Archaeology & Evolution Glossary (O)


objective piece: The rock or artifact being modified by the removal of detached pieces. Objective pieces may be cores that are used solely as sources of raw material or they may be tools such as bifaces or flake tools.

obsidian: A volcanic rock formed into natural glass. This rock is usually black but may be found in greenish and reddish colors or banded.

obsidian hydration dating: This technique involves the absorption of water on exposed surfaces of obsidian; when the local hydration rate is known, the thickness of the hydration layer, if accurately measured, can be used to provide an absolute date.

obstetrical: Of or relating to childbirth.

obturator foramen: A space at the front of the pelvis enclosed by the pubis and ischium.

occiptal bone: The bone forming the vault posterior and much of the basicranium.

occipital bun: A backward extension of the cranial rear in the form of a protuberance bounded by the nuchal plane below, a shaft vertical face for the occiput behind, and a flat surface above (lambdoidal flattening). See also chignon.

occipital condyles: Raised, elongated-oval, convex articular eminences on either side of the foramen magnum of the occiptal bone, for the junction of the head and the uppermost neck vertebra occiptal lobes: Back part of the cerebral hemispheres of the brain.

occipital plane (upper scale): The portion of the occiput above the superior nuchal line, and for the most part above the nuchal muscles.

occipitomastoid: A process, usually in the form of a crest, paralleling or straddling the occipitomastoid suture and separated from the most lateral paramastoid process, if there is one, by an occipital grove. See juxtamastoid eminence.

occlusal: The surfaces of the opposing teeth that meet for chewing; in an occlusal view the crowns of the teeth are shown.

occlusal force: The force produced between the teeth during chewing.

occlusion: The positions of the teeth when the jaws are closed and their biting surfaces touch.

oestrus: See estrus.

Okazaki fragments: The relatively short, single-stranded DNA fragments in discontinuous DNA replication that are synthesized during DNA replication and that are subsequently covalently joined to make a continuous strand.

Olduwan industry: One of the earliest toolkits, comprising flake and pebble tools, used by hominids in the Olduvai Gorge, East Africa.

Old World primate: Any primate from Africa or Eurasia.

olecranon fossa: A depression at the posterior side of the distal humerus, at the elbow, for the accommodating the olecranon process of the ulna when the elbow is extended.

olecranon process: A beak-like projection on the proximal end of the ulna, at the elbow, for articulation with the humerus and attachment of the triceps muscles.

olfaction: The sense of smell.

oligomers: Short DNA molecules.

oligopithecine: Member of the family Oligopithecinae.

omnivore: An organism that eats a diversity of food types, including animals and plants.

oncogene: A gene whose action promotes cell proliferation. Oncogenes are altered forms of proto-oncogenes.

oncogenesis: Tumor (cancer) initiation in an organism.

one gene-one enzyme hypothesis: The hypothesis, based on Beadle and Tatum’s studies in biochemical genetics, that each gene controls the synthesis of one enzyme.

one gene-one polypeptide hypothesis: Updated version of the one gene-one enzyme hypothesis, which states that each gene controls the synthesis of a polypeptide chain.

ontogeny: The developmental history of an individual from egg to adult.

oogenesis: The development in the gonad of the female germ cell (egg cell) of animals.

opal: An amorphous form of quartz unstable at temperatures and pressures found on the surface of the earth.

open-area excavation: The opening up of large horizontal areas for excavation, used especially where single period deposits lie close to the surface.

open reading frame: In a segment of DNA, a potential protein-coding-sequence identified by an initiator codon in frame with a chain-terminating codon.

operational sequence: The stages of artifact production, reflecting the technological decisions of the toolmakers that are assumed to be technical traditions (they are unlikely to be genetically encoded). The operational sequence is divided into three stages: raw material procurement, core reduction, and tool manufacture and use.

operator: The controlling site, that is adjacent to a promoter, that is responsible for controlling the transcription of genes that are contiguous to the promoter.

operon: A cluster of genes whose expressions are regulated together by operator-regulator protein interactions, plus the operator region itself and the promoter.

opisthion: The midline point of the posterior margin of the foramen magnum.

opisthocranion: The back of the school, located as far from the center of the brows as is possible to get on the midline.

opportunistic evolution: Species adapt to fill in all available niches.

opposability: The ability to touch the thumb tip to the fingertips of the same hand.

optical emission spectrometry (OES): A technique used in the analysis of artifact composition, based on the principle that electrons, when excited (i.e. heated to a high temperature), release light of a particular wavelength. The presence or absence of various elements is established by examining the appropriate spectral line of their characteristic wavelengths. Generally, this method gives an accuracy of only 25 percent and has been superseded by ICPS (inductively coupled plasma emission spectrometry).

oral: Pertaining to the mouth.

orbit: Bony socket for the eye.

orbital pillar: The outer bony rim found on orbits that face anteriorly, made up of the zygomatic process of the frontal and the frontal process of the zygomatic bone.

order: A monophyletic higher-level taxon (made up of suborders, superfamilies, etc.) whose members generally share a basic structural pattern.

ordered tetrads: A structure resulting from meiosis in which the fouor meiotic products are in an order reflecting exactly the orientation of the four chromatids at the metaphase plate in meiosis I.

origin: A specific site on a chromosome at which the double helix denatures into single strands and continues to unwind as the replication fork(s) migrates.

origin of replication: A specific DNA sequence that is required for the initiation of DNA replication in prokaryotes.

orthognathous: Having a relatively vertical, nonprotruding face (cf. prognathic).

orthoquartzite: A sandstone converted to quartzite with grains cemented only through infiltration and pressure. The cementing agent is usually quartz.

ossicle: Very small bone, such as the ear ossicles or the finger joint sesamoid bones.

ossification: The process of forming new bone.

osteo: Pertaining to bone.

Osteodontokeratic: Artifacts made of bone, tooth, or horn, as in the Osteodontokeratic “culture” of the Makapansgat australopithecines.

osteology: The study of bones and their variation.

outbreeding: Preferential mating between nonrelated individuals.

overdominance (heterozygote advantage): Condition in which the heterozygote has higher fitness than either of the homozygotes.

overshot termination: See plunging termination.

overspecialized: Adapted to a particular niche so specifically that the genetic variation necessary to meet changing conditions has been lost.

ovulation: Release of an unfertilized gamete (egg) from the ovary.

ovum: A mature egg cell. In the second meiotic division, the secondary oocyte produces two haploid cells; the large cell rapidly matures into the ovum.


Andrefsky, W., Jr. 1998. Lithics: Macroscopic Approaches to Analysis. Cambridge: Cambridge University Press.
Keesing, R.M. 1975. Kin Groups and Social Structure. Fort Worth: Harcourt Brace.
Renfrew, C., and P. Bahn. 1996. Archaeology: Theories, Methods, and Practice. New York: Thames and Hudson Inc.
Russell, P.J. 1998. Genetics. Menlo Park: Addison Wesley Longman, Inc.
Wolpoff, M. 1999. Paleoanthropology. second edition. Boston: McGraw-Hill.