The Chinese people's front teeth are like small shovels. Is it for eating better?

When I'm not eating, I always like to lick my teeth, especially the inner side of my upper front teeth, where I can always feel a protruding ridge on each side of the teeth, which is quite interesting.

See those raised ridges?

But later I found out that not everyone has protruding edges on the back of their front teeth. The back of European front teeth is actually flat???

Black hair, black eyes, yellow skin, not as obvious as front teeth

When talking about the physical features of Chinese people, you may think of the poem "Descendants of the Dragon": "Black eyes, black hair, yellow skin, forever and ever we are descendants of the dragon." However, black eyes and black hair are actually very common among many ethnic groups around the world; the skin color of the more than one billion Chinese people also has a wide spectrum from white to black. In fact, the real "typical features" of Chinese people are the protruding edges on the back of their teeth.

The back of the upper incisors of many Chinese people are high on the sides and low in the middle, like a small shovel. This feature is called "shovel-shaped incisors" in physical anthropology.

Shovel-shaped incisors

Image source: twitter.com

Statistics show that nearly 90% of Chinese people have shovel-shaped incisors. The proportion of shovel-shaped incisors is also quite high among neighboring East Asian ethnic groups such as Japan and South Korea, but it is extremely rare among people of European and African ethnic groups. For example, only about 2% of Europeans have shovel-shaped incisors.

The shovel-shaped features of the human maxillary central incisors are divided into four levels. Most Chinese people belong to the last three types, that is, they have shovel-shaped incisor features to varying degrees.

From the appearance, this "shovel" on the back of the teeth is completely invisible. However, due to its high frequency in East Asian populations and the fact that teeth can be preserved for a long time in remains, shovel-shaped incisors are the main identifying feature of East Asian populations for anthropologists, archaeologists and forensic doctors.

By the way, there are 8 incisors in the upper and lower rows of a person's mouth, and the other 6 usually have a "shovel" of varying depths. However, the maxillary central incisors are the most visible and prominent, and the differences between different ethnic groups are the most obvious, so they are used as a standard for ethnic identification.

Shovel-shaped and non-shovel-shaped incisors

Image source: wikipedia

We have relatives in America, but no relatives in Southeast Asia?

There was a popular joke on the domestic Internet that said the Native Americans of America were actually the descendants of the Shang Dynasty who traveled across the ocean. There was even a saying that "Indians = Yindian". Although this saying is extremely unreliable (they were called "Indians" because Columbus mistook America for India), the skin color and appearance of Indians are indeed somewhat similar to those of Chinese people, and the frequency of shovel-shaped incisors is also very high. Are the Native Americans and the Chinese really relatives?

The answer is yes.

The ancestors of the Indians entered the American continent from Northeast Asia during the Ice Age about 20,000 to 10,000 years ago. At that time, the climate was cold, the glaciers expanded, and the sea level dropped, turning the Bering Strait between Asia and North America into a land bridge. The hunting tribes of Northeast Asia followed the herds of animals and came to this strange continent through the land bridge.

The "Bering Land Bridge" in the Ice Age and the modern inferred migration route of the American ancestors. The Bering Land Bridge is located in a high-latitude area with dry and cold winters and lack of sunshine. The characteristics represented by the shovel-shaped incisor gene help improve people's adaptability to this environment, so most Native Americans also carry this gene.

From the perspective of paleoanthropology, the ancestors of Indians and East Asians have not been apart for a long time. In this case, it is not surprising that the two groups have similar appearances and the same type of front teeth.

Native Americans, the Indians, look a lot like East Asians and have the typical shovel-shaped incisors of East Asians. They are also genetically close. The term "Asian-Americans" is named after East Asians and Native Americans.

Image source: history.com

Native American shovel-shaped incisors

Image credit: pinedaleonline.com/Dave Vlcek

However, Austronesians, another large ethnic group that is closely related to East Asians and is widely distributed in Southeast Asia and the Pacific, rarely have shovel-shaped incisors. It seems that the relationship hidden in the big teeth is not as simple as we think.

Many island nations in Southeast Asia and the South Pacific belong to Austronesians, who migrated south from mainland China 8,000 to 5,000 years ago and belong to the "Asian-American race" (formerly known as the Mongoloid race) like us. Although they are close to East Asians in blood, they generally have darker skin because they have lived in the tropics for a long time, and rarely have shovel-shaped incisors.

