Hunanese As a Ethnicity

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I originally wanted to write about the history of the concept of “Chinese people,” but the topic turned out to be far too vast—I had no idea where to begin. Not to mention that the territory of “China” has constantly shifted over time, with completely different ethnic groups and customs under various regimes. Some of these cultures might have even entered what we now call “China” by entirely different routes, possibly migrating from the African tectonic plate. And whether these Homo sapiens or Homo erectus actually migrated from Africa is still an unresolved debate in the academic world. So I had to narrow the scope and look instead at the history of Hunan people. What exactly does “Hunanese ethnicity” mean? How far back do we have to trace it? And am I really what they call a Hunanese? I seriously doubt it.

The earliest fossil evidence in the Hunan region seems to be the Fuyan Cave Man from Daoxian, Yongzhou, but there’s intense debate about how old these fossils actually are. The team that excavated them, led by Liu Wu, suggested that they might be early modern humans from 80,000 to 120,000 years ago. Another group, led by Li Hui, argued that they might be only about 9,000 years old.

The fossils were unearthed between 2010 and 2011 at Fuyan Cave in Tangbei Village, Lefutang Township, Daoxian County, Yongzhou, Hunan Province, in a dig led by Liu Wu and Wu Xiujie from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP). They discovered 47 human teeth, along with many mammal bones and stone tools. In their 2015 paper published in Nature, The earliest unequivocally modern humans in southern China, they claimed these 47 teeth, dated using uranium-series methods, could be as old as 120,000 years and morphologically belonged to anatomically modern humans. That would mean southern China had “real humans” 30,000 to 70,000 years earlier than the Middle East and Europe. This discovery challenges the late dispersal theory of the “Out of Africa” model—something that mainstream pop culture tends to accept, and which is also echoed in Sapiens: A Brief History of Humankind.

If Liu Wu’s “discovery” holds up, it would completely overturn the mainstream consensus. It would mean that this piece of land—Hunan—could be one of the earliest known homes of modern human communities on Earth.

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Early Pleistocene fossil records of hominins in southern Asia are extremely rare—especially those that can be clearly attributed to Homo sapiens and have reliable dating. The 47 human teeth found in Fuyan Cave, Daoxian, Hunan, were dated using uranium-series dating, which suggested the fossils were at least 80,000 years old, possibly up to 120,000 years. The morphology of the teeth is highly modern, clearly consistent with anatomically modern humans.

The team didn’t date the teeth themselves but rather the stalagmites above the teeth, using uranium-series (U-series) dating. Uranium decays radioactively into thorium. This decay process is stable and predictable, with a half-life of around 75,000 years. By analyzing the Th-230 / U-234 ratio, researchers can infer the age of the carbonate material.

Even if we’re not familiar with the specific properties of every element, most of us memorized the periodic table in school. With that foundation, you can look up a lot of this information yourself. For example, the uranium used here is pronounced you2 in Chinese. The word was phonetically borrowed; in English, it’s “uranium”—also the core material used to build the atomic bomb in Oppenheimer. From Wikipedia:

“All known isotopes of uranium are unstable. The most long-lived are U-238 (half-life 4.47 billion years) and U-235 (half-life 704 million years), which are the most common in nature. Uranium is the heaviest primordial element still found in large quantities on Earth. Elements heavier than uranium (transuranic elements) have short half-lives and have mostly decayed since Earth’s formation. They are not formed naturally today and are only created artificially, although trace amounts of some like neptunium and plutonium have been found in uranium ores.

Naturally occurring uranium consists of three isotopes: U-238 (99.2739% to 99.2752%), U-235 (0.7198% to 0.7202%), and trace amounts of U-234 (0.0050% to 0.0059%). Natural uranium emits alpha particles as it decays. Due to their extremely long half-lives, these isotopes are used to estimate the age of the Earth.

Uranium’s unique nuclear properties have high practical value. U-235 is the only naturally fissile uranium isotope, meaning it can undergo fission when hit by a slow neutron. If its mass exceeds the critical threshold, it can sustain a chain reaction. Even a tiny loss in mass during the reaction can release massive amounts of energy, which makes it ideal for both nuclear power generation and nuclear weapons.

However, its natural concentration is very low and it must be enriched before use. Uranium metal is highly reactive and forms a dark gray oxide layer when exposed to air. Natural soils, rocks, and water contain about 1 to 10 parts per million of uranium. The mining industry extracts uranium from ores such as pitchblende.”

U-series dating relies primarily on two radioactive decay chains: U-238 → Th-230 and U-234 → Th-230. In nature, U-238 and U-234 are water-soluble and can be transported into stalagmites or bones, but Th-230 is nearly insoluble in water and only forms via decay. So if you find Th-230 in a sample, it must have come from the decay of U-234.

Because U-234 has a half-life of about 245,000 years and Th-230 about 75,000 years, their ratio (Th-230 / U-234) can be used to infer the age of calcium carbonate deposits.

Thorium-230 is the most commonly used isotope in U-series dating. By calculating the Th-230 / U-234 ratio and considering Th-230’s half-life of 75,000 years, researchers can estimate when the material formed.

The name “Thorium” comes from the Norse god Thor. It was first discovered in 1828 by the Swedish chemist Berzelius. Thorium is weakly radioactive and pronounced tu3 in Chinese. It is relatively common in nature, found in thorite and monazite. It was once studied as a safer and more abundant alternative to uranium in nuclear reactors, although it has not seen widespread use. Thorium is a soft, silvery, paramagnetic metal. Pure thorium is quite ductile and, like most metals, can be cold-rolled, extruded, and drawn into wire.

