It’s fair to state that the ancient human family tree has always been subject to revision. Take the Denisovans, for instance. These enigmatic ancient hominins were once primarily identified through mere bone fragments. However, in June, molecular analysis revealed that a peculiar skull from China belonged to the Denisovans, thus giving them a more defined identity.

Yet, not everyone is convinced. Anthropologist Christopher Bay, a professor at the University of Hawaii at Manoa, contests this finding, asserting that the skull is more likely associated with a species named Homolonghi. Bay has been foundational in ongoing discussions regarding our ancestral lineage. For over five years, he, alongside colleagues, has advocated for the recognition of two ancient human species: Homo bodoensis and Homo juruensis.

These proposals have stirred debate, especially since Bay and his team have intentionally disregarded traditional naming conventions. He argues that such rules have become outdated, failing to accommodate the removal of names that are now considered offensive or unpronounceable. In a conversation with New Scientist, he elaborated on how his personal quest for identity fueled his passion for human evolution.

Michael Marshall: What initially encouraged you to explore the study of ancient humans?

Christopher Bay: The ultimate aim of paleoanthropology is to piece together historical narratives, even when all elements are not available. This field resonates with me personally as I was adopted and spent my first year without any concrete memory. I was born in South Korea, abandoned around one year of age, spent six months in an orphanage, and was later taken in by an American family.

During my undergraduate studies, I had the opportunity to visit Korea for the first time as an exchange student. On this trip, I visited an adoption center in my hometown, inquiring if there was any possibility of locating my birth parents. Unfortunately, I was informed that my Korean name and birth date were not legitimate, and there was virtually no chance of finding them. That was a moment of resignation for me.

Although I was intrigued by my origins, I didn’t know how to pursue them. Then, I enrolled in an introductory biological anthropology course, which allowed me to navigate my curiosity about origins—almost like constructing my own foundation.

Two species frequently debated regarding our direct ancestry are Homo heidelbergensis and Homo rhodesiensis. In 2021, you joined a team proposing the substitution of these names with a new species, H. bodoensis. Could you elaborate on this?

My colleague, Mirjana Roksandic from the University of Winnipeg and I discussed H. heidelbergensis at the 2019 Anthropology Conference. It became apparent that this species had been labelled a “trash can taxon,” becoming an easy classification for fossils that didn’t belong to Homo erectus, Homo neanderthalensis, or Homo sapiens.

What response did your paper receive?

Upon peer review submission, half of the reviewers contended the argument had to be published for its significance, while the other half deemed it entirely flawed. Unsurprisingly, the paper was met with polarized reactions once it was released.

Have any workable agreements emerged from this debate?

We held a workshop in Novi Sad, Serbia in 2023, with approximately 16 to 17 paleoanthropologists participating. A consensus emerged around the notion that H. heidelbergensis is indeed an inappropriate taxonomic category. Another significant finding was that H. rhodesiensis should be excluded due to its colonial implications—remarkably, only one paleoanthropologist present believed otherwise.

The ultimate arbiter in such cases is the International Commission on Zoological Nomenclature (ICZN). Have you received feedback on your argument for H. bodoensis?

The ICZN published a statement in 2023, indicating it “does not involve itself in removing names that may be ethically problematic.” This direction prompted us to challenge the ICZN. Editor’s note: The ICZN’s 2023 announcement recognized that some scientific names might be offensive but asserted it’s beyond their remit to weigh the morality of individuals honored in eponyms. Moreover, it stressed the necessity for zoologists to adhere to its ethical code while naming new species.

Are the names of species significant enough to merit conflict?

Yes and no. For instance, several beetles from Slovenian caves were named after Adolf Hitler in the 1930s by an Austrian entomologist, Oskar Scheibel. One species, Anophthalmus hitleri, has gained popularity as a collector’s item among neo-Nazis, which could lead to this innocent beetle’s extinction.

What alternatives do you propose?

I advocate working with local collaborators to choose species names that they find acceptable since they live with and experience these species regularly. Ideally, I believe we should refrain from using personal names for species, as this could lead to ongoing issues. Change is on the horizon; the ICZN is re-evaluating the inclusion of members from the Global South to provide them a stronger say. Recently, the American Ornithological Society voted to remove names with negative connotations associated with historical figures from their species designations.

Last year, you again disputed ICZN regulations concerning ancient human fossils excavated at a site, Xujiayao, in northern China. What occurred there?

In the 1970s, researchers uncovered multiple hominin fossils representing over ten individuals at the site, though they were found as separate pieces. Together with my colleagues, Wu Xiujie from the Chinese Academy of Sciences worked extensively on these fossils. Wu has virtually reconstructed part of one skull, and upon seeing this, we noted it appeared distinctly different from other hominins of a comparable age.

What differentiates these specimens?

The variations lie in size and shape; our average cranial capacity is around 1300 to 1500 cubic centimeters, whereas these fossils have cranial volumes between 1700 cm³ and 1800 cm³, significantly larger than typical humans. Shape analysis similarly indicated that the Xujiayao fossils correlated differently compared to those from a nearby site called Xuchang, leading us to propose a new species name.

The name you ultimately selected has been met with criticism. Can you clarify the rationale behind it?

The origin of the species name is intriguing; in this case, we could have opted for Homo suziayaoensis, named after Xujiayao, aligning with ICZN guidelines.

In Latin, it translates to “homo“, but you found that option unsatisfactory?

The challenge lies in the fact that only fluent Chinese speakers can pronounce it, and even spelling it correctly can be an issue. Names must be both pronounceable and memorable. Thus, we came up with “julu,” which translates directly to “big head.” However, adhering to ICZN guidelines, we would need to modify the name to “Homo juui”. In our view, since non-Chinese speakers struggle to pronounce it correctly, we ultimately decided upon Homo juruensis.

How does your new species intersect with the enigmatic Denisovans, who inhabited what is now East Asia during the Stone Age?

If you compare the second molars from Denisova Cave with those from Xujiabao, they appear strikingly similar. It’s even plausible to interlink Xujiayao’s and Denisova’s molars, as the distinction is often so subtle.

This year, another research team suggested a link between the same Denisovan fossils and another ancient species, Homolonghi, which has garnered a positive reception among numerous researchers.

Most ancient hominin experts in China tend to side with our argument for H. juruensis, while many Western scholars familiar with China’s historical records also find it agreeable.

Concerning the June-discovered skull, researchers managed to extract ancient proteins associated with H. longhi that corresponded with known Denisovan fossils. What are your thoughts?

Most geneticists argue that protein analysis isn’t robust enough for accurate species identification. While it can differentiate between broader categories—like cats and dogs—its utility in distinguishing more nuanced levels is quite limited.

Do you still consider H. longhi a legitimate species?

I personally appreciate H. longhi and the fossils associated with it. The debate revolves around which other fossils should be allocated to longhi or juruensis. It’s interesting to note that advocates for longhi are attempting to consolidate all fossils under that designation, despite the evident morphological diversity present in Chinese fossils.

Many paleoanthropologists have expressed strong criticism of your research. How do you and your colleagues respond to this?

Over time, we’ve developed resilient skin regarding our work.