The story about how plants and animals became domesticated is an interesting one. With time, species of animals and plants have become friendly to humans, while others are reared for food or for assisting in jobs like carrying loads. Plants have also been domesticated all over the world.

There is keen interest among scientists, who are researching how and when plant and animal species were tamed by humans. The topic is being approached from three disciplines: zoology, the study of animals; archaeology, the study of history through excavations; and genetics, to understand how the genes of species were changed over time. Studies from genetic, anthropological and environmental aspects help in understanding how humans have affected the development and evolution of domesticated species, which can help in conservation efforts [1,2].

Domestication is a two-way process: the wild species were either tamed by humans or they found ecological niches to co-exist with the human race. Animals that are domesticated, for instance, tend to be friendly to humans. Such changes have produced genetic differences between domesticated and wild populations in both plants and animals.

Several techniques are being used to study the evolution of plant and animal species as they started to live with humans. Studies of DNA in ancient bones are coupled with archaeological findings to show the genetic structure of the animals and plants that have been domesticated [3]. These studies can shed light on changes in DNA that have taken place over time, and help answer questions about how plants and animals changed over time. For instance, some domesticated species change in appearance and differ in physiology from wild populations, as was explained by Darwin’s “domestication syndrome.” It is seen that when animals become friendly to humans, changes in neural crest cells occur in their brains [4]. Tameness is a result of changes in these cells.

Studies on populations of dogs, wolves, horses, silkworms and other species have been conducted, sometimes getting surprising results. For instance, it was believed that dogs started living with humans 14,000 years ago, but the study of a skull found in Goyet, Belgium, puts the date back to 36,000 years, or even before the Ice Age [5].

Beliefs about domestic horses have also been questioned. It was earlier believed that some wild horses were captured by humans and domesticated, but studies of the DNA of horses from ancient cultures show selective breeding only started about 2,300 years ago. Similarly, it was believed that chicken were reared for their egg laying through ages, but genetic analysis shows that the gene promoting egg laying became prevalent only about  920 AD. This shows that though chicken have been domesticated thousands of years ago but not for their egg laying capacity.

Plant species have also been studied widely. Rice cultivation is known from archaeological finds to have started in China and India some 8,000 years ago. However, recent findings show that it was domesticated only in China, when rice varieties with non-scattering seeds started replacing shattering seeds varieties about 7,000 years ago.

The studies of how species learnt to live with humans are interesting. They change many notions about evolution and shed light on how species changed not only in behaviour but in genetic development as well [6].

References

1. Alves RRN, Souto WMS. Ethnozoology: a brief introduction. Ethnobio Conserv 2015; 4(1):1-13. doi:10.15451/ec2015-1-4.1-1-13.
2. Digard JP. Relationships between humans and domesticated animals. Interdiscipl Sci Rev 1994;19(3):231-236. doi: 10.1179/isr.1994.19.3.231
3. MacHugh DE, Larson G, Orlando L. Taming the past: ancient DNA and the study of animal domestication. Annual Review of Animal Biosciences. 2017;5:329. doi: 10.1146/annurev-animal-022516-022747.
4. Wilkins AS, Wrangham RW, Fitch WT. The “domestication syndrome” in mammals: a unified explanation based on neural crest cell behavior and genetics. Genetics 2014;197 (3):795-808. doi: 10.1534/genetics.114.165423
5. Drake AG, Coquerelle M, Colombeau G. 3D morphometric analysis of fossil canid skulls contradicts the suggested domestication of dogs during the late Paleolithic. Scientific Reports 2015;5:8299. doi: 10.1038/srep08299.
6. Saey TH. DNA evidence is rewriting domestication origin stories. Science News 2017;191(13):20.