Adaptation An adaptation is a feature that increases the fitness and the reproductive success of an individual. It is shaped by natural selection. An adaptation helps an organism survive in its environment. Adult An adult is a fully developed or mature organism. Adulthood is one of the later stages of life that an organism goes through. Anatomy Anatomy is the branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts. Ape An ape is a relatively large-bodied, tail-less primate native to Africa or Southeast Asia. Humans are apes and are closely related to the great apes (common chimpanzees, bonobos, gorillas and orangutans). The term lesser apes is often used to refer to the hylobatids (gibbons and siamangs). Arboreality Arboreality is the act of living primarily in trees. Arboreality is associated with several physical adaptations that allow for living in trees (such as certain adaptations for climbing, for example). Artery An artery is a vessel that carries blood away from the heart to the rest of the body.


Bipedalism Bipedalism is a form of locomotion which involves the movement of two feet. Humans are bipedal organisms since we walk upright on two feet. Bonobo A bonobo is one type of chimpanzee, sometimes referred to as a pygmy chimpanzee. Its closest relative is the common chimpanzee. Bonobos are found in a small portion of Africa known as the Congo Basin, which is a forested part of the Democratic Republic of the Congo. Like common chimpanzees, bonobos feed primarily on fruit and other plant food items, and occasionally supplement this diet with animal meat and insects. Its scientific name is Pan paniscus. Brachiation Brachiation is a form of locomotion which involves arm-swinging. Gibbons often use brachiation to travel between trees.


Canine tooth A canine tooth is a sharp, pointed tooth located in between the incisors and pre-molars in primates. In primates, males and females of the same species can have canine teeth of different sizes. Cartilage Cartilage is smooth, elastic tissue that can be found at the end of long bones, in the nose and ear, and throughout other parts of the skeleton. Cervical vertebrae The first seven vertebrae in primates are called cervical vertebrae. They make up the top portion of the spinal column. They extend from the base of the cranium to the bottom of the neck. Chewing muscles Muscles like the temporalis, masseter and pterygoid muscles attach to the cranium and mandible and allow the jaw to open and close while chewing food. Common chimpanzee The common chimpanzee is one of two chimpanzee species. Its closest relative is the bonobo. Common chimpanzees are typically found in tropical rainforests and savannahs. Common chimpanzees have varied diets but primarily rely on fruit and other plant food items. They also consume insects and small portions of meat they acquire from other animals. There are currently four subspecies of common chimpanzees. The scientific name for common chimpanzees is Pan troglodytes. Cranium The cranium is the portion of the skull that surrounds the brain CT CT is the abbreviation for computed tomography. A computed tomography (CT) scan is a computerized X-ray image that is often used to create detailed three-dimensional of bones and other tissues.


Dimorphism Dimorphism means two forms. In particular, many primate species exhibit sexual dimorphism in which males and females exhibit different characteristics such as differences in body size, canine tooth size, or fur (pelage) coloration.


Encephalization Encephalization is the proportional size of the brain relative to body size. Human brains are the most encephalized, as we have the largest ratio of brain size relative to our body size among mammals. High encephalization is often associated with higher levels of intelligence in a species.


Folivory Folivory is the act of eating leaves. An animal that engages in folivory is a type of herbivore that is called a folivore. Due to high cellulose and plant toxins found in leaves, folivorous animals have slow metabolisms and long digestive tracts to help them process all of this plant material. Fontanelle A fontanelle is a soft spot of connective tissue found in the gaps in between the cranial bones of an infant. Fontanelles allow for the postnatal growth of the brain, as the brain grows more rapidly than the surrounding bone does. In apes, fontanelles close sooner than in humans, since ape brains grow less than human brains do after birth. Frontal bone The frontal bone contributes to the cranium and is located in the forehead region of the head. It protects the frontal lobe of the brain. Frugivory Frugivory is the act of eating fruits. An animal that engages in frugivory is a type of herbivore that is called a frugivore. Frugivorous animals also incorporate fruit-like vegetables, roots, nuts, and seeds into their diets.


Genetics Genetics is the biological study of genes, DNA, heredity, trait variations, and inherited traits. Genome A genome is the complete set of genetic material, or DNA, of an organism. Genus A genus is a taxonomic category used to classify living and fossil organisms. It ranks below the family level and above the species level of categorization. A genus can contain more than one species that share similar traits. For example, organisms classified under the genus Homo are defined by being bipedal, having a relatively big brain, and having tool-making capabilities. The plural form of genus is genera. A genus name should always be italicized. Gibbon A gibbon is a small ape. There are four genera (Hoolock, Hylobates, Nomascus, and Symphalangus) and many species and subspecies of gibbons. Gibbons belonging to the genus Symphalangus are referred to as siamangs. They are found in the forests of Southeast Asia. Gibbons exhibit the type of locomotion known as brachiation. Gluteal muscles The gluteal muscles are a group of muscles that make up the buttocks. The three muscles are gluteus maximus, gluteus medius, and gluteus minimus. Gorilla A gorilla refers to the apes that are designated under the genus Gorilla. There are two species of gorilla, the eastern gorilla (Gorilla beringei) and western gorilla (Gorilla gorilla). Gorillas are the largest apes and the largest living primate. They are primarily herbivorous and eat leaves and other green plants. Gorillas live in heavily forested areas and many gorillas live at high elevations in the mountains of Central Africa. Gracile Gracile is a synonym for slender or slight. It is a word used to describe the build and appearance of skeletons and animals. It is considered the opposite of robust.