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It’s important to note that what uranium-series dating measures here is not the age of the teeth themselves, but rather the age of the stalagmites covering the teeth, which is then used to infer that the teeth must have existed before that point in time. This is called “minimum age dating.”

Minimum age dating refers to cases where anthropologists can’t directly determine how old something is, but they can determine how old it must at least be. In other words, we can’t say this fossil is definitely 100,000 years old, but we can say: “It can’t possibly be younger than 80,000 years.” Liu Wu’s team didn’t measure the teeth directly, but instead measured the stalagmites that had formed over them. Since stalagmites are formed by calcium carbonate deposits accumulating over time—on top of something—the logic is simple: if the stalagmites are 80,000 years old, then the teeth must have been there already for the stalagmites to form on top of them. So the conclusion is: the teeth must be at least 80,000 years old. However, the age of the covering material tells us when the “roof” formed—it doesn’t tell us how long the teeth had already been there before that.

Directly dating the teeth is tricky, especially when we’re talking about extremely old specimens. First, teeth are not closed systems. Radiometric dating requires the sample to be a closed system—meaning no exchange of material with the environment. But teeth, buried in soil for tens of thousands of years, can absorb water or lose minerals, throwing off the dating results.

To complicate things, tooth enamel is extremely hard and chemically stable—basically insoluble—so it doesn’t absorb uranium easily. But dating methods often require a certain amount of uranium to kickstart the decay chain. If the tooth hasn’t absorbed enough uranium over thousands of years, there’s no meaningful decay chain to measure—and no date to calculate.

U-series dating depends on there being uranium to begin with, and then watching it decay into thorium over time. If the initial uranium content is too low—or nonexistent—then there’s nothing to decay. It’s like trying to read a clock that was never wound up.

Teeth, being biological rather than mineral, contain almost no uranium when they form. So scientists hope that after a tooth is buried in soil, groundwater carrying dissolved uranium will gradually seep in. That’s when the “decay clock” starts ticking. But if the soil is poor in uranium, or the burial environment is too dry or too deep for water to reach the tooth, or if uranium seeped in inconsistently over time, then the decay model falls apart. Worse, if uranium absorption occurred very late, the calculated age might be tens of thousands of years younger than the actual burial time.

In the Fuyan Cave controversy, Liu Wu’s team used exactly this kind of “stalagmite-over-tooth” U-series dating method and concluded that the teeth must be at least 80,000 years old. But after Liu’s article was published, Li Hui and others re-measured the teeth themselves and concluded that they were only about 9,000 years old.

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In 2015, Liu Wu’s team published a paper in Nature, asserting that the 47 human teeth from Fuyan Cave were 80,000 to 120,000 years old and belonged to early anatomically modern humans. In the following years, Li Hui’s team formally applied for sample access, conducted collaborative research, and obtained some of the original teeth or replicas for independent dating. In 2021, they published a paper in PNAS titled Ancient DNA and multimethod dating confirm the late arrival of anatomically modern humans in southern China, using multi-method dating to reassess the age of the teeth and concluding they were only about 9,000 years old.

Li Hui’s team used Electron Spin Resonance (ESR) dating to measure the teeth—a technique that reads “annual rings” of radiation damage based on trapped electrons. After being buried, the teeth are bombarded with natural background radiation from uranium, thorium, potassium, and other elements. As mentioned earlier, uranium decays into thorium. While Liu Wu’s team calculated dates based on uranium and thorium ratios in overlying stalagmites, here the researchers used the same radioactive elements, but a completely different method.

In this case, they directly measured the electrons that were knocked out of position and got trapped inside the hydroxyapatite lattice of the tooth enamel. These electrons accumulate year after year within the crystalline structure. Hydroxyapatite forms the structural framework of both teeth and bones: tooth enamel is 96% hydroxyapatite; bones are around 65–70%.

Tooth enamel is the translucent white shell on the outside of our teeth—hard, avascular, non-regenerative, and mineral-rich. That’s why people get fillings: because once enamel is damaged, it doesn’t grow back—unless you discover some kind of stem cell-based regeneration method, I suppose. Hydroxyapatite provides that extreme hardness to resist wear, and also constitutes the inorganic backbone of bones, supporting structure and calcium storage.

Electron Spin Resonance was discovered in 1944 by Soviet physicist Yevgeny Zavoisky. It involves the magnetic resonance of spin-1/2 particles under a static magnetic field. (You probably learned about spin-1/2 electrons in general chemistry—maybe didn’t understand the details, but you know the term.) Since most electrons in molecules exist in pairs with opposing spins (up and down), their magnetic effects cancel each other out. Only unpaired electrons can exhibit magnetic resonance—such as the ones knocked out of place and trapped in the hydroxyapatite lattice.

In ESR dating, scientists use microwaves to excite these trapped electrons, measuring how many are present to get the total “accumulated dose.” They then measure the annual radiation dose rate of the surrounding soil—essentially asking, “how much uranium is this soil giving off each year?” Dividing total trapped dose by annual dose rate gives the estimated age of the tooth.

To measure the annual dose rate in the surrounding sediment, Li Hui’s team used Optically Stimulated Luminescence (OSL)—a method I don’t fully understand. Apparently, it requires that the soil hasn’t been exposed to light, otherwise the signal resets. But these teeth were excavated, stored, transported, and eventually handed over to Liu Wu—I find it hard to believe they were never exposed to light during all of that. So I’m skeptical about that part of the data.

Comparing the two, it seems Liu Wu’s result might actually be more reliable—though honestly, both dating methods seem prone to uncertainty in different ways.