Glossary

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Ma
acronym for "million years ago."
macroevolution
change over long periods of evolutionary time.
magnetic field
a force surrounding a polarized object (i.e., a magnet) whose axis of rotation is aligned with the earth's magnetic field.
magnetic reversals
irregular reversals of the earth's magnetic field; observed in the geologic record.
mandible
the lower jaw.
mandibular symphasis
the joint located at the center of the jaw that connects the two halves of the mandible that may or may not be fused.
mastication

chewing food.

maturation

the attainment of the final stages of tissue or organ differentiation; marked in primates by attainment of puberty, full dental eruption, and epiphyseal union of the skeletal elements.

medial
a relative term used to describe features that are closer to the midline or center of the body; the opposite of lateral.
megadont

very large teeth, relatively to the size of the mouth.

melanin
pigmentation in the skin that is a component of color in plants and animals.
member
a stratagraphic unit within a larger geologic formation.
mental
associated with the chin.
Mesolithic
see Middle Paleolithic.
Mesozoic

[Greek: "middle life"] a geological era that approximately dates from 245 million years ago to 65 million years ago; contains the geologic periods Cretaceous, Jurassic and Triassic.

metacone
the distal cusp located on the buccal side of the upper molar.
metaconid
the distal cusp located on the lingual side of the lower molar.
metaphysis
cartilage located between the diaphysis and the epiphysis that expands and eventually ossifies into bone; location of the growth plate.
metopic suture
a place of articulation in the frontal bone of the cranium that divides the bone in half. Fusion of the frontal bones begins about the second year of age in humans.
microevolution
changes over short periods of evolutionary time within a species or lineage.
microfossil
a fossilized skeleton of a tiny or unicellular organism.
microlith
a technology common in the late Pleistocene and early Holocene consisting of small (>3 cm), often geometric, pieces of knapped stone; often produced from small blades. Several microliths may be used to form a composite tool, such as barbs for an arrow or spear.
microwear
very small wear from teeth, tools, or organic material on a tool that is only large enough to be seen with a microscope.
midden
an accumulation of trash or excess deposits made by human activity; could be animal and/or food remains, and/or discarded artifacts.
Middle Paleolithic

[syn. Middle Stone Age or Middle Paleolithic] the time period of tool manufacture approximately dated between 250,000 and 40,000 years; tool associated with this time period include those of the Mousterian tool technology used by Homo neanderthalenis that deal with hunting, gathering and agricultural activities.

Middle Stone Age

see Middle Paleolithic.

migration
the movement of an organism or group of organisms from one location to another with the intention of relocating to that new area for an extended period of time.
minimum number of individuals

the minimum number of individuals (MNI) that would have had to have died in order to make up the assemblage. MNI is calculated by dividing the number of time each element occurs in an assemblage by the number of times it occurs in the skeleton of a single living individual. The MNI is the highest of the resulting numbers.

Miocene

an epoch in the Cenozoic era on the geologic time that approximately dates from 23 million years ago to 5.3 million years ago; marked by the evolution of apes.

Mississippian
a period in the Paleozoic era on the geologic time scale that approximately dates from 360 million years ago to 325 million years ago; marked by an abundance of planktonic protozoa, brachiopods and corals. The Mississippian is commonly referred to as the Carboniferous period outside of the United States.
mitochondrial DNA

deoxyribonucleic acid found within mitochondria.

MNI

see minimum number of individuals.

molecular clock
a hypothetical estimate of time used to date the existence of a common ancestor for two or more organisms; based on molecular differences that accumulate at a constant rate, allowing for statistical estimates.
monkey
a primate that possess a tail, exhibits quadrupedal locomotion, and is arboreal at least part of the time; found in either the Old or New World; members of the Callitrichidae, Cebidae, and Cercopithecidae families. In taxonomic classifications, monkeys are graded lower than hominins, but higher than prosimians.
monogamy
a mating relationship involving only one male and one female.
monophyletic group

in cladistics, a clade (i.e., group) that consists of a single common ancestor and all its descendants. Holophyletic is often preferred to its synonym monophyletic.

morphology
the form and structure of a feature.
Mousterian

a tool industry that approximately dates from 250,000 years ago to 40,000 years ago; associated with Homo neanderthalensis and possibly early Homo sapiens; characterized by blades and burins prepared using the Levallois prepared-core technique. The tool kit also contained side scrapers and spear points.

mRNA
the abbreviation for messenger RNA.
mtDNA

see mitochondrial DNA.

Multiregional Hypothesis
a hypothesis that states anatomically modern humans evolved as a single species from archaic forms that were already living in Africa, Asia and Europe. The Multiregional Hypothesis suggests a significant amount of gene flow between modern Homo sapiens and the ancestral hominin form.
muscle
fibrous tissue in the body that contracts, which pulls on an attached structure creating movement.
mutation

a change in the genetic code as a result of an error during DNA reproduction.

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