Scientists analyze 30,000-year-old mammoth tusks and uncover mating aggression

Traces of ancient hormones have been detected in the tusks of a woolly mammoth that lived more than 33,000 years ago, revealing that the now-extinct creatures had bouts of raging testosterone.

The findings provide what researchers believe is the first direct evidence that, like elephants, mammoths also experienced the “must”. A study detailing the findings published Wednesday in Nature magazine.

“Musth,” which means “intoxicated” in Hindi and Urdu, is a period of heightened aggression and unpredictable behavior fueled by testosterone during the mating season, when male elephants become rivals.

Previously, researchers inferred that mammoths, extinct relatives of modern elephants, may have suffered from musth due to the discovery of broken tusk tips and other skeletal injuries preserved in fossils.

Evidence of increased testosterone from musth can be detected in blood and urine tests from live elephants.

A team of researchers has turned to the tusks of elephants and mammoths to see if their layers can also preserve the presence of steroid hormones like cortisol, said study lead author Michael Cherney, an affiliated researcher at the University of Michigan Museum of Paleontology. and researcher at the University of Michigan School of Medicine.

In addition to cortisol, mammoth tusks showed recurrent annual increases in testosterone up to 10 times higher than baseline, according to the study.

“We really didn’t know what to expect, so almost everything was a surprise,” Cherney said. “I think the biggest surprise, however, was how clear the testosterone pattern was.”

Stuck like time capsules

The researchers studied three tusks during the analysis, including two tusks from an adult mammoth and one from an African elephant that was between 30 and 40 years old when it was killed by a hunter in Botswana in 1963.

The male mammoth’s right tusk, which lived about 55 years, was discovered by a diamond mining company in Siberia in 2007 and is estimated to have died between 33,291 and 38,866 years ago.

A tusk from a female mammoth that lived between 5,597 and 5,885 years ago on Wrangel Island was also used in the study. Wrangel Island, once connected to northeastern Siberia, is the last known place where woolly mammoths lived until they went extinct some 4,000 years ago.

Annual growth increments were identified in each prey using CT scans. Next, the researchers used a drill operated under a microscope to grind samples of dentin, the mineralized tissue inside the teeth, as the fangs are elongated incisors.

The dentin powder was analyzed using a mass spectrometer or an instrument that can identify chemicals by classifying charged particles.

“We have developed steroid mass spectrometry methods for human blood and saliva samples and have used them extensively for clinical research studies. But never in a million years did I imagine we’d be using these techniques to explore ‘paleoendocrinology,'” study co-author Rich Auchus, professor of internal medicine and pharmacology at the University of Michigan School of Medicine, said in a statement.

“We had to modify the method a little bit, because those setting powders were the dirtiest samples we’ve ever analyzed. When Mike (Cherney) showed me the elephant tusk data, I was blown away. Then we saw the same patterns in the mammoth – wow!”

Both the elephant’s and the male mammoth’s tusks contained evidence of fungus-related testosterone surges. Meanwhile, the female mammoth tusk showed little variation and very low testosterone, as expected.

What Hormones Reveal

Tusks are a bit like tree rings. They grow throughout an animal’s life, recording molecules like hormones that are linked to an animal’s behavior and physiology. Testosterone accumulates in tissues and circulates in the bloodstream.

“Fangs are particularly promising for reconstructing aspects of mammoth life history because they preserve a record of growth in the dentin layers that form throughout an individual’s lifetime,” said study co-author Daniel Fisher, curator of the Museum. of Paleontology at the University of Michigan and professor in the Department of Earth and Environmental Sciences, in a note.

When scientists study elephant tusks, they can identify the age at which the animals experience musth, whether it happens at the same time of year, and other factors that help them uncover more information about environmental factors and population dynamics, Cherney said. Collecting this kind of information from mammoth tusks can reveal more information about the extinct creatures’ lives.

The researchers believe their findings show that hormonal records in teeth can hold important information that could span thousands of years, especially when studying ancient populations.

“This study establishes dentin as a useful repository for some hormones and sets the stage for further advances in the developing field of paleoendocrinology,” said Cherney. “In addition to broad applications in zoology and paleontology, dental hormone records can support medical, forensic, and archaeological studies.”