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Catalogue number: Sometimes also called a field number, this is the number given a fossil by the researcher during the time of discovery. Catalogue numbers usually consist of a location abbreviation (i.e. 'OH' standing for 'Olduvai Hominid') followed by a number assigned to the fossil, normally in the order that it was found. So OH5 is the fifth hominid that was found at Olduvai Gorge.
Dental microwear: Dental microwear is the study of the microscopic wear on a tooth's surface that occured as a direct result of use (chewing). Dental microwear studies look for tooth scratches and pits that occur on teeth predominantely through chewing, and can orovide evidence of what an individual ate in the past.
Endocast: An endocast is a cast that shows the brain's impression on the inside of the skull. Endocasts can be artificially made by spreading a mold into an empty skull to represent the skull's brain. The artificial brain is then removed to show the brain's impression, or lines and ridges on its outside surface, that formed against the skull's inside. Endocasts can also form naturally by sediments filling up the inside of an empty skull and fossilizing.
Field number: Sometimes also called a catalogue number, this is the number given a fossil by the researcher during the time of discovery. Field numbers usually consist of a location abbreviation (i.e. 'OH' standing for 'Olduvai Hominid') followed by a number assigned to the fossil, normally in the order that it was found. So OH5 is the fifth hominid that was found at Olduvai Gorge.
Foramen magnum: The foramen magnum is the hole at the base of the skull through which the spinal cord enters into the skull and connects to the brain. This hole is one of the key ways scientists can tell the difference between a bipedal human skull and the skull of a quadrupedal great ape. In humans, the foramen magnum is underneath the skull, allowing humans to hold their head upright and look forward. In a great ape, where the ape’s head rests in front of the neck instead of on top, the foramen magnum is positioned at the rear of the head so its eyes face forward, and not down, as it moves.
Holotype: Similar to a ‘type specimen,’ for fossil species, the ‘holotype’ of a species is the fossil specimen used when the species is formally described.
Humerofemoral index: The humerofemoral index is measure comparing arm length to leg length. The index is defined by the arm length divided by the leg length times 100. Modern apes and chimpanzees have arms and legs that are almost the same size in length, giving them a humerfoemoral index of about 100. Humans, with shorter arms than legs, have a humerofemoral index of about 70.
In situ: The words 'in situ' are Latin meaning 'in the place.' In prehistoric studies, in situ refers to an artifact or fossil that has not been taken out of the original location where it was found. In situ materials are undisturbed, which allows archaeologists to date them and/or give them better context by looking at what artifacts or sediments are found nearby.
Sexual dimorphism: Sexual dimorphism is size or shape difference between males and females of the same species. Similarly-sized males and females within a species show less sexual dimorphism, and this phenomenon is generally attributed to monogamous bonding between males and females (like in many modern humans). Greater sexual dimorphism generally means a species is more polygamous.
Sagittal crest: A sagittal crest is the bony ridge on the top of the skull where the jaw muscles of some early humans were anchored allowing powerful chewing (a modern human’s jaw muscles are anchored beside their ears). This ridge runs lengthwise down the middle of the top of the skull.
Stratigraphic layer: A stratigraphic layer is a geological layer of rock and/or soil. The law of superposition says that if you were to dig a hole, the layers of earth at the bottom of the hole would be older than the layers of earth at the top. By recognizing these stratigraphic layers, scientists can date fossil or archaeological finds, or other features, and compare their ages to one another.
Zygomatic arch: The zygomatic arch is the bone forming your cheek that rests above the indention you feel in front of your ear, which allows the passage of your chewing muscles through from your jaw to where they connect to your skull. Robust species had larger, or flaring, zygomatic arches, allowing space for more powerful chewing muscles.
Contemporaneous: ‘Contemporaneous’ means occurring or happening at the same time. In paleoanthropology this term is often used to describe two or more early human species living during the same period as one another.
Diastema: A diastema is space between two teeth. In paleoanthropology, scientists look at the space between the lower canine teeth and first premolars where the upper canine fits as a common characteristic of apes, who have larger canines than humans.
Megadont: Megadont ('megadont' meaning 'having large teeth') species have huge, broad cheek teeth with thick enamel while their incisor teeth stay small. The emphasis for megadont species is on the rear teeth, which are designed to support the stresses of heavy chewing. Combined with the morphology of the other parts of the skull -- large zygomatic arches to allow the passage of large chewing muscles and a large sagittal crest to provide a large area to anchor these muscles to the skull -- megadont early humans showed adaptations to chewing tough, fibrous foods.
