Male woolly mammoths also had elevated hormones

Indeed, there is no shortage of interesting courtship and mating rituals in the animal kingdom. From trilobites “bumping” to win mates to the important pee-sniffing rituals of giraffes, keeping up is serious business. As well as winning a partner.

[Related: Male California sea lions have gotten bigger and better at fighting.]

For the first time, scientists have found direct evidence that adult male woolly mammoths have experienced an event called a must. Musth comes from the Hindi and Urdu word for intoxicated, and in the case of giant mammals such as adult elephants, it is a testosterone-fueled event where the male sex hormone rises and aggression against rival males intensifies.

The study, published online May 3 in the journal Nature, found evidence that testosterone levels are recorded in the growth layers of elephant and mammoth tusks. In living male elephants, blood and urine tests have recognized elevated testosterone, but grudge fights from its extinct relatives are only suggested by the fossilized effects of testosterone-fueled combat, such as chipped tusk tips and skeletal injuries.

In the study, an international team of researchers reported the presence of annually recurring testosterone peaks (up to 10 times higher than baseline levels) in a permafrost-preserved wavy mammoth tusk.

The team took tusks from an adult African bull elephant from Botswana and two adult woolly mammoths: a male that roamed Siberia more than 33,000 years ago, and an approximately 5,597-year-old female found on Wrangel Island. This island in the Arctic Ocean was connected to northeastern Siberia and was the last place where woolly mammoths survived until about 4,000 years ago.

“This study establishes dentin as a useful repository for certain hormones and sets the stage for further progress in the emerging field of paleoendocrinology,” study co-author and University of Michigan Museum of Paleontology paleontologist Michael Cerny said in a statement. “In addition to broad applications in zoology and paleontology, dental hormone records could support medical, forensic, and archaeological research.”

Hormones are signaling molecules that help regulate physiology and behavior. Testosterone in male vertebrates is part of the steroid group of hormones. Testosterone circulates in the blood and accumulates in various tissues.

[Related: How much acid should you give an elephant? These scientists learned the hard way.]

According to the authors, their findings show that records of steroids in teeth can provide scientists with meaningful biological information that can even be preserved for thousands of years.

“Tusks hold particular promise for reconstructing aspects of a mammoth’s life history because they preserve a record of growth in the layers of dentin that form throughout an individual’s lifetime,” study co-author and UM Museum of Paleontology Daniel Daniels said in a statement Fisher. “Because tusks are associated with dramatically increased testosterone in modern elephants, it provides a starting point for evaluating the feasibility of using hormones preserved in tusk growth records to study temporal changes in endocrine physiology.”

Traces of sex hormones extracted from the tusk of a woolly mammoth provide the first direct evidence that adult males have experienced a must, an episode of increased aggression against rival males triggered by testosterone. CREDIT: University of Michigan.

They used computed tomography to detect annual growth increments deep within the tusks, such as tree rings. The tusks of the modern elephant and the ancient mammoth are elongated upper incisors and contain only traces of testosterone and other steroid hormones. All of the chemical compounds are incorporated into the dentin, which is the mineralized tissue that forms the inner part of the teeth.

The study also calls for new methods to extract steroids from tusk dentin with a mass spectrometer. Mass spectrometers identify chemical substances by sorting the ions present by their mass and charge.

“We had developed steroid mass spectrometry methods for human blood and saliva samples and used them extensively for clinical research. But never in a million years would I have imagined that we would be using these techniques to study “paleoendocrinology,” study co-author and UM endocrinologist Rich Aukus said in a statement.

The results and the new measurement technique are likely to contribute to new approaches to studying reproductive endocrinology, life history and even disease patterns in modern and prehistoric contexts.

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