Introduction to Physical Anthropology

by Arnie Schoenberg
version: 31 July, 2023

monkey selfie showing teeth

Figure 5.1 Self Portrait by Naruto the Celebes crested macaque ©2008 (used without permission)

Section 5 Contents

full table of contents

5    primatology

5.1    primate evolution

5.1.1    prosimians

5.1.2    anthropoids

5.1.3    hominoids

5.2    primate taxonomy

5.3    ethology

5.3.1    behavioral ecology

5.3.2    primate sexuality

5.3.3    primate culture

5.3.1 primate tools

5.3.2 ape language?

5.3.3 ape music?

5.3.4    theory of mind

5.3.5    agonistic behavior

5.3.6    affiliative behavior

5.3.7    K-selection vs. r-selection

5.4    conservation

5.4.1    habitat loss

5.4.2    bush meat

5      primatology

We are primates. One way to learn about humans is to study them as a kind of primate. This works especially well to explain how we got the physical structure that we have. It works a little bit to explain a few of our behaviors. It hardly works at all to explain our culture. Studying primates can't tell us who we are, but it can help tell the story of how we got to be who we are. Sadly, that story is being erased in our lifetime as the primate extinction continues to accelerate.

An example of our shared physical structures is the Darwin tubercle -- a projection on the helix of the ear resulting from a thickening of the cartilage. The actual size of the tubercle varies. It is one of many vestiges of our primate ancestry.

side by side photos of a human and macaque monkey. The human ear has an inward facing bump towards the top rear of the ear. The monkey has a pronounced point at the top of its ear.

Figure 5.2 Darwin's Tubercle derived by Luis Fernández García from Ear with earring.jpg and Image:Macaca fascicularis.jpg. 2008-07-25 (CC BY-SA 3.0)

A common misuse of primatology is to compare human and primate sexuality. When I channel my inner-Hippy, I love the work Susan Block does to promote peace and bonobo conservation.

But, Block's comparisons between human and bonobo sexuality have so many scientific errors that her good intentions often lose credibility (* Ryan M. Ellsworth review of Susan Block's The Bonobo Way: The Evolution of Peace through Pleasure).

A broad research question in primatology is to compare and contrast primates to other mammals, and then compare and contrast primates to themselves.



Jane Goodall is famous for studying chimpanzees in their natural habitat, and the impetus for her research came from comparing primates to our fossilized human ancestors.


* Skim the first chapter of Augustín Fuentes Race, Monogamy, and Other Lies They Told You
Busting Myths about Human Nature

* a guide to doing Primate observation at the zoo

5.1     primate evolution

There is a direct correlation between primate evolution and primate taxonomy. Our goal in evolutionary systematics is to make a taxonomy of living organisms and trace their ancestors and provide the dates when the groups of species split apart from one another.

Skim O'Neil on primate evolution

* Video on primate evolution:

5.1.1     prosimians

Linnaeus named this group of primates as the ones "before apes", and works well in an evolutionary framework, as they happen to be the most primitive. If you saw the first "Madagascar" movie, the primates there were all prosimians, and most of the world's prosimians are found on this island off the east coast of Africa. A variety of prosimian fossils are found all over Africa and Asia, but they were replaced by other primates most everywhere but Madagascar.

Skim Strepsirrhines

* evolution of Lemurs

a small grey mammal on a tree branch at night, with huge eyes, big ears, long folded hind legs, and a long tail.

Figure 5.3 Galago moholi Joachim S. Müller (CC BY-NC-SA 2.0) tarsiers

Tarsiers used to be classified as prosimians, because they look and move like prosimians (compare the galago above to the tarsier below), but Tarsiers turned out to be genetically more similar to monkeys and apes. So, scientists had to come up with a new division that was named after the differences in their noses (strepsirrhine versus haplorrhine; wet versus dry).

a small furry mammal with huge eys, big ears, long folded hind limbs, long toes grasping a branch, holding a grasshopper with its hands

Figure 5.4 Tarsier eating by Davide Baj & Alastair Robinson © 2013 Wild on Camera (Facebook) (YouTube)

Watch more insectivore predation and vertical clinging and leaping locomotion:

Notice that the alignment of the tarsier body tends to be vertical like the tree trunks, and notice how they grasp trees and objects with their hands.

read about Haplorhines

5.1.2     anthropoids

Anthropoids are monkeys, and apes (which includes humans). Anthropoids are primates, but not prosimians.