Sexually dimorphic: Sexual dimorphism is size or shape difference between males and females of the same species; a species is said to be sexually dimorphic if these differences exist. Similarly-sized males and females within a species show less sexual dimorphism, and this phenomenon is generally attributed to monogamous bonding between males and females (like in many modern humans). Greater sexual dimorphism generally means a species is more polygamous.
Type specimen: In paleontological studies, a species' type specimen is a specific fossil for which the species was first named.
Hominin: Refers to the human evolutionary group of species, including fossil and modern. This word comes from Hominini, a formal biological term in between the level of genus (e.g., Homo, Australopithecus, etc.) and the level of family (Hominidae).
Hominid: Refers to the evolutionary group of great apes, including living Asian great apes (orangutans), living African great apes (chimpanzees, bonobos, and gorillas), and humans. This word comes from Hominidae, a formal biological term that is more specific than Hominoidea (= all apes – the great apes and the lesser apes, which include gibbons and siamangs). Some researchers still use the word hominid to refer to the human evolutionary group alone (what we call hominin). This usage goes back to the tradition when humans (hominids) were considered completely divided from all great apes (pongids).
Primates: The biological order of mammals consisting of lemurs, lorises, galagos, tarsiers, monkeys, and apes (including humans).
Fossil: A preserved trace of a once-living organism. A fossilized bone occurs when the living (organic) cells and tissue have become replaced with external minerals while buried in the ground. Virtually all early human fossils are bones in which this process of mineral replacement has taken place. However, footprints can also be considered ‘fossils’, and archeological remains (such as stone tools, the remains of hearths, and butchery marks on animal bones) are sometimes called ‘fossilized behavior’.
Post-cranial: A bone or bone(s) from any part(s) of the skeleton that does not include the skull (cranium and mandible).
Cranial: Refers to a bone of the cranium, which is part of the skull (but does not include the mandible).
Cranium: Part of the skull (along with the mandible).
Prognathic: A fossil skull is called prognathic when the lower face, and sometimes jaw, protrudes forward.
Sagittal keel: A thickening (or widening) of bone running along the middle of the top of the skull.
Adaptation: An adaptation is a feature produced by natural selection for its current function.
Australopith: Member of a species in the genus Australopithecus
Bipedal: Habitually walking upright on two legs
Brow ridge: Bony ridge above the eye sockets
Calcareous: Composed of calcium carbonate
Cerebral cortex: Outermost layer of the cerebrum, typically consisting of "grey matter"
Cerebrum: Largest part of the brain, including the frontal, occipital, temporal, and parietal lobes
Chromosome: Organized package of DNA and proteins found in a cell nucleus
Cytoplasm: Thick, jelly-like substance that fills a cell
Domestication: Human-induced artificial selection, taming, or breeding of plants or animals
Environmental variability hypothesis
Environmental variability hypothesis: The hypothesis that adaptation to a variable environment, rather than a static environment or directional change, has characterized human evolution
Evolution: Descent with modification
Flake: A sharp piece of stone intentionally removed from a core
Core: In stone tool terminology, a source stone reduced in size by the intentional removal of flakes
Foraminifera: Single-celled microorganisms with calcareous shells
Frontal lobe: Most forward part of the cerebrum
Gene: The unit of heredity; a region of DNA with a particular observable effect
Genera: Plural of genus, the rank above species in Linnean classification
Genome: All the genetic information in an organism
Greenhouse gases: Atmospheric gases that trap heat, warming the earth's surface
Hammerstone: Cobble used to strike flakes from a stone core
Hypothesis: A proposed, testable scientific explanation for a particular set of phenomena
Lithic: Consisting of stone or rock
Lumbar: Relating to the lower back and its vertebrae
Mandible: Lower jaw
Metabolism: Chemical reactions necessary to maintain life
Microcephaly: Neurodevelopmental disorder resulting in an abnormally small head and brain
Mitochondria: Parts of a cell that generate most of its chemical energy
Molecular: Having to do with DNA sequences or the amino acid sequences of proteins
Mutation: Change in a DNA sequence
Natural selection: Differential survival or reproduction in a population leading to change in its genetic makeup
Neocortex: Outer layer of the cerebral hemispheres of the brain
Neolithic: Last part of the Stone Age, before the origin of metal tools
Neural: Relating to a nerve or the nervous system
Nucleus: Part of a cell containing genetic material
Miocene: Geologic time period ranging from about 23 million to 5.3 million years ago
Pliocene: Geologic time period ranging from about 5.3 million to 1.8 million years ago - or, for some researchers, 2.6 million years ago
Pleistocene: Geological time period ranging from about 1.8 million years ago - or, for some researchers, 2.6 million years ago - to about 10,000 years ago
Species: (singular and plural) All members of a population or set of populations that actually or potentially interbreed over time