As modern humans ventured out of Africa and dispersed around the world, they faced novel environmental challenges that led to geographic adaptations including skin colour. Over the long history of human evolution, skin colour has changed dramatically, showing tremendous diversity across different geographical regions, for example, the majority of individuals from the expansive lands of Africa have darker skin, whereas the majority of people from Eurasia exhibit lighter skin. What adaptations did lighter skin confer upon modern humans as they migrated from Africa to Eurasia? What genetic mechanisms underlie the diversity of skin colour observed in different populations? In recent years, scientists have gradually gained a deeper understanding of the interactions between pigmentation gene and skin colour through population-based genomic studies of different groups around the world, particularly in East Asia and Africa. In this review, we summarize our current understanding of 26 skin colour-related pigmentation genes and 48 SNPs that influence skin colour. Important pigmentation genes across three major populations are described in detail: MFSD12, SLC24A5, PDPK1 and DDB1/CYB561A3/TMEM138 influence skin colour in African populations; OCA2, KITLG, SLC24A2, GNPAT and PAH are key to the evolution of skin pigmentation in East Asian populations; and SLC24A5, SLC45A2, TYR, TYRP1, ASIP, MC1R and IRF4 significantly contribute to the lightening of skin colour in European populations. We summarized recent findings in genomic studies of skin colour in populations that implicate diverse geographic environments, local adaptation among populations, gene flow and multi-gene interactions as factors influencing skin colour diversity.

Pulse oximeters\' (POs) varying performance based on skin tones has been highly publicised. Compared to arterial blood gas analysis, POs tend to overestimate oxygen saturation (SpO2) values for people with darker skin (occult hypoxemia). The objective is to develop a test bench for assessing commercial home and hospital-based POs in controlled laboratory conditions. A laboratory simulator was used to mimic different SpO2 values (~ 70 to 100%). Different neutral density and synthetic melanin filters were used to reproduce low signal and varying melanin attenuation levels. Six devices consisting of commercial home (Biolight, N = 13; ChoiceMMed, N = 18; MedLinket, N = 9) and hospital-based (Masimo Radical 7 with Neo L, N = 1; GE B450 Masimo SET with LNCS Neo L, N = 1; Nonin 9550 Onyx II™, N = 1) POs were reviewed and their response documented. Significant variations were observed in the recorded SpO2 values among different POs when exposed to identical simulated signals. Differences were greatest for lower SpO2 (< 80%) where empirical data is limited. All PO responses under low signal and melanin attenuation did not change across various simulated SpO2 values. The bench tests do not provide conclusive evidence that melanin does not affect in vivo SpO2 measurements. Research in the areas of instrument calibration, theory and design needs to be further developed.

Equitable representation is key for successful clinical and research work. Inequalities in gender, skin colour, and education have been found among professionals in many medical, surgical and academic fields, but have not been examined yet in the current UK neurologists\' workforce. This cross-sectional study examined whether there are disparities in gender, perceived skin colour, education, academic productivity, and career progression among UK neurologists. The names of consultant neurologists working in the UK anytime between December 2021 and March 2022 were found via an online search. Online data were collected regarding education, research activity, academic productivity, impact and progression. A total of 1010 consultant neurologists were found to be working in the UK. There was predominance of men at consultant level, with a university affiliation, and with a full professor position. All 24 female full professors had white skin colour. There were no skin colour or gender disparities in currently being affiliated with a top university, obtaining a Master\'s degree, or duration between medical degree obtainment and becoming full professors. However, less black or brown neurologists had obtained a PhD, were consultants, andit took them a longer time from medical school graduation until becoming consultants.Less females were currently affiliated with a university and had obtained their medical degree from a top university. There were also skin colour and gender disparities in bibliometrics. In conclusion, this study revealed that there are gender, skin colour, education, academic productivity, and career progression gaps among UK consultant neurologists, which need to be addressed.