* A fossil found in Thailand suggests that anthropoids evolved in Asia first (~45mya), and then migrated to Africa (~38mya).

5.1.3     hominoids

chimpanzee skull by NHM_Imaging on Sketchfab

human skull by Museu d'Historia de Manacor on Sketchfab

Hominoids are apes. Hominoids are Anthropoids but not monkeys.

The Miocene (23-5mya) was an important a time period for hominoid evolution and the adaptive radiation of apes led to extreme variation, and the ones in our clade were relatively generalized compared to Gigantopithecus for example. Compare the mandibles of Gigantopithecus to a modern orangutan:

Gigantopithecus blacki by AJL on Sketchfab

Pongo pygmaeus (modern) (2501.1rp12-2) by RLA Archaeology on Sketchfab


5.2     primate taxonomy

Watch this 5-minute video overview of primates:

a collage of 7 primates: a pair of lemus grooming, a howler monkey in the trees, a human climbing a tree, a chimpanzee, a bonobo, a gorilla, an orangutan

Figure 5.5 "Primate Collage" by Arnie Schoenberg modified from "Primates can be divided into prosimians, such as the (a) lemur, and anthropoids. Anthropoids include monkeys, such as the (b) howler monkey; lesser apes, such as the (c) gibbon; and great apes, such as the [(c) human,] (d) chimpanzee, (e) bonobo, (f) gorilla, and (g) orangutan. (credit a: modification of work by Frank Vassen; credit b: modification of work by Xavi Talleda; credit d: modification of work by Aaron Logan; credit e: modification of work by Trisha Shears; credit f: modification of work by Dave Proffer; credit g: modification of work by Julie Langford)" by OpenStax, Download for free at Credit c: modification of work by C. Hernández (CC BY-NC 4.0)

a black and white furry mammal with large folded hind legs and a small head with furry ears, grabbing a branch.

Figure 5.6 Indri Lemur by Christophe Germain, "Indri indri au parc national d'Andasibe-Mantadia, dans l'est de Madagascar." (CC BY-SA 4.0)

a light tan ape with a black face hanging from a branch by one extremely long arm

Figure 5.7 Brachiating gibbon by Troy B Thompson via Wikimedia Commons(CC BY 3.0)

5.2.1 primate locomotion

Notice how vertical these last two primates are, but for very different locomotion reasons, the indiri jumps from trunk to trunk, and the gibbon swings from branch to branch. This vertical orientation of primates suggests how human bipedalism is a logical extension of our primate continuum. When moving on the ground, all non-human primates prefer to use all four limbs. Quadrapedalism means using four feet. Humans are the only primate that is habitually bipedal, but primates in general tend to be oriented towards being upright. The small clingers and leapers hang on to tree trunks, the brachiators hang vertically from their arms, many prosimians jump bipedally, most apes go on two feet for a more dramatic display and to carry food and infants.

Watch these jumping Lemurs:

5.3     ethology

Ethology is the study of animal behavior. Don't confuse it with "ethnology" the study of "ethnos", ethnicities, the comparative study of human cultures.

I think videos are the best way to get a sense of both primate behavior and our place in the primate continuum. Captivity is a bad place to study behavior, because the behavior has evolved in a certain environment, to solve problems in that environment, and you can't expect to see natural behavior outside of a natural setting, and I hate zoos because they justify the destruction of natural habitat. But, some of these psychological experiments are useful to blur the line between human and non-human primate.

