Photo: BBC.com- Artist rendition of what Dragon man may have looked like
The big story of the summer in paleoanthropology was the description of an ancient human cranium discovered in northeast China that has led to the naming of a new species of human ancestor. The Harbin cranium was discovered in 1933 by Chinese laborers building a bridge over the Songhua River in Harbin, China. In order to protect it from the Japanese army during World War II, the cranium was hidden in a well where it remained until 2018, when the man who hid it revealed its existence shortly before his death (seriously, what a great story...you can’t make this stuff up). The cranium was then passed on to a team of researchers headed by Qiang Ji at Hebei GEO University.
Due to its unusual history, it is not known precisely where the cranium was first discovered, making it difficult to understand its geological context and thus determine its age. Despite this, geochronologists (scientists who study the ages of rocks, fossils, and sediments) were able to estimate that it is probably 146,000 - 309,000 years old. The research team has suggested that the Harbin cranium represents a previously unknown fossil human species they have dubbed Homo longi, meaning “Dragon Man”. But should the cranium be considered a new species? To address this question, we need to take a closer look at the specimen’s anatomy.
Often, fossils will become distorted from the crushing weight of the earth, rendering them into shapes one might find in a painting by Picasso. This makes it more difficult to assess the features and shape of a fossil without extensive and time-consuming reconstruction. What’s more, there is no guarantee that a fossil reconstruction will be accurate. Fortunately and incredibly, the Harbin cranium is undistorted and almost intact, although it is missing most of its teeth. This allows scientists to be more confident in their assessment of the specimen’s anatomy.
A key feature of the Harbin cranium is its enormous size. It has a cranial capacity of about 1,420 ml, making its brain roughly the size of a cantaloupe and comparable to those of modern humans and Neanderthals. But the cranium lacks distinctive facial features found in Neanderthals and also exhibits traits not seen in modern humans such as a massive brow ridge, and a receding forehead. When viewed from the side, the cranium has a profile that is short, and elongated from front to back. This is drastically different from the tall cranium of our species, Homo sapiens. So we can confidently conclude that the specimen does not represent a Neanderthal or a modern human.
The research team examined more than 600 anatomical traits that were used to compare the Harbin cranium with 95 other hominin fossils from around the world. Their analysis reconstructed a phylogeny (like a family tree) depicting how closely or distantly related the Harbin specimen is to these other hominins (humans and our close extinct relatives). The Harbin specimen appears to be closely related to other “archaic” human fossils from China who lived at about the same time. These fossils are sometimes considered transitional forms between Homo erectus, the first hominin species to leave Africa,and Homo sapiens. Interestingly, among the fossils from China found to be close relatives of the Harbin specimen is a mandible from the site of Xiahe on the Tibetan Plateau, which is thought to be a Denisovan. Denisovans are an enigmatic population of hominins known mostly from DNA. It is intriguing to consider the possibility that the Harbin cranium represents a Denisovan.
Does the Harbin cranium belong to a previously unknown species? That’s a complicated question. It can be very difficult to identify new species in the fossil record. Basically, one has to determine whether the anatomical differences between the new fossils and those that are already known are sufficient to show that one is sampling two independent populations that have permanently separated from each other. That can be a tough judgement call if the differences are subtle, as they are between Harbin and other archaic humans. Paleoanthropologists often disagree about new species, so our educated guess is that the species-status of this cranium will be debated. Indeed, Dr. María Martinón-Torres, a paleoanthropologist at El Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), the National Center for Human Evolution Research in Spain has stated, “It’s premature to name a new species, especially a fossil with no context, with contradictions in the data set.” Dr. John Hawks, a paleoanthropologist at the University of Wisconsin-Madison has said, “I think that the appearance of morphological distinctiveness between these human groups is mostly a result of poor sampling.” It is going to take some time for the broader paleoanthropological community to evaluate the species-status of Homo longi, but perhaps that will provide enough time for a movie to be made about its discovery.