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Glossary of Biological and Paleontological Terms
(Compiled by Charles J Vella, PhD: thanks to Wikipedia, Smithsonian, etc.)
Acquired trait: A phenotypic characteristic, acquired during growth and development,
that is not genetically based and therefore cannot be passed on to the next generation
(for example, the large muscles of a weightlifter).
Adaptation: An adaptation is a feature produced by natural selection for its current
function.
Adaptive radiation: The diversification, over evolutionary time, of a species or group of
species into several different species or subspecies that are typically adapted to
different ecological niches (for example, Darwin's finches).
Advanced (synonym: derived; opposite: primitive): In phylogenetic studies, an organism
or character further removed from an evolutionary divergence than a more primitive
one.
Allele: A known variation (version) of a particular gene
Allen's Rule: Within species of warm-blooded animals (birds + mammals) those
populations living in colder environments will tend to have shorter appendages than
populations in warmer areas.
Allometry: The relation between the size of an organism and the size of any of its
parts. For example, an allometric relation exists between brain size and body size, such
that (in this case) animals with bigger bodies tend to have bigger brains.
Allopatric speciation: Speciation following geographical isolation of subpopulations of
the species.
Analogous structures: Structures in different species that look alike or perform similar
functions (e.g., the wings of butterflies and the wings of birds) that have evolved
convergently but do not develop from similar groups of embryological tissues, and that
have not evolved from similar structures known to be shared by common ancestors.
Contrast with homologous structures.
Ancestral homology: Homology that evolved before the common ancestor of a set of
species, and which is present in other species outside that set of species. Compare with
derived homology.
Anthropoid: A member of the group of primates made up of monkeys, apes, and
humans.
Apomorphy: a characteristic that is different form the form of an ancestor, i.e., an
innovation, of use in determining membership in a clade. In other words, it is an
apomorphy shared by members of a monophyletic group, and thus assumed to be
present in their most recent common ancestor. A derived trait is an apomorphy, which
means a trait that has changed since the time of a common ancestor.
Artificial selection: The process by which humans breed animals and cultivate crops
to ensure that future generations have specific desirable characteristics. In artificial
selection, breeders select the most desirable variants in a plant or animal population
and selectively breed them with other desirable individuals
Australopithecus: The extinct genus of Plio-Pleistocene hominids found in South and
East Africa. The evolutionary link between apes and humans.
Australopithecine: A group of bipedal hominid species belonging to the genus
Australopithecus that lived between 4.2 and 1.4 mya.
Australopithecus afarensis: An early australopithecine species that was bipedal;
known fossils date between 3.6 and 2.9 mya (for example, Lucy).
Bergmann's Rule: Northern races of mammals and birds tend to be larger than
Southern races of the same species.
Biological species concept: The concept of species, according to which a species is a
set of organisms that can interbreed among each other. Compare with cladistic species
concept, ecological species concept, phenetic species concept, and recognition species
concept.
Bipedal: Habitually walking upright on two legs
Bottleneck: A drastic reduction in the population size followed by an expansion. This
often results in altered gene pool as a result of subsequent genetic drift.
Brow ridge: Bony ridge above the eye sockets
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.
Catarrhini: One of the two divisions (suborder) of Primates containing the old world
monkeys and apes (extinct and extant). The other division is Platyrrhini (new world
monkeys).
Clade: A clade (from Ancient Greek: κλάδος, klados, "branch") is a group of organisms
that consists of a common ancestor and all its lineal descendants, and represents a
single "branch" on the "tree of life". All descendants of any given species. A single
whole branch of a phylogeny. Synonym of monophyletic group.
Cladistics: Cladistics (from Greek κλάδος, klados, i.e., "branch") is an approach to
biological classification in which organisms are categorized based on shared derived
characteristics that can be traced to a group's most recent common ancestor and are
not present in more distant ancestors. Therefore, members of a group are assumed to
share a common history and are considered to be closely related. In terms of strict
cladistical analysis, the age of the fossils does not matter. Cladistics establishes
evolutionary relationships strictly by grouping organisms according to their sharedderived characteristics. In the case of paleontology, the characteristics are almost
always morphological, but in living organisms, the traits may be behavioral or genetic as
well.
