Abstract

AbstractTestosterone is a key regulator in vertebrate development, physiology and behaviour. Whereas technology allows extraction of a wealth of genetic information from extant as well as extinct species, complementary information on steroid hormone levels may add a social, sexual and environmental context. Hair shafts have been previously used to sequence DNA from >50 000 14C years old Siberian woolly mammoths (Mammuthus primigenius). Hair‐testing has also been used to measure endogenous steroids in multiple extant species. Here we use small quantities of woolly mammoth hair samples to measure testosterone, and a genomics‐based approach to determine sex, in permafrost‐preserved mammoths dated to c. 10 000–60 000 14C years. Our validated method opens up exciting opportunities to measure multiple steroids in keratinized tissues from extinct populations of mammals. This may be specifically applied to investigating life histories, including the extinct Quaternary megafauna populations whose remains are preserved in the permafrost throughout the northern hemisphere.

Highlights

  • Testosterone is a key regulator in vertebrate development, physiology and behaviour

  • We use small quantities of woolly mammoth hair samples to measure testosterone, and a genomics-based approach to determine sex, in permafrost-preserved mammoths dated to c. 10 000–60 000 14C years

  • In order to avoid a bias in mapping due to the presence of nuclear mitochondrial DNA copies, raw sequences were mapped against a merged nuclear-mitochondrial reference consisting of a nuclear genome of the African elephant (Loxodonta africana) generated by the Broad Institute (LoxAfr4) and a mitochondrial genome of a known woolly mammoth (‘Krause’, DQ188829) (Krause et al 2006)

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Summary

Introduction

Testosterone is a key regulator in vertebrate development, physiology and behaviour. Whereas technology allows extraction of a wealth of genetic information from extant as well as extinct species, complementary information on steroid hormone levels may add a social, sexual and environmental context. Endogenous testosterone has been measured in the circulation through blood samples This matrix is not available for extinct species. Hair samples have been used for genetic analysis, with DNA sequenced from >50 000 14C year old Siberian mammoths (Mammuthus primigenius) (Gilbert et al 2007, 2008). We applied our published method for quantitation of steroids from hair (Koren et al 2002, 2008; Koren & Geffen 2009; Di Francesco et al 2017) on Siberian woolly mammoth hair shaft samples that had been previously utilized by Gilbert et al (2007, 2008) for mitogenome sequencing. Our goal was to validate a method to measure long-term integrated testosterone levels in mammoth hair in order to establish means to gain insight on the life history of extinct species

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