Dogs are descended from wolves, but in the process of domestication their look and behaviour have been modified, and so have their genes.
Dogs Descended From Wolves
Some wolves had become dogs at least 15,000 years ago, but exactly how this domestication came about is not clear.
- • Maybe early human hunters actively captured and bred wolves, thus domesticating them, or perhaps some wolves learnt to hang around humans to scavenge on scraps – gradually developing into separate populations, and the most efficient of these early wolf-dogs got tamer and tamer.
- • However it happened, the alliance between dogs and humans was beneficial to both. The dogs had a plentiful food supply, and the humans benefited from the dog’s excellent hearing and keen sense of smell.
- • Early humans used dogs in a variety of ways – as guards, for hunting, and for pulling sleds.
- • When humans developed agriculture and settled down in villages and towns dogs performed the useful task of removing human waste and food rubbish. This was good for the dogs (good regular food supply), and also good for the humans (reducing diseases associated with poor sanitation and piles of rubbish).
- • It has even been suggested that the domestication of the dog was a crucial stage in the evolution of modern humans (‘Dogs make us human’ – Tacon and Pardoe, Nature Australia).
Different Dog Breeds
All dogs are the same subspecies of the Grey Wolf – all dogs are classified scientifically as Canis lupus familiaris. Within this subspecies there are many (thousands) of distinct types known as ‘breeds’ of dog.
There are thought to be around 400 million dogs in the world, and there is more variation in size, appearance, and behavior between dog breeds than there is in any other domestic animal, for example size ranges from a few inches (Chihuahua) to a few feet (Irish Wolfhound).
The study of the genetics of some dog breeds has helped people understand the genetics of certain human genetic disorders.
Dog Genes and Human Genetic Disorders
The genes that cause the particular characteristics of some dog breeds have been identified, and in a few cases the same gene has been found to be present in humans with a genetic disorder. Two examples will suffice:
The Rhodesian Ridgeback has duplications in the fibroblast growth factor genes FGF3, FGF4 and FGF19. This gives the breed its characteristic ‘ridge-back’. In humans it has been found that mutations in the genes encoding certain FGFs cause cleft palate, while mutations in FGFR2 have been linked to spina bifida.
In Boxers the MITF gene, that helps control the development and function of pigment-producing cells, is also important for hearing. White Boxers are frequently deaf. In humans mutations of the MITF gene cause pigment changes and loss of hearing (Waardenburg syndrome type 2).
Further studies of dog genetics are likely to shed light on a range of human genetic problems.