Chapter 2: Human Evolution

Rickets

A childhood disease characterized by the softening and bending of leg and pelvis bones. Related to insufficiency of vitamin D and/or calcium.

Primates

A member of a biological order of mammals that includes human beings, apes, and monkeys as well as prosimians.

Melanin

A pigment found in the skin, hair and eyes of human beings, as well as many other species, that is responsible for variations in color.

Mutation

A random change in genetic material; the ultimate source of all biological variation.

Atlatl

A spear thrower, a device used to increase and extend the power of the human arm when throwing a spear.

Homo erectus

A species of early human found in Africa, Asia, and Europe. Homo erectus were present between 1.8 and about 200,000 years ago.

Homo habilis

A species of early human found in Africa. Homo habilis were present between 2.5 and 1.8 million years ago.

Homo sapiens

A species of human found throughout the world. The earliest Homo sapiens appeared about 500,000 years ago.

Multiregional model

A theory that seeks to explain the transition from Homo erectus to Homo sapiens by arguing that different populations of Homo sapiens are descendant from different populations of Homo erectus.

Hybridization model

A theory that seeks to explain the transition from archaic to modern Homo sapiens by proposing that modern and archaic forms interbred.

Omnivore

An animal that eats both plant and animal foods

Genetic drift

Changes in the frequencies of specific traits caused by random factors

Species

In biological classification, a group of organisms whose members are similar to one another and are able to reproduce with one another but not with members of other species.

Genus

In biological classification, a group of similar species

Evolution

In its broadest sense, directional change. For biologists, descent with modification from a single common ancestor or ancestral population.

Neanderthal

Members of a population of archaic Homo sapiens that lived between 130,000 and 35,000 years ago.

Australopithecines

Members of an early hominid genus found in Africa and characterized by bipedal locomotion and small brain size

Gene flow

Mixing of genetic material that results from the movement of individuals and groups from place to place

"Venus" figurines

Small stylized statues of females made in a variety of materials by early modern humans.

Oldowan tools

Stone tools made by Homo habilis

Clinal distribution

The frequency change of a particular trait as you move geographically from one point to another.

Termite fishing

The learned use of twigs or blades of grass to extract termites from their mounds characteristic of some groups of chimpanzees.

Natural selection

The mechanism of evolutionary change; changes in traits of living organisms that occur over time as a result of differences in reproductive success among individuals.

Parallax

The slight difference in the image of an object seen from two different vantage points.

Replacement model

The theory that modern people evolved first in Africa then spread out to inhabit virtually all the world, outcompeting or destroying other human populations in the process.

Sexual selection

The theory that the evolution of certain traits can be explained by competition for opportunities to mate.

Arboreal

Tree-dwelling

Bipedalism

Walking on two feet, a distinctive characteristic of humans and our ancestors