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the action of moving a skeletal element away from the midline of the body; opposite of adduction.

an original inhabitant of an area.
absolute date
the exact date of an artifact or site based on the calendar. Absolute dates can be determined by radiocarbon dating (14C or Carbon-14), Potassium-Argon (K-Ar), or Argon-Argon (Ar-Ar) dating; contrasts with relative dating.
the socket of the hip joint; an articular surface that encompasses the head of the femur.

a Lower Paleolithic tool culture first associated with Homo ergaster and Homo erectus; characterized by bifacially-flaked hand axes dating from around 1.5 million years ago to 150,000 years ago.


the process of adjusting to a particular environment or niche; a morphological or behavioral feature of an organism that evolved through natural selection to play a role or fulfill a particular function.

adaptive radiation
the rapid divergence and spread of a group of organisms into available ecological niches, followed by a slower period of adaptations to their new environment, commonly resulting in a speciation event; similar to punctuated equilibrium, but on a larger scale.

the action of moving a skeletal element toward the midline of the body.

considered to be between the ages of 12-24 years; the period of growth between puberty and complete fusion of the epiphysis of the long bones.
sediments deposited by the wind.
the intentional cultivation of land and the production of plants and animals

a unit of hereditary information; an alternate form of a gene that sits at the same position on a chromosome.

the study of the relationship between the growth of an organism's specific part(s) in relation to its entire body.
allopatric speciation
the evolution of a daughter species from a parent species as a result of some barrier to gene flow between the new population and the ancestral population; requires complete reproductive isolation.
amino acid
chains of molecules that make up proteins. In total, there are 20 amino acids.
anagenetic speciation
when change is found solely within a lineage, and as changes accumulate over time, successive population differ more and more from the "original" population. Eventually the two separate populations differ enough to be recognized as separate species. In this case, speciation results from microevolutionary changes.
[adj. analogous] characteristics of organisms that are similar and share the same function(s), but are not the result of common ancestry.
anatomic position
a position generally accepted as the natural stance for an organism. In bipedal hominins, the anatomic position is an upright, erect posture with the arms at the sides and the palms of the hands facing forward; in quadrupedal primates, the anatomical position is an upright, bent posture with all four limbs outstretched and palms flat on the ground.
the study of the structure of the body and the relationship to its parts.
angular unconformity
a break in the geologic record; a distinct line that separates a layer of sedimentary rock deposited over an earlier layer of tilted or folded sedimentary rock.
the time period before death.
a relative term used for bipedal hominins (those that travel on two legs) to describe features that are closer to the belly or front of the body; opposite of posterior. The term ventral is a synonym commonly used when referring to quadrupedal anatomy.
[Greek: "human-like shape"] in taxonomic classification, any member of the suborder Anthropoidea, including monkeys, apes, and humans, but excluding tarsiers and lemurs.

the scientific study of humans, human culture, and the evolution of humans; subfields include archeology, cultural anthropology, linguistic anthropology, and physical anthropology.

a large, stationary surface (such as a rock) that a core is struck against in order to remove a flake.

under the superfamily Hominoidea, this includes gibbons and siamangs in the family Hylobatidae and orangutans, gorillas, bonobos, and chimpanzees in the family Pongidae. Characteristics of apes include a larger body size, no tail, more complex behavior and cognitive abilities, and an increase period of infant development.


[syn. derived trait] a new or specialized trait. The presence of nails instead of claws is an apomorphy of primates that sets them apart from other mammals.


refers to activity in trees; tree living

arboreal quadrupedalism

a mode of locomotion in which the animal moves along horizontal branches with a regular gait pattern involving all four limbs.

arboreal theory of primate evolution
the idea that primates evolved adaptations for living in trees.

the investigation of culture through the study of remains left by humans.

ancient; old.
Archaic Homo sapiens

[see also Homo heidelbergensis] refers to ancient fossilized humans with features exhibited by both modern H. sapiens and Homo erectus. Archaic H. sapiens fossils date between 600,000 and 30,000 years. There is disagreement over whether Archaic H. sapiens is a separate species (i.e., H. heidelbergensis).

an era on the geologic time scale that approximately dates from 4.6 billion years ago to 2.5 billion years ago. The oldest fossils found on earth (i.e., procaryotes) date back to the Archean era.
Ardipithecus kadabba
an extinct hominin species that existed in Africa approximately 5.8 to 5.2 million years ago; fossil remains found at Middle Awash and Gona, in Ethiopia, shows relatively thin dental enamel, possible canine-third premolar honing complex, and a humerus and manual phalanges typically of arboreality. Some scientists argue that Ardipithecus may represent the last common ancestor to chimpanzees and humans. The type specimen for Ard. Kadabba is ALA-VP 2/10, found at the Middle Awash site and approximately dates between 5.8 and 5.5 million years ago.
Ardipithecus ramidus

an extinct African hominin species, possibly ancestral to humans, that existed approximately 4.4 million years ago in Ethiopia; very few post-cranial fossil remains have been found, but dental characteristics from a known Ardipithecus ramidus specimen indicate relatively thin enamel, primitive first molars (i.e., similar to chimpanzees) and a more derived third molar (i.e., more elongated and large relative to the other molars). The forward placement of the foramen magnum hints at possible bipedal positioning. Some scientists argue that Ardipithecus may represent the last common ancestor to chimpanzees and humans. The type specimen for Ard. ramidus is ARV-VP 6/1, found at the Middle Awash site and dates to approximately 4.4 million years ago.

