For the first time scientists have detected evidence that woolly mammoths experienced musth during the mating season, a hormone-driven surge in aggression that would’ve spurred on rival males at they competed for a mate. The discovery has also revealed that such hormone changes can be detected in the growth rings of tusks, something that can be applied to modern day elephants as well as their ancient ancestors.
Two woolly mammoth (Mammuthus primigenius) tusks from a male and female, and one adult African elephant (Loxodonata) bull tusk were used in the study. CT scans were able to identify the annual growth rings within the tusks, allowing researchers to go into with a tiny drill bit and grind away samples from different months’ dentin growth.
This powder was then chemically analyzed for signs of steroids, a category natural testosterone falls under. The technique used to do this was actually initially created for use in human medicine, so taking it for a spin on woolly mammoth tusks was a surprise for the research team.
"We had developed steroid mass spectrometry methods for human blood and saliva samples, and we have used them extensively for clinical research studies. But never in a million years did I imagine that we would be using these techniques to explore 'paleoendocrinology,'" said endocrinologist and study co-author Rich Auchus, professor of internal medicine and pharmacology at the University of Michigan Medical School, in a statement.
"We did have to modify the method some, because those tusk powders were the dirtiest samples we ever analyzed. When Mike (Cherney) showed me the data from the elephant tusks, I was flabbergasted. Then we saw the same patterns in the mammoth – wow!”
The male woolly mammoth tusks dated back 33,291 – 38,866 years ago and it is thought to have died aged 55. It was preserved in permafrost and eventually discovered by a diamond mining company in Siberia in 2007 before being enrolled into the study.
Analysis of the tusk revealed annually recurring testosterone surges that were up to 10 times higher than baseline levels. By comparison, the female woolly mammoth tusk (dating back 5,597 to 5,885 years) showed stable testosterone levels that didn’t change over time. The African elephant bull tusk showed similar surges in testosterone to the male mammoth, demonstrating the technique can be used in extant animals and could even extend to smaller dentin samples.
"With reliable results for some steroids from samples as small as 5 mg of dentin, these methods could be used to investigate records of organisms with smaller teeth, including humans and other hominids," concluded the study authors. "Endocrine records in modern and ancient dentin provide a new approach to investigating reproductive ecology, life history, population dynamics, disease, and behavior in modern and prehistoric contexts."
The study is published in Nature.