* Reintroducing Lemurs into Madagascar (7 part series with John Cleese)

* Documentary about the World's Most Genius Ape:

5.3.1     behavioral ecology

In our phylogenetic taxonomy we are closest to chimpanzees and bonobos, and then gorillas. But in terms of behavior we share many characteristics with other primates who have more genetic differences. For example, we share a tendency towards monogamy with orangutans and lesser apes, and an adaptation to coming down from the trees and living in more arid environments with baboons. Understanding the ecosystems where primates have evolved is important to understanding their behavior.

* Baboon adaptations to the savanna

* Safety in numbers, boa constrictor eats Purús red howler monkey

* The Monkey and the Snake: How the Primate Brain Reacts to Serpents


5.3.2     primate sexuality

Quick Guide to non-human Great Ape Sexy Times. Orangutan: female-male 'antisocial monogamy'. Gorilla: female- female- female-male 'polygamy'. Chimpanzee: female-male female-male female-male 'competitve promiscuity'. Bonobo: -female-male-male-male-female-female- 'nonstop orgy'.

Figure 5.8 "Great Ape Sexy Time" by Beatrice the Biologist © 2013

Gibbons are monogamous and sing duets.

It is tempting to use analogies from non-human primates to describe your friends' sexuality, e.g. you may have one friend who is more of a gibbon, and another who acts more like a bonobo, but be careful not to make too much out of these analogies because most of human sexuality is a learned behavior. Our primate ancestors left us our unremarkable mechanical structures and a few hard-wired visual and pheromone responses. All the good juicy stuff comes from our voluptuous brains.

5.3.3 primate culture

With most plants and animals, we can make a direct connection between natural selection and evolution, because there is a direct connection between genes and behaviors. This is more difficult with primates because we have so many more learned behaviors. We can find anecdotes for some natural selection in the correspondence between Vervet monkey calls and predators, and why humans tend to be afraid of snakes, but it's the exception, not the rule.

When we see different behaviors of the same species in similar ecological areas that are separated geographically, we assume the difference comes from the independent invention of primate cultures. The identical genetics should produce identical instinctual behaviors. There is no way for the separate groups to share these behaviors through diffusion. The similar ecological areas imply that differences in behaviors aren't just different reactions to different environments. So when we see complex behavior in primates, we assume it's culture and not biology; nurture is more important than nature.

* Orangutans plan ahead and share trip plans a day before leaving:

* altruism in chimps and children    Primate tools

* Capuchin Monkey tool use:

* Chimpanzees from Bossou tool use

* article on social transmission of tool use, Sonso chimp leaf sponges Ape language?

Apes don't have the same physical apparatus that lets them speak, but they can learn sign language and symbolic keyboard languages. Apes have a higher larynx that doesn't allow for the same range of sounds as human speech. The brains of apes are relatively large compared to other mammals and allow for complex social communication in the wild, and to be taught rudimentary language in captivity. But the brains of apes are relatively small compared to humans, so they can never match the complexity of human language, and most scientists reserve the word "language" for how humans communicate.

* book on Koko, a gorilla who was taught sign language

* Evolution of human vocal production Ape music?

Language is often defined as an exclusively human form of communication, but the line between human language and animal communication is not so sharp, as we see with Koko, Kanzi, and the dozens of other apes taught to use languages. Can the same be said about music? Gorillas make up little songs when they are eating. When we find regional variations of sounds produced by chimps, can we say they are like musical styles?

* watch Chimpanzee's from Bossou clip leaves because they like the sound it makes, and they are bored, frustrated, or want to attract a mate (you need to turn the sound up on the video to hear it)

* review of Chimpanzee drumming styles

* article on Gorilla eating songs

5.3.4     theory of mind

 Theory of mind refers to an individual's ability to think about what other individuals are thinking. The term has various definitions which can range from mirroring, copying another's actions, to mentalizing, predicting how another will react. Humans are definitely the best at this, but other animals demonstrate this behavior, including dogs, dolphins, elephants, some birds, and of course primates. Dogs are actually better at recognizing human pointing than chimpanzees.

