The Woolly Mammoth, Mammuthus primigenius, is thought to have diverged from the earlier Steppe Mammoth Mammuthus trogontherii in northeast Asia around 700 000 years ago and by 200 000 years ago spread across Asia and into Europe and across the Bering Strait into North America. As a widespread and apparently numerous species living in the recent past they have left an extensive fossil record, primarily of isolated teeth and bones, but also including a number of mummified and frozen specimens, trapped within the Arctic permafrost. This has allowed a number of detailed anatomical and molecular studies of the Woolly Mammoth, using specimens that were excavated in the nineteenth and early twentieth centuries. Despite this wealth of data there is relatively little direct information on the behaviour of these animals available, with most of our ideas about the social structure of Mammoths based upon extrapolation from living Elephant species rather than direct evidence.
In a paper published in the journal Current Biology on 2 November 2017, Patrícia Pe cnerova of the Department of Bioinformatics and Genetics at the Swedish Museum of Natural History, and the Department of Zoology at Stockholm University, David Díez-del-Molino and Nicolas Dussex, also of the Department of Bioinformatics and Genetics at the Swedish Museum of Natural History, Tatiana Feuerborn, again of the Department of Bioinformatics and Genetics at the Swedish Museum of Natural History, amd of the Centre for GeoGenetics at the Natural History Museum of Denmark, Johanna von Seth, again of the Department of Bioinformatics and Genetics at the Swedish Museum of Natural History, and the Department of Zoology at Stockholm University, Johannes van der Plicht of the Centre for Isotope Research at Groningen University, and the Faculty of Archaeology at Leiden University, Pavel Nikolskiy of the Geological Institute of the Russian Academy of Sciences, Alexei Tikhonov of the Zoological Institute of Russian Academy of Sciences and the Institute of the Applied Ecology of the North at the North-Eastern Federal University, Sergey Vartanyan of the North-East Interdisciplinary Scientific Research Institute N.A.N.A. Shilo of the Far East Branch of the Russian Academy of Sciences, and Love Dal én, once again of the of Bioinformatics and Genetics at the Swedish Museum of Natural History, present the results of a study in which they determined the sexes of 98 Woolly Mammoth specimens from different locations in Siberia and on Wrangel Island.
The Siegsdorfer Mammut, in the Südostbayerisches Naturkunde und Mammut-Museum, the largest complete Mammoth specimen in Europe, thought to be a male. Lou Gruber/Wikimedia Commons.
Pecnerova et al. were able to identify the sex of 95 Mammoths, of which 66 were male and 29 were female, a noteworthy and clearly significant difference. Modern Elephants, like almost all Mammals, produce male and female offspring in equal proportions, and there is no reason to suspect that Mammoths were any different in this regard, suggesting that male Mammoths were more likely to enter the fossil record than female Mammoths.
Elephants show distinct sexual dimorphism, with males significantly larger than females. As a rule of thumb, the hard tissues of larger animals are more likely to survive intact until they are buried than those of smaller animals, simply because they are harder for other animals to break down. However Pecnerova et al.do not believe that this is likely to have been a significant factor in the case of Mammoths, as all Mammoths were sufficiently large to be difficult for any other animal found in their environment to break down. Furthermore most Mammoth specimens for which data on their origins are available seem to have come from natural traps, such as sinkholes, mudflows or pools, where their remains were buried rapidly, whereas remains left on open tundra will tend to remain exposed for years or even centuries, where the action of the weather can break down even the largest bones.
Instead, Pecnerova et al. suggest that the behaviour of the Mammoths when they were alive may have played a role in how likely they were to enter the fossil record.Modern Elephants have a complex social structure, with female Elephants living in family groups with their young and each such group having a set territory which they know very well. Males leave these groups when they approach sexual maturity, and live in male groups which are much wider ranging, and less defined in structure, with the youngest males not being automatically accepted into such a group, and often having to range over very large areas before they find a male pack that will accept them - if they do so at all. The largest, sexually mature, males leave these packs, becoming intolerant of other males, particularly when they are in musth (a heightened state of sexual agitation, and range over very wide areas looking for available females.
This more adventurous lifestyle means that male Elephants, unlike females, spend much of their lives in unfamiliar territory. If the same held true for Woolly Mammoths then males of this species would have been more likely to encounter unfamiliar hazards, such as sinkholes or swamps, which females would be taught to avoid by older members of the herd if they lie within their territory. This matches closely with what is observed in the fossil record, with predominantly male specimens preserved in geographical traps, which Pecnerova et al. believe is evidence of a similar social structure in Mammoths to that in Elephants.
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