Why i hate pugs

I really have a problem with pugs, to me they are the most disfigured and inbred looking dogs around. My brother has recently decided to get one, and I'm still not sure if it's a joke or not. However, when trying to rationalise my dislike for this particularly ugly breed of dog I realised that it was probably because of inbreeding. This realisation has led me to the idea of writing about inbreeding, and the problems that this causes in domesticated species and wild species close to extinction. But first, just to prove my point about how horrid pugs are, here is a picture of a pug skull and a wolf skull (the ancestor of all domestic dogs).  

Domesticated animal species are the result of artificial selection, a process by which humans selectively breed together individuals who possess desired traits. Strangely, when domesticating a wild species this process often selects for similar traits: floppy ears, changes in reproductive cycle and curly hair. This was famously demonstrated in a long-term study on the domestication of the silver fox by Dimitry Belyaev LINK. Relatively few animal species have been domesticated, and Jared Diamond has hypothesized that this is due to animals needing to posses a pre-existing set of characteristics to allow them to be domesticated, espoused in his famous Nature paper LINK. 

• right diet
• fast growth rate
• friendly disposition
• easy breeding system
• social hierarchy
• won't panic

Good blog to read about domestication: http://animals.howstuffworks.com/animal-facts/animal-domestication.htm 

However, the problem with domestication (bringing this back to the pug) is that the gene pool for the population is artificially reduced and this can lead to inbreeding. This shrinking of the gene pool can be significant, for example in the pug: the British population of 10,000 pugs have a gene pool that is equivalent to just 50 individuals LINK. But why is this bad? A reduced number of breeding individuals can lead to a rise in the prevalence of 'bad gene', and this genetic bottleneck can lead to these being spread to a higher proportion of the descendants of this population. These 'bad genes' or deleterious alleles can lead to inbreeding depression and lower a populations viability. High levels of inbreeding, resulting from the increased mating of closely related individuals results in lower fitness for the offspring because of the increased prevalence of deleterious alleles and this can directly cause:

• reduced fertility
• increased genetic disorders
• fluctuating facial asymmetry
• lower birth rate
• higher mortality
• depression of growth
• smaller adult size
• loss of immune system function

In wild population inbred individuals can often be less attractive to the opposite sex, due to reduced song variation or plumage colouration. There are a few wild populations were inbreeding is seen as a potentially major problem, such as the cheetah, having implications for conservation.

Hopefully I have shown why inbreeding is bad, but in domesticated population there is less of a driver to get rid of highly inbred individuals as they may possess desired traits that more outbred individuals do not. Human selection has thus led to the breeding of some hideous animal species, such as the disfigured pug, and the fish species pictured below. You may still like pugs, and other 'pedigree' breeds of dogs, but at least now you might have some more of an idea about how they came about and the reasons behind the problems they have. My advice is to get a 'side-walk special' from an animal rescue centre, as not only are you giving a home to a dog that needs one but it is also likely to be less inbred and so reduce your vet bills!