Dog Size a Function of their Genes

Have you seen this big guy in your email box this week? Claims have been circulating the internet that this dog is Hercules an English Mastiff that weighs over the 300lb that is typical of this large dog breed. Unfortunately this photo is a hoax – you can read more about the real Hercules here.

Isn’t it strange though that dogs vary in size so widely compared to other species of mammals? Think about other animals such as cats, giraffes, goats, rabbits etc. The different breeds of these animals are all about the same size.  Of course many of the dogs we see today have been bred for specific purposes including hunting and farm work in which the size of the breed was important. 

A recent study by scientists at Cornell University revealed that the size varitation can be attributed to gene sequences that are shared between dogs of similar size. They believe that a gene mutation that occurred 10,000 years ago created the smaller dogs that are common house pets today such as the chihuahuas, fox terriers and pomeranians. Visit the BBC article to read more.