Princeton Lab’s research on elephant defectiveness draws public attention to human impact on evolution


More and more elephants in Mozambique are being born without tusks. An ocean and thousands of miles away, Princeton researchers wanted to understand why.

“It started after a YouTube frenzy at 3 a.m.,” said Shane Campbell-Staton, assistant professor in the Department of Ecology and Evolutionary Biology (EEB), speaking about his research in Gorongosa National Park, who were covered by The Atlantic, The New York Times, and “The Daily Show” with Trevor Noah.

“I came across this video made by the Howard Hughes Medical Institute on the lack of defense of the elephants in Gorongosa,” said Campbell-Staton.

Survey data from Gorongosa National Park in Mozambique showed an increase in helplessness after the Mozambican civil war, in which prized elephants without ivory tusks were more likely to survive poaching. Intrigued, Campbell-Staton sent emails and was put in touch with Robert Pringle, a professor in the university’s EEB department. Pringle was due to visit Gorongosa in the summer of 2016.

Campbell-Staton and his friend Brian Arnold, a Schmidt DataX scholar at the University, decided to join Pringle on the mission to investigate the genetics behind the lack of defense.

As an evolutionary biologist, Campbell-Staton studies how animal traits are affected by human interactions with the environment.

“One of the most profound things that we have found in contemporary biology is that evolution can happen very quickly,” he explained. “I think this fundamentally changes our understanding of what the process of evolution is.”

Pringle pointed out that studying evolution on a short time scale is not easy; it requires creativity and the ability to examine entire systems.

Campbell-Staton has a team to help him. He is the principal investigator of the Campbell-Staton Group, a lab he started building at UCLA and which moved to Princeton University last summer.

Campbell-Staton emphasizes science communication in his lab.

“Sharing what we find in the lab and what we find in the field is really important to me,” he said. “Bringing evolution and biology into the mainstream, making it a natural part of everyday conversation, is my ultimate goal. “

True to this mission, the team’s research into the absence of elephant tusks has certainly reached a large audience.

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Trevor Noah and Ronny Chieng of “The Daily Show” recapped the study’s results in a segment of the show in October 2021. The two gave their own comedic interpretations of the results.

“A new study in Mozambique found that elephants in a park evolved to lose their tusks,” Noah said. “In fact, in the year 2000 there were three times as many defenseless female elephants as there were 30 years earlier. Which makes sense. Elephants no longer need tusks. We now have can openers.

“Being able to avoid poachers is great news for elephants. With the exception of the elephants who just graduated from dental school – I mean, that’s their future, ”Noah continued.

“Hearing Trevor Noah talk about Comedy Central research was probably the strangest thing. But it’s pretty cool. I’m happy that evolution is able to break through barriers in popular culture like this, ”Campell-Staton said.

Pringle is also pleased with the media attention.

“It brings knowledge to people, and I think it’s fantastic,” he said.

The path to producing and publishing research has certainly not always been easy. Looking back, Campbell-Staton recalled that the search did not go exactly as planned when they arrived in Mozambique.

Originally they wanted fecal samples to extract DNA from, but they couldn’t just pick up samples they found in the park. In order to know if a sample was from an elephant with or without tusks, they actually had to see an elephant excrete it.

Yet, Arnold said, during the first few weeks they were there, they didn’t see a single elephant. He didn’t expect large mammals to be so difficult to spot, assuming they would be able to gaze out over the savannah with ease. Yet the aptly named “elephant grass” that covers the park can reach up to three meters in height, inhibiting their sight.

Fortunately, they were able to team up with a group of researchers who were tranquilizing elephants for a follow-up project and obtained blood samples from the tranquilizers.

Campell-Staton said he used these blood samples to sequence the genomes of several female elephants. Every elephant, just like humans, has a unique genome resulting from the mixing of two distinct genomes different from their biological parents, as well as mutations or modifications in their DNA.

If this mutation is passed on to their offspring and creates a different set of instructions, such as not asking the elephant’s body to build tusks, its frequency in the population can eventually change, which means evolution is happening. .

Now that Campbell-Staton had found its source of DNA, it was time to analyze it.

“We had several matriarchs, from different families across the park. About half of them had tusks and half did not, ”said Campbell-Staton.

They used this “genomic data to look for signatures and selection … to look for regions of the genome that differ between defenseless and defenseless females,” he explained.

In addition to the differences between the tusked and helpless elephants, they were looking for signs of another recent development; if a mutation increases in frequency very quickly within a population, mutations located nearby in the genome often do the same.

“We have found these candidate regions of the genome, but we have not found the specific allele or alleles that … can cause lack of defenses,” said Campbell-Staton. An allele is a particular form of a single gene – for example, one allele might have DNA from brown eyes, while another allele from the same gene would code for green.

Researchers believe it’s possible that the elusive “defenseless gene” is deadly for humans; this could happen if the gene for lack of defense also has other impacts essential to survival and resides on the X chromosome. Since female elephants have two copies of the X chromosome and males do not. that one, females could compensate for a dysfunctional copy of the gene, while males would have no luck.

Defenseless mothers have more female offspring than you might expect: Survey data shows that about two-thirds of their offspring are females, which Arnold says could be proof that they harbor a mutation that is fatal for males.

Arnold noted that while they have candidate genes that could be responsible for the lack of defense, genomic data still needs validation.

“This is a theme common to many genomics projects,” he said. “The research never stops.”

Campbell-Staton explained that the group is looking to expand their research with more samples and analysis.

“We’re also sort of branching out and looking at other populations to ask ourselves what the extent of the patterns we’re seeing in Gorongosa,” he said. He explained that the group plans to work in South Africa, northern Mozambique and potentially other places in Africa, to draw comparisons between several populations.

However, the ongoing COVID-19 pandemic has disrupted the group’s plans, given travel restrictions.

“We will remain flexible depending on what happens with the variants and any travel restrictions put in place. And, of course, the University’s recommendations, ”continued Campbell-Staton.

Although research continues, Campbell-Staton and his group have already succeeded in attracting the attention of the general public to the science of evolution. He hopes that when people hear about the work they do, they will understand differently the impact humanity has on other species.

“I think when most people think of humans, we somehow see ourselves as disconnected from the natural world or disconnected from the evolutionary process. Which is not true at all, “he said.

Humans, he added, are not detached from nature, but rather intrinsically involved in ongoing natural processes, from the evolution of our own species to that of others.

“Evolution is always a fundamental part of who we are, where we come from and where we are going,” said Campbell-Staton. “It is also a fundamental part of how we impact the planet and the species that live in and around us and among us. “

Madeleine Lausted is a writer for the Features team and editor for “Daybreak” in the Podcast section. She can be contacted at mlausted@princeton.edu.

Paige Cromley is a writer for the Features, News and Leads sections. She can be reached at pcromely@princeton.edu.


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