have a little bit of a forehead in which doesn't recede as much as the apes or other australopithecines but we're still looking at a pretty small brain about 405 CCS at the age of the tongue child as an adult we do have adult specimens by the way of also pithicus africanus which I I don't want you to have the impression that this is the only evidence that we have of these species because We could literally go through a whole semester of looking at nothing but fossil evidence. So I am Extremely limiting the amount of fossil evidence I'm discussing here But there are a lot more specimens than just the ones that I'm mentioning here at adult age Osteopithecus africanus would be about 440 cc's which is may be slightly larger than we see Osteopithecus afarensis, but not very much.
So the foramen magnum is further forward than in apes, less than humans, again showing that transitionary state, more than likely bipedal. Teeth-wise, we're looking at some very small canines. That's a modern trait. And then also molars that are very large and broad. That's a primitive trait.
So an interesting mix. a little bit of hints of modernity here and there with a couple of well some very primitive traits Dating is from about 3.3 to 1 million years ago quite a broad range That's because there are a whole bunch of australopithecus africanus specimens and then also the dating techniques as I mentioned before the here's a reconstruction of australopithecus africanus I think it's a pretty good depiction of the child. I don't know, this woman they have depicted holding her, I mean, she looks a little freaked out to me.
But otherwise, I think it's an interesting reconstruction here. Alright, so what we really see with the Australopithecines are two types. There are the gracile Australopithecines, which is basically Australopithecus africanus, and then the more robust Australopithecines, which are basically all the other species. And... I introduced this here because I like these two terms gris grass aisle and robust Okay, so grass aisle means something that's more delicate a little more modern So humans are often described as being grass aisle And particularly in comparison with chimpanzees and gorillas Chimpanzees and gorillas are more robust.
That means heavier features more primitive features heavy skeleton skeleton, heavy musculature. So and then and then we do see in the Osteopithecines variation in the amount of robusticity going on. So let's take a look at some more recent Osteopithecines that are amazing because they actually show even more robusticity than what we've seen before. I know it's hard to imagine but more robusticity. We're looking at Osteopithecus Robustus in South Africa and Osteopithecus boisei in Tanzania, so the robustus specimen comes from Svartzk Sphoriscans, South Africa, and then the Boisei specimen comes from Olduvai Gorge in Tanzania.
Let's take a look at these. Alright, look at this guy, Australopithecus robustus. You can tell, named for that particular reason. Highly robust, dated to about 2 to 1 million years ago. Marked sagittal crest, heavy jaw muscles going on, heavy brow ridges.
Big flaring broad cheekbones, that's a primitive trait. Megadont, we're looking at huge molar teeth, even larger than we see in the older Osteopathycine specimens, so we're moving even larger teeth. That's a very primitive trait.
Small incisors in canines though, that's modern, so that's an interesting contrast. And really what we're looking at here is probably a heavily plant-based diet. using those teeth to process food break open nuts and so forth there's even speculation that perhaps these robust osteopithecines were using their teeth to break open bones you might think well why why break bones open but that's to get to the marrow inside which is highly rich full of protein and fats and so forth and so wonderful nutrition wise and so perhaps they're using their teeth to do that Just heavy robusticity and heavy cranium in general marks sexual dimorphism.
We have both male and female specimens in which there's a big difference in male and female size. That shows competition as well. Two to one million years ago.
That's even more recent in time than we see with the early osteopithecines like Lucy, Osteopithecus africanus, and Afarensis. And, um, um. trend towards more robust icity more primitive traits, so I this is a great Illustration of how primitive traits do not primitive versus modern traits do not have time indicators we see That primitive traits last for a very long time Furthermore we often have the impression that evolution moves in a general trend Towards something more modern and that's not necessarily the case right When we talk about traits, remembering that traits are adaptive. So let's say a primitive trait is adapted to a certain kind of environment. The environment changes.
