Geneticists who compared the genes of large dogs, small dogs and wild relatives, found a version of a gene that is carried by all small dogs and very few of the others, apart from grey wolves in the Middle East, suggesting that today’s small domesticated dogs evolved from them.
The study was led by evolutionary geneticist Melissa Gray of the University of California, Los Angeles, and a paper on it appeared online in the journal BMC Biology on 24 February.
Previous studies on the origins of the domestic dog have used mitochondrial DNA, which is passed on only through the mother. These suggest that the domesticated dogs we see today originate from animals that lived between 5,000 and 16,000 in East Asia. However, archaeologicists digging in Europe and the Middle East have found evidence that suggests domestic dogs were already around 31,000 years ago.
For this study, the researchers focused on a nuclear DNA gene called IGF1 (insulin-like growth factor 1), which previous studies have linked to skeleton size variation in domestic dogs.
They found that a variant of IGF1 in small dog breeds (dogs weighing under 9 kilos) is almost absent in large breeds and wild canines, except they found a similar variant in grey wolves from the Middle East.
The authors wrote that:
“Grey wolf haplotypes [groups of genes that an organism inherits together from a single parent] from the Middle East have higher nucleotide diversity suggesting an origin there.”
They confirmed their finding using “PCA and phylogenetic analyses”, and also, because the small dogs all carried the same version of the gene, they proposed that the smaller body size evolved only once, and since it is present in small dogs worldwide, it must have appeared just after dogs first became domesticated.
“Our results show that the small dog haplotype is closely related to those in Middle Eastern wolves and is consistent with an ancient origin of the small dog haplotype there. Thus, in concordance with past archeological studies, our molecular analysis is consistent with the early evolution of small size in dogs from the Middle East,” they concluded.
Gray stressed to the media that their findings don’t necessarily suggest dogs were first domesticated in the Middle East, but point to a “strong indication” that the region “played a significant role in the early history of domestic dogs”.
Dr Adam Boyko, a geneticist based at Stanford University in Palo Alto, California, who specializes in investigating the evolution of the domestic dog and who was not involved in the study, told the press he was impressed by the findings:
“This really pokes a hole in the argument of this relatively simple domestication in East Asia … which is what people have been arguing based on mitochondrial DNA ,” said Boyko.
“The IGF1 small dog haplotype is derived from Middle Eastern gray wolves.”
Melissa M. Gray, Nathan B. Sutter, Elaine A. Ostrander and Robert K. Wayne.
DOI:10.1186/1741-7007-8-16
Sources: Stanford School of Medicine, Scitable, ScienceNOW.
Written by: Catharine Paddock, PhD