In the working definition used in this lesson, primates are —
Choose an answer, then check it.
Anthropology · Foundations
Primates: Our Living Relatives
On this page 9 sections
In 30 seconds
Primates are the order of mammals that includes prosimians, monkeys, apes, and humans. Three hallmark traits run through the whole order: grasping hands with opposable thumbs, forward-facing eyes that give binocular vision Vision in which both eyes face forward and see the same image, giving depth perception; a defining primate trait. Full entry →, and relatively large brains. Primates split into three groups — prosimians, monkeys, and apes — and humans belong to the apes. They are social, they use tools, and they communicate. The honest framing: living primates are our cousins, not our ancestors, and studying them illuminates what makes humans human.
Why this matters
Every human being is a primate The order of mammals that includes prosimians, monkeys, apes, and humans, marked by grasping hands, forward-facing eyes, and relatively large brains. Full entry →, so studying primates is studying ourselves at one remove. Knowing what all primates share — grasping hands, forward-facing eyes, large brains, group life — anchors the biological half of anthropology and gives the human story a starting point instead of a blank page. Primate research also feeds conservation, medicine, and psychology, and it trains a habit of honest comparison: notice real similarities, name real differences, and resist the two easy errors of treating humans as just another ape A tailless primate of the superfamily Hominoidea, including gibbons, orangutans, gorillas, chimpanzees, bonobos, and humans; mostly ground-dwelling. Full entry → or as utterly unlike any animal. Our place in the order is the first fact of the human story; the question of what we made of that place is everything after.
The college version
What primates are
Primates are an order of mammals — the same taxonomic rank that contains carnivores and rodents — and the order includes prosimians, monkeys, apes, and humans. OpenStax's Introduction to Anthropology opens its primate section by noting that primates, human beings included, are set apart from other mammals by a cluster of physical features. The Smithsonian Human Origins Program puts the membership plainly: humans are part of the biological group known as primates, and that group includes lemurs, lorises, tarsiers, monkeys, and apes. The working definition used here, synthesized from both: primates are the order of mammals that includes prosimians, monkeys, apes, and humans. Membership is not a lifestyle; it is a family fact that every human being carries from birth.
The primate body plan: grasping hands, forward-facing eyes, big brains
Three traits run through the whole order, and each can be stated in one line. Grasping hands: primate hands and feet are built to hold — an opposable thumb A thumb that can touch the other fingers of the same hand, enabling grasping; a hallmark primate trait shared by no other mammal group. Full entry → that meets the other fingers (and, in nonhuman primates, an opposable big toe), five digits, flat nails instead of curved claws, and sensitive pads at the fingertips. Forward-facing eyes: both eyes look ahead and see the same image, which gives depth perception, the eye sockets are ringed with bone, and the snout is small because primates rely on vision far more than on smell. Big brains: primate brains are relatively large for body size, and the reproductive rate is slow compared with other mammals. These are shared facts, not a report card: every living primate carries all three, from a lemur to a lecturer.
The three groups: prosimians, monkeys, apes
Scientists divide the order into two suborders — Strepsirrhini and Haplorrhini — but for a first map, three groups carry the lesson. Prosimians are the earliest-evolving primate group: lemurs, lorises, and galagos, most of them found on Madagascar or in parts of Africa and Asia. Original example: a ring-tailed lemur sunning itself on a branch in a Madagascar forest is a prosimian A member of the earliest-evolving primate group, which includes lemurs, lorises, and galagos, found mostly on Madagascar and in parts of Africa and Asia. Full entry →. Monkeys are the largest group: New World monkeys, whose nostrils open sideways and many of which have prehensile tails that grip like a fifth hand, and Old World monkeys, with downward nostrils and no prehensile tails. Original example: a white-faced capuchin cracking a nut on a log in Costa Rica is a New World monkey A primate of the two great monkey groups — New World monkeys with prehensile tails and sideways nostrils, and Old World monkeys with downward nostrils and no prehensile tails. Full entry →. Apes form the superfamily Hominoidea — gibbons, orangutans, gorillas, chimpanzees, bonobos, and humans — and among living primates they are the tailless, largely ground-dwelling group with the largest relative brain sizes. Original example: a mountain gorilla group resting in the bamboo of Rwanda is an ape. Tarsiers sit inside Haplorrhini as a scientist's puzzle with a mix of prosimian and anthropoid traits — a footnote here, not a fourth group.
The ape connection: humans are apes
Stated simply, and attributed: humans are apes. The Smithsonian's Human Origins Program says that humans are primates and that physical and genetic similarities show Homo sapiens has a very close relationship to the apes; OpenStax places humans squarely in Hominoidea alongside gibbons, chimpanzees, gorillas, and orangutans. Now the honest note, because this is where popular confusion lives. Humans are not descended from chimpanzees or from any other living ape. Humans and chimpanzees share a common ancestor A species from which two or more descendant lineages evolved; humans and chimpanzees share a common ancestor from 8 to 6 million years ago. Full entry → dating to between 8 and 6 million years ago, and the two lineages evolved differently from that ancestor. The chimp is not a stalled human; the human is not a talking chimp. They are two branches that grew apart from one shared trunk.