Habitat A habitat is a natural environment for living species, such as humans, plants, or other organisms.

Hallux A hallux is the big toe on a foot. It is the first pedal digit.

Hard tissue Hard tissue is a tissue that is mineralized and has a hard intercellular matrix, referring to bones and teeth.

Hominin Hominin refers to humans, their fossil ancestors, and the fossil species that are more closely related to humans than they are to other primates.

Hominoid Hominoid refers to any species of ape, human, or hominin. Homo Homo is the genus to which humans belong. Its meaning comes from the latin word for ‘man.’ Based on research of hominin fossils, researchers believe that the genus Homo originated around 2.5 million years ago.

Hoolock Hoolock is one of four genera of gibbons.

Hylobates Hylobates is one of four genera of gibbons.

Hylobatid Hylobatid refers to any species of gibbon or siamang.


Incisors Incisors are the tiny chisel-shaped, four front teeth in your mouth. They are located at the front of the mouth on both the upper and lower jaws.

Infant An infant is a baby or a child that is very young.

Intermediate tendon of omohyoideus The intermediate tendon of omohyoideus is a small tendon that separates the inferior and superior bellies of the omohyoideus. Among the apes, only the common chimpanzee and human have this tendon. The two bellies of omohyoideus are continuous in bonobos, gorillas, orangutans, and humans.




Knuckle-walking Knuckle-walking is a form of locomotion usually done by gorillas and chimpanzees when they travel on the ground. During knuckle-walking, apes press their body weight onto their knuckles and walk on them, having their fingers in a flexed position.


Last common ancestor A last common ancestor is the last known, common ancestor species shared by two descendant species. Ligament A ligament is a fibrous and flexible tissue that connects two bones or two cartilages together. Ligaments can also support an organ and keep it in place.

Limb proportions Limb proportions refers to the ratio of upper limb length (arm length) to lower limb length (leg length). Apes have relatively short lower limbs, and a relatively larger proportion of their muscle mass is situated in their upper limbs. Humans exhibit the opposite pattern. Humans have relatively longer lower limbs, and their lower limbs have more girth, they are more robust.

Lineage A lineage is a lineal descendant from an ancestor. It refers to a sequence of species which is considered to have evolved from its predecessor.

Locomotion Locomotion refers to the ability to move from one place to another and the type of movement used. For example, walking would be a locomotive behavior.

Lower limb Lower limbs are body parts that extend all the way from the hips to the toes, otherwise known as the legs.

Lumbar vertebrae Lumbar vertebrae refers to the bones that make up the spine located in the lower back. Humans have five lumbar vertebrae, while the great apes typically have three or four, and the gibbons can have anywhere from four to six.


Mandible Mandibles are the lower jaw, or jaw bone. It is the strongest and largest bone in the human face.

Miocene epoch The Miocene epoch is a geological period that took place about 23.03 to 5.3 million years ago. During this time, the climates were warmer than the periods that came before. Based on fossils from this time period, researchers know that there were many more species of apes than there are living today.

Muscle Muscles are the soft tissues in the body that are composed of both cells and fibers. The contraction of muscles allows us to move our bodies.

Molars Molars are the large teeth located at the back of the mouth in mammals and are used for chewing food. In humans, the third molar can sometimes not fully erupt, and is known as the wisdom tooth.

Monkey Monkeys are typically small to medium sized primates that often live in trees and have tails. Monkeys that are native to South America are sometimes referred to as New World Monkeys (the preferred term is platyrrhines). Monkeys that are native to Africa and Asia are sometimes referred to as Old World Monkeys (the preferred term is cercopithecoids). MRI Magnetic resonance imaging. MRI is a medical imaging technique that relies on magnetic fields and radio waves to create detailed images of structures in the body.


Nerve A nerve is a bundle of fibers composed of neurons that sends sensory information to the brain and spinal cord and transmits impulses to the muscles and organs.

Nomascus Nomascus is one of four genera of gibbons.


Occipital bone An occipital bone is a bone located at the back of the skull. It lies on top of the occipital lobe of the brain.

Opponens digiti minimi The opponens digiti minimi refers to a triangular formed muscle in the hand.

Opponens hallucis The opponens hallucis refers to the big toe area of the foot.

Orangutan Orangutans are apes that belong to the genus Pongo. They have long, reddish colored hair with long arms, and curved hands and feet. Orangutans have varied diets and consume fruit, leaves, tree bark, flowers, and insects. Orangutans are only found in the rainforests of Borneo and Sumatra, which are Southeast Asian islands (parts of Indonesia and Malaysia).

