The Domestic Dog

How did wolves become dogs?

The wild grey wolf is the most closely related canid (mammal in the dog family) to the domestic dog. The evolution of dogs was changed significantly by the process of domestication. Until this point, the evolution of the species would have been driven by natural selection. Those with the strongest and fittest genes would have survived and reproduced. After domestication, humans began to purposefully breed dogs for specific functions. This process is known as artificial selection. 

The domestic dog- how it started

Whilst it is unclear exactly where and when the domestication of dogs first occurred, a study from Pang et al (2009) has indicated that domestication likely occurred in South-eastern Asia between 15,000 and 20,000 years ago. There are a number of theories as to how dogs came to be domesticated by humans. The most popular and most likely theory, based on recent research, is known as Population Selection. This speculates that wolves would have been drawn to areas of human settlement by the potential to scavenge food. Wolves that were too scared of humans appearing would have left on sight of a human. Wolves that could tolerate humans would have greater access to the leftovers and dumped food remains of humans. The distance at which a species can tolerate a threat, such as humans, and remain eating is known as flight distance (Coppinger & Coppinger, 2001). Some of these wolves would have been naturally less nervous than others. Those who could tolerate the humans at the shortest flight distance would have been those who got the most food. 

The role of genetics

Every dog has its own DNA, inherited from its parents. The DNA of each individual varies, even between puppies of the same litter, due to the process of meiosis. Epigenetics refers to the body’s ability to alter the expression of DNA without actually altering the DNA itself. The epigenetic process is directed by a number of proteins, which play an important role in the expression of DNA. Mutations in these proteins can alter gene expression, which in turn can lead to the onset of diseases, such as cancer. Whilst genetic mutations are irreversible, epigenetic drugs are now being developed that can treat cancer (Seyhan et al, 2020). Epigenetic influence may also occur in response to environmental changes, such as climate change or loss of habitat (Leonard, 2014). 

Breeding

After centuries of breeding for various functions and forms, the domestic dog’s genome has a highly diverse phenotype (Boyko, 2011). Traits such as coat type, colour, size and ear shape have all been purposefully selected for and bred from specifically to create the breeds we know today. However, excessive breeding for the same traits may result in genetic mutation that may result in health problems for the individual dog. This is potentially caused by homozygosity (two identical forms of a gene, inherited from each parent) in the genome (Parker, 2012). 

The domestic dog- where we are today

In conclusion, the domestic dog is in many ways similar to its cousin, the wild grey wolf. However, the artificial selection and breeding that occurred after domestication has led to the wonderful diverse range of pet dogs we know and love today. Every dog has a DNA sequence individual to them but the epigenome may alter the expression of that DNA in response to environmental factors. 

References

Dogs: A Startling New Understanding of Canine Origin, Behavior & Evolution. Raymond Coppinger & Lorna Coppinger, 2001. 

Jun-Feng Pang, Cornelya Kluetsch, Xiao-Ju Zou, Ai-bing Zhang, Li-Yang Luo, Helen Angleby, Arman Ardalan, Camilla Ekström, Anna Sköllermo, Joakim Lundeberg, Shuichi Matsumura, Thomas Leitner, Ya-Ping Zhang & Peter Savolainen. mtDNA Data Indicate a Single Origin for Dogs South of Yangtze River, Less Than 16,300 Years Ago, from Numerous Wolves, Molecular Biology and Evolution, Volume 26, Issue 12, December 2009.

The Domestic Dog. James Serpell, 1995. 

Xavier, Müller & Fukumasu.  Epigenetic Mechanisms in Canine Cancer. Sec. Cancer Molecular Targets and Therapeutics. Volume 10 – 2020. 

Jennifer A. Leonard. Ecology drives evolution in grey wolves. Evolutionary Ecology Research, 2014, 16: 461–473

Boyko, A.R. The domestic dog: man’s best friend in the genomic era. Genome Biol 12, 216 (2011). 

Parker HG. Genomic analyses of modern dog breeds. Mamm Genome. 2012 Feb;23(1-2):19-27. 

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