Where do mammals get their names?

Mammals are a class of the vertebrate subphylum, commonly known as mammals. They are the most advanced animal group with the most complex body structure and functional behavior among vertebrates. They are named for their ability to secrete milk through the mammary glands to feed their young.

But where did the name "mammal" come from?

Smiling dolphin one of the mammals

Early animal classification

The first person to classify animals was the ancient Greek philosopher Aristotle. He divided animals into two categories: those with blood and those without blood.

"Animals with blood" have warm red blood and are higher animals; while "animals without blood" have body fluids similar to blood but are colorless and heatless and belong to lower animals.

Among Aristotle's "blooded animals", tetrapods are a very important category, including all animals that walk on four legs, while birds have two legs and wings, and their feet cannot stand upright, so they are of a lower level. Some. In addition, fish live in water and are considered imperfect without legs, forelimbs and wings.

In the 17th century, the British scientist John Ray first challenged Aristotle's classification. He believed that all organisms have life-sustaining body fluids and cannot be classified based on the color of the life-sustaining body fluids. He also pointed out that whales and dolphins have red blood, The main quadrupedal features are the biventricular heart and lungs. He believed that they were the same type of animals as tetrapods, but whales and dolphins had no legs, so it was obviously inappropriate to call them tetrapods. John Ray referred to them collectively as "viviparous animals".

primitive mammal platypus

In 1758, the Swedish naturalist Linnaeus introduced the name "mammal" for the first time in his book "Nature and System" to replace the classification of "viviparous animals". The name "mammal" conforms to the principles of being pleasant to the ears, easy to read and easy to remember. The famous zoologist Cuvier also believed that it is most convenient to use breasts to distinguish the class of mammals, although some taxonomists at that time also used four-legged animals with hair. and other characteristics as classification options, but only the name "mammal" survived and is still recognized by the International Convention on Nomenclature.

Why use breastfeeding as a classification criterion

You may find it strange that only female animals can breastfeed, and males cannot produce milk to feed their young. Doesn’t “mammal” only represent females and not males?

All the characteristics based on previous classifications, such as blood, hair and feet, were both male and female. Why did Linnaeus use lactation as a classification criterion? In fact, this was related to the cultural and political trends in Europe at that time.

Europe in the 18th century was the heyday of wet wet nurses. Not only aristocrats and wealthy businessmen, but also clergy and craftsmen sent their children to the countryside to be nursed. In the 1880s, up to 90% of children in Paris and Lyon were cared for by wet nurses, but this also resulted in high infant mortality. It was against this background that the naturalist Linnaeus published a paper opposing wet nurse breastfeeding and requiring mothers to breastfeed themselves.

Linnaeus believed that it was cruel not to breastfeed one's own flesh and blood. Even animals would breastfeed the next generation. It was a natural law for mothers to feed their children in person. Humans should also follow this natural law, so women should feed the next generation in person.

At the same time, as a naturalist, Linnaeus introduced the word "mammal" into the classification of animals, thereby emphasizing that it was only natural for females to nurse their offspring in person, and helped European society reconstruct the idea of mothers nurturing their children in person. legitimacy.

The French National Convention enacted a law in 1793 that only mothers who breastfed themselves were eligible for state subsidies (those in poor health were exempted from the obligation to breastfeed). In 1794, a similar bill came into effect in Prussia. At this point, Linnaeus's classification method was accepted by the cultural and political environment of the time, and the name "mammal" was finally recognized and retained by society.

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