Various facial colour cues were identified as valid predictors of facial attractiveness, yet the conventional univariate approach has simplified the complex nature of attractiveness judgement for real human faces. Predicting attractiveness from colour cues is difficult due to the high number of candidate variables and their inherent correlations. Using datasets from Chinese subjects, this study proposed a novel analytic framework for modelling attractiveness from various colour characteristics. One hundred images of real human faces were used in experiments and an extensive set of 65 colour features were extracted. Two separate attractiveness evaluation sets of data were collected through psychophysical experiments in the UK and China as training and testing datasets, respectively. Eight multivariate regression strategies were compared for their predictive accuracy and simplicity. The proposed methodology achieved a comprehensive assessment of diverse facial colour features and their role in attractiveness judgements of real faces; improved the predictive accuracy (the best-fit model achieved an out-of-sample accuracy of 0.66 on a 7-point scale) and significantly mitigated the issue of model overfitting; and effectively simplified the model and identified the most important colour features. It can serve as a useful and repeatable analytic tool for future research on facial impression modelling using high-dimensional datasets.

In a prepurchase situation, consumers base their choice decision on external fruit characteristics, from which they infer internal characteristics. This study investigates consumer preference for pomegranate appearance using a choice-based conjoint analysis with 320 participants. We created 27 images of pomegranates that differed in varietal characteristics: colour (yellow, bicoloured, and red), shape (round, oval, and flattened), and calyx shape (open, semi-open, and closed). Colour was by far the most important factor for consumers, followed by fruit shape and calyx shape. Two preference profiles were identified. Most consumers liked bicolour and red pomegranates equally, and rejected yellow ones, while a smaller group concentrated their choice on bicolour pomegranates. In terms of fruit and calyx shape, oval and flattened fruit and open calyx were the most preferred by both consumer groups. Barriers and drivers for consumption were also investigated. There is still plenty of room to increase pomegranate consumption. Greater availability of pomegranates and ready-to-eat arils in grocery shops, obtaining new unseeded/easier-to-peel varieties, and providing a sensory label would help to overcome current barriers. Marketing campaigns should focus on a pomegranate\'s health benefits and its versatility in consumption.

Sun safety research has mainly been conducted in the West, whereas little is known about sun protection practices in India. Using a survey design with a representative sample, we aimed to understand the frequency of sun protection practices in India. We also examined associations between demographic covariates and sun safe behaviours. We surveyed a representative sample (N = 1560) from the Indian population in November 2022. The study variables included sun safe behaviours, sunburn experience, demographic information, and skin tone. We employed descriptive and regression analyses to examine the prevalence of behaviours and their associations. To mitigate potential sampling biases, we applied poststratification weights in the analyses. More than half of the participants (64.2%) routinely performed at least one sun safe behaviour, with only 4.9% of the sample reporting no engagement with sun safe behaviours in the last 12 months. Physical protection (e.g., long sleeves, shade/umbrella) were more common than sunscreen use. Regression analysis showed that higher subjective social status, being younger, and living in one of the Eastern Indian states were the strongest predictors of sun protection practices. Our findings fill an important knowledge gap in global sun safe research, highlighting the urgent need for public sun safety education. Scalable and targeted interventions are needed to promote sun safety awareness and practices among people.

OBJECTIVE: The present study aimed to observe the anatomical distribution of gingival melanin pigmentation and evaluate its intensity and extent in different age groups and in correlation with skin and tooth shades.
METHODS: The participants of this study were 391 patients attending the Dental University Hospital. The presence of gingival pigmentation was assessed using De Krom\'s Oral Pigmentation Chart and its intensity was assessed using the Dummett-Gupta Oral Pigmentation Index. Skin colour and tooth shade were measured using the Fitzpatrick scale and the VITA classical shade guide, respectively. Statistical analyses included descriptive statistics and Pearson\'s Χ2 test for the association between the study variables.
RESULTS: The prevalence of gingival pigmentation among the sample size was 74.4%, and pigmentations were present on both arches in 57.6% (n = 224) of the participants. The extent (category 1) was highest when pigmentation was evident in both arches, with category 4 being the least extent. Age and sex did not show a correlation with gingival pigmentation. Gingival pigmentation intensity was mild when pigments were present in one arch (p < 0.00), whereas it was heavy when both arches presented with gingival pigmentation. Medium brown colour and tooth shade A1 were the most common among participants with gingival pigmentation (p < 0.00). The association between gingival pigmentation intensity and extent in relation to skin colour was statistically significant (p < 0.00), as was tooth shade (p < 0.05).
CONCLUSIONS: Gingival pigmentation is highly prevalent in the Saudi population, with different severity and extent levels. The effect of gingival pigmentation on smile and overall facial aesthetics should be considered when providing dental and cosmetic treatments.

