Musth, a time of high testosterone levels and aggressiveness in male elephants related to reproduction, has now been identified in the tusks of woolly mammoths. Remarkably, this is the first time that existing or extinct hormones have been seen. And it opens up an exciting new field of paleontology that the team behind the find has dubbed “fossil endocrinology” — the study of hormones in ancient species.
A paper published Wednesday in the journal Nature describes this work, in which an international team of scientists studied African elephant and woolly mammoth tusks. Elephants and woolly mammoths are closely related, and both belong to a group of animals known as proboscis.
Michael Cherny is lead author and research partner at the University of Michigan Paleontology Museum. He said his team started by testing elephant tusks. “We wanted to start with something that offered the best chance for data recovery, because we didn’t know we were going to see any,” Cherny told Ars in the video interview. No one knew for sure if hormonal signatures were present in the tusks of modern elephants prior to this study, but the team was able to identify testosterone in the tusks.
Once researchers identify hormones in elephant tusks, they can compare them with the hormonal signatures, if any, in the extinct proboscideans.
He described the search for musth as “hanging fruit because we have a male [woolly] Mammoth tusks are in our possession. We found that testosterone provided a really clean-looking slate in a modern elephant’s tusk.” By contrast, they couldn’t test female hormones for a “pregnancy, for example” test, because they didn’t have a modern female elephant’s tusk for comparison.
The exceptionally well-preserved fossils were a good place to start. The woolly mammoths of Arctic regions such as Siberia and Wrangel Island off the coast of Russia (where the tusks they sampled were found) are better preserved than the remains of other Pleistocene animals such as the mastodon, another elephant-like animal.
The right time to mate
The team found similar testosterone elevations recorded during the adult years of male African elephant and male woolly mammoth tusks, consistent with those that occur during worship. These bumps were absent in the prepubertal years of the same male woolly mammoth, evidence to support the absence of musth in the years before sexual maturity, and were completely absent in the female woolly mammoth.
Total levels of testosterone were lower in both mammoth samples than they were in the elephant, something the team hypothesizes may be due to conservation limitations. However, the fact that the hormones were preserved at all is amazing after thousands of years (more than 33,000 years for the male woolly mammoth).
Given their close relationship to Asian elephants, is it surprising that musth was discovered?
“It’s no surprise that the woolly mammoth had a problem,” Cherny admitted. “What He is Surprisingly, we can see it. And what’s powerful is the ability to not only know they had musth, but to know when they were in need of musth. We can see what age they were, we can see how frequent it is, and see how intense the testosterone increase compared to, say, between periods. “
There’s a lot we can relate to hormone levels, because the proboscis’s tusks record this animal’s life. His episodes record the days and years of growth, for example, the seasons in which she experienced famine or abundance, from her birth to her death. So if more information can be uncovered, such as additional hormones, this opens a new window into the life of the extinct species.
How do you go about tracking a single hormone within the complex mix of chemicals found in canines? The team relied on a technology called liquid chromatography-mass spectrometry (LC-MS/MS). “We started with the method other people have used to extract hormones from hair, but we’ve modified it,” Cherny said. “Then we used the method of isolating hormones from serum samples, and tweaked it a bit.”
LC-MS/MS involves a two-step process. The first step, liquid chromatography, separates particles based on how well they dissolve in a mixture of solvents. The different parts of the solvent contain a subset of the entire mixture of molecules originally present. These fractions can then be further separated by the next step, mass spectroscopy.
As its name suggests, mass spectroscopy involves identifying molecules based on their mass. The molecules are first broken into fragments, and then those fragments are spread out based on their mass so that each molecule creates a distinct “fingerprint” of the fragments.
Cherny said this approach offers several advantages when identifying which molecules are present. “One is that it’s very accurate,” he told Ars. “The other thing is that it’s hard to deceive. And then another is that we can look at several things at once.”