Cladogram: A branching diagram that illustrates hypotheses about the evolutionary
relationships among groups of organisms. Cladograms can be considered as a special
type of phylogenetic tree that concentrates on the order in which different groups
branched off from their common ancestors. A cladogram branches like a family tree,
with the most closely related species on adjacent branches.
Co-evolution: Joint evolution of two unrelated species that have a close ecological
relationship resulting in reciprocal adaptations as happens between host and parasite,
and plant and insect.
Convergent evolution: independent evolution of similar features in species of different
lineages. Convergent evolution creates analogous structures that have similar form or
function but were not present in the last common ancestor of those groups. Same as
homoplasy. Evolution of two or more different lineages towards similar morphology due
to similar adaptive pressures. Examples of convergence are: fins or fin-like structures in
fish, cuttlefish and whales; extreme similarity in alarm calls by five small birds;
endothermy in dogs and ducks, wings of butterflies and birds.
Coprolite: The fossilized waste (dung; fecies) matter of animals.
Core: In stone tool terminology, a source stone reduced in size by the intentional
removal of flakes
Cranial: Refers to a bone of the cranium, which is part of the skull (but does not include
the mandible).
Creationism: The religious doctrine that all living things on Earth were created
separately, in more or less their present form, by a supernatural creator, as stated in the
Bible; the precise beliefs of different creationist groups vary widely.
Darwinian evolution: Evolution by the process of natural selection acting on random
variation.
Darwinism: Darwin's theory that species originated by evolution from other species and
that evolution is mainly driven by natural selection. Differs from neo-Darwinism mainly in
that Darwin did not know about Mendelian inheritance.
Dental microwear: Dental microwear is the study of the microscopic wear on a tooth's
surface that occurred as a direct result of use (chewing). Dental microwear studies look
for tooth scratches and pits that occur on teeth predominantly through chewing, and can
provide evidence of what an individual ate in the past.
Derived: A derived character is a character that is derived from an ancestral character
over evolutionary history; a newer characteristic; in phylogenetics, a derived character
of a clade that has been inherited from a common ancestor and distinguishes the clade
from other potentially related organisms is called a "synapomorphy," a shared ("syn")
character that sets the clade apart ("apo")
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.
Divergent evolution: A kind of evolutionary change that results in increasing
morphological difference between initially more similar lineages.
Ecological species concept: A concept of species, according to which a species is a
set of organisms adapted to a particular, discrete set of resources (or "niche") in the
environment.
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.
Environmental variability hypothesis: The hypothesis that adaptation to a variable
environment, rather than a static environment or directional change, has characterized
human evolution
Epigenetics: The study of heritable changes in gene expression that occur without a
change in DNA sequence.
Evolution: Descent with modification. The process that results in heritable changes in a
population spread over many generations (change in allele frequencies over time).
Biological evolution refers to populations and not to individuals and that the changes
must be passed on to the next generations. Genes mutate, individuals are selected, and
populations evolve.
Evolutionary Developmental Biology (Evo-Devo): The branch of evolutionary biology
studying the relationships between changes in developmental pathways due to
mutations in regulatory parts of genes and evolutionary changes (macroevolution). The
emphasis is on the changes in expression patterns of the genes involved in
developmental pathways rather than structural changes in genes.
Extinction: The disappearance of a species or a population.
Fauna: animals that are characteristic of a certain age, locality, or formation.
Fitness: Lifetime reproductive success of an individual (i.e., the total number of
offspring who themselves survive to reproduce). It can be seen as the extent to which
an individual successfully passes on its genes to the next generation. It has two
components: survival (viability) and reproductive success (fecundity). Variation in fitness
is the major driving force in biological evolution. The success of an individual (or allele
or genotype in a population) in surviving and reproducing, measured by that individual's
(or allele's or genotype's) genetic contribution to the next generation and subsequent
generations.
Flake: A sharp piece of stone intentionally removed from a core
Flora: Plant life; often used to distinguish from animal life ("fauna").
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.
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. Footsteps can be fossilized.
