The biology of human hair: A multidisciplinary review Koch, Sandra L.; Tridico, Silvana R.; Bernard, Bruno A. ...
American journal of human biology,
March/April 2020, 2020-03-00, 20200301, Volume:
32, Issue:
2
Journal Article
Peer reviewed
In the last century, human scalp hair morphology has been studied from multiple, and sometimes mutually exclusive, perspectives by anthropologists, biologists, geneticists, forensic scientists, and ...cosmetic scientists. Here, we review and synthesize historical and current research on hair to better understand the scientific basis and biological implications of hair microstructure and morphology. We revisit the origins of existing nomenclature regarding hair morphology and classifications, discuss the currently recognized limitations to hair analysis within the varied scientific disciplines studying hair, point out aspects of hair biology that remain unknown, and the great potential for integrating these diverse perspectives and expertise in future scientific investigations, while highlighting the benefits of combining nondestructive microscopical analysis with chemical and genomic analyses for explicating hair biology. Further, we propose consensus terminology for root growth stages through descriptions and images that will aid in the morphological and microscopical analysis of human scalp hair, thereby reducing confusion and the promulgation of inaccurate information that is presently in the literature.
The large extinct megafaunal species of the Late Pleistocene, Mammuthus primigenius (woolly mammoth) and Coelodonta antiquitatis (woolly rhino) are renowned for their pelage. Despite this, very ...little research has been conducted on the form and function of hair from these iconic species. Using permafrost preserved hair samples from seven extinct megafaunal remains, this study presents an in-depth microscopical characterisation of preservation, taphonomy, microbial damage, pigmentation and morphological features of more than 420 hairs. The presence of unique structural features in hairs, from two extinct megafauna species, such as multiple medullae and unparallelled stiffness suggests evolution of traits that may have been critical for their survival in the harsh arctic environment. Lastly, despite popular depictions of red-haired and/or uniformly coloured mammoths, a closer examination of pigmentation reveals that mammoth coats may have exhibited a mottled/variegated appearance and that their ‘true’ colours were not the vivid red/orange colour often depicted in reconstructions. Insights gained from microscopical examination of hundreds of extinct megafauna hairs demonstrate the value of extracting as much morphological data as possible from ancient hairs prior to destructive sampling for molecular analyses.
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•Investigation into form and function of hairs from two extinct megafauna species.•Suggestions of convergent evolution of hair structure in two extinct megafauna species.•Appearance of woolly mammoth likely to differ from current portrayals.•Investigation of effects of taphonomy on permafrost preserved ancient hair.
Mammalian hairs are one of the most ubiquitous types of trace evidence collected in the course of forensic investigations. However, hairs that are naturally shed or that lack roots are problematic ...substrates for DNA profiling; these hair types often contain insufficient nuclear DNA to yield short tandem repeat (STR) profiles. Whilst there have been a number of initial investigations evaluating the value of metagenomics analyses for forensic applications (e.g. examination of computer keyboards), there have been no metagenomic evaluations of human hairs-a substrate commonly encountered during forensic practice. This present study attempts to address this forensic capability gap, by conducting a qualitative assessment into the applicability of metagenomic analyses of human scalp and pubic hair.
Forty-two DNA extracts obtained from human scalp and pubic hairs generated a total of 79,766 reads, yielding 39,814 reads post control and abundance filtering. The results revealed the presence of unique combinations of microbial taxa that can enable discrimination between individuals and signature taxa indigenous to female pubic hairs. Microbial data from a single co-habiting couple added an extra dimension to the study by suggesting that metagenomic analyses might be of evidentiary value in sexual assault cases when other associative evidence is not present.
Of all the data generated in this study, the next-generation sequencing (NGS) data generated from pubic hair held the most potential for forensic applications. Metagenomic analyses of human hairs may provide independent data to augment other forensic results and possibly provide association between victims of sexual assault and offender when other associative evidence is absent. Based on results garnered in the present study, we believe that with further development, bacterial profiling of hair will become a valuable addition to the forensic toolkit.
Although the taphonomic (post-mortem) degradation processes relevant to teeth and bones have been well described, those taking place with regards to mammalian hairs have not been characterized to the ...same extent. This present article describes, in detail, microscopic changes resulting from the actions of biological agents that digest and degrade hairs. The most noteworthy and prevalent agents responsible for the destruction of hair structure are fungi, which use a range of strategies to invade and digest hairs. One of the most important finds to emerge from this study is that taphonomic structures and processes can easily be interpreted by the unwary as ‘real’, or as class characteristics for a particular animal taxon. Moreover, under certain conditions, ‘taphonomic’ processes normally associated with the dead are also present on the hairs of the living. This work will improve the reliability of hair examinations in forensic, archaeological and palaeontological applications—in addition, the finding has relevance in the protection of mammalian collections susceptible to infestation. This article also addresses the popular myth that ancient peoples were often red-haired and discusses phenomena responsible for this observation. Insights gained from detailed characterization of taphonomic processes in 95 hairs from a variety of species demonstrate the range and breadth of degradative effects on hair structure and colour. Lastly, the study demonstrates that hairs often tell a story and that there is value of extracting as much morphological data as possible from hairs, prior to destructive sampling for biomolecules.