We see a trend toward a different kind of trait. But if the environment goes back to what it was before, you may see the reappearance of primitive traits. They become more common in populations because they're adaptive to that previous style of environment. So evolution doesn't... work in a very nice finely graded transitions that happen slowly progressing towards modernity over time sometimes they're just play times where it seems like like our traits go back go back to primitiveness and that's it's because evolution isn't about progression towards something it's simply about adaptation to the environment at that time all right we continue look at this guy this is the also because boisei Also nicknamed the Nutcracker Man.
And you can see why. I would not want to meet this guy in a back alley because he would have been very robust. Okay. Heavy brow ridge as well. That marked sagittal crest.
Broad cheekbones. Huge, massive mandible. My goodness.
Small incisors and canines. That's a modern trait. But those megadont, huge molar teeth.
I mean, definitely being used as food. processing and breaking down very very very coarse diet dating 2.4 to 1.2 million years ago so one other characteristic of the robust osteopithecines you can see looking at the skull from above something called post-orbital constriction in which you see that the the skull actually narrows highly that's that term constriction right post-orbital meaning behind the eyes you Narrows here's the brow Ridge right here at the eye orbits and then it narrows down Immediately and the brain is located back here and the reason for that is because of these huge holes right these holes What's going through them those huge jaw muscles those huge jaw jaw muscles are coming up and then? Attaching to the sagittal crest at the top so that post orbital constriction is what really shows how huge those jaw muscles are Alright, so here's a general list of what?
robust osteopithecines have post orbital constriction mark sagittal crest broad cheekbones megadont dentition huge molars very coarse diet Heavy brow ridges and cranium, smaller incisor and canine teeth, marked sexual dimorphism, definite bipedalism, likely far less arboreal than less robust osteopithecines. Alright, here's some early hominid trends that I want to go through here. Number one, these early osteopithecines They had very restricted ranges or territories. Each species exploited a small area and could have been easily isolated from other populations of its species leading to speciation.
So that's the reason why we see lots of different species of australopithecine going on at the same time. Secondly, despite obligate bipedalism, most early hominid species are at least partially tied to arboreal habitat. So this doesn't mean that they're up in trees a lot, but they are tied to arboreal habitats in terms of protection and finding food resources and that means it's keeping them more adapted to our boreal environments than modern humans are okay third there is little to no trend toward increased body size or of markedly greater encephalization encephalization is this increase in brain size so relative brain size increases by no more than 10 to 15 percent over a period of 3 million years so there is very little trend towards increased brain size. Tied to this, there's no clear association of any of these hominids with sophisticated stone tool manufacture. And that's likely not coincidental, right?
You need sophisticated brain power to be able to imagine a target design when you have tool manufacture. It does not seem that these austropithecines have that sophistication in brain power. This does not mean that they did not use tools at all. They likely used tools in a fashion that's very similar to what we see with modern chimpanzees or gorillas and orangutans, in which they would have employed things like stones, like a hammer and anvil, to break open nuts or even bones. They might have fashioned sort of crude tools out of sticks for spearing purposes, to get at insects like we see with gorillas.
So, um... They would have used tools just in a simplistic fashion. And then fourth, we see an accelerated developmental pattern, reaching adult maturity quickly. It's very similar to the great apes, different than the delayed developmental pattern characteristic of humans.
So the overall message here with all of the earliest hominids, including austropithecines, is that basically early hominid evolution involved bipedality, lots of... modifications to the body to the body for efficient bipedality and That's majorly it like There's there's not a lot of Brain sophistication. There's not a lot of cultural sophistication They likely had behavior that's very similar to chimpanzees and gorillas that would have been competition for mates and They they just were basically like chimpanzees that were upright walking around. So that's what early hominid evolution look like. We're gonna see though that they're gonna be some big changes as soon as we see the introduction of our own genus, the homo genus.
So that's when we really start to see some of the unique characteristics of the hominid line start to appear. Alright, well thanks for tuning in with me through this journey through the earliest hominids and I hope this finds you having a great week.