agrammatic: an adjective meaning "without grammar," which characterizes pre-linguistic systems of human communication

agrammatic aphasia: a language disease affecting the Broca's Area that cripples the patient's ability to construct grammatically correct sentences, although the patient can still communicate using nouns and verbs. Noun and verb use is often highly compromised in other forms of aphasia, such as Wernicke's aphasia

cerebral: similar to neural, but refers to a specific part of the brain (the cerebrum)

Chomsky, Avram Noam: arguably the most important linguist of the 20th century, Chomsky developed the theory of Universal Grammar within his Principles and Parameters framework, and has asserted that language could not have evolved though natural selection

Darwinist: see "selectionist"

evoked responses: an electrical response manifested in the brain when it performs a cognitive process; these are used to demonstrate neural pathways

evolutionary biology: the study of the evolution of living things

exaptation: an evolutionary process in which a given adaptation is first naturally selected for, and subsequently used by the organism for something other than its original, intended purpose

Gould, Stephen Jay: one of the foremost evolutionary biologists of his time until his recent death. Gould, along with Richard Lewontin, coined the notion of "spandrels," and although Gould considers himself a selectionist, he has proposed numerous nonselectionist evolutionary theories, such as exaptation. Gould is probably best known for his theory of punctuated equilibrium, asserting that evolutionary changes often happen in short bursts, where many rapid changes can take place

grammar: a part of language comprised of both morphology and syntax, grammar allows an infinite expression of ideas, makes language itself possible, and may have been naturally selected for

hominid: an adjective referring to primate human ancestors and the rest of the human line or family, starting from Australopithecus

Homo erectus: our first immediate ancestor, named for their completely upright, bipedal gait. Homo erectus started appearing about 2 million years ago and later gave rise to Homo sapiens, our species

Homo habilis: literally, the 'handyman', Homo habilis was the first of the Homo genus and started appearing a little less than 2.5 million years ago

Homo sapiens: our species. Includes both archaic and modern humans, as well as the subspecies Homo sapiens neanderthalensis, also known as the Neanderthals. Homo sapiens first started appearing about 500,000 or fewer years ago

language: more than merely a system of communication, language is unique to the human species and, for the purposes of this investigation, involves a lexicon (consisting at the very least of nouns and verbs) and a grammatical system (comprised of morphology and syntax) that determines the way words are formed, the order in which they appear, and the categories through which concepts are interrelated. Language is also the primary vehicle used to transmit human culture

naive adaptationism: a concept delineated by Stephen Jay Gould that refers to ad hoc and arbitrary evolutionary theories, such as noses being made for our glasses

neural: adj., of or pertaining to the brain

nonselectionist: referring to theories of evolution that do not involve natural selection, such as exaptation or co-optation

occipital lobe: anterior part of the brain, located above the base of the skull

oromotor: refers to the neural pathways that control the speech muscles

parietal lobe: top and center part of the brain, located above the ear

phenotype: the physical expression of the genotype, ie, that which is coded in the genes and observable in the physical structure of a given organism

preadaptation: the term that Darwin used for "exaptation," was left poorly explained in the Origin of Species

selectionist: an account of evolution that uses Darwinian natural selection to explain change, also refers to Darwinian natural selection in general

speciation: the evolutionary process of differentiation, in which a population of organisms becomes two or more different species

stochastic: a synonym for random. In statistics, the only sample that can be truly representative of a population is a random sample

temporal lobe: the middle part of the brain, located behind the ear and just under the parietal lobe

Universal Grammar: Chomsky's hypothesis of a single grammatical system which is transmitted genetically and accounts for the ability of all normal humans to learn and speak their native language

vertebrates: every animal with a notocord (spinal cord). Humans, grizzly bears, penguins, snakes, and even the lowly tunicate are all vertebrates

vestigial or vestigial structures: structures that serve no function but are generally not harmful, vestigial structures are believed to be derived from evolutionary ancestors that may have actually needed them at one time. Classic examples of vestigial structures in humans are our appendixes and the nictitating membranes in our eyes