* John Rubin "The Gap Between Humans and Apes"

* watch a lecture by Tetsuro Matsuzawa, "Mind Reading" in Chimpanzees

* skim Charles Darwin's 1872 "The Expressions of the Emotions in Man and Animals", especially look at the pictures:

drawing of chimpazee with pursed open lips

Figure 5.9 "Chimpanzee disappointed and sulky. Drawn from life by Mr. Wood."* The expression of the emotions in man and animals by Charles Darwin, 1872 (public domain)

watch an amazing test of chimp short term memory :

* the cognitive tradeoff hypothesis tries to explain why chimps are smarter than us in some ways:

* apes and mirrors:

The three clips are arranged from agonistic (aggression) to affiliative (grooming and sex)

* ape self-awareness:

* read an article on contagious yawning in chimpanzees

* read an article on Chimp attitudes towards death

5.3.5    agonistic behavior

Agonistic means "aggressive", but it is usually more bluff and intimidation than physical violence. Natural selection is going to generally select for conflict resolution that avoids members of the same species injuring each other. Many primates are aggressive, but they don't kill each other very often. They learn hierarchies to avoid injury. But when push comes to shove, primates make bad pets.

* The potential for agonistic behavior is one of the best arguments against the primate pet trade.

* watch another Violent Chimp Attack

5.3.6     affiliative behavior

Affiliative means "social". There is a push and pull of conflict and resolution in primate societies. Primates fight to see who's on top, and then make-up to keep the group together. Agonistic behavior helps to establish dominance hierarchies, and is usually followed by reconciliation, a kind of affiliative behavior. The most common primate affiliative behavior is grooming. We tend to think of grooming as keeping clean, but its main function for primates is social bonding.

* read about how Bonobos comfort each other

* James Fowler research on how humans chose their friends based on genetic closeness

5.3.7     K-selection vs. r-selection

If you say something is r-selected or K-selected, you are comparing a species or group of species to another, and comparing their strategies for growing their population. The terms come from variables in a math equation that describes how populations grow:

dN/dt = rN((K-N)/K)


N = the population density; how many individuals in a certain area

r = the reproductive rate; how fast can new individuals be produced

K = the carrying capacity; how many individuals can a certain area feed

r-selected animals have plenty of habitat to grow into, so they crank out lots of kids and hope a few survive. K-selected animals have limitations on their resources, so they have few infants per birth, and longer birth spacing, and invest more parental care in making sure they survive. For a cultural analogy, think of human parenting styles: free-range versus helicopter.

K-selection follows the human phylogenetic continuum closely. Vertebrates are more K-selected than invertebrates. Mammals are more K-selected than other vertebrates. Primates are more K-selected than other mammals. Anthropoids are more K-selected than prosimians. Hominoids are more K-selected than monkeys. Humans are one of the most K-selected species on the planet.

Based on this phylogenetic history of reproductive strategies we should have one of the smallest populations of any mammal on the planet. Our huge population comes by cheating the equation. The K = carrying capacity is supposed to be a constant, but through culture, humans make it into a variable. We intentionally build the environment that would otherwise constrain us. We decide to grow our own food, and the more food we grow, the more people we can feed in that area, so K goes up.

Figure 5.10 "Carrying Capacity: The area in the orange box, which is not under cultivation, might provide enough resources for a family of four to survive for a year. An equivalent area, marked by the blue box, could provide enough resources for a significantly larger population under intensive agricultural cultivation." by Isaac Shearn from "Subsistence" Perspectives: An Open Invitation to Cultural Anthropology which contains work by Andreas Lederer. and Dennis Jarvis (CC BY-NC 4.0)

* Jane Goodall on chimpanzee motherhood:

* Population Dynamics simulation comparing exponential and logistic growth (also see the Student Worksheet)

* Population Biology virtual lab

* logistic growth equation


carrying capacity
sexual dimorphism

5.4 conservation

"Are primates going extinct?"

