Domestication is the process when animals adapt to a life with humans. The first target of selection, intentionally or unconsiously, was probably reactivity against humans and other potential threats. There are three processes that are central to domestication:

1. selection by humans, so called artificial selection, with behaviours that are preferred by humans
2. a natural selection occurs in captivity which leads to adaptation
3. a relaxation of natural selection occurs, certain factors such as reproduction and predation decrease.

"The domestic phenotype" have been found with comparative studies of domestic species and their widl ancestors. Examples of behavioural changes are reduced fear, increased sociability and reduced antipredator response. 

The wild ancestor to all domestic chickens is the read junglefowl, which still live as a wild specie in Southeast Asia. The domestication process of chickens started around 8000 years ago. During the last 100 years the domesticated chicken diverged into broilers (meat) and laying (egg) respectively. There are mainly four behaviour aspects that differ between the wild ancestor and the domestic breed:

1. the domestic chicken are in general less active, with a reduced foraging and exploratory behaviour
2. the domestic chicken has a less intense social behaviour, with a reduced frequency of social interactions
3. the antipredator behaviours are modified and less intense in domestic chickens
4. the domestic chickens show a modified foraging strategy, less inclined to explore unknown food sources.

Thyroid hormones are important in the development and growth in birds. Thyroid stimulating hormone can affect a wide range of domestication phenotypes, such as behaviour, growth rate and pigmentation. The thyroid stimulating hormone receptor (TSHR) gene, which has mutated in domestic breeds and is homozygote at the TSHR locus, regulates the control of photoperiod in reproduction. One thing that all domesticated species have in common is the loss of seasonal reproduction, which likely has been favoured during domestication. 

The loss of fear related behaviours have been favoured during domestication and are common for all domestic species, as like seasonal reproduction. It could be that the loss of fear is due to a mutation in the TSHR-gene, it is also involved in the loss of seasonal reproduction. 

The aim of this project is to see whether the TSHR-gene is involved in the domestication effect of fear related behaviours.

My hypothesis was that there would be an effect in fear related behaviours of a mutation in the TSHR-gene, which is considered to be central for domestication in chickens. The chickens with the TSHR mutation would show less fear related behaviours than the wild type chickens.