New research reveals mammoths fought to the death for mating rights

By Mark Waghorn via SWNS

Woolly mammoths fought to the death in epic battles over the right to mate with females, according to new research.

They entered a state known as musth when temporal glands became swollen with testosterone.

Levels of the male sex hormone soared tenfold making them very aggressive - and randy.

It would have been a sight to behold. They were one of the largest land mammals that ever lived - reaching up to 15 feet tall and 12 tons in weight.

Smashing heads together, interlocking tusks and pushing with all their might left only the strongest standing. Some individuals were killed.

All species of living elephants express similar displays of dominance. It was always suspected their prehistoric distant cousins did the same.

Now scientists have obtained direct evidence - in traces of sex hormones extracted from a woolly mammoth's tusk.

Lead author Dr. Michael Cherney, of the University of Michigan, said: "Temporal patterns of testosterone preserved in fossil tusks show that, like modern elephants, mature bull mammoths experienced musth."

The same phenomenon occurs in bull elephants on the African savannah today. It is also similar to the rutting season of male deer.

In elephants, elevated testosterone during musth was previously recognized from blood and urine tests.

Musth battles in extinct relatives of modern elephants have been inferred from skeletal injuries, broken tusk tips and other indirect lines of evidence.

But the new study in Nature is the first to show testosterone levels are recorded in the growth layers of mammoth and elephant tusks.

An international team found recurring testosterone surges up to ten times higher than normal.

They were identified within a woolly mammoth tusk - preserved in permafrost. The adult individual lived more than 33,000 years ago.

The surges are consistent with musth-related testosterone peaks the researchers observed in an African bull elephant tusk.

The word 'musth' comes from the Hindi and Urdu word for intoxicated.

It demonstrates that both modern and ancient tusks hold traces of testosterone and other steroid hormones.

The chemical compounds are incorporated into dentin, the mineralized tissue that makes up the interior portion of all teeth. Tusks are elongated upper incisors.

Dr Cherney said: "This study establishes dentin as a useful repository for some hormones and sets the stage for further advances in the developing field of paleondocrinology.

"In addition to broad applications in zoology and paleontology, tooth-hormone records could support medical, forensic and archaeological studies."

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

Scientists have previously analyzed steroid hormones present in human and animal hair, nails, bones and teeth, in both modern and ancient contexts.

But the significance and value of such hormone records have been the subject of ongoing scrutiny and debate.

The findings should help change that by demonstrating that steroid records in teeth can provide meaningful biological information that sometimes persists for thousands of years.

Co-author Professor Daniel Fisher, a curator at the university's Museum of Paleontology, said: "Tusks hold particular promise for reconstructing aspects of mammoth life history because they preserve a record of growth in layers of dentin that form throughout an individual's life.

"Because musth is associated with dramatically elevated testosterone in modern elephants, it provides a starting point for assessing the feasibility of using hormones preserved in tusk growth records to investigate temporal changes in endocrine physiology."

The researchers carried out CT scanning on tusks from an adult African bull elephant and two adult woolly mammoths - a male and a female - from Siberia.

They identified annual growth increments. A tiny drill bit, operated under a microscope and moved across a block of dentin using computer-actuated stepper motors, was used to grind contiguous half-millimeter-wide samples representing approximately monthly intervals.

The powder produced during this milling process was collected and chemically analysed.

State-of-the-art techniques extracted steroids from tusk dentin for measurement with a scanning device that identifies chemical substances by sorting chemicals according to their mass and charge.

Co-author Rich Auchus, also from Michigan, said: "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.'

"We did have to modify the method some because those tusk powders were the dirtiest samples we ever analyzed.

"When Mike showed me the data from the elephant tusks, I was flabbergasted. Then we saw the same patterns in the mammoth - wow."

The African bull elephant is believed to have been 30 to 40 years old when it was killed by a hunter in Botswana in 1963.

According to estimates based on growth layers in its tusk, the male woolly mammoth lived to be about 55 years old.

Its right tusk was discovered by a diamond-mining company in Siberia in 2007. Radiocarbon dating revealed that the animal lived 33,291 to 38,866 years ago.

The tusk from the female woolly mammoth was discovered on Wrangel Island, which was connected to northeast Siberia in glacial periods of lower sea level but is now separated from it by the Arctic Ocean.

Carbon dating showed an age of 5,597 to 5,885 years before the present. Wrangel Island is the last known place where woolly mammoths survived, until around 4,000 years ago.

In contrast to the male tusks, testosterone levels from the female woolly mammoth tusk showed little variation over time - as expected - and the average testosterone level was lower than the lowest values in the male mammoth's tusk records.

Dr. Cherney said: "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.

"Hormone 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."