ANS 104 - DOMESTICATION

3-6

what is domestication?

process of adaptation to humans and captive environments

domestication is a result of interplay between

genetic changes across generations AND environmental stimulation and experiences during development of the animal

Domestication= genetic changes + env influences

1st wave of domestication

• 8000-15,000 years ago

• traditional agricultural species, dogs, cats

2nd wave of domestication

• within last 100 years

• new meat producers, laboratory animals, fur animal

what shapes the behavior of an animal in wild or in nature?

forces of evolution:

• natural selection

• random drift

• mutation

• gene flow among populations

natural selection

traits that increase/maximize fitness are favored

• surviving to the best of your ability AND leaing behind as many survivng offspring as you can

what shapes the behavior of an animal in captivity?

forces of evolution:

• natural selection (in captivity)

• random drift

• mutation

• gene flow among populations

artificial selection

relaxation of natural selection

how does domestication occur?

1. natural selection in captivity 

2. artifical selection

3. relaxation of natural selection

all processes occur simultaneously, some work at greater pressures than others

natural selection in the wild

experience differential fitness 

• ‘bigger’ male expected to leave behind more offspring and have genetic info as the big male 

• smaller male→evolutionary dead end 

what is environmental conditions change?

color and behavioral changes in polar bears in response to env change

• physical phenotype is no longer a match to the snow 

what about a novel env condition?

fitness in captivity=survival in captivity+reproduction in captivity

• in new env, there are some traits that may help indiv survive and/or reproduce better in captivity

relaxation of natural selection

in captivity, pressure associated with natural selection become relaxed (passive process)

in relaxation of natural selection, the expression of traits in the population can…

• stay the same/no change

• shift in frequency

  • decreased if not favored 

  • increase if trait no longer selected against

• become more variable throughout the population

artificial selection

• anthropogenic=generated by humans 

• intentional

• produces rapid changes 

Belyaev’s foxes ex. 

1. tolerate petting

2. accept food from human hand

focus specifically on behavior, no phenotypic trait

domestication timeline: selection pressures

As time goes on…

• natural selection decreases

• relaxation of natural selection stays the same

• artificial selection increase

understanding selective pressure can help explain

tradeoffs

• captivity is just another env that operates to shape behaviors

effects of changes in traits due to domestication

not necessarily a single trait leads to domestication

• combination of various traits in the genotype

Domestication does not change motor patterns

the way they perform a behavior stays the same→ use same muscles in same way whether or not they are domesticated

Domestication changes when and how often animals perform a behavior

threshold

• stimulation required to elicit a given response

domestication changes the quantity not the quality

no new behaviors created

• same behavioral repertoire in wild to domesticated

• if threshhold is so high, you may never see the behavior elicited

contrafreeloading

behavior where an animal chooses to work for food even when identical food can be obtained without any effort

• in JF energy is distributed evenly physiological 

• in WL reprioritize energy distribution

why do JF have more motivation to explore/acquire information

they have no relaxation of natural selection 

• contra-freeloading is part of their repertoire and is still something they find rewarding to engage in

changes in selection pressures cause changes in

phenotypic expression, both behavioral and physiological traits

reproduction for domesticated animals…

is under human control for several generations →artificial selection

• express common and predictable outcomes such as tameness

non domesticated animals

• wild caught or 1st/2nd gen 

• tameness result of training/env

  • not enough time for artificial selection to have an effect