Abstract
Hair is preserved for millennia in permafrost; it enshrines a record of biologic rhythms and offers a glimpse at chronobiology as it was in extinct animals. Here we compare biologic rhythms gleaned from mammoth's hairs with those of modern human hair. Four mammoths' hairs came from varying locations in Siberia 4600 km, four time zones, apart ranging in age between 18,000 and 20,000 years before present. We used two contemporaneous human hairs for comparison. Power spectra derived from hydrogen isotope ratios along the length of the hairs gave insight into biologic rhythms, which were different in the mammoths depending on location and differed from humans. Hair growth for mammoths was ∼31 cms/year and ∼16 cms/year for humans. Recurrent annual rhythms of slow and fast growth varying from 3.4 weeks/cycles to 8.7 weeks/cycles for slow periods and 1.2 weeks/cycles to 2.2 weeks/cycles for fast periods were identified in mammoth's hairs. The mineral content of mammoth's hairs was measured by electron microprobe analysis (k-ratios), which showed no differences in sulfur amongst the mammoth hairs but significantly more iron then in human hair. The fractal nature of the data derived from the hairs became evident in Mandelbrot sets derived from hydrogen isotope ratios, mineral content and geographic location. Confocal microscopy and scanning electron microscopy showed varied degrees of preservation of the cuticle largely independent of age but not location of the specimens. X-ray fluorescence microprobe and fluorescence computed micro-tomography analyses allowed evaluation of metal distribution and visualization of hollow tubes in the mammoth's hairs. Seasonal variations in iron and copper content combined with spectral analyses gave insights into variation in food intake of the animals. Biologic rhythms gleaned from power spectral plots obtained by modern methods revealed life style and behavior of extinct mega-fauna.
Highlights
Hair is often well preserved for centuries; it resists decay especially in Siberian permafrost where it can be conserved for millennia.Modern sequencing has spawned remarkable advances in the study of ancient DNA
We offer here a glimpse at biologic rhythms as they were in extinct mammoths that lived millennia ago and compare those to results obtained from modern humans
A major shift in biorhythm research is the availability of new tools such as hydrogen isotope ratios and micro-focused synchrotron X-ray fluorescence analyses which facilitated this look into the past
Summary
Modern sequencing has spawned remarkable advances in the study of ancient DNA. These include the sequencing of 28 million base pairs of mammoth DNA, which established that this behemoth split from its African elephant cousin about 6 million years ago. The physiological underpinnings of life in the cold Siberian winter, where mammoths roamed, have been revealed by the special hemoglobin sequence found in mammoth DNA and subsequently reproduced in modern bacteria [1]. These studies showed that substitutions in hemoglobin confer biochemical properties adaptive for cold-tolerance. The genetic material from which these details were gleaned originated in mammoth hair found in permafrost [2]
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