We Are Primates: On Primate Diversity & Variation

In Intro to Anthro 2022 after discussing Why Anthropology?, we read chapter 2, “We Are Primates” in Through the Lens of Anthropology. The next class elaborated on the evolutionary relationships of non-human primates: Do baboons have friends?

Transcript: We Are Primates

The most important sentence for me is the title of the chapter: “We Are Primates.” I’ll be a tiny bit pedantic about this, just to reinforce that this is slightly different than the way most people think about the world. . . . What I want to say is: we are primates and we are still primates. . . . We didn’t evolve from the chimpanzees, we share a common ancestor with the chimpanzees, who have also been evolving in their own peculiar chimpanzee way. They’ve been changing too. We are classified with chimpanzees, and a whole bunch of other creatures including little, tiny lemurs and creatures like that in the primate order. Now you might wonder: “Who did that to us? Who put us in the primate order?” [You might think it was] probably some bad evolutionist, but no, it was Linnaeus. Linnaeus is the person who we can blame for all that kingdom, phylum, family, order stuff, not that all his terminology stuck, but especially his genus-species or his binomial nomenclature designation for things like Pan paniscus and Homo sapiens.

I don’t always tell when people were born and died, but Linnaeus is 1707-1778, which you might notice that he was born and died before Darwin was ever born, which is in 1809. We’ll be talking about evolution and evolutionary theory in the next chapter. I’m pulling a page number from further along in Muckle, González, and Camp than we’ve read yet, but Linnaeus firmly believed that he was classifying the world according to God’s divine order, that he was simply describing the way that God had ordered creation. He was not thinking in evolutionary terms, although it turns out that his work has been quite useful to evolution because a lot of the relationships that he was describing turn out to be evolutionary ones, not divine creation ones. He’s the one who’s responsible for putting us humans in this larger primate order with other species. Why did he do this? Why did he decide that humans should be part of the primate order? That we should be included with these other creatures? What did he see as the similarities? Here I want to talk about some things that especially occur among the larger primates. Some trends and traits that we observe most of, which are on page 33 of Muckle, González, and Camp. Now these appear with the primates we call the Haplorrhines, which starts with the New World and Old World monkeys. Then especially with the Catarrhines, which includes the Old World monkeys, apes, and humans.

One of the things I want to just point out is the interesting thing, or frustrating, or liberating thing about anthropology is one day we’re talking about these huge human-wide things. Then the next thing, we’re talking about the number of teeth, the dental formula of the Old World and New World monkeys. . . . In this class we’ll mainly be going over just the general characteristics of the primates. Then we’ll talk more about their evolutionary relationships. What do we see with some of these larger-bodied primates, coming from again especially in Old World monkeys, apes, and humans? We see what is called the reduction of facial projection. Not so much a jutting jaw, and an enhancement in the sight rather than the nose, resulting in the great apes and humans basically all have very similar vision. Stereoscopic, or can see in three dimensions. The eyes are oriented toward the front of the face. In evolutionary terms, this is sometimes called a trading of sight for smell, which is to say that unlike dogs and creatures with great noses, we gave up the goodness of smelling things in order to be able to see things better. Again, this is part of something we’ll learn about more in evolution, but every trait has its ups and downs. You don’t just get better and better in every trait. Sometimes you trade-in things. You’re good in one and bad in the other.

The larger primates have grasping hands and feet, and so they are able to grasp tree limbs. Among chimpanzees, bonobos, and humans especially, have an opposable thumb. That’s remarkably developed among us. That’s what gives us the capability to do what you’re doing now, which is writing things down on pieces of paper, but chimpanzees and orangutans also can do things with their thumbs, and do grasping things with their hands and feet. They’re probably better with their grasping feet than we are. We gave that up when we went over to walking. We also share with the great apes a very long period of infant dependency. For some of the chimpanzees and orangutans it can be six or seven years of dependency on their parents. Human beings extended that out to about 36 years (no, I’m just kidding). . . . What this does, importantly for anthropology, and for what we talked about in terms of culture, is that then you learn things from the people, the creatures who are raising you. You need to learn to survive in your environment. It becomes crucial not just what you’re doing on your own, but what you learn from your group and your parents and your peers.

Something that people get really excited about is that in relation to our body size, the large primates have a large brain. It’s not necessarily the biggest brain in the world, but in relation to the percentage or mass of the body, it is large and complexly organized. This happens among all of the great apes. Of course, this becomes especially pronounced as we get into the human primate.

