What accounts for size variation in breeds of dogs?

Question

My assumption is that dogs vary so much in size because of artificial selection pressures coming from human breeders, but are there genetic loci that roughly determine approximate size? Do other feral species of animals exhibit such a wide range in sizes or is this something that only occurs when breeders intervene?

Answer 1

National Geographic had a great article on this very topic in a past issue. As you surmised, it turns out that human intervention bears most of the responsibility for the variety we see in dog breeds. And it also occurs on a surprisingly small number of genes.

There has also been other research on this topic. Here are some references to consider:

1. https://www.nationalgeographic.com/magazine/2012/02/build-a-dog/#close
2. https://www.nationalgeographic.com/animals/2004/05/dog-dna-study-yields-clues-to-origins-of-breeds/
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5357063/

With dogs having such an ancient history with man, survival and the needs of living together create an over-arching relationship between canine DNA and cause.

I hope this helps--and that you enjoy exploring your question.

--Heidi