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How a mislabeled wolf skull spurred an erroneous scientific conclusion

A cautionary tale about what happens when museum specimens are incorrectly labeled

Jazmin Murphy

Ecology and Science Journalism

In August of last year, two researchers, Fabio Machado and Pablo Teta, were publicly corrected by fellow scientists. They had made a mistake that started with a simple museum specimen mislabeling and snowballed into a consequential taxonomic mishap. 

Their original study, published in February 2020, investigated physical variations in the golden wolf species complex, and how those variations revealed their relationships to other species in the genera Canis (dogs, wolves, jackals, and coyotes) and Lupulella (jackal). 

Machado and Teta were particularly interested in the similarities and differences between the golden and grey wolves, a comparison that scientists have continuously studied since the 400s BCE. They analyzed specimens of Canid species that shared significant geographical or physical overlap with the golden wolf, including the Nubian wolf and side-striped jackal. 

However, the pair's big mistake lies in their hypothesis, perpetuated by a common mishap in museum collections’ organization practices. The researchers predicted that the Nubian wolf (Canis lupaster soudanicus; also known as the variegated wolf), a type of golden wolf, was actually another variant of the side-striped jackal (L. adusta). This would remove the Nubian wolf from the golden wolf species group, against current knowledge.

Unfortunately, Machado and Teta confirmed this hypothesis by looking at the wrong samples. They relied on seven skulls sourced from the Smithsonian National Museum of Natural History. And, while authentic Nubian wolf skulls were available in the Natural History Museum in London, the Smithsonian skulls had been mislabeled during their transfer from the Field Museum in Chicago (where they were correctly identified) to the Smithsonian. 

Machado explained via email that their decision not to use London’s specimens was due to “a lack of time and funding.” But after seeing the specimens in person at both the Field Museum of Natural History in Chicago and the Smithsonian, the scientists began to realize there was a logistical issue underlying their study, later pointed out by fellow academics: the Nubian wolf specimens had been mislabeled as side-striped jackal skulls. This created a confirmation bias that led the researchers to confirm their erroneous hypothesis that the Nubian wolf and side-striped jackal were one and the same. 

Although it may seem to be a mere logistical mistake concerning an organism's name, such a mistake can have significant ripple effects in taxonomy and ultimately, wildlife management. If conservationists and biologists have to work with faulty understandings of a species and its evolutionary history and relationships, they will be poorly equipped to regulate its existence in vulnerable environments. Problems like this can snowball into greater crises like muddled genetics and out-of-control species invasions.

a museum specimen of a horse skull, with a label and scale bar, set against a white background

An example of a museum specimen (in this case, a horse skull), complete with a label and scale bar to assist researchers in getting accurate information and measurements

Museum of Veterinary Anatomy FMVZ USP / Wagner Souza e Silva (Wikimedia Commons)

Machado stated, “In fact, when I first came across the Soudanese specimens on [sic] the Field Museum, I decided not to measure them. But once I got to the Smithsonian museum and realize [sic] that the Soudanese specimens on [sic] that institution were also diagnosed, that’s when I thought it would be better to measure them and to maybe later figure out what they were.” 

Still, the duo persisted in their work and ultimately concluded that “C. l. soudanicus [the Nubian wolf] is a synonym of Lupulella adusta [the side-striped jackal] rather than being part of the golden wolf complex.” (In taxonomy, a “synonym” is a current species name, widely accepted as a replacement for an old name. A “species complex” refers to a group of species that are so similar it’s hard to tell whether they’re distinct species or not.)

Yet, in recent correspondence, Machado expressed that their original intention was never to author a taxonomic publication, but to “draw attention to the fact that the U.S. samples from Sudan were consistently misclassified.” Their hypothesizing about the Nubian wolf was only an afterthought that arose “in passing,” but all the while, they were “aware that these specimens had different tag names when originally collected.”

Machado and Teta’s intention was seemingly lost in translation, as Andrew Kitchener and other scientists (including Fabio Machado himself) corrected in another study about six months after the original was published. 

Kitchener's group focused on Machado and Teta’s failure to include the correct Nubian wolf specimen in the analysis and their alleged decision to take the museum’s labeling at face value, instead of studying the discrepancies any further. Kitchener’s greatest concerns were the “important ramifications” that could unfold because of researchers assuming museum collection’s correctness. 

They suggested a review and corrections of such errors and urged other researchers to verify specimens’ identifications before working with collections in the future. 

Misunderstandings about species’ evolutionary pasts can have devastating consequences for the present. This is an issue that wildlife managers are presently dealing with in invasive species management, for example. 

Without a correct understanding of an animal’s taxonomic relationships and evolutionary patterns, these professionals cannot predict or contain ecosystem damage appropriately. This is especially important when dealing with canines like wolves and jackals. These animals have a strong potential for invading new habitats, shown by their historical and present-day patterns. 

Past and present research accuracy is non-negotiable to wildlife managers’ ability to protect and preserve the habitats and animals in their care. As other experts have pointed out, this job cannot be done without the ability to rely on such knowledge, especially in environments that are severely impacted by flux the climate and biodiversity. 

Most of the world’s ecosystems are increasingly facing unprecedented species invasions, weakening the status of native plants and animals, exposing them to abnormal scarcity, competition, and disease. Now, more than ever, research based on accurate data pertaining to living organisms, their taxonomic relationships, and their ancestral species is crucial to mitigating these threats

For instance, when managers can base their work on precise taxonomic knowledge, they can correctly predict an invasive animal’s behaviors and how an invasion might play out. This minimizes the amount of time the scientists need to contain the problem, reducing the potential for damage and new invasions. Instead, this mislabeling perpetuates misinformation in scientific work and may have also misled visitors with similarly kept and labeled items, as the Field Museum (like other natural history museums) puts a small fraction of their 40 million specimens on display

Some scientists have noted that reliable taxonomic research is in painfully short supply and is riddled with systemic problems. These issues include a bias toward more developed geographic areas and inconsistencies in species identification. Experts further emphasize this by asserting that species groups that are infamously difficult to tell apart (like the golden wolf complex) are subject to the greatest biases. 

Machado and Teta aren't the only ones to be caught off guard by labeling confusion. Past research showed that the issue is just as prevalent – if not more so – in botanical sciences. In a survey spanning 40 herbaria located in 21 countries, scientists confirmed that a whopping 58 percent of African ginger specimens were labeled incorrectly. Morning glories and dipterocarp trees are two more groups of plants commonly affected by false naming in museum exhibitions. Other scientists have found that misidentification seeps into entomological studies, too, with a "large proportion" of museum specimens being falsely named

For the scientists who find themselves in such conundrums, Machado offers you this word of advice: 

“I would advise people to be more dispassioned and open to criticism. Errors happen, the review process might not deal with all of them and we have to correct them, somehow. That can only be done by listening to your peers and to the evidence and argument that they provide.” 

Machado expressed thankfulness for “constructive dialogue with Dr. Kitchener and other researchers, and emphasized that there is “more to gain in conversation than in defending relentlessly one point of view.”