Denisovans: Exploring Why Mysterious Ancient Groups Lack Species Names

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In human stories, I aim to address common questions about human evolution. In February 2021, I tackled a query that many find perplexing—whether Neanderthals and modern humans are distinct species (short answer: species boundaries are ambiguous).

This month, we confront another frequently asked question: Do Denisovans, the extinct human group once prevalent in Asia, have a designated species name? If so, what should that name be?

The debate regarding the “official” name of the Denisovans has been lively since their discovery in 2010. Notably, in June, the skull of Harbin, dubbed the Dragon Man from northern China, was classified as Denisovan through molecular evidence. This marked the first acquisition of a Denisovan skull, giving us insights into their facial features.

While participating in New Scientist discussions, host Rowan Hooper asked why Denisovans lack a species name. Why can’t we refer to them as Homo Denisovanensis, similar to how Neanderthals are called Homo Neanderthalensis?

I preferred a straightforward explanation: insufficient information has hindered a definitive classification of Denisovans. Their DNA shows significant divergence from Neanderthal DNA; yet, we require detailed insights into their anatomy and skeletal structure.

However, this inquiry is multifaceted. First, we must identify which fossils unequivocally belong to Denisovans. This involves analyzing numerous specimens and decades of research, complicating the resolution. Secondly, we need to determine which of the assigned names should take precedence under our classification norms—a legal question that adds to the complexity.

Who’s Included and Who’s Excluded?

A brief reminder about Denisovans: they are an enigmatic group of humans initially identified in 2010 from fragments of a finger bone discovered in the Denisova Cave in Siberia’s Altai Mountains. Genetic analysis revealed they were distinct from both modern humans and Neanderthals. Moreover, many contemporary individuals, especially in Southeast Asia and Melanesia, carry Denisovan DNA.

This suggests that Denisovans were quite widespread in East Asia over the past several hundred thousand years. So, where are the Denisovan fossils?

Fifteen years later, a handful of Denisovan fossils have been actively categorized. For example, mandibles discovered on the Tibetan Plateau were identified through fossil proteins and sediment DNA. Similarly, a jawbone retrieved from the Pengle waterway off the coast of Taiwan was confirmed as Denisovan in April.

Nonetheless, we still lack a complete skeleton. Identifying the Harbin skull as Denisovan brought us closer to understanding their appearance, yet many more discoveries are necessary.

Numerous human fossils in East Asia potentially belong to Denisovans. However, categorizing these remains has proven challenging, as they often do not resemble established species like modern humans, Neanderthals, or even Homo Erectus. If adequate specimens surface, thus confirming their Denisovan identity, our understanding could significantly improve, leading to a formal classification.

But how do we determine which fossils are Denisovan? Ideally, we seek molecular evidence of preserved DNA or protein for comparison with the original Denisovan remnants. However, many fossils remain unanalyzed or inaccessible.

One notable effort to address this issue was a preliminary study submitted by a team led by Xijun Ni from the Chinese Academy of Sciences in March 2024. By comparing 57 human fossils for various physical traits, they constructed familial relationships between these findings.

The team found three primary groups among Eurasian hominins: Modern Humans, Neanderthals, and a third group composed of the original Denisovan fossil, the Tibetan cave jawbone, the Pengle jawbone, and the Harbin skull. This third category appears to represent those we refer to as Denisovans.

This is an intriguing proposition, but others disagree.

A collection of contentious fossils from Hualongdong, southern China, offers a wealth of material: an almost complete skull, 14 teeth, an upper jaw, six isolated teeth, and additional fragments dating back around 300,000 years.

While the NI team classified the Hualongdong specimens as part of the Denisovan group, a study led by Xiujie Wu in July suggested that these teeth did not show clear correlations, proposing instead that they may belong to a different hominin group. Another interpretation could be that the Denisovans at Hualongdong were somewhat disparate from those in other regions.

In the meantime, other intriguing fossils from Asia continue to emerge. Among them are specimens from Dariscal and Jinniushan, both around 260,000 years old, which Ni’s team has suggested might also belong to the Denisovan lineage.

As the list of contending Denisovan fossils grows, we must decide how to categorize them.

Homo — What Does It Mean?

Interestingly, I was part of the team that described the Harbin skull in 2021, and we named it Homo Longhi. So, could that be the name we assign to Denisovans?

However, last year a competing proposition was put forth by Woo and Christopher Beh from the University of Hawaii, who suggested that we should center around fossils from Xujiayao in northern China, proposing to call this new species Homo Jurensis—fossils that would include the original Denisovan findings.

This idea’s strength lies in the resemblance of Xujiayao fossils to Denisovan remains, a point also observed by the NI team. However, Bae and Wu aimed to designate the Xujiayao fossils as “type specimens.”

This raises two issues: the classification of fossils and the naming protocols. Let’s examine each aspect separately.

In classification, the Homo Jurensis proposal faces challenges. Bae and Wu classify the Harbin skull as Homo Jurensis or Denisovan, yet it lacks sufficient resemblance to warrant such designation. A study published in June demonstrated molecular evidence clearly linking the Harbin skull to Denisovans. Hence, identifying those fossils as Denisovan would contravene objective realities, making Homo Jurensis seem unfounded.

What about taxonomy? This area is intricate. A crucial factor is the concept of priority, where the first proposed name tends to gain precedence. Hence, Homo Longhi might likely take precedence over Homo Jurensis as it was suggested three years earlier.

Are there alternative names for Denisovans?

The excavators of Denisova Cave never formally classified Denisovans as a distinct species. Anatoly Derebianco, part of that team, suggested the name Homo Sapiens Altaiensis, implying they would serve as a modern human subspecies—yet this proposal lacked formal status, rendering it typically insignificant.

This year, Derebianco has published a series of papers discussing what Denisovans could be. His references include locations in Mongolia, Uzbekistan, Tajikistan, and Iran, referring to them collectively as Homo sapiens denisovan. I remain unsure if formal explanations were provided, as only abstracts were published, and if completed, it occurred post the naming of Homo Longhi.

In deeper investigations, a few additional designations emerge. A 2015 study proposed Homo Denisovensis, while a 2018 paper considered Homo Denissys. Neither is widely accepted.

Lastly, it’s possible that one of the names was assigned to an Asian human fossil within an obscure publication decades ago. If the fossil is ultimately identified as Denisovan, the name takes precedence (assuming it was adequately introduced). Nevertheless, Wu, Bae, Ni, and others assessed this notion in 2023 and concluded that many crucial fossils were not appropriately named. For instance, there was a suggestion to label Dali’s skull as Homo Dariensis, yet such ideas amounted to informal statements rather than formally recognized classifications.

Your head might be swirling from this cascade of names and species classifications, so let’s recap: the critical takeaway is our evolving understanding of Denisovans, which brings us closer to officially designating their name.

Given our comprehension of taxonomic norms and their significance, Homo Longhi could emerge as the official designation. Although I can’t influence the decision, they will always remain Denisovans in my mind.