Human Origins: Glossary

adaptation: A change in an organism that improves its ability, and the ability of its offspring, to survive in an environment.

base: Biological compounds that pair up on a strand of DNA and make up genes. The bases are adenine, thymine, cytosine, and guanine, and are denoted with the letters A, T, C, and G.

common ancestor: An ancestor shared by two or more descendant species.

body fossil: A fossil of a body or body part of an organism.

DNA (deoxyribonucleic acid): The molecule that encodes genetic information. It is shaped like a double helix held together by bonds between base pairs.

evolution: The scientific theory for how groups of living things change over time.

evolutionary tree: A representation of how a specific taxonomic group evolved new species over time. All trees are hypotheses, and are based on comparison of living species, fossils, and genetic data.

fossil: Remains or traces of an organism turned to stone by geochemical processes.

function: The activity of a body part.

gene: A specific sequence of DNA base pairs that controls the expression of one or more traits.

genetic drift: An evolutionary mechanism in which genes and traits in small populations increase in abundance over generations by chance, not because they impact an individual’s ability to survive.

heredity: The passing on of genetic traits from parent to offspring.

hominid: A member of the family of primates that includes humans, their ancestors, and close relatives.

Homo sapiens: The taxonomic name for our species: modern humans.

mutation: A change in a gene’s structure that may be passed on to future generations.

natural selection: An evolutionary mechanism whereby individuals tend to pass on heritable features that enable them to cope better with their environment to future generations. Over time, populations of individuals will exhibit more of the better-adapted features.

node: A point on evolutionary trees from which two or more lines branch. A node represents a common ancestor.

population: A group of organisms of one species, occupying a defined area and usually isolated from other groups of the same species.

primate: A member of the order Primates, which includes lemurs, monkeys, apes, and hominids.

structure: The shape and organization of a body part.

symbolic thought: The ability to interpret and re-create the world mentally using symbols. Evidence of symbolic thought includes language, music, art, and complex tools and technology.

trace fossil: Indirect evidence of an ancient organism and/or its behavior. Examples are footprints, skin impressions, and nests.

trait: Any genetically determined characteristic.

tree of life: A representation of evolutionary relationships among species. Scientists call trees of life “cladograms.”

variation: Genetic variation represents differences between individual members of a species. Variation comes from both recombination of parental DNA and genetic mutation