Fossil record: the history of life on Earth through geological time, as preserved through
fossil remains in sedimentary rock (sometimes referred to poetically in older books as
the record of the rocks). Also the fossil history of any particular group.
Fossilization: All the processes that involve the burial of a plant or animal in sediment
and the eventual preservation of all, part, or a trace of it
Founder effect (Sewall Wright effect): A type of genetic drift in which allele frequencies
are altered in a small population, which is a nonrandom sample of a larger (main)
population.
Gene flow: The movement of genes within a population or between two populations
following genetic admixture. Gene flow creates new combinations of genes or alleles in
individuals that can be tested against the environment. This way it is one of the sources
of variation in the process of natural selection.
Genetic drift: Evolutionary change over generations due to random events in small
populations (not to be mixed with sampling error due to a small sample size). It operates
unless overcome by strong selective forces. Changes in the frequencies of alleles in a
population that occur by chance, rather than because of natural selection.
Genetic fitness: Classic genetic fitness is the average direct reproductive success of
an individual possessing a specific genotype in comparison to others in the population.
Inclusive fitness is described as the classic fitness plus the probability that an
individual's genotype may be passed on through relatives.
Genotype: The set of two genes possessed by an individual at a given locus. More
generally, the genetic profile of an individual.
Genus: is a taxonomic rank used in the biological classification of living and fossil
organisms in biology. In the hierarchy of biological classification, genus comes above
species and below family. In binomial nomenclature, the genus name forms the first part
of the binomial species name for each species within the genus. i.e. Homo sapiens –
sapiens is a genus in the species Homo
Geological timescale: The period between the origin of earth (4,500 Mya) and the
beginning of the Cambrian period (540 Mya) is called the Precambrian Eon. The last
540 million years (Phanerozoic Eon) are divided into three eras: Palaeozoic (540-245
Mya); Mesozoic (245-65 Mya); Cainozoic. The geological periods (included in an era,
longer than an epoch) are as follows: Vendian (immediately before the Cambrian; 610540 Mya); Cambrian (540-510 Mya); Ordovician; Silurian; Devonian; Carboniferous;
Permian; Triassic / Jurassic / Cretaceous (altogether the Mesozoic Era); Tertiary (651.64 Mya) and Quaternary. An epoch is a subdivision of a period
Glaciation: The formation of large sheets of ice across land. Glaciation of the
continents marks the beginning of ice ages, when the makeup of Earth and organisms
on it changes dramatically.
Great Apes: Chimpanzees (including bonobos), gorillas, and orangutans.
Hammerstone: Cobble used to strike flakes from a stone core
Holocene: An epoch of the Quaternary period, spanning the time from the end of the
Pleistocene (10,000 years ago) to the present. The most recent period of geologic
history, which extends from 10,000 years ago to the present.
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.
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).
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).
Homologous structures: The structures shared by a set of related species because
they have been inherited, with or without modification, from their common ancestor. For
example, the bones that support a bat's wing are similar to those of a human arm.
Homology: A similarity due to inheritance from a common ancestor.A character shared
by a set of species and present in their common ancestor. Compare with analogy.
Homo erectus: A species of hominid that lived between 1.8 mya and 300,000 years
ago; the first Homo species to migrate beyond Africa.
Homo habilis: A species of hominid that lived between 1.9 and 1.8 mya, the first
species in genus Homo, and the first hominid associated with clear evidence of tool
manufacture and use.
Homo neanderthalensis: A species of hominid that lived between 150,000 and 30,000
years ago in Europe and Western Asia, originally thought to be a geographic variant of
Homo sapiens but now generally accepted to be a distinct species.
Homo sapiens: Modern humans, which evolved to their present form about 100,000
years ago.
Homoplasy: a character state that is shared by two or more taxa due to some cause
other than common ancestry. The two main types of homoplasy are convergence
(evolution of the "same" character in at least two distinct lineages) and reversion (the
return to an ancestral character state)
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.
Hypothesis: A proposed, testable scientific explanation for a particular set of
phenomena
Inheritance of acquired characters: Historically influential but factually erroneous
theory that an individual inherits characters that its parents acquired during their
lifetimes. Lamarckian inheritance.