So, these are some of the . . . things that Linnaeus and others observed and said, “aha, lots of similarities.” There are enough similarities that even though they weren’t thinking about evolution, they classified humans as part of the primate order.

One of the things that I most want to impress upon you as you read through all these primates, the names, the terms, and the numbers . . . is how much diversity and flexibility there is among the non-human and human primates. We have variations in movement. The ways they get around: quadrupedal (knuckle walking), climbing, clinging, jumping, brachiation, and bipedal. So, there are all kinds of ways in which the non-human primates and the human primates can move around. We also have dietary variability. Some primates are more what they call frugivore or eat fruits. They can be folivore, eating leaves or insectivore, concentrating on insects. One of the things that is fascinating about this is that for a long time we tried to classify the species of primate according to whether it was frugivore, folivore, or insectivore. We have now discovered that their diets can vary by group within a species, it’s not that the whole species does the same thing, and even seasonally, or by month. They’ll move around into various areas, in one month eat a bunch of fruit, next month eat a bunch of foliage, in the next month eat a bunch of insects. Now, of course, there might be some species specialization, but there’s quite tremendous flexibility even in the things that they eat. We used to think you could classify primates by their diet, but it turns out they are more flexible than that.

There’s also a lot of social variability. On the one hand there are groups that are mainly dominated by males. There are others that are mainly dominated by females. There are groups that are relatively egalitarian, where you don’t have male or female dominance. A lot of this has to do with the different ways in which they mate. In some cases, the males of the species will leave their place of birth and join other groups. In other cases, it will be the females. They develop different social groupings around that.

Why are they doing that? That’s hard to know. It’s hard to ask them these things. They can’t explain it to us, and you’re right, maybe it’s something that they don’t know, but that’s a pattern that they’ve established over time. It might change. It’s a big word to use, but maybe it’s “cultural.” They think about things, and they go off and do different things. It does seem that in some cases it’s the females of the group that leave, in some cases the males, and other cases it gets mixed up. There’s a number of different social groups that they have, and they seem to be able to keep track of these hierarchies, or lack of hierarchies, and keep track of different individuals over time. . . .

Why are we interested in, or why do we study non-human primates?

Non-human primates give us clues about our own evolution, behavior, and anatomy of the most recent common ancestors. So, those creatures that led to what we now see out there as humans, chimpanzees, bonobos. Studying these primates might give us clues about this evolution. It also might give us clues to the way we behave today. So, do we share with the non-human primates different social groupings, the ways that we mix up our gene pool? Does that have anything to do with the social groupings we see among non-human primates?

Muckle, González, and Camp also discussed . . . that the large non-human primates are very important to ecological sustainability (51-52). They are good at seed dispersion in some of the great tropical forests. Their ability to use different kinds of food and be variable can help us understand food strategies that might be sustainable over time for us human beings and the planet.

There are a couple dangers when we look at the non-human primates. One thing that we have to be careful of is what we call anthropomorphism, which is projecting human traits onto other species. That’s why I was trying to be as careful as possible in answering the question “why?” because it’s hard to say and I don’t want to project human emotions and human reasons on to other creatures. People do this all the time, as they assume, “ah, I found them, they’re just like us, we’re just like them.”

The second danger is the idea that we have nothing in common with our non-human primate relatives. You have to navigate between these two extremes: the people who would say we have nothing to do with the non-human primates and those who would try to claim that they’re exactly the same as us. If you can navigate between those two, we can come up with some tentative findings about what we can learn from the non-human primates.

Before we get into some of the primate findings, I want to highlight some of the people who have helped us learn the most about the non-human primates: Jane Goodall, Dian Fossey, Birutė Galdikas (48-49). I will also include Barbara Smuts as one of the pioneering primatologists. You might notice something about all of these people, scientific pioneers. . . . All women. We have women and STEM here. Maybe not all for the best reasons. Back in the 1960s and 1970s, people thought that women were closer to nature, and this seemed to be a field that they could go into, that nobody else wanted to do, because it was simply observing. [People thought women] could communicate better with the non-human primates. Maybe this wasn’t the best reason, but some of the most amazing breakthroughs and studies were done by people that you may have heard of. Jane Goodall of course is still with us and still saying important things. Women were truly pioneers in this field.

