The dog-shaped scorpion unearthed from Sanlihe River in Jiaoxian County, Shandong Province is vivid and lifelike, which makes us see the morphological characteristics of domestic dogs in Neolithic Age. The dog bones unearthed from Anbanpo site in Xi 'an, Shaanxi, have small skulls, protruding frontal bones, small cracked teeth and curved horizontal edge of mandible, which is quite different from that of North China wolves, indicating that the history of human domestication of dogs is indeed very early.
First, the ancestors of dogs
No one knows exactly when the first interaction between man and wolf took place. Some scientists think it may be 50,000 years ago, because it took wild wolves at least so long to show today's genetic differences. At that time, humans and wolves were distributed in many places on the earth's surface, and the evolution process may have occurred in several different areas.
Some scholars believe that wolves were domesticated from wild wolves to domestic animals for playing, hunting and housekeeping, that is, dogs, before 14000 years or even before 16000 years in Southeast Asia. At present, all kinds of dogs in the world originated from wolves domesticated in the south of the Yangtze River valley in China about10.6 million years ago. Peter Sa Flening, a scientist from the Royal Swedish Institute of Technology, confirmed the origin, location and time of dogs.
Second, the domestication process
The biological origin of dogs can be traced back to tens of millions of years ago, and the domestication history of dogs was about10.5 million years ago in the Middle Stone Age. Some scientists even demonstrated from the perspective of genetics that dogs may have been domesticated by humans as early as 654.38 million years ago. ?
Humans deciphered the dog's genome for the first time in 2005-even before researchers used genetic tools to track the dog's earliest home. Early studies have found that dogs in East Asia have a high degree of genetic diversity, and other key markers have been found in many rural dogs. Therefore, they pointed out that East Asia was the first place where humans domesticated dogs. ?
Researchers at the University of Arizona in the United States unearthed two dog skulls at least 33,000 years ago from Belgium and Siberia, respectively, indicating that dogs have been tamed by humans as early as ancient times.
Third, the genetic code
14000 years, after constant domestication, more than 400 kinds of dogs have been produced. Each species has a unique physique, coat color and habits. In order to find the gene mutation that causes specific traits in dogs, in 2009, Akey et al. analyzed the genomes of 275 domestic dogs of 10 breed * * *. Previous studies have found genes that bring specific characteristics, such as the short legs of dachshunds.
They analyzed a series of dog breeds to determine the impact of centuries of selective reproduction on the entire dog genome. The author scanned the genetic records of nearly 300 dogs, including beagles, border collies, Jack Russell, Sharp and standard poodles, and determined how selective reproduction affected the genomes of these animals.
The author found that 155 different genetic positions may play a role in producing the characteristics of purebred dogs, and suggested that this information may provide clues for finding genes that produce the appearance of specific breeds. For example, this group of scientists suggested that different versions of the HAS2 gene may bring unique folds or smooth skin to Sharp dogs. Compared with the research on the appearance characteristics of dogs, the research on physiological characteristics is less.
20 12 Chen et al. classified and sequenced the olfactory receptor gene families of dogs and wolves. It was found that due to reproductive isolation caused by domestication, the olfactory receptor gene evolution directions of dogs and wolves were different, and the olfactory receptor gene sequence of rural dogs in China was conservative.
Lindblad-Toh and Erik Axelsson sequenced the whole genome of 12 wolves and 60 dogs representing 14 different breeds from all over the world. The research team finally got a list of *** 122 genes in 36 regions. Half of these regions contain brain genes. There are 6 genes related to fat and starch digestion, 10.
Specifically, dogs carry extra copies of the amylase gene, and they now produce 28 times more protein than their wolves. In addition, the maltase-glucoamylase produced by dogs is more than 12 times, which is due to several mutations in the enzyme gene. The mutation of the third gene SGLT 1 improved the function of intestinal sugar absorption protein. It shows that starch digestion is related to the evolution of dogs.
Extended data:
In view of the huge differences in body shape and appearance of various dogs, before the emergence of molecular biology, people could only judge the origin of dogs by their appearance, and infer the origin of dogs by observing their appearance characteristics and behavior habits, so the view that dogs originated from multiple ancestors was widely accepted.
Charles Darwin is one of the representatives. 1868, published "Variation of Animals and Plants" at home. In the book, Darwin expounded his views on the multi-ancestor origin of dogs. He believes that the phenotypes of different dogs are too different to originate from the same ancestor, and it is most likely to originate from multiple ancestors such as wolves, coyotes or jackals. These ancestors mated with each other and formed today's complex and diverse dog families.
Austrian zoologist Konrad Lorenz is a pioneer of modern animal behavior, and he also supports the view that dogs have multiple ancestors. He wrote in "Dog Family" published in 1950s that some dogs are descendants of wolves, while others are domesticated by jackals.
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