Image source: wiki

Millions of years of East Asian standard

Shovel-shaped incisors are not only used to divide ethnic groups, but have also been involved in a huge dispute: where do we come from?

In the field of paleoanthropology, there have long been two schools of thought. One school of thought holds that modern humans (Homo sapiens) around the world migrated from East Africa tens of thousands of years ago, which is called the "African origin theory"; the other school of thought holds that humans in all regions evolved from local early humans in situ, which is called the "multi-regional origin theory."

The mainstream "African origin theory" is based on genetic analysis, while the "multi-regional origin theory" is also supported by fossil evidence in East Asia: among the fossil hominins unearthed in China, from the famous Peking Man, Lantian Man, Yuanmou Man and other Homo erectus, to the later Dingcun Man, Maba Man and other early Homo sapiens, and modern humans such as Shangdingdong Man, almost all have shovel-shaped incisors. In other places outside East Asia, it is very rare for hominins to have shovel-shaped incisors.

The figure shows the proportion of shovel-shaped incisors in some populations around the world. However, since the data was collected from surveys conducted by different researchers at different times, the identification standards used were not uniform. According to the latest estimates, the data from China, Mongolia, and Japan only counted "typical shovel-shaped incisors", while the data from the Pima people in North America included "typical shovel-shaped incisors" and "semi-shovel-shaped incisors". In fact, the proportion of shovel-shaped incisors in East Asians and Native Americans is not much different.

Two incisor fossils of Yuanmou Man

Image source: wiki

Foodies may ask, does the presence of a "shovel" on the front teeth have any impact on eating?

The answer is: No.

Some supporters of the "multi-regional origin theory" believe that the shovel-shaped incisors that are common among ancient humans in East Asia are unlikely to be the result of natural environmental selection, but are more likely to be inherited from our ancestors... Could it be that the ancestors of us East Asians are really different?

Are shovel-shaped incisors “given as a gift when you recharge your phone bill”?

With the development of biotechnology, anthropologists began to study DNA as a new breakthrough direction, which is molecular anthropology. Soon, researchers found the key to controlling shovel-shaped incisors - EDAR gene, which is responsible for regulating the development of skin, hair and sweat glands.

Compared to other modern human populations, most East Asians and Indians have a mutation in the EDAR gene: EDARV370A. The shovel-shaped incisors are the result of this mutation.

However, it has more and greater uses than changing the shape of the front teeth: the mutation caused by EDARV370A can make people grow coarser and harder hair that is not easy to curl, and have more sweat glands and sebaceous glands (but East Asians generally have underdeveloped sweat glands, so they have less body odor). Since the mammary gland is essentially a special sweat gland, women who carry this mutant gene have denser and more developed breast tissue, can produce milk with special nutrition, and have less breast fat and a smaller appearance.

A mutation in a gene associated with shovel-shaped incisors (ARV370A) causes several physical traits.

Straight hair, easy sweating, small breasts, all of which are consistent with the overall physical characteristics of modern East Asians (represented by the Chinese). Why is this mutant gene so common in East Asia?

Researchers believe that this is an adaptation to the East Asian environment: East Asia is dominated by a continental monsoon climate, with a huge temperature difference between cold winters and hot summers. Dense sweat glands and more sweating help to survive the hot summer; more sebum can protect the skin from the dry and cold winds in winter; special mammary glands can provide babies with milk containing more fatty acids and vitamin D. From this point of view, the shovel-shaped incisors are just a "gift" of gene association. The above characteristics are the reason why this mutant gene was selected.

Especially in Northeast Asia, where the latitude is high, the winter is long, dry and cold, and there is a lack of sunshine, well-developed sebum can be called a life-saving artifact. The high vitamin D in breast milk can reduce the baby's dependence on sunlight - if it is not obtained from food, the human body needs the help of ultraviolet rays in the sun to synthesize vitamin D.

The extremely high proportion of shovel-shaped incisors among Indians is probably the mark left by their ancestors crossing the Bering Land Bridge in the Arctic Circle. This also explains why Austronesians rarely have shovel-shaped incisors: they live on warm and humid tropical islands, without the troubles of dryness, severe cold and too little sunshine, so this mutation will naturally not be selected.

Source: Museum