The Origin and Evolutionary History of Rats

Rats are one of the smallest mammals in the world. From the perspective of animal taxonomy, they include some animals of the order Rodentia and Lagomorpha. Rats were born earlier than humans. According to paleontologists' research on fossils, primitive humans appeared in the Pliocene Epoch 1.2 million years ago, while rats appeared in the Oligocene Epoch 3.5 million years ago, 2.3 million years earlier than humans. Chinese archaeologists excavated a cave of the Lantian Man in Wanggongling one million years ago and found piles of burnt rat bones, and there were still traces of chewing by the teeth of the ancients. The earliest rodent fossil discovered by humans was found in the North American strata 55 million years ago, and was called pararat.

There are more than 2,300 species of rodents in the world. Each species has its own place of origin and evolutionary history, and there are also some endemic species in special areas. After tens of millions of years of evolution, rats have escaped meteorites hitting the earth, survived the long ice age, and become a species with extremely long standby times. The most abundant rat in the world is Rattus norvegicus. Most rats are underground workers and like to live in holes.

Paleontologists have discovered that plague has already formed in the Tertiary Period of geological history (30 million years ago). There are three largest plagues in the world: the first and second occurred in my country's Sui Dynasty (AD 6th century), the third time was the Song Dynasty (14th century AD), the first time the number of lives devoured was nearly 100 million worldwide; the second time 25000000 people died in Europe alone, and 40000000 people died in Asia (13 million in China) . The third time occurred in the late 19th and early 20th centuries, endangering 32 countries. Not only do rats spread diseases, but they also kill people naked. In 1982, 45,000 people in the United States were bitten or killed. The economic value of rats’ damage is also staggering. According to statistics from biologists, there are 4 billion rats in the world. If each rat eats 8 kilograms per year, it will swallow 32 million tons of food every year, which can feed 250 million people for a year. Our country is the first country to prevent and eliminate rats.

The most chilling thing is that of the more than 2,000 species of rats, about two-fifths are related to zoonotic diseases. Among them, 186 species of rats can infect and spread plague. Plague is a severe infectious disease caused by Yersinia pestis, spread among rodents and fleas, and is common to humans and zoonoses. In the fourteenth century, the Asian plague spread to Europe, directly reducing the population by one-third. Hemorrhagic fever with renal syndrome is the most serious rodent-borne disease in China, and there is currently no special treatment or effective medicine.

But rats are not useless. With the help of modern scientific breeding technology, many rats have become human delicacies. In traditional Chinese medicine, "Wulingzhi" and "Caolingzhi" are the feces of moles and rats. Cantonese people in China have been eating mice for more than a thousand years. They call newborn mice Miji, and they also have the custom of brewing mouse wine. Eating roasted rat in Vietnam is as common as eating roasted chicken in China.

Some mouse species share more than 95% of their genes with humans, and have 99% human homologous genes. Therefore, mice have become a reliable biological model animal, and hundreds of millions of mice are raised in major scientific research institutes around the world.

Living together day and night for millions of years, rats have become an important part of human civilization. In ancient Egypt, rats were considered to be the incarnation of the moon because of their habit of working the night shift. Mummy rats have also been found in ancient Egyptian tombs.

Because it is most active in the early morning (midnight), the rat ranks first among the twelve animals in the Chinese zodiac. In ancient India, rats were the messengers of the Hindu God of Wisdom, and there were rat temples in India dedicated to rats. Thousands of years of species shining in the galaxy, millions of years of loving and killing humans. Rats have changed human civilization in the most special way and have accompanied countless innocent childhoods.

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