This is a trick question. One answer is "no". The total world primate population has skyrocketed in the last 10,000 years and especially in the last 200 years. But, another answer is "yes". The total number of primate species has declined drastically and primate extinction is expected to continue. One primate is doing really well, at the expense of all the other primates. The primary cause is habitat loss, but a significant and very symbolic factor is that one primate is literally eating all the others.

* Jane Goodall video on conservation:

5.4.1    research on primates

Primates are valued as research subjects because their physiology is so similar to ours, but the same similarity makes captive breeding and research unethical.

We are good at sending primates into space, but are not as good at getting them back alive.

5.4.2      habitat loss

When we cut down forests, we push primates towards extinction. This is happening to all primates around the world. The bulk of deforestation is to provide luxury food products (like hamburgers or palm oil) to meet consumer demand in the US.

* GRASP statement on palm oil plantations

a grid of red and black gorilla icons, mostly red.

Figure 5.11 Only 1 in 5 gorillas are safe, by the World Conservation Society (permission pending)

5.4.3 anthropozoonotic diseases

Eco-tourism is generally good for primates because it adds monetary incentives for conservation, but because human and non-human primate biology is so similar (~98%), the diseases that infect us can often jump species and infect the primates we came to watch.

* Gorillas at the San Diego Zoo Safari Park recovering from COVID-19

* non-human primates can get COVID-19

* protecting primates from COVID-19

* Ecotourism can transfer disease from humans to primates

5.4.3     bush meat

 I think the story of primate extinction is better told in pictures. The problem with the pictures is that they don't explain the root cause of why people resort to eating other primates: colonialism. The reason people are hungry is because of how resources are distributed. Even with overpopulation, there is enough food in the world to feed everyone. It is a question of distribution. There are the rich and the poor. Colonialism exacerbated existing class distinctions to better extract natural resources and send wealth to Europe. Colonialism led to post colonialism, where even after "independence", patterns of corruption continue today.

It's easy for us to judge people and say we need to stop eating bush meat, but as anthropologists we strive for cultural relativity. Imagine your family was starving, and you had to choose between your children or another primate on the verge of extinction. Would you let YOUR family starve for the sake of another animal?

One of the most paralyzing factors in primate conservation is the long and sordid history of Europe, the US, and Africa, and how our most well-intentioned actions often backfire. Look at the backlash to the San Diego based Kony 2012 campaign. How can the US claim any moral superiority when they perpetuated slavery and racism? How can we claim that we have Africa's best interests at heart, after what we did in the Congo in 1960--sending the CIA to assassinate their democratically elected leader? After we propped-up the racist South African Apartheid regime? The sadness of these pictures goes way beyond the extinction of primates in our generation. It reflects a very difficult political situation, where everyone, especially the primates, loses.

The following inline graphics are linked without permission:

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The above inline images are linked without permission

I was getting very depressed gathering these photos, but I stumbled on an innovative program that is trying to substitute beekeeping for the hunting of bushmeat, and it cheered me up for a moment:

* The Lebialem Hunters' Beekeeping Project

As human populations grow they crowd out other habitats, and one of the most effective programs for conservation is to focus on helping the people who live near the primates.

* article: Outlook is grim for mammals and birds as human population grows.

* Conservation Through Public Health focuses on people who live near primates

* article on alternatives to bush meat

* Mountain Gorilla census over 100

* The NonHuman Rights Project promotes Legal rights for chimpanzees in the US

* Vaccinating Lemurs:

* the Green Corridor Project includes research and reforestation to connect isolated chimpanzees to larger reserves, and help them coexist with humans:

There is a crisis and we need to all do something about it, but things aren't hopeless, we just need to work quickly and do more.

Imagination Questions

an oil painting of a monkey headmaster beating a student monkey with a switch, while another monkey begs for forgiveness, and other student monkeys look up from their reading

Figure 5.12 "Apen op School" [Monkeys in school], David Teniers the Younger, circa 1660 (public domain)

Imagination Actions

selfie: the monkey's hand is taking the picture

Figure 5.13 Self Portrait by Naruto the Celebes crested macaque ©2008 (used without permission)


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