What do we find? What we first find is how many different species there are, how much flexibility and diversity and variation there is within the species. We also see variation within species by group. There are differences between mountain gorillas and lowland gorillas, between different habits of chimpanzee groups. You also see variation by individuals. You might see some that are particularly angry, and others that are particularly nice. You see a whole range of behavior, which we can try to make generalizations about, but there’s lots and lots of variation.

This also of course gives us clues about the most recent common ancestor to our own lineage. We need to be very careful about that. The primates that are with us today have also been evolving. We can look for characteristics that we think by observing non-human primates would have existed a long time ago. We always should remember that they didn’t just stop back there.

Recently a politician wondered why there are still chimpanzees around. Well, we have common ancestors. The chimpanzees that are around have also been evolving. They may not be like the chimpanzees of 6-8 million years ago.

Of course, we also see some parallels–maybe in different kinds of patterns of mating and behavior and sociability–to our own behavior. Again, we must be careful. There are some famous books that said that humans were just “naked apes.” This would be a mistake.

We do see some tool use among the chimps. That was one of Jane Goodall’s discoveries among the great apes. The development of tools among the Homo lineage has been much more pronounced. We’ve been co-evolving with those tools for more than two million years. We should be careful about simply assuming that we humans are just great apes who’ve been denuded of hair.

Which ones are the closest to us? The chimpanzees and the bonobos. These are two species of the genus _pan_, two living species that are both in Africa. One of them we may know better–they’re known as the common chimpanzee because there’s more of them and we know more about them. . . . Their scientific name is Pan troglodytes. Then there are the bonobos who were originally called “pygmy chimpanzee” because they seemed to be a smaller version of the chimpanzee. It was later discovered that they are their own species. We know quite a lot less about them. They’re now known as Pan paniscus. There are fewer of them, and they have a very limited geographical range in Africa. What’s interesting about bonobos and chimpanzees is their speciation. They split off about two million years ago, which is after the split between the lineages that would lead to Homo. . . . For any common ancestor behavior, some people are like, “oh let’s look at the chimpanzees,” and other people are like, “No, let’s look at the bonobos.” We don’t really know because there was a speciation split after our own. If the Homo/Pan divergence split off about 6-8 million years ago, the bonobos and the common chimpanzees split off about two million years ago.

Chimpanzees make and use tools. By tools we don’t mean hammers and saws. We do mean things like termite digging sticks, or fishing sticks, and various things that are mainly made from leaves and twigs. We do see a form of tool use that is passed along and learned from generation to generation, passed along by a group.

Chimpanzees are known for having male-dominated groups and aggressive behavior. Some of the more lethal interactions, both within and between groups, are observed among chimpanzees. People who get really excited about lethal interactions and violent male dominance; they get excited about chimpanzees. On the other hand, the bonobos are known for eroticized social interactions. Slightly perhaps exaggerated in Muckle, González, and Camp when they say that “sex among bonobos is as common as a handshake or hug among humans” (47). That’s a little bit exaggerated, but they have been observed to do all sorts of things. They have extremely broad sexual repertoires, as broad as human beings. They also are known for having a pretty central role for females in the group and might even be considered female dominated. Again, we need to be careful here. Neither one of these are exactly what our own common ancestor would have been like, but there are certainly people who claim we are more closely related to the bonobos than we are to the chimpanzees. I’d be careful in both chimpanzees and bonobo behavior. Some of what we observe has been highly influenced by our own interactions. By the time we send in primatologists usually their habitat has already been reduced. Jane Goodall says today that if she were to do it again, she would have been much more careful about food provisioning. They left out food, and the chimpanzees got habituated to being able to interact with humans. At least some of the things that we see both among chimpanzees and bonobos are in some ways artifacts of the ways that we’ve reduced their habitat and kept them in captive situations. When chimpanzees get really bored in captivity, they tend to be mean to each other. When bonobos get bored in captivity, they tend to have a lot more sex than they do in the wild. This is interesting, but you should be careful about making too many generalizations.

The big point for today is that if non-human primates are so diverse and flexible, then when we turn to the human primate, we should be careful of making generalizations like “of course humans are like this, it all goes back to the chimpanzees, or to the bonobos.” When we talk about diversity and flexibility, we already see that extensively among the non-human primates, before we even get to our own kind.

In Intro to Anthro 2022 after discussing Why Anthropology?, we read chapter 2, “We Are Primates” in Through the Lens of Anthropology. The next class elaborated on the evolutionary relationships of non-human primates: Do baboons have friends?