The multi-scale complexity of human genetic variation beyond continental groups.

Traditional clustering and visualization approaches in human genetics often operate under frameworks that assume inherent, discrete groupings . These methods can inadvertently simplify multifaceted relationships, functioning to entrench the idea of typological groups . We introduce a network-based pipeline and visualization tool grounded in relational thinking , which constructs networks from a variety of genetic similarity metrics.

Human scalp hair as a thermoregulatory adaptation.

Humans are unique among mammals in having a functionally naked body with a hair-covered scalp. Scalp hair is exceptionally variable across populations within . Neither the function of human scalp hair nor the consequences of variation in its morphology have been studied within an evolutionary framework.

High-throughput phenotyping methods for quantifying hair fiber morphology.

Quantifying the continuous variation in human scalp hair morphology is of interest to anthropologists, geneticists, dermatologists and forensic scientists, but existing methods for studying hair form are time-consuming and not widely used. Here, we present a high-throughput sample preparation protocol for the imaging of both longitudinal (curvature) and cross-sectional scalp hair morphology. Additionally, we describe and validate a new Python package designed to process longitudinal and cross-sectional hair images, segment them, and provide measurements of interest.

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

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.

Shades of complexity: New perspectives on the evolution and genetic architecture of human skin.

Like many highly variable human traits, more than a dozen genes are known to contribute to the full range of skin color. However, the historical bias in favor of genetic studies in European and European-derived populations has blinded us to the magnitude of pigmentation's complexity. As deliberate efforts are being made to better characterize diverse global populations and new sequencing technologies, better measurement tools, functional assessments, predictive modeling, and ancient DNA analyses become more widely accessible, we are beginning to appreciate how limited our understanding of the genetic bases of human skin color have been.

Focus on African diversity confirms complexity of skin pigmentation genetics.

Renewed focus on African populations confirms the complexity of skin pigmentation genetics, and suggests future directions for pigmentation research.

Quantifying variation in human scalp hair fiber shape and pigmentation.

Objectives: This study aims to evaluate the use of quantitative methods of measuring variation in scalp hair fiber shape and pigmentation and carry out exploratory data analysis on a limited sample of individuals from diverse populations in order to inform future avenues of research for the evolution of modern human hair variation.

Methods: Cross-sectional area and shape and average curvature of scalp hair fibers were quantified using ImageJ. Pigmentation was analyzed using chemical methods estimating total melanin content through spectrophotometric methods, and eumelanin and pheomelanin content through HLPC analysis of melanin-specific degradation products.