The widely accepted “family tree” of ancient humans isn’ve been set in stone for decades, and a new wave of discoveries and differing interpretations are challenging established classifications. The case of the Denisovans, ancient hominins known primarily from limited skeletal fragments until recently, highlights this instability. A major breakthrough in June occurred when molecular evidence linked a previously mysterious skull from China to this elusive group, effectively giving the Denisovans a recognizable face – or so it seemed.
However, this seemingly definitive identification is being contested by anthropologist Christopher Bae of the University of Hawai’i at Mānoa. He believes the skull should remain classified within a different species, Homo longi, demonstrating the ongoing debate about how to categorize our ancient ancestors. Bae is at the center of this debate, and his team has recently proposed adding two new species to the mix: Homo bodoensis and Homo juluensis.
These proposals have generated controversy, partly because Bae and his colleagues have challenged the traditional rules governing species naming. He argues that these rules have become outdated and fail to account for the need to retire offensive names or ensure pronounceability and clarity. His perspective underscores a broader issue: can rigid adherence to established scientific rules hinder progress in understanding the complexity of human evolution?
Bae’s Journey: Origins and the Quest for Understanding
Bae’s passion for understanding human origins stems from a personal journey. Born in Korea and adopted by an American family after being abandoned as an infant, he experienced a profound desire to uncover his own background. After being denied access to information about his biological parents by the adoption agency, he found solace and purpose in the field of biological anthropology, a discipline that allows him to explore human origins even in the absence of complete information – mirroring his own incomplete personal history.
“The basic goal of palaeoanthropology is to reconstruct the past, even without all of the pieces of the puzzle… In my own case, I was born in Korea, then I was abandoned… But then I took an introduction to biological anthropology course, and I found a field where I could actually explore origins.”
Challenging Established Classifications: Homo bodoensis and Homo juluensis
Two species frequently discussed in the context of human ancestry are Homo heidelbergensis and Homo rhodesiensis. In 2021, Bae’s team proposed replacing both with a single new species, Homo bodoensis. This suggestion arose from observing that Homo heidelbergensis had become a “wastebasket taxon”— a catch-all category for fossils from a specific time period that didn’s neatly fit into established categories like Homo erectus, Homo neanderthalensis, or Homo sapiens.
The response to this proposal was mixed, with some praising the need for a broader discussion, while others dismissed it as unfounded. Nonetheless, a 2023 workshop involving 17 palaeoanthropologists resulted in agreement that Homo heidelbergensis should be reconsidered and that Homo rhodesiensis, due to its namesake’s colonial history, should be removed from scientific usage.
The International Commission on Zoological Nomenclature (ICZN), the body responsible for judging such cases, has resisted these changes, asserting that it won’t retire species names based on ethical concerns. Bae challenged this decision, highlighting a fundamental conflict between the desire for inclusive scientific practices and the ICZN’s adherence to traditional guidelines.
The Importance of Names: From Hitler Beetles to Xujiayao
The debate over scientific names isn’t merely an academic exercise. Bae illustrates the potential consequences of inappropriate names using the example of a beetle from Slovenia, originally named after Adolf Hitler. Today, these beetles are sought-after collector’s items among neo-Nazis, potentially driving the species to extinction. This underscores the need for names that are respectful, accessible, and won’t inadvertently contribute to harmful ideologies.
Bae advocates for a more collaborative approach to naming, encouraging scientists to consult with local collaborators to choose names that are both scientifically accurate and culturally acceptable. He believes the trend will shift towards names that are easier to pronounce and understand, leading to broader accessibility and greater understanding of human evolution.
Recent Controversies: Xujiayao and the Denisovan Connection
Bae and his colleagues recently encountered further challenges with the ICZN when proposing a new species based on fossils from Xujiayao, China. Researchers discovered several hominin fossils at this site in the 1970s, and after detailed analysis, including virtual reconstruction of a skull fragment, Bae’s team concluded that these fossils represented a previously unknown species.
While they initially proposed Homo xujiayaoensis, a name derived from the site’s name, they ultimately chose Homo juluensis, meaning “big head,” believing the former would be difficult to pronounce for non-Chinese speakers. However, even this choice sparked controversy, as the accepted scientific nomenclature requires the addition of an “i” to the end of names, leading to potentially confusing pronunciations.
Furthermore, the Xujiayao fossils share striking similarities with Denisovan molars, leading to speculation about a possible connection. Recent research has linked the same Denisovan fossils to Homo longi, an alternative interpretation supported by many researchers. Bae emphasizes, however, that genetic protein analysis for species identification at this level of distinction is prone to error.
He remains supportive of Homo longi and encourages further investigation to determine whether the fossils from Xujiayao and Xuchang should be assigned to Homo longi or Homo juluensis, noting the current trend among Homo longi proponents to include all fossils in this single species.
Facing Criticism: A Thick Skin
Despite facing considerable criticism, Bae remains undeterred, emphasizing the importance of resilience in the face of opposing views.
“At this point in our careers, we’ve developed thick skin.”
The ongoing debate surrounding the naming and classification of ancient human species underscores the complexity of interpreting the fossil record and the need for open dialogue, inclusivity, and a willingness to challenge established norms in the pursuit of a more complete understanding of human evolution
