Widespread male sex bias in mammal fossil and museum collections

Abstract

A recent study of mammoth subfossil remains has demonstrated the potential of using relatively low-coverage high-throughput DNA sequencing to genetically sex specimens, revealing a strong male-biased sex ratio [P. Pečnerová et al., Curr. Biol. 27, 3505–3510.e3 (2017)]. Similar patterns were predicted for steppe bison, based on their analogous female herd-based structure. We genetically sexed subfossil remains of 186 Holarctic bison (Bison spp.), and also 91 brown bears (Ursus arctos), which are not female herd-based, and found that ∼75% of both groups were male, very close to the ratio observed in mammoths (72%). This large deviation from a 1:1 ratio was unexpected, but we found no evidence for sex differences with respect to DNA preservation, sample age, material type, or overall spatial distribution. We further examined ratios of male and female specimens from 4 large museum mammal collections and found a strong male bias, observable in almost all mammalian orders. We suggest that, in mammals at least, 1) wider male geographic ranges can lead to considerably increased chances of detection in fossil studies, and 2) sexual dimorphic behavior or appearance can facilitate a considerable sex bias in fossil and modern collections, on a previously unacknowledged scale. This finding has major implications for a wide range of studies of fossil and museum material.

Examining Natural History through the Lens of Palaeogenomics

“…Although originally applied to human remains, the read-dosage approach has the twin benefits of working on practically any taxon with heteromorphic sex chromosomes and requiring minimal input DNA, meaning that the method can successfully be applied up to the temporal limits of DNA preservation. For example, Gower et al [31] and Pečnerová et al [32] used read-dosage to determine the sex of hundreds of Quaternary specimens of bison (Bison spp. ), brown bears (Ursus arctos), and mammoths (Mammuthus spp.…”

Biomolecular analyses reveal the age, sex and species identity of a near-intact Pleistocene bird carcass

“…Nevertheless, the exceptionally high degree of morphological preservation of this specimen and of similarly wellpreserved animal remains from the area around Belaya Gora holds great promise for further research into the region's evolutionary history. For instance, molecular identification of the sex of animal remains, which is not always possible based on skeletal remains, allows for investigations into the behavioural ecology of extinct species 5,8 , while sequencing of mitochondrial or nuclear genomes can enable studies of temporal range shifts associated with past climatic fluctuations 25 , as well as reconstructing the past demography in extant and extinct species 11,26,27 . Moreover, because estimates of substitution rates from modern pedigree data can be biased 28 , whole genome sequencing of permafrost specimens could provide more accurate estimation of molecular clocks and thus allow improved studies of the micro-evolution of a range of species (e.g., 29,30 ).…”

“…The high degree of preservation of both tissue and DNA in permafrost remains has been particularly beneficial to the field of ancient DNA (aDNA). For instance, sequencing of DNA from Pleistocene and Holocene mammal remains has provided a better understanding of the behaviour of extinct species 5,8 , while the sequencing of complete Pleistocene genomes has allowed studies of evolutionary rates, extinction dynamics and inter-specific hybridisation [9][10][11] . However, most examples of this type of frozen permafrost tissues have been from large mammals.…”

A Multidisciplinary Review of the Inka Imperial Resettlement Policy and Implications for Future Investigations

“…In general, matrilineal and patrilineal genetic information can be used as a proxy for global settlement processes while autosomal DNA can inform both global and fine-scale regional demographic history. Genetics can also reveal the biological sex of a sample from the archaeological record [ 36 , 37 , 38 ], which can be a useful complement to physical anthropology methods. Sexing of individuals is particularly relevant for the analysis of sex ratio in Aqllakuna , Yanakuna and Mitmaqkuna burials.…”