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.
Intelligent design: The non-scientific argument that complex biological structures have
been designed by an unidentified supernatural or extraterrestrial intelligence.
Land bridge: A connection between two land masses, especially continents (e.g., the
Bering land bridge linking Alaska and Siberia across the Bering Strait) that allows
migration of plants and animals from one land mass to the other.
Linnaean classification: A hierarchical method of naming classificatory groups,
invented by the 18th-century Swedish naturalist Carl von Linné, or Linnaeus. Each
individual is assigned to a species, genus, family, order, class, phylum, and kingdom,
and some intermediate classificatory levels. Species are referred to by a Linnaean
binomial of its genus and species, such as Homo sapiens.
Lithic: Consisting of stone or rock
Lyell's notion of gradual change: Also called uniformitarianism, Lyell's notion was that
Earth has been shaped by the same forces and processes that operate today, acting
continuously over very long periods of time. For example, the ongoing erosion caused
by flowing water in a river could, given enough time, carve out the Grand Canyon.
Macroevolution: Evolution that occurs at the higher levels of taxa (genera, families
etc). A vague term generally used to refer to evolution on a grand scale, or over long
periods of time. There is no precise scientific definition for this term, but it is often used
to refer to the emergence or modification of taxa at or above the genus level. The origin
or adaptive radiation of a higher taxon, such as vertebrates, could be called a
macroevolutionary event.
Mandible: Lower jaw
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.
Meme: The word coined by Richard Dawkins for a unit of culture, such as an idea, skill,
story, or custom, passed from one person to another by imitation or teaching. Some
theorists argue that memes are the cultural equivalent of genes, and reproduce, mutate,
are selected, and evolve in a similar way.
Mendelian inheritance: The mode of inheritance of all diploid species, and therefore of
nearly all multicellular organisms. Inheritance is controlled by genes, which are passed
on to the offspring in the same form as they were inherited from the previous
generation. At each locus an individual has two genes -- one inherited from its father
and the other from its mother. The two genes are represented in equal proportions in its
gametes
Microevolution: Evolution of species over relatively short times like several
generations. Evolutionary changes on the small scale, such as changes in gene
frequencies within a population.
Miocene: Geologic time period ranging from about 23 million to 5.3 million years ago
Missing link: An absent member needed to complete an evolutionary lineage. Use
transitional form instead
Modern synthesis: The synthesis of natural selection and Mendelian inheritance. Also
called neo-Darwinism.
Molecular (Protein) clock hypothesis: The idea that amino acid replacements occur
at a constant rate in a given protein family (ribosomal proteins, cytochromes, etc) and
the degree of divergence between two species can be used to estimate the time
elapsed since their divergence. The theory that molecules evolve at an approximately
constant rate. The difference between the form of a molecule in two species is then
proportional to the time since the species diverged from a common ancestor, and
molecules become of great value in the inference of phylogeny.
Monophyletic: In cladistics, a monophyletic group is a taxon (group of organisms)
which forms a clade, meaning that it consists of an ancestral species and all its
descendants. Monophyletic groups are typically characterized by shared derived
characteristics (synapomorphies). A monophyletic taxon is also called a clade
Morphology: study of form, shape and structure of animals and plants and their fossil
remains.
Most recent common ancestor: (MRCA, also last common ancestor LCA, or
concestor) of any set of organisms is the most recent individual from which all
organisms in a group are directly descended
Mutation: Any heritable change (not only point mutation) brought about by an alteration
in the genetic material. Includes gene conversion, deletion, duplication, insertion and so
forth. A change in genetic material that results from an error in replication of DNA.
Mutations can be beneficial, harmful, or neutral.
Mya: Million years ago. Also Ma.
Natural selection: Natural selection is the differential survival and reproduction of
individuals due to differences in phenotype. Darwin's definition, 1859: "As many more
individuals of each species are born than can possibly survive; and as, consequently,
there is a frequent recurrent struggle for existence, it follows that any being, if it varies
however slightly in any manner profitable to itself, under the complex and sometimes
varying conditions of life, will have a better chance of surviving, and thus be naturally
selected." The differential survival and reproduction of classes of organisms that differ
from one another in on or more usually heritable characteristics. Through this process,
the forms of organisms in a population that are best adapted to their local environment
increase in frequency relative to less well-adapted forms over a number of generations.
