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

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

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

We are going to know what this phenomenon consists of and how it appeared in evolution.

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Domestication syndrome and the studies of Charles Darwin

The 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.

More than 140 years ago, Charles Darwin began to study this phenomenon when he noticed that domestic animals shared a variety of characteristics that are not found in wild animals, such as having white patches on their fur, floppy ears, a short face, youthful faces, a curved tail, and shorter jaws little. He also noted, when comparing domesticated animals with their wild relatives, that

they were more docile.

Despite Darwin's observations, it was difficult to explain the reason for this pattern.

Characteristics of the syndrome

The British anthropologist and researcher at Harvard University, 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 animals wild. One of them, for example, is the very low rate of face-to-face aggression that we manifest.

R. Wrangham claims that we share with our pets and farm animals some of their characteristics. These traits are unusual among wild animals and common among pets. Furthermore, Darwin claims that humans did not choose their pets specifically for having these traits.

Also, r. Wrangham claims that our skeleton has many quirks characteristic of pets. In addition, according to him there are four characteristics that we have related to pets and that wild animals do not have; a shorter face, smaller teeth, reduction of sexual differences with males becoming more feminine; and finally, a smaller brain.

In relation to the latter, it is worth mentioning that the natural evolution of the species has always been a tendency to a continuous increase in the brain; however, this trend has been reversed in the last 30,000 years. The domestication process began to unfold about 300,000 years ago, and brain size only began to decrease at the end.

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How did the domestication syndrome appear?

Still it is not clear what biological mechanisms produce the domestication syndrome, but there is some evidence, for example, that many of the domestication traits are typical of young animals.

While some species have been domesticated by humans, others have been domesticated on their own, for example by reducing their aggressiveness, such as us humans.

R. Wrangham, together with Adams Wilkins (Humboldt University in Berlin) and Tecumseh Fitch (University of Vienna), proposed that these traits so distinctive mentioned in the "domesticated" species arose from a group of embryonic stem cells, the crest neural.

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

According to these researchers, domesticated mammals could present problems in the development of the neural crest. They maintain that probably, when raising these animals, humans have been selectively selecting unconscious those with alterations in the neural crest, presented these adrenal glands more small and less fearful and more docile behavior and prone to collaboration.

Consequences of Neural Crest Deficiency

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

domesticated animals in the wild

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

R. Wrangham claims that female bonobos probably domesticated males, since bonobos live in a habitat that allows females to travel together all the time, unlike chimpanzees. This has favored social alliances between females.

The case of the human

In the case of the human being, however, it cannot be affirmed that women “domesticated” or civilized men as well; yes it is true that there has been a lot of mythological tradition that held that power was in the hands of women, but currently it is not Does matriarchy exist anywhere in the world (indeed, the opposite system still exists, patriarchy) and there is no evidence to support it either. hold up

If women were not the ones who "domesticated" men, we wonder... Who did it? But it's all speculation, since the fossils don't tell us exactly what happened. According to the author, we should look at how hunters and gatherers today treat people who behave aggressively.

In communities where there are no prisons, neither military nor political, they only find a way to defend against the determined perpetrator of aggressive behavior: execution. Thus, the murder is carried out by agreement among the other members of society.

Today, it is known that without domestication, human societies would not have evolved or progressed in the same way.

Bibliographic references:

• Adam S. Wilkins, RichardW. Wrangham and W. Tecumseh Fitch. (2014). The “Domestication Syndrome” in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics. Genetics, 197(3), 795-808.
• Groll, J. (2019). The Emergence of Homo Sapiens 'Those Who Obeyed the Rules Were Favored by Evolution'. Spiegel Online, interview with Richard Wrangham.