Domestication syndrome: what it is and how it is expressed in animals

Do you know why some animals, when they coexist with humans, acquire certain distinctive characteristics, such as cats or dogs? This is explained by domestication syndrome, a fundamental process of social evolution.

This phenomenon was originally studied by Charles Darwin, but recently researchers Adam Wilkins, Richard Wrangham, and W. Tecumseh Fitch have re-examined the phenomenon. 5 years ago, in 2019, they published the results of their studies in the journal Genetics.

Let’s find out what this phenomenon consists of and how it appeared in evolution.

    Domestication Syndrome and Charles Darwin Studies

    Domestication syndrome is considered one of the greatest mysteries in genetics. It is the process by which a species acquires certain morphological, physiological and behavioral characteristics as a result of prolonged interaction with humans.

    Over 140 years ago, Charles Darwin began to study this phenomenon by noting that domestic animals shared a variety of peculiarities not found in wild animals, such as having white patches on their fur, ears drooping, a short face, juvenile faces, a face curved tail and smaller jaws. He also noticed, comparing domestic animals with their wild relatives, that they were more docile.

    Despite Darwin’s remarks, it was difficult to explain why this pattern.

    Characteristics of the syndrome

    British anthropologist and Harvard University researcher Richard Wrangham also talks about this concept of domestication syndrome to refer to the fact that humans exhibit a number of biological characteristics more typical of pets than wild animals. One of them, for example, is the very low rate of face-to-face aggression that we exhibit.

    R. Wrangham states that we share some of their characteristics with our pets and farm animals. These traits are not common in wild animals and common in pets. Additionally, Darwin claims that humans did not choose their pets specifically to have these traits.

    In addition, R. Wrangham states that our skeletons exhibit many peculiarities characteristic of pets. In addition, according to him, there are four characteristics that we have related to pets that wild animals do not have; a shorter face, smaller teeth, reduced sex differences, men becoming more feminine; and finally, a smaller brain.

    Regarding the latter, it should be mentioned that the natural evolution of the species has always been a tendency towards a continuous increase in the brain; however, this trend has reversed over the past 30,000 years. The process of domestication began to develop about 300,000 years ago, and the size of the brain only began to decrease at the end.

      How did the domestication syndrome come about?

      again it is not known which biological mechanisms produce the domestication syndromeBut there is some evidence, such as that many domestication traits are typical of young animals.

      If some species have been domesticated by humans, others have been domesticated alone, for example by reducing their aggressiveness, like us humans.

      R. Wrangham, with Adams Wilkins (Humboldt University in Berlin) and Tecumseh Fitch (University of Vienna), proposed that these distinctive traits mentioned in “domesticated” species originate from a group of embryonic mother cells, neural crest.

      The neural crest is a structure that forms in vertebrates near the spinal cord of the embryo.. As this develops, the cells migrate to different parts of the body, giving rise to different tissues such as parts of the skull, jaws, teeth and ears, as well as the adrenal glands which control the reaction of “Fight or flight”.

      According to these researchers, domesticated mammals could present problems in the development of the neural crest. They argue that probably, in breeding these animals, humans unconsciously selected those with neural crest alterations, presented these small adrenal glands, and less fearful and more docile behavior and prone to collaboration.

      Consequences of a deficient neural crest

      Some of the consequences of this deficient neural crest can be depigmentation of certain areas of the skin, dental abnormalities, cartilage defects in the ear, and changes in the jawbone. These alterations appear in the domestication syndrome.

      Domesticated animals in nature

      For example, we find among our closest relatives the bonobos. They are animals very similar to chimpanzees, but their skulls have domestication characteristics (a shorter face, smaller teeth, a smaller brain, and reduced gender differences). In addition, they are less aggressive, more peaceful.

      R. Wrangham states that probably female bonobos of domesticated malesAs bonobos live in a habitat that allows females to travel together all the time, unlike chimpanzees. This promoted social alliances between women.

      The case of the human being

      In the case of human beings, however, it cannot be said that women also “domesticate” or civilize men; yes it is true that there has been a lot of mythological tradition that power was in the hands of women, but currently there is no matriarchy anywhere in the world (moreover, there is still the system opposite, patriarchy) and there is no supporting evidence either.

      If it was not the women who “domesticated” the man, one wonders … Who did this? But that’s all speculation, as the fossils don’t tell us exactly what happened. According to the author, we need to examine how hunters and gatherers today treat people who behave aggressively.

      In communities where there are no prisons, no military or politicians, they find only a way to defend oneself against the determined perpetrator of aggressive behavior: execution. Thus, the murder is committed by agreement between the other members of the society.

      Today, we know that without domestication, human societies would not have evolved or progressed in the same way.

      Bibliographical references:

      • Adam S. Wilkins, Richard W. Wrangham, and W. Tecumseh Fitch. (2014). The “domestication syndrome” in mammals: a unified explanation based on the behavior and genetics of neuronal crest cells. Genetics, 197 (3), 795-808.
      • Grolle, J. (2019). The Emergence of Homo Sapiens “Those who obeyed the rules were favored by evolution.” Spiegel Online, interview with Richard Wrangham.

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