The global ornamental fish trade is expanding in response to increased demand for indigenous fish on the global market, while exogenous carotenoids can improve colouration. The 60-day trial investigated the effect of carotenoid supplementation, via Artemia, on colouration, growth and immunophysiology of Badis badis (dwarf chameleon fish). Carotenoid was enriched at 40 ppm (T1), 80 ppm (T2) and 120 ppm (T3) and compared with controls, C1 (unenriched) and C2 (oil-enriched). Fish larvae (average weight 0.12 g) were fed enriched-unenriched Artemia in triplicates (5 × 3) in aquarium tanks (15 L). C1 and T2 had better skin colour (lightness and whiteness) in the posterolateral and caudal fins respectively. The value of redness (a*) in the anterolateral region was higher in T2 and T3 (p < 0.05). The anterolateral red index was higher (p < 0.05) in T2 and T3, whereas in the posterolateral and caudal fins, T1 and T2 were higher (p < 0.05). Compared to C1 and C2, the hue angle in carotenoid groups was found to be low (p < 0.05). No significant change in the growth performance was noticed (p > 0.05). Immune scores such as lysozyme and alkaline protease were highest in T3 (p < 0.05), whereas protease activity was highest in T2 (80 ppm). Stress biomarkers, viz., superoxide dismutase, catalase and malondialdehyde were low in groups fed enriched Artemia (p < 0.05). The integrated biomarker response means and star plot area were lower in the enriched groups (T1-T3), while T2 was the lowest. Overall findings reveal that dietary carotenoid improves the colouration and immune status, but fail to promote growth. Furthermore, 80 ppm enrichment dose improves the overall performance. The findings can help fish keepers improve fish colour and health status through carotenoid supplementation.

Skin pigmentation is the most variable human characteristic that can be observed and has been used throughout history to classify humans into distinct groups. Many factors influence skin colour, but the melanin pigment is considered the most important because its type and quantity can determine variations in pigmentation shades. The evolution of skin pigmentation started around 1.6-2 million years ago. As a result of migratory phenomena to places with less ultraviolet radiation (UVR) and other seasonal regimes, the selection of depigmented skin and different tanning capabilities occurred over time. Thus, genetic adaptation to new environmental conditions gradually led to changes in skin pigmentation. Despite the biological importance of pigmentation, variation in skin colour has led to social and health inequalities. Since Linnaeus, skin colour classifications have been used to describe different human groups, encouraging the misuse of a biological characteristic. This review examines the characterisation of pigmentation and its evolution through history and society. The unequal perception of pigmentation diversity has led to an incomplete state of dermatological training and issues in medical approach in dermatology. The consciousness of all these aspects increases the need to address and overcome dermatologic and social health disparities related to skin pigmentation.

Some freshwater teleost fish have pigment cells whose arrangement and shape are affected by the environment. Natural light has a wide range of light intensity. Fish are sensitive to the background and exposed light colour. Fish body colour is a significant criterion in fixing its market value, whether it is ornamental or edible. By favourable light exposure, a culturist may get a good market value of fish on most ethical grounds. In this study, we recorded the changes in melanophore response with the changes in light colour on Channa punctata. Adult fish were treated with monochromatic lights (darkness, white, blue and red light) for 5 and 28 days. After treatment, their body colour and melanophore size, number, length and the number of dendrites were studied. The results showed a significant influence of monochromatic light on melanophore arrangement in fish skin. The data showed that blue light is appropriate for the overall species colour of photic C. punctata. Continuous black or white light caused severe damage to the fish\'s appearance.