Abstract An initial investigation of the application of laser scanning confocal microscopy to the examination of hairs and fibers has been conducted. This technique allows the production of virtual ...transverse and longitudinal cross-sectional images of a wide range of hairs and fibers. Special mounting techniques are not required; specimens that have been mounted for conventional microscopy require no further treatment. Unlike physical cross-sectioning, in which it is difficult to produce multiple cross-sections from a single hair or fiber and the process is destructive, confocal microscopy allows the examiner to image the cross-section at any point in the field of view along the hair or fiber and it is non-destructive. Confocal microscopy is a fluorescence-based technique. The images described in this article were collected using only the autofluorescence exhibited by the specimen (i.e. fluorescence staining was not necessary). Colorless fibers generally and hairs required excitation at 405 nm in order to stimulate useful autofluorescence; longer wavelength excitation was suitable for dyed fibers. Although confocal microscopy was found to be generally applicable to the generation virtual transverse cross-sections from a wide range of hairs and fibers, on some occasions the autofluorescence signal was attenuated by heavy pigmentation or the presence of an opaque medulla in hairs, and by heavy delustering or the presence of air-filled voids in the case of fibers. In these situations only partial cross-sections were obtained.
Sloths: The unusual hairs from these shaggy heteroclites Tridico, Silvana R.; Vongsvivut, Jitraporn; Kirkbride, K.Paul
Forensic science international. Animals and environments,
December 2023, 2023-12-00, 2023-12-01, Volume:
3
Journal Article
Peer reviewed
Open access
Modern sloths, comprising six species within the Bradipopidae and Choloepodidae families, together with the anteaters and armadillos represent an ancient order of distinctive and remarkable placental ...mammals. Unfortunately, these animals are both endangered and trafficked. Whilst there have been many in-depth studies surrounding the physical and genetic adaptations of sloths required in order to live an almost exclusive arboreal lifestyle, in comparison, literature describing another remarkable feature that they are renowned for – their hair – are somewhat varied in their conclusions. In keeping with their distinctiveness among mammals, sloths exhibit striking and unusual morphological features in their hair. Microscopical images of these features captured using transmitted visible light microscopy and scanning electron microscopy (SEM) are presented, which it is hoped will assist those carrying out forensic wildlife examinations or those called upon to identify the origins of unknown hairs that they may encounter, for example in cultural heritage investigations or animal tracking studies. Although the hairs from Bradipus spp and Choloeps spp exhibit unusual morphology, the results obtained using both laboratory-based and synchrotron-sourced Fourier transform infrared (FTIR) spectrometry indicated that the keratin composition of their hairs did not differ greatly from each other or from that found in other mammals.
•Hairs from Choloepus and Bradypus spp each display unusual morphology.•Morphology is easily and reliably observed using transmitted light microscopy, even in the field.•Scanning electron microscopy reveals unusual fine-structure within Bradypus hairs.
Abstract Parrots and cockatoos are highly prized aviary birds and the demands for such species has fuelled their illegal trade and harvest from the wild. Here we report on three forensic case studies ...involving black-cockatoos ( Calyptorhynchus spp.) endemic to Australia. These cases involve suspected poaching and illegal killing of endangered red- and white-tailed black-cockatoos. Through the prior development of 20 polymorphic microsatellite loci and population databases for white- and red-tailed black-cockatoos, the tools are available to conduct high-resolution paternity and individual identity testing. In one case, we matched a red-tailed black-cockatoo nestling to a tree hollow from which it was poached through the use of DNA from eggshell recovered from the nest. For the second case, we utilized our provenance population database (nest sites), and identified the kinship and geographic origin of a white-tailed black-cockatoo, which was illegally harvested from the wild. The third case determined the number individual white-tailed black-cockatoos allegedly shot at a fruit grower's orchard from body part remains. These genetic investigations highlight the significance and statistical confidence of DNA profiling and associated databases for endangered taxa, such as exotic birds. Our cockatoo population databases are the first of their kind in Australia, and demonstrate the efficacy of such approaches to identify such illegal activity. With a robust set of genetic markers and methodologies in place, we aim to broaden our population databases to include other cockatoo species of conservation concern.
Ancient human mobility at the individual level is conventionally studied by the diverse application of suitable techniques (e.g. aDNA, radiogenic strontium isotopes, as well as oxygen and lead ...isotopes) to either hard and/or soft tissues. However, the limited preservation of coexisting hard and soft human tissues hampers the possibilities of investigating high-resolution diachronic mobility periods in the life of a single individual. Here, we present the results of a multidisciplinary study of an exceptionally well preserved circa 3.400-year old Danish Bronze Age female find, known as the Egtved Girl. We applied biomolecular, biochemical and geochemical analyses to reconstruct her mobility and diet. We demonstrate that she originated from a place outside present day Denmark (the island of Bornholm excluded), and that she travelled back and forth over large distances during the final months of her life, while consuming a terrestrial diet with intervals of reduced protein intake. We also provide evidence that all her garments were made of non-locally produced wool. Our study advocates the huge potential of combining biomolecular and biogeochemical provenance tracer analyses to hard and soft tissues of a single ancient individual for the reconstruction of high-resolution human mobility.
We report here the genome sequence of an ancient human. Obtained from approximately 4,000-year-old permafrost-preserved hair, the genome represents a male individual from the first known culture to ...settle in Greenland. Sequenced to an average depth of 20x, we recover 79% of the diploid genome, an amount close to the practical limit of current sequencing technologies. We identify 353,151 high-confidence single-nucleotide polymorphisms (SNPs), of which 6.8% have not been reported previously. We estimate raw read contamination to be no higher than 0.8%. We use functional SNP assessment to assign possible phenotypic characteristics of the individual that belonged to a culture whose location has yielded only trace human remains. We compare the high-confidence SNPs to those of contemporary populations to find the populations most closely related to the individual. This provides evidence for a migration from Siberia into the New World some 5,500 years ago, independent of that giving rise to the modern Native Americans and Inuit.
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