arrested evolution
when there is little change in morphology or genetics over a long period of time. In some cases, organisms exhibiting arrested evolution are referred to as "living fossils."
the point where two or more bones are joined together. Some articulations are movable joints like the elbow or knee, while some are unmovable like the sutures between cranial bones.
an object modified and/or used by hominins.
artificial selection
the process of selecting and breeding only those plants and animal with desired inherited features for the purpose of producing organisms with more of those desirable features. An example of artificial selection is the breeding of two parent horses known to run fast in the hopes of producing offspring that will win races.

a set of artifacts or bones found in association with each other in an archaeological setting; an accumulation of bones or artifacts.

the wearing away of a surface through grinding or friction; the gradual reduction in number or strength resulting from stress.
auditory meatus
opening in the temporal bone that is commonly referred to as the ear canal.

a form of extinct hominins ancestral to human that existed between approximately 4.2 million years ago to 1.8 million years ago; fossil australopiths show evidence of bipedalism, but generally retain relatively small brains and stature. The genus Australopithecus includes, but is not limited to, the species Au. anamensis, Au. afarensis, Au. bahrelghazali, Au. africanus, Au. garhi, and Au. sediba.

Australopithecus afarensis

an extinct African hominin species, possibly ancestral to humans, that existed approximately 4 million years ago to 3.8 million years ago; fossil remains found in East and Northeast Africa indicate that an adult Australopithecus afarensis had an absolute brain size approximately 415 cubic centimeters; with a forward projecting face similar to a chimpanzee, thick enamel on the teeth, and large incisors; the species exhibited sexual dimorphism in body size and in the teeth. Au. afarensis appears to be a bipedal hominin but retained the primitive upper body morphology similar to arboreal primates (i.e., relatively longer arms than legs and curved manual phalanges). The type specimen for Au. afarensis is LH 4, found at Laetoli in Tanzania and dates to approximately 3.7 to 3.4 million years ago. The most famous Au. afarensis fossil is AL288-1, "Lucy", found at Hadar in Ethiopia and dates to 3.2 million years ago.

Australopithecus africanus

an extinct south African hominin species, possibly ancestral to humans, that existed approximately 3 million years ago to 2 million years ago; fossil remains found in South Africa (e.g., Sterkfontein, Makapansgat, and Taung) indicate Australopithecus africanus was similar to Australopithecus afarensis in its post-crania, with an absolute adult brain size of approximately 440 cubic centimeters, somewhat molarized premolars and an forward placement of the foramen magnum; exhibits high sexual dimorphism. The type specimen for Au. africanus is the Taung Child found at the Taung site.

Australopithecus anamensis

an extinct African hominin species, possibly ancestral to humans, that existed approximately 4.2 to 3.9 million years ago; fossil remains found near Alia Bay, Kanapoi, Kenya, include cranial and dental remains, a humerus and a tibia; based on these remains, Australopithecus anamensis appears to have been bipedal but with arms more like those seen in arboreal primates; the dentition is both primitive, with very large canines, and derived, with very thick enamel and large broad molars. The type specimen for Au. anamensis is KP 29281, found at Kanapoi and dates to approximately 4 million years ago.

Australopithecus bahrelghazali

an extinct African hominin species, possibly ancestral to humans, that existed approximately 3.4 million years ago to 3 million years ago; fossil remains have been found in Chad, and consists of a partial mandible and maxilla, including three-rooted mandibular premolar, relatively thinner tooth enamel, and a more vertical lower face. In other ways, Australopithecus bahrelghazali is similar to Australopithecus afarensis. The type specimen for Au. bahrelghazali is KT 12/H1, or "Abel", found at Bahr el Ghazal in Chad, and approximately dates between 3.4 and 3 million years ago.

Australopithecus garhi

an extinct African hominin species that existed approximately 2.5 million years ago; fossil remains found in Bouri, Ethiopia, indicate Australopithecus garhi molars were large and more like Paranthropus than Australopithecus; post-cranial fragments offer a modern-like humerofermoral ratio and a Pongo-like brachial index; associated fauna found at the site show evidence of butcher marks suggesting Au. garhi may have used stone tools. The type specimen for Au. garhi is BOU-VP-12/130, found at the Middle Awash site in Ethiopia, and dates to approximately 2.5 million years ago.

[adj. autosomal] all chromosomes except for the sex chromosomes.
a sharp tool used to punch holes in leather or wood; typically made of stone, bone, or antler.