This difference in survival and reproduction is not due to chance.
Neo-Darwinism: (1) Darwin's theory of natural selection plus Mendelian inheritance. (2)
The larger body of evolutionary thought that was inspired by the unification of natural
selection and Mendelism. A synonym of the modern synthesis.
Neolithic: Last part of the Stone Age, before the origin of metal tools
Neoteny: Retention of juvenile features in sexually mature adult animals. Neoteny
frequently correlates with recent evolution of the species (like Homo sapiens).
Niche: The ecological role of a species; the set of resources it consumes and habitats it
occupies.
Orthogenesis: The erroneous idea that species tend to evolve in a fixed direction
because of some inherent force driving them to do so.
Paleoanthropology: the study of fossil hominids, especially human ancestors.
Paleocene: Earliest epoch of the Tertiary period, spanning the time between 65 and
55.5 million years ago.
Paleomagnetism: Study of the Earth's past magnetism as it is recorded in the rocks.
Paleontology: The study of fossils.
Parallel evolution: Evolution of roughly similar changes in two or more closely related
lineages.
Parapatric speciation: Speciation that occurs as a result of two populations diverging
in adjacent geographical areas.
Peripheral isolate speciation: A form of allopatric speciation in which the new species
is formed from a small population isolated at the edge of the ancestral population's
geographic range. Also called peripatric speciation.
Phenotype: composite of an organism's observable characteristics or traits. The
physical or functional characteristics of an organism, produced by the interaction of
genotype and environment during growth and development.
Phyletic gradualism: A model of evolutionary mode characterized by slow and gradual
modifications of biological structures leading to speciation. This is the opposite of
punctuated equilibrium
Phylogeny: the study of ancestral relations among species; (also known as a
phylogenetic tree) – a diagrammatic hypothesis about the history of the evolutionary
relationships of a group of organisms
Platyrrhini: New world monkeys found in South America with widely spaced nostrils.
They last had a common ancestor with the old world monkeys (Catarrhini) about 55
million years ago.
Plesiomorphy: the ancestral trait state, usually in reference to a derived trait state. The
scientific term for an ancestral trait is called a plesiomorphy, which means it is a
character that has been inherited from a common ancestor and has remained
unchanged. A plesiomorphy for the genus Homo is an opposable thumb. All members
of Homo have one, as do all other hominins and primates, suggesting that the groups
inherited this trait from a common ancestor. Whether a trait is ancestral or derived
changes depending on the groups you are comparing. A small canine tooth is a
synapomorphy for hominins, but it'd be considered a plesiomorphy for the genus Homo
when compared to other hominin groups.
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
Pliocene: Final epoch of the Tertiary period, spanning the time between 5.3 and 1.8
million years ago
Polyphyletic: (Greek for "of many races") group is characterized by one or more
homoplasies: phenotypes which have converged or reverted so as to appear to be the
same but which have not been inherited from common ancestor. A set of species
descended from more than one common ancestor. The ultimate common ancestor of all
species in the group is not a member of the polyphyletic group, usually because the
common ancestor lacks the characteristics of the group.
Population: A group of organisms, usually a group of sexual organisms that interbreed
and share a gene pool.
Post-cranial: A bone or bone(s) from any part(s) of the skeleton that does not include
the skull (cranium and mandible).
Primates: One of the Mammalian Orders which includes Lemurs (suborder Prosimii),
old world and new world Monkeys, Apes and Humans. The suborder Anthropoidea
covers all Primates except Prosimii. Prosimians and Anthropoids diverged from each
other 65 Mya; Apes and Old World Monkeys 35 Mya. The separation of the two groups
of Anthropoids (Platyrrhini and Catarrhini) occurred about 55 Mya.
Prognathic: A fossil skull is called prognathic when the lower face, and sometimes jaw,
protrudes forward.