Primate behavior: sociality, tool use, communication
Three behaviors stand out across the order, each stated factually. sociality The tendency to live in organized social groups; a hallmark of primate life across the order. Full entry →: most nonhuman primates live in social groups, where grooming, alliances, and rank structure daily life. tool use The making or using of an object to achieve a goal; practiced by some nonhuman primates, such as chimpanzees termite-fishing with sticks. Full entry →: some nonhuman primates make and use tools — chimpanzees at Gombe fish termites out of mounds with stripped twigs, and chimpanzees at Fongoli adapt sticks into spears for hunting small primates called galagos. Communication: primates are very vocal and communicative with members of their social group, and some can be taught to communicate with symbols. One line each, and together they are why primatologists watch wild primates at all: these behaviors are the raw material for asking what humans do with the same capacities.
The honest note: illumination, not reduction
Primate studies illuminate humans without reducing us to them. OpenStax makes the point directly: without the comparative perspective primatology The branch of biological anthropology that studies primates, especially their behavior and biology in the wild. Full entry → provides, anthropologists would be missing an important piece of the puzzle of what makes humans human. The Smithsonian adds the other half: humans are an unusual species of primate. Complex symbolic language, cumulative culture that builds across generations, and habitual walking on two legs are ours alone among living primates. Comparison is a spotlight, not a verdict — it shows what we share and what we alone have made of it.
The honest framing: cousins, not ancestors
The reality check, once, clearly: every living primate is our cousin; none is our ancestor. The Smithsonian FAQ answers the familiar question directly — humans and monkeys are both primates, but humans are not descended from monkeys or any other primate living today. We share a common ape ancestor with chimpanzees from 8 to 6 million years ago, and apes and monkeys share a more distant relative from about 25 million years ago. Think of a family tree, not a ladder: no living species is anyone's ancestor, and every living primate has been evolving for exactly as long as we have.
Eli explains
The same idea, in plain words
Explain it like I’m 10
Every human being is a primate, and primates are one branch of the mammal family tree. The branch includes lemurs and lorises, monkeys, apes, and us. What ties the branch together is a shared body plan — hands that grasp, eyes that face forward, brains that are large for the body — and a shared way of life: living in groups, using tools, communicating. When anthropologists watch chimpanzees, they are not watching our ancestors. They are watching a close cousin, and using that closeness to see what is true of all primates and what is only true of us.
Picture it like this
A family reunion is the right picture. You and your cousins share grandparents; you do not descend from your cousins. Every living primate — lemur, capuchin, gorilla, human — is at that reunion. Humans and chimpanzees are the closest cousins there, sharing a grandparent that lived 8 to 6 million years ago. Nobody at the reunion is anybody else's ancestor; every branch has been growing since the shared trunk.
Where the picture stops working
Family trees have clear generations, and a reunion gathers one generation at a time. Evolution has no generations in that sense: branches split, then keep evolving, and a cousin species today is not frozen in the past. The reunion also suggests closeness among equals, but humans and chimpanzees diverged and then evolved very differently — the chimpanzee is not a human waiting to happen, and we are not a chimpanzee that learned to talk.
Worked example
Naledi, a primatologist, spends a morning with a chimpanzee community in a forest in Tanzania and logs three observations. First, two adults groom each other's fur for twenty minutes — sociality, the group life that holds primate societies together. Second, a juvenile breaks a twig, strips its leaves, and pokes it into a termite mound, then lifts it covered in termites — tool use, manufactured on the spot. Third, a loud pant-hoot sweeps through the group when a rainstorm arrives — communication, exchanged among group members. Later she classifies the animals themselves: chimpanzees are apes, tailless hominoids; the white-faced capuchin she watched last month in Costa Rica is a New World monkey; the lemur in a zoo video is a prosimian. One morning, three behaviors; one order, three groups.
Key takeaway
Primates are the order of mammals that includes prosimians, monkeys, apes, and humans, bound together by grasping hands, forward-facing eyes, and relatively large brains. Humans are apes, and every living primate is our cousin — sharing ancestry with us, never standing in for our ancestors.
Quick check
3 questions here, of 5 in this lesson’s practice set. Answers stay hidden until you check.
Which set of traits belongs to primates as a group?
Choose an answer, then check it.
A field observer records an animal with flat nails, an opposable thumb, forward-facing eyes, binocular vision — and no tail. Which primate group does it belong to?
Choose an answer, then check it.