It sure worked well here. Co-author Richard Ochos is Professor of Translational Medicine, Pharmacology, and Internal Medicine at the University of Michigan. “There are very few times in my scientific career when I have just received a piece of data,” he said. When Mike [Cherney] Show me the elephant results, it was black and white what’s going on. I never thought we’d be able to see testosterone change so clearly.”
The study was “very exciting” for Chase LaDue, a postdoctoral fellow in animal behavior at the Oklahoma City Zoo who was not involved in the research but was involved. mustth lesson in elephants today. Beyond the results, Ladio felt the techniques developed here could have a range of applications. “I am also excited to see these tools applied to reveal secrets about other aspects of extinct proboscis life (for example, female reproductive cycles, including reproductive patterns and reproductive aging),” he wrote. “[It] It provides possibilities for studying the effects of environmental changes (including human influences) on the life history and physiology of extinct and living elephants.”
The study of woolly mammoth tusks and the questions it might answer is, for Cherni, “more powerful in many ways”. Being able to definitively determine pregnancies and birth periods will provide deep insights into population dynamics and may help provide more clues regarding their eventual extinction. “If we could get calf spacing out of canine logs, that would be very robust,” Cherny continued. “It’s a tool that we can use to assess what happens when a population is doing well and what happens when a population is not doing so well. And we know, when they die, they weren’t doing well.”
Co-author Adam Rountree explained that male elephants experience different experiences in different environments. If resources are plentiful all year round, males can go through misfortune at any time, and reproduction in these elephant groups can occur throughout the year. This is not the case in environments where resources are only plentiful during certain seasons. In those environments, males tend to experience multiplication (and females tend to become pregnant) when resources are plentiful.
“to [woolly] Mammoth [in Siberia and on Wrangel Island]He said, “It’s a very seasonal environment. We’re talking about Arctic latitudes where plants only grow for a few months out of the year. I think, given that we already see musth in Arctic mammoths, it’s likely that many of the male mammoths are coming of age.” They were entering dysbiosis around the same time.”
Lovers And fighters
If male Arctic woolly mammoths experienced mauling in a similar way to today’s elephants, shouldn’t we see more evidence of woolly mammoth aggression? The battle wounds of male mastodons are well known in North America, but these same wounds are not seen very often in fossils of the woolly mammoth.
Cherny agreed that most of the evidence we have of proboscis fighting “comes from mastodons,” noting that co-author Daniel Fisher has done important work a job about this subject. “We have at least two really clear examples of that.” However, at the moment, it is not known if mastodons are amniotic or if their canines conserve hormones.
Rowntree offered a possible explanation. “In the mastodon,” he noted, “the tusks are oriented so that these fatal blows to the throat could occur fairly easily during combat. But the tusks of a mammoth have a different direction and a tighter curvature, and it may be difficult to make a hole in the throat region of which we see evidence In the skulls of mastodons, so that may be [the woolly mammoth] The fighting style was different or they relied more on aggressive stances and gestures than on deadly physical confrontations.”
The possibility of understanding more about the reproductive biology of the woolly mammoth in the context of its extinction is what interests Rountrey most. He said he would like to see in the future “what difference, if any, we get in the occurrence or emergence of the goblin through time, up to its extinction”. Because, he added, “knowing how these things have changed over time may tell us something about the cause of the extinction.”
LaDue agreed, noting that the stresses of a changing climate or human hunting may have altered testosterone spikes.
For co-author Dick Moll, a researcher at the Natural History Museum Rotterdam who has been studying mammoths for decades and helped obtain fossil tusks, this research “is another major contribution to the scientific study of the extinct giants of the Ice Age.” He was keen to see what future research reveals, “because there is still more to investigate.”
Nature, 2023. DOI: 10.1038 / s41586-023-06020-9
Gene Timmons (@employee) is a freelance writer with a strong passion for paleontology. Based in New Hampshire, she writes about paleontology (and some archaeology) on her blog mostmammoths.wordpress.com.
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