Punctuated equilibrium: Put forward by Niles Eldredge and Stephen Jay Gould in
1972 as a counter theory to Darwin's gradualism in speciation (see phyletic
gradualism). It suggests that new species may have arisen rapidly over a few thousand
years and then remained unchanged (stasis) for many millions of years. Punctuated
equilibrium postulates that change occurred in only a small part of the population (rather
than the whole population is evolving gradually). The most plausible explanation for a
sudden and drastic change would be mutations in regulatory sequences that affect a
whole operon (see Gould SJ & N Eldredge. Punctuated equilibria: the tempo and mode
of evolution reconsidered. Paleobiology 1977;3:115-51)
Race: Described in population genetics as a geographic subdivision of a species
distinguished from others by the allele frequencies of a number of genes. A beautiful
discussion that there are no genetically defined races within Homo sapiens can be
found in Cavalli-Sforza's book Genes, Peoples, and Languages (2000).
Radiometric dating: A dating technique that uses the decay rate of radioactive
isotopes to estimate the age of an object.
Reproductive isolation: Two populations or individuals of opposite sex are considered
reproductively isolated from one another if they cannot together produce fertile
offspring. See prezygotic isolation and postzygotic isolation.
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.
Science: A way of knowing about the natural world based on observations and
experiments that can be confirmed or disproved by other scientists using accepted
scientific techniques. Requires falsifiability.
Sedimentary rocks: Rocks composed of sediments, usually with a layered
appearance. The sediments are composed of particles that come mostly from the
weathering of pre-existing rocks, but often include material of organic origin; they are
then transported and deposited by wind, water, or glacial ice. Sedimentary rocks are
deposited mainly under water, usually in approximately horizontal layers (beds). Often
site of fossils.
Selective pressures: Environmental forces such as scarcity of food or extreme
temperatures that result in the survival of only certain organisms with characteristics
that provide resistance.
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.
Sexual selection: Natural selection operating on factors that contribute to an
organism's mating success. Described by Darwin as natural selection in relation to sex.
Speciation: It is now almost universally agreed that the prevailing process of speciation
is geographical (allopatric) speciation. (There are also parapatric and sympatric
speciation concepts.) According to biological species concept, however, species are
defined as aggregation of populations that are reproductively isolated from one another.
Species: the basic unit of biological classification and a taxonomic rank. A species is
often defined as the largest group of organisms in which two individuals can produce
fertile offspring, typically by sexual reproduction. All members of a population or set of
populations that actually or potentially interbreed over time
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.
Stratigraphy: Branch of geology concerned with the formation, composition, ordering in
time, and arrangement in space of sedimentary rocks.
Sympatric speciation: Speciation via populations with overlapping geographic ranges.
Synapomorphy: a characteristic present in an ancestral species and shared
exclusively (in more or less modified form) by its evolutionary descendants.
Synapomorphy is a shared derived character or trait that distinguishes a clade from
other organisms. Researchers must decide which character states are "ancestral"
(plesiomorphies) and which are derived (synapomorphies), because only
synapomorphic character states provide evidence of grouping. The term synapomorphy
refers to an apomorphy shared by a group. A synapomorphy for hominins, for example,
is greatly reduced canine teeth. Male chimpanzees and other close non-hominin
relatives have huge canine teeth, probably used in threat displays. Hominins do not
have this character, suggesting that the trait changed sometime after the hominin
lineage and chimpanzee lineage split.
Systematics: A near synonym of taxonomy
Taxonomy: The theory and practice of biological classification
Taxon: a group of one or more populations of an organism or organisms seen by
taxonomists to form a unit. Any group of organisms to which any rank of taxonomic
name (classification) is applied
Taxonomic hierarchy: All taxa are classified within the following groups (starting from
the most inclusive): kingdom, ('division' in plants), phylum, class, order, family, genus,
species, subspecies (race).
Teleology: Teleology, from the Greek word telos (purpose), asserts that there is an
element of purpose or design behind the workings of nature. Attributing any purposeful
direction to evolutionary change would be called teleological. Not true.
