Evolution, 4th Edition

SuMMARy

■■Evolution is the unifying theory of the biological

sciences. Evolutionary biology aims to discover

the history of life, the causes of the diversity and

characteristics of organisms, and the mechanisms

that underlie evolutionary change.

■■Charles Darwin’s major work, On the Origin of

Species, published in 1859, contains two ma-

jor hypotheses: first, that all organisms have

descended, with modification, from common

ancestral forms of life, and second, that the chief

agent of modification is natural selection.

■■Darwin’s hypothesis that all species have de-

scended with modification from common ances-

tors is supported by so much evidence that it has

become as well established a fact as any in biol-

ogy. His theory of natural selection as the chief

cause of evolution was not broadly supported

until the evolutionary synthesis that occurred in

the 1930s and 1940s.

■■Modern evolutionary biology is based on the

evolutionary synthesis, which united Darwin’s

ideas with Mendelian genetics. The major causes

of evolution within species are those that change

the frequencies of alleles, and hence of the

phenotypes they may affect. Different popu-

lations of a species may experience different

genetic changes, and ultimately become differ-

ent species. over long time periods, many slight

changes accumulate to yield large genetic and

phenotypic differences among species and their

ancient ancestors.

■■Evolutionary biology makes important contribu-

tions to other biological disciplines and to social

concerns in areas such as medicine, agriculture,

computer science, and our understanding of

ourselves.

■■The implications of Darwin’s theory, which revo-

lutionized Western thought, include the ideas

that change, rather than stasis, is the natural or-

der; that biological phenomena, including those

seemingly designed, can be explained by purely

material causes rather than by divine creation;

and that no evidence for purpose or goals can

be found in the living world, other than in human

actions.

■■l ke other sciences, evolutionary biology cannot i

be used to justify beliefs about ethics or morality.

nor can it prove or disprove theological hy-

potheses such as the existence of a deity. Many

people hold that evolution is compatible with

religious belief. However, evolution is incompat-

ible with a literal interpretation of some passages

in the Bible. Evolutionary biology and other sci-

ences can test and reject claims for supernatural

causes of observed phenomena.

TERMS AnD ConCEPTS

adaptation

blending inheritance

creationist

movement

descent with

modification

diverge

evolution (biological

evolution; organic

evolution)

evolutionary

synthesis (modern

synthesis)

frequency

genetic drift

genotype

higher taxa

hypothesis

inheritance

of acquired

characteristics

Lamarckism

macroevolution

microevolution

mutationist theories

natural selection

neo-Darwinism

neo-Lamarckism

neutral theory

of molecular

evolution

orthogenesis

particulate

inheritance

phenotype

phylogeny

population

proximate cause

scientific theory

speciation

ultimate cause

uniformitarianism

SuggESTIonS FoR FuRTHER READIng

The readings at the end of each chapter include ma-

jor works that provide a comprehensive treatment

and an entry into the professional literature. The

references cited in each chapter also serve this

important function.

no one should fail to read at least part of Darwin’s On

the Origin of Species by Means of Natural Selec-

tion, or The Preservation of Favoured Races in the

Struggle for Life, in either the first edition (1859) or

the sixth edition (1872), in which Darwin deleted

“on” from the title. After some adjustment to the

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