High-throughput phenotyping methods for quantifying hair fiber morphology

Lasisi, Tina; Zaidi, Arslan; Webster, Timothy H.; Stephens, Nicholas; Routch, Kendall; Jablonski, Nina G.; Shriver, Mark D.

doi:10.1038/s41598-021-90409-x

Cited by 4 publications

(4 citation statements)

References 32 publications

(43 reference statements)

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“…Hair torsion may be a useful trait for studies searching for the effects from specific genes or gene regions on hair form among diverse populations. With limited exceptions (Hrdy, 1973; Lasisi et al, 2016; Lasisi et al, 2021), analysis of hair curl has not been the focus of much study among anthropologists, though with recent advances in studies of gene expression there will likely be more to come.…”

Section: Discussionmentioning

confidence: 99%

The Trotter collection: A review of Mildred Trotter's hair research and an update for studies of human variation

Koch,

Zaidi,

González

et al. 2024

American Journal of Biological Anthropology

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ObjectivesMildred Trotter was an anatomist and physical anthropologist whose studies on hair morphology, growth, somatic distribution, and trait relationships to age and ethnogeographic population were foundational to the field of microscopical hair analysis. The collection of human hair samples she assembled for her research has been an underutilized resource for studies on human hair variation. We applied updated methods and reviewed Trotter's original data to reassess the relationship hair traits have to diverse population labels.MethodsHair form and pigmentation patterns were measured from a subset of the hair samples accumulated by Trotter and we compared our data to Trotter's original results. Variability in hair traits were tested within individuals, within populations, and among ethnogeographic groups.ResultsMeasured hair cross‐section dimensions and melanosome density and distribution revealed substantial variability within individuals and ethnogeographic populations. Hair traits were found to not be distinctly separable by ancestry but instead showed continuous variation across human populations. Trotter's measurements were precise and the dataset she compiled remains valid, though the conclusions should be reviewed in light of our current understanding of human variation.DiscussionOur findings support moving away from categorical ancestry classifications and eliminating the use of outdated racial typologies in favor of more descriptive trait analysis. Detailed analysis of trait pattern distributions are presented that may be useful for future research on human variation. We point to the need for additional research on human variation and hair trait relationships with reference to known population affinity.

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Section: Discussionmentioning

confidence: 99%

The Trotter collection: A review of Mildred Trotter's hair research and an update for studies of human variation

Koch,

Zaidi,

González

et al. 2024

American Journal of Biological Anthropology

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“…Together with the phase of the hair growth cycle, seasonal effects will need to be considered, when investigating the variation of any and, namely, subtle properties for hair samples. These may include a wide range of differences in origin, environmental, and chemical conditions [29,[31][32][33][34][35], the changes of hair properties along its length [9,36], and differences and similarities of individual hairs in a forensic context [37].…”

Section: Discussionmentioning

confidence: 99%

A consumer cross‐over trial suggests that there are significant seasonal changes of the tensile properties (wet) of human hair

Wortmann,

Wortmann

2023

Intern J of Cosmetic Sci

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ObjectivesThrough the cooperation with an industrial partner, we gained a set of data for the tensile properties (wet) of human hair. The hair samples originated from a cross‐over study with two groups of individuals, using for a topical application sequentially two products (A and B). Each phase of the study lasted six months. The phases of the study were by chance covering first largely the winter and then the summer period. Initially, tensile variables were chosen, which not only reflect the mechanical properties of hair (modulus, break strain, break stress) but which are also considered to have a good connection to practice‐relevant hair properties. The initial analysis of the data showed that changes were observed for the variables due to the treatment phases. However, these were either small or difficult to interpret.MethodsAgainst this background and using Two‐Factor Analysis of Variance, we investigated the hypothesis that the tensile properties of hair (wet) may show significant seasonal changes. For this we chose those two independent variables, which reflect the properties of the intermediate filaments (modulus) and the matrix (break strain) in the composite structure of the hair cortex.ResultsThe results support the ‘seasonal’ hypothesis and clearly show that the variables show significant changes from Winter to Summer (modulus: 10% increase, break strain: 3% decrease). The seasonal effect was thus a major reason, why the first stage of the analysis of the data was inconclusive.ConclusionsThe tensile properties of the main morphological components of the cortex show distinct seasonal changes. Towards the summer the hair becomes stiffer and more brittle. Furthermore, the results suggest that seasonal effects may need to be taken into account when conducting studies on lengths of hair grown during different seasons.

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“…With regards to hair texture, the most common classification is straight, wavy, curly, and sometimes the addition of a “frizzy” category or further subdivisions within these qualitative descriptors (Adhikari et al, 2016; Liu et al, 2018). These qualitative descriptors are inconsistently interpreted and mask the range of variation that exists within tightly curled or “frizzy” hair (Lasisi et al, 2020).…”

Section: Classification and Distortionmentioning

confidence: 99%

“…Yet, what we know about hair biology suggests that variation is more complex than the asserted racial classifications suggest (Adeola et al, 2020; Khumalo, 2007; Lasisi et al, 2016, 2020; Loussouarn et al, 2007). Various studies of hair fiber curvature and cross‐sectional geometry show continuous variation across populations (Fujimoto et al, 2008; Hrdy, 1973; Lasisi et al, 2016; Loussouarn et al, 2007).…”

Section: Classification and Distortionmentioning

confidence: 99%

The constraints of racialization: How classification and valuation hinder scientific research on human variation

Lasisi

2021

American J Phys Anthropol

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Human biological variation has historically been studied through the lens of racialization. Despite a general shift away from the use of overt racial terminologies, the underlying racialized frameworks used to describe and understand human variation still remain. Even in relatively recent anthropological and biomedical work, we can observe clear manifestations of such racial thinking. This paper shows how classification and valuation are two specific processes which facilitate racialization and hinder attempts to move beyond such frameworks. The bias induced by classification distorts descriptions of phenotypic variation in a way that erroneously portrays European populations as more variable than others. Implicit valuation occurs in tandem with classification and produces narratives of superiority/inferiority for certain phenotypic variants without an objective biological basis. The bias of racialization is a persistent impediment stemming from the inheritance of scientific knowledge developed under explicitly racial paradigms. It is also an internalized cognitive distortion cultivated through socialization in a world where racialization is inescapable. Though undeniably challenging, this does not present an insurmountable barrier, and this bias can be mitigated through the critical evaluation of past work, the active inclusion of marginalized perspectives, and the direct confrontation of institutional structures enforcing racialized paradigms.

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High-throughput phenotyping methods for quantifying hair fiber morphology

Cited by 4 publications

References 32 publications

The Trotter collection: A review of Mildred Trotter's hair research and an update for studies of human variation

The Trotter collection: A review of Mildred Trotter's hair research and an update for studies of human variation

A consumer cross‐over trial suggests that there are significant seasonal changes of the tensile properties (wet) of human hair

The constraints of racialization: How classification and valuation hinder scientific research on human variation

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