## 1 Introduction  
The content of macro- and microelements in human and animal hairs is a good indicator of their accumulation in the body as a result of environmental exposure, including intake with food and water [1, 2]. Hair records the levels of toxic (lead, cadmium, arsenic, etc.) and vital elements (zinc, selenium, iron, etc.), reflecting the elemental status of the whole organism. Hair analysis is used for evaluation of health state, metabolic disorders, mineral maintenance of human and animals, and also the ecological state of the territory where they live [3, 4, 5]. The level of toxic metals in the environment indicates a potential risk for the ecosystem and for human and animal health because of bioaccumulation of some metals (particularly mercury) in the body [6, 7]. The World Health Organization (WHO) recommends using hair as major biological material for testing the pollution of the human body by heavy metals, since sampling, storage, and analysis of hair samples are easier than they are for other biological materials [8]. The International Atomic Energy Agency (IAEA) useshair for the monitoring of global changes in element levels in the environment worldwide [9; 10; 11]. Ancient hairs are also \"keepers of history\" [12; 13; 14] which help to assess the level of environmental pollution by the degree of pollutants impact on the body during previous epochs. Hairs of prehistoric animals can be the key to understanding the relationship of environmental changes with climate. The aim of our study was to understand whether Hg concentration in the hair of prehistoric mammals could be used as a proxy indicating that changes of mercury level in the environment reflect climate changes during the Late Pleistocene-Early Holocene. Permafrost and substantial precipitation are the deciding factors in preservation of mammoth soft tissues and hair over tens of thousands of years. Hairs of the woolly mammoth are studied very actively nowadays for decoding and sequencing DNA [15; 16; 17]; revealing biologic rhythms [18]; determining the type of nutrition from the balance of stable isotopes of nitrogen, carbon, and phosphorus [19; 20]; and their response to short-term (seasonal) environmental changes [21]. It is therefore surprising that studies of trace elements in the hair of mammoth fauna mammals have not been done until now. There are some studies of trace element in museum samples of animal hair [22] and bird feathers [23; 24], and seal hairs from a lake sediment core spanning the past 2000 years [25]. The results of these studies are useful for assessing environmental changes and anthropogenic impacts on the environment. However, most of the studies cover the span of the last thousand years, whereas the analysis of mammoth fauna mammals' hair provides a unique opportunity to evaluate environmental changes that were happening tens of thousands of years ago, during different climatic stages. It should be noted that there is a potential problem with reliability of analytical data associated with possible contamination or loss of elements during storage and analysis of samples [26]. Therefore, the development of methodological details of sample preparation and analysis of the prehistoric animals' hair require a special attention.