Big, soulful eyes, a wagging tail, and playful cuddles are a pet parent’s ultimate weakness. These heartwarming traits are not by chance: Shaped by domestication, these behavioral and anatomical features are etched into a pet dog’s genetics.
Humans began domesticating animals more than 15,000 years ago, with hunter-gatherers forming an association with wolves.1 They eventually selected for characteristics that gave rise to the domestic dog. Gradually, ancient humans bred other species like sheep, goats, cattle, pigs, chickens, and horses for providing food, clothing, protection, or as companions. With advances in the field of genomics, researchers have been trying to understand the genetic changes that accompanied animal domestication.2
Decoding Genetic Variations in Domesticated Animals
“Understanding how we’ve gotten to where we are now might inform how we can further either manage populations or [breed] for animals that are used in agriculture,” said Pam Wiener, an animal geneticist at The University of Edinburgh. The other motivation, she noted, is to understand how animals underwent evolutionary changes parallelly with humans.
To this end, Wiener and other researchers compared the patterns of microsatellites—short, repetitive DNA segments prone to higher mutation rates—between wild and domestic animal species to identify the regions in the genome associated with specific traits such as meat production.3 To complement this work, researchers analyzed single-nucleotide polymorphisms to further link genetic variation among domesticated and wild members of a species.4
Now, with advancements in next-generation sequencing methods, researchers can reconstruct and analyze the genomes of extinct animals using ancient DNA extracted from museum samples and archeological sites.5 Comparing this with the genomes of modern-day animals provides insights about the origins of some domesticated animals and the genetic changes that took place through the ages.
Humans Selected for Genes Related to Animal Behavior, Food Supply, and Appearance
Studies using all of these techniques revealed a more complete picture of the genetic changes underlying different traits that were selected and passed down in domesticated animals. For instance, researchers compared the genetic architecture of dogs and wolves and identified variants in two genes that resulted in extreme sociability.6
Other scientists, including Wiener, discovered the genetic changes associated with production-related traits. They found that cattle bred for their meat contained a deletion in the myostatin gene, whose functional protein product prevents muscle growth.7 Over time, farmers selectively bred this variant into certain cow breeds, and eventually produced animals with an extremely lean, hyper-sculpted, and muscular physique.3
“One would expect that these production-type traits would [be most commonly selected for],” said Wiener. But studies revealed that humans largely also selected for physical features related to animals’ attractiveness, she said. “That says something more about humans than it does about the animals themselves, and the kinds of things that are important to humans.”
Evidence suggests that humans actively selected for particular coat colors in domestic animals, leading to the proliferation of new mutations to suit aesthetic preferences.8 For instance, domestic pigs differ from their wild relatives in having accumulated mutations in the gene encoding melanocortin receptor 1, which influences pigmentation of the skin and hair.9 Most white horses contain a genetic mutation that drives premature hair graying, giving a lighter appearance.10
Wiener hypothesized that selecting for color may have a practical aspect in people being able to distinguish the animals on their farm. However, coat color is just one of the physical traits that humans selected for: They also bred dogs to have floppy ears and shorter, wider skulls resembling cute, childlike features.11
Over decades, research has revealed that people selectively bred animals for certain desirable characteristics related to agriculture and produce. Along the way, they also ended up selecting for the beloved qualities of fur babies that melt pet parents’ steely resolve. These quirky traits are actually the genetic imprints shaped by thousands of years of evolution, with a little help from humans.
- Frantz LAF, et al. Animal domestication in the era of ancient genomics. Nat Rev Genet. 2020;21(8):449-460.
- Wiener P, Wilkinson S. Deciphering the genetic basis of animal domestication. Proc Biol Sci. 2011;278(1722):3161-3170.
- Wiener P, Gutiérrez-Gil B. Assessment of selection mapping near the myostatin gene (GDF-8) in cattle. Anim Genet. 2009;40(5):598-608.
- Boyko AR, et al. A simple genetic architecture underlies morphological variation in dogs. PLoS Biol. 2010;8(8):e1000451.
- Thalmann O, et al. Complete mitochondrial genomes of ancient canids suggest a European origin of domestic dogs. Science. 2013;342(6160):871-874.
- vonHoldt BM, et al. Structural variants in genes associated with human Williams-Beuren syndrome underlie stereotypical hypersociability in domestic dogs. Sci Adv. 2017;3(7):e1700398.
- McPherron AC, Lee SJ. Double muscling in cattle due to mutations in the myostatin gene. Proc Natl Acad Sci USA. 1997;94(23):12457-12461.
- Cieslak M, et al. Colors of domestication. Biol Rev Camb Philos Soc. 2011;86(4):885-899.
- Fang M, et al. Contrasting mode of evolution at a coat color locus in wild and domestic pigs. PLoS Genet. 2009;5(1):e1000341.
- Andersson L. White horses—non-coding sequences drive premature hair greying and predisposition to melanoma. Ups J Med Sci. 2024;129:e10626.
- Wright D. The genetic architecture of domestication in animals. Bioinform Biol Insights. 2015;9(Suppl 4):11-20.