Theory: A well-substantiated explanation of some aspect of the natural world that
typically incorporates many confirmed observations, laws, and successfully verified
hypotheses.
Transitional fossil: A fossil or group of fossils representing a series of similar species,
genera, or families, that link an older group of organisms to a younger group. Often,
transitional fossils combine some traits of older, ancestral species with traits of more
recent species (for instance, a series of transitional fossils documents the evolution of
fully aquatic whales from terrestrial ancestors).
Type specimen: In paleontological studies, a species' type specimen is a specific fossil
for which the species was first named.
Young Earth creationism: The belief that the universe came into being only a few
thousand years ago. Most young Earth creationists interpret the Bible literally, including
not just the special, separate creation of human beings and all other species, but the
historicity of Noah's flood
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.
Glossary of human bones
Skull:
Mandible: lower jaw or jawbone (from Latin mandibula, "jawbone") is the largest, strongest and lowest
bone in the face. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath
the maxilla.
Maxilla: upper jawbone formed from the fusion of two bones. The upper jaw includes the frontal
portion of the palate of the mouth
Arm:
Humerus: a long bone in the arm or forelimb that runs from the shoulder to the elbow; upper arm bone
Radius: one of the two large bones of the forearm
Ulna: a long bone found in the forearm that stretches from the elbow to the smallest finger, and when
in anatomical position, is found on the medial side of the forearm. It runs parallel to the radius, the
other long bone in the forearm, and is the larger and longer of the two.
Legs:
Femur: the thigh bone, is the most proximal (closest to the hip joint) bone of the leg. The head of the
femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of
the femur articulates with the tibia and kneecap forming the knee joint. The longest and strongest bone.
Fibula: the calf bone is a leg bone located on the lateral side of the tibia, with which it is connected
above and below. It is the smaller of the two bones
Tibia: the shinbone, is the larger and stronger of the two bones in the leg below the knee
Hand and fingers:
Carpal bones: the eight small bones that make up the wrist (or carpus) that connects the hand to the
forearm
Metacarpals: bones that form the intermediate part of the skeletal hand located between the phalanges
of the fingers and the carpal bones of the wrist which forms the connection to the forearm.
Phalanges: digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes
have two phalanges while the other digits have three phalanges.
Toes:
Metatarsals: group of five long bones in the foot, located between the tarsal bones of the hind- and
mid-foot and the phalanges of the toes
Condyle: is the round prominence at the end of a bone, most often part of a joint – an articulation with
another bone.
Foramen: any opening, particularly referring to those in bone.
Joint, or articulation: the region where adjacent bones contact each other, for example the elbow
Ramus: (Latin: branch) refers to an extension of bone, such as the ramus of the mandible in the jaw
Scapula: a.k.a. shoulder blade, is the bone that connects the humerus (upper arm bone) with the
clavicle (collar bone).
Sinus: a bony cavity, usually within the skull.
Suture: an articulation between cranial bones.
Vertebra: bones of the spine
Teeth:
20 primary (deciduous, "baby" or "milk") teeth and 32 permanent (adult) teeth
Among permanent teeth, 16 are found in the maxilla and 16 in the mandible, for a total of 32. The
dental formula is 2.1.2.3/2.1.2.3
The maxillary teeth are the central incisor (I2), lateral incisor (I2), canine ©, first premolar (P3), second
premolar (P4), first molar (M1), second molar (M2), and third molar (M3). The mandibular teeth are the
central incisor (I1), lateral incisor (I2), canine (C), first premolar (P3), second premolar (P4), first molar
(M1), second molar (M2), and third molar (M3). Third molars are commonly called "wisdom teeth" and
may never erupt into the mouth or form at all. Eruption = anatomically modern humans have the
sequence M1 I1 I2 C P3 P4 M2 M3.
Incisors are generally spatulate with a single root while canines are also single rooted but are single
cusped and conical. Premolars are bicuspid while molars are multi-cuspid. The upper molars have three
roots while the lower molars have two roots.
General patterns of dental morphological evolution throughout human evolution include a reduction in
facial prognathism, the presence of a Y5 cusp pattern, the formation of a parabolic palate and the loss of
the diastema.