Behavioral Genetics and Animal Domestication - Genetics and the Behavior of Domestic Animals - page 41

Chapter 2

Behavioral Genetics and
Animal Domestication

Per Jensen and Dominic Wright
IFM Biology, Linko¨ping University, Sweden

DEFINITION OF DOMESTICATION
When Darwin first formulated his ideas on evolution, domesticated plants
and animals played a central role. The first chapter of On the Origin of
Species was devoted to a discussion about the rapid selection responses
occurring during domestication, affecting widely different aspects of animal
phenotypes. Darwin noted that size, color and shape could all be modified in
few generations when the selection pressure was sufficiently intense, and he
also rightly noted that the behavior of domesticated animals differs from
wild relatives in a number of aspects. Hence, Darwin saw domestication as
a rapid evolutionary process, something that has received massive support
from research during the last century, and behavior was conceived as a
phenotype amongst others.
The basic principles underlying any evolutionary process are few. In
essence, evolutionary development of a trait relies on three conditions: the trait
varies between individuals within the population (the variation principle), the
variation has a genetic component (the heritability principle) and individuals
with different variants of the trait contribute unequally to the gene pool of the
next generation (the principle of natural selection). The phenotypes of animals
undergoing domestication develop according to the same principles. What
makes domestication special is the fact that humans exert a large part of the
selection pressure in deciding which individuals will be most likely to have
their genes propagated to the next generation.
Attempts to define domestication are often based on the different selection
pressure as compared to the natural situation. Hence, Price (2002) suggested it
should be defined as the process whereby captive animals adapt to man and
the environment he provides. Price further argued that this is achieved through
genetic changes occurring over generations and through environmental stimu-
lation and experiences during an animal's lifetime. This has become the
most influential definition and is widely cited by researchers in the field.