Orthograde posture Orthograde posture is an upright or vertical body position. Individuals that are orthograde have an erect back (e.g. the apes).


Pan Pan is the only genus of chimpanzee.

Parietal bone The parietal bones are located on each side of the skull and form most of the sides and roof of the cranium.

Phalanges Phalanges are the bones that make up the fingers and the toes.

Phylogeny Phylogeny refers to the evolutionary history of a species. It is typically visualized with a phylogenetic tree, which is a way to illustrate evolutionary relationships between species.

Pectoral girdle The pectoral girdle is part of the upper limb that connects the arm to the rest of the skeleton. It includes the clavicle and scapula and many muscles.

Pelvis The pelvis, or the hip bone or pelvic girdle, are the group of bones that connect the torso and the legs. The pelvis is made up of three individual bones-- the ilium, ischium, and pubis--that fuse together over the course of an individual’s’ development.

Premolars Premolars are teeth that are found between the canines the molars. The adult human mouth usually has eight premolars.

Pronograde posture Pronograde posture is a horizontal body position. Individuals that are pronograde have a horizontal back (e.g. monkeys).

Primate Primates are the order of mammals that include apes, humans, and monkeys. Primates belong to a diverse clade of mammals and not all primates share the exact same suite of traits. As a group, primates tend to exhibit many of the following morphological or behavioral characteristics: five digits on the hands and feet, grasping hands and feet, opposable thumbs and big toes, nails instead of claws, highly mobile shoulder joints, well-developed vision, including forward-facing eyes encased within closed eye orbits, reduction of the sense of smell and size of the snout, generalized dentitions with incisors, canines, premolars, and molars, highly social, single offspring with long juvenile periods and high parental investment, complex brains that are large compared to body size, and a long lifespan.

Primatology Primatology is the scientific study of primates. A person who works in the field of primatology is a primatologist.

Pongo Pongo is the only genus of orangutan.


Quadrupedalism Quadrupedalism is a mode of locomotion where animals use all four limbs to travel on the ground or in the trees. Monkeys are quadrupedal.


Robust Robust is a synonym for stocky or strong. It is a word used to describe the build and appearance of skeletons and animals. It is considered the opposite of gracile.


Sagittal crest A sagittal crest is a prominent ridge of bone on the midline of the cranium. It provides an area of attachment for the large chewing muscle, temporalis. The presence of a sagittal crest can be an indicator of powerful chewing muscles.

Scansorius Scansorius is a muscle on the posterior portion of the upper leg. While bonobos have the scansorius muscle, common chimpanzees and humans do not typically present this muscle.

Skeleton A skeleton is the entirety of the bones of a human or animal that form the framework for the body.

Skull The skull forms the bony skeleton of the head, and is comprised of the cranium and mandible

Siamang Large-bodied gibbons belonging to the genus Symphalangus.

Sister species Sister species are species that are descendant from the same species. They are each other’s closest relatives. Common chimpanzees and bonobos are an example of sister species.

Social system A social system is the specific pattern of how relationships are organized and mediated between relatives and mates in a group of primates.

Species A species is the basic unit of taxonomic classification in biology, below the level of genus. There are many definitions of what a species can be. A species is often considered to be a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. A species name should always be italicized.

Sub-adult A sub-adult is an individual that has passed the juvenile period but has not yet acquired all the characteristics that are typical of an adult.

Symphalangus Symphalangus is one of four genera of gibbons.


Taxonomy Taxonomy is the scientific classification of organisms.

Temporal bone The temporal bones are found on either side of the cranium and enclose the middle ear and inner ear.

Tendon A tendon is a tough band or bundle of connective tissue that attaches muscle to bone.

Terrestriality Terrestriality is the act of living primarily on the ground. Terrestriality is associated with several physical adaptations that allow for efficient travel on the ground (such as certain adaptations for running and walking, for example).

Third molar The third molar is also referred to as the wisdom tooth in humans. In the apes, the eruption of the third molar usually signifies that the individual has reached adulthood. The third molar does not erupt in many humans and sometimes needs to be extracted during dental surgery.

Thoracic vertebrae Thoracic vertebrae refers to the bones that make up the spinal column in the center of the back, between the neck and the lower back. Ribs are attached to the thoracic vertebrae. Humans typically have twelve thoracic vertebrae, and apes usually have twelve or thirteen.

Thorax The thorax are the bones of the ribcage, including the thoracic vertebrae, ribs, and sternum. It contains the heart, lungs, and other important soft tissues.

Three-dimensional model A three-dimensional (3D) model is a visual representation of an object in three dimensions.

Torso The torso, or the trunk, is the part of the body extending between the neck and the lower limbs. It is comprised of the thorax, pelvis, and abdominal cavity.


Upper limb Upper limbs are body parts that extend from the shoulder all the way to the fingers, otherwise known as the arms.


Vein A vein is a vessel that carries blood from the body toward the heart.













The Visible Ape Project is funded by NSF grant #1856329.

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