Study tools & related lessonsYou’ll learn to · Common mistakes · Easily confused · Key vocabulary · Related
You’ll learn to
- Define primates as the order of mammals that includes prosimians, monkeys, apes, and humans, using the Smithsonian/OpenStax working definition.
- Name the three hallmark primate traits — grasping hands, forward-facing eyes, and relatively large brains — and state what each does in one line.
- Distinguish the three major primate groups — prosimians, monkeys, and apes — giving an original example of each.
- Explain the ape connection: humans are apes, sharing ancestry with today's great apes rather than descending from them.
- Identify sociality, tool use, and communication as core primate behaviors, with an original example of each.
- Analyze the two reality checks: primate studies illuminate humans without reducing us to them, and living primates are cousins, not ancestors.
Common mistakes
Humans evolved from chimpanzees.
No living ape is our ancestor. Humans and chimpanzees share a common ancestor dating to between 8 and 6 million years ago, and each lineage evolved separately from it — per the Smithsonian, humans are not descended from any living primate.
Monkeys are the ancestors of humans.
Humans and monkeys are both primates, but humans are not descended from monkeys or any other living primate. The common ancestor of apes and monkeys lived about 25 million years ago.
Primates are just monkeys and apes.
The order also includes prosimians — lemurs, lorises, and galagos — which evolved earliest, plus tarsiers, the classification puzzle that sits within Haplorrhini.
Only humans are social or use tools.
Most nonhuman primates live in social groups, and some make and use tools, such as chimpanzees termite-fishing with stripped twigs. What is unusual about humans is scale and complexity: symbolic language and culture that accumulates across generations.
A living 'primitive' primate is a frozen ancestor.
No living species is anyone's ancestor. Prosimians evolved earlier than other primates, but every living primate has been evolving for exactly as long as humans have.
Easily confused
Prosimians vs. Anthropoids (monkeys, apes, humans)
Prosimians evolved earliest and keep traits such as a grooming claw and a toothcomb; anthropoids dominate the order today. Both are primates with grasping hands and forward-facing eyes.
New World monkeys vs. Old World monkeys
New World monkeys have nostrils that open sideways and many have prehensile tails; Old World monkeys have downward nostrils and no prehensile tails. Both are monkeys; only the New World forms carry an extra gripping limb.
Apes vs. Monkeys
Apes are tailless, largely ground-dwelling, and include humans; monkeys keep tails and mostly live in trees. Both are haplorrhine primates, and the ape group is the one humans belong to.
Humans vs. Other great apes
Humans are apes with complex symbolic language, cumulative culture, and habitual bipedalism; chimpanzees, gorillas, and orangutans share our sociality and tool use but not those three. Same family, different branches.
Key vocabulary
- primate
- The order of mammals that includes prosimians, monkeys, apes, and humans, marked by grasping hands, forward-facing eyes, and relatively large brains.
- prosimian
- A member of the earliest-evolving primate group, which includes lemurs, lorises, and galagos, found mostly on Madagascar and in parts of Africa and Asia.
- monkey
- A primate of the two great monkey groups — New World monkeys with prehensile tails and sideways nostrils, and Old World monkeys with downward nostrils and no prehensile tails.
- ape
- A tailless primate of the superfamily Hominoidea, including gibbons, orangutans, gorillas, chimpanzees, bonobos, and humans; mostly ground-dwelling.
- opposable thumb
- A thumb that can touch the other fingers of the same hand, enabling grasping; a hallmark primate trait shared by no other mammal group.
- binocular vision
- Vision in which both eyes face forward and see the same image, giving depth perception; a defining primate trait.
- sociality
- The tendency to live in organized social groups; a hallmark of primate life across the order.
- tool use
- The making or using of an object to achieve a goal; practiced by some nonhuman primates, such as chimpanzees termite-fishing with sticks.
- primatology
- The branch of biological anthropology that studies primates, especially their behavior and biology in the wild.
- common ancestor
- A species from which two or more descendant lineages evolved; humans and chimpanzees share a common ancestor from 8 to 6 million years ago.
Sources & references
- 4.5 What Is a Primate? — Introduction to Anthropology — OpenStax, Rice University
- 4.6 Origin of and Classification of Primates — Introduction to Anthropology — OpenStax, Rice University
- 4 Key Terms — Introduction to Anthropology — OpenStax, Rice University
- Primate Behavior — Human Origins Program, Smithsonian Institution — Smithsonian Institution
- Introduction to Human Evolution — Smithsonian Human Origins Program — Smithsonian National Museum of Natural History, Human Origins Program
- Frequently Asked Questions (How are humans and monkeys related?) — Human Origins Program, Smithsonian Institution — Smithsonian Institution
EliExplains lessons are original prose written from the open, credible references above. See Copyright & Licensing.
Researched 2026-08-22
Educational content only. It is not medical, legal or professional advice. Found an error? Tell us.