Pigmentation in Skolt Saamis (Lapps)

Henrik Forsius, Aldur W. Eriksson, Johan Fellman
Folkhälsan Institute of Genetics, Department of Genetic Epidemiology, Helsinki, Finland.

People living in the tropics are strongly pigmented, but populations in Northwestern Europe are lighter pigmented in the skin, hair and eyes. The reason for why recessively inherited genes, which according to Eiberg et al. (2008) appeared 6000-10000 years ago, becoming so dominant in Nordic countries remains unclear. However, the main factor underlying the success of new mutations was likely that lighter skin better synthesizes vitamin D, providing superior protection against rickets, a problem in childbirth for both mother and child due to the deformed, narrow pelvis of rachitis-affected mothers.

The population is increasingly lighter pigmented moving in a northward direction in Europe until reaching the Arctic Circle, where the Saamis (Lapps) are clearly more pigmented, to about the same degree as those living in Middle Europe.
What causes this difference between neighbouring Nordic populations? Do the Saamis have an advantage or a disadvantage as a result of their stronger pigmentation? We have intensively studied pigmentation in Finns as well as Saamis in an attempt to answer these questions.

Like the other circumpolar populations in Europe and Asia, the main source of livelihood for Saamis is reindeer herding. In contrast to the other Saami populations, the hair of Skolt Saamis is softer and their pigmentation is lighter. Their language belongs to the Fenno-Ugric group. The anthro-pology of the Saamis shows short stature, high cephalic index, broad cheekbones and relatively strong pigmentation. Hence, earlier physical anthropologists believed that the Saamis were of Asiatic Mongoloid origin, but population genetic studies have revealed no unequivocal genetic resemblance between Saamis and the Asiatic Mongoloid populations (Eriksson, 1988; Beckman, 1996). When mitochondrial DNA sequence variation was analysed in 14 European populations, most populations showed little differentiation with respect to each other. However, the Saamis distinguished themselves by a comparatively large amount of sequence difference. Thus, the Saamis seem to have a long history distinct from other European populations (Sajantila et al., 1995).

About 2000 years ago, the Saamis populated most of Finland, but they were pushed increasingly northwards by the Finns and today form the majority of the population only in Utsjoki, the northernmost parish of Finland

Differences in pigmentation also exist among the Saamis. The Skolt Saamis are the lightest pigmented, probably as a result of mixing with neighbouring populations.

The Finns are among the lightest populations in the world, particularly in the hair. Interestingly, in the Finnish population in Savukoski, the most north-easterly situated population and a close neighbour of the Saamis, the pigmentation is increased in relation to the Finns, probably because they have partly Saami genes.

The importance of pigmentation in humans is best highlighted in the interest researchers have shown in molecular studies. More than 100 genes located in several different chromosomes have been identified as taking part in pigmentation. The OCA2 region of 15q accounts for 74% of the variation in human eye colour (Duffy et al., 2007; Sturm, R. A., 2009).

Pigmentation changes with age up to adolescence in European (Caucasian) populations. The changes in the children up to adulthood have been studied by Matheny and Dolan (1975) and others. Most reports in the abundant literature of pigmentation in the iris and hair describe women as being more pigmented than men.

Our investigations
In 1966-1970 a total of 1092 subjects were investigated by us in the villages of Sevettijärvi and Nellim, which are situated on opposite sides of Inari lake. The Saamis population that we studied most intensively is the Skolt Saamis, the most easterly situated population in Finland. We investi-gated pigmentation in 595 pure Skolt Saamis of different ages. “Pure” refers to persons whose parents were Skolts.

We have also studied the pigmentation of eyes in several other locations, Russia, and North America (Inuits), and in American Indians in Peru and in Asian Indians in the Himalayas and in two populations in Africa. In all of these people, the pigmentation was stronger than in Finns and Saamis.

Preliminary results of our pigmentation studies among Nordic populations have been reported in Eriksson and Forsius (1991). In this publication, an introduction is given of pigmentation of the skin, iris and hair in different Nordic populations.

For estimation of the colour of the iris, the Martin-Saller scale with eight different colours from blue to black, and for the hair pigmentation the Fisher-Saller scale with 30 different colours were used. To assess translucency of the iris, Waardenburg’s method was applied. Pigmentation of the eye ground, eyebrows and eyelashes was estimated in three different shades.

In most investigations, pigmentation the iris, hair and skin is studied, but here we have also examined pigmentation in the eye ground, eyebrows and eyelashes.

The translucency of the iris is clinically used to evaluate the destruction of the pigment epithelium. To our knowledge we are the only researchers who have studied the degree of pigmentation in the iris and eye ground according to age and sex. The pigmentation curves follow each other quite well

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Table 1 shows the correlations between pigmentation variables in the Skolt Saami population. Pigmentation of the lashes is black throughout life, but the colour of the eyebrows is lighter in children than later in life.

To our knowledge, population studies of the translucency of the iris have never before been conducted. As expected, iris translucency is highly negatively correlated with iris pigmentation. The darker the iris, the less translucent.

Generally, pigmentation increases over the life span. In Skolt Saamis many children have a light-coloured hair and a light pigmented iris and eye ground, which upon reaching adulthood darken. Pigmentation of the iris shows only a slight dependency on age.

Figure 3 sows a typically coloured iris of a Skolt Saami.

Figure 4
Interestingly, when evaluating pigmentation in the retina and choroids, pigmentation in the choroids is better correlated with pigmentation in the iris than pigmentation in the retina. Embryology reveals that the choroids as well the iris parenchyma develop from the mesoderm.

Figure 5. A lightly pigmented eye ground of a Skolt Saami. Pigmentation in the choroids is scarce. Retinal pigmentation is normal in the macular region.

Curiously, only one investigator, Rozprym (1934), has studied pigmentation of the eyelashes and the eyebrows at a population level and their correlation with the skin, iris and hair. He noted the highest correlation in pigmentation between the hair and the eyebrows, whereas correlation of the colour of the eyelashes and the pigmentation in all other investigated parts was virtually non-existent.
We discussed earlier the importance of UV light for the synthesis vitamin D, and that light pigmentation of the skin benefits most from this process. In the arctic, UV light is, however, also a problem because the reflection from the snow can cause snowblindness. This problem is of less importance for the Saamis, as shown by the fact that they earlier did not use protection for their eyes, unlike the Inuits and Siberian populations. UV light can cause secondary problems with vision known as photokeratitis.

Snowblindness is the acute form of photokeratitis, manifested as epithelial changes in the cornea, as we ophthalmologists have seen when welders receive an overload of UV light. The epithelium can definite degenerate also in the centre of the cornea if year after year an individual receives an overdose of UV light, as arctic inhabitants and subjects living near the Red Sea do. We have observed that the degeneration may cause problem with vision as well in Saamis as in Inuits (Eskimos). Using a biomicroscope we observed small changes in epithelial haziness of the corneal periphery laterally and medially in most persons spending the majority of the day working outdoors. We did not find a correlation between the amount of photokeratis and the degree of pigmentation of the iris.

The Saamis north of the Arctic Circle live in darkness up to two months during the winter. We studied dark adaptation in some of the Saamis and found it to be similar to populations in Southern Finland

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In Figure 6 we compare the iris pigmentation among Skolts and some neighbouring populations. The Skolt data were obtained in this study. The other data were presented in Eriksson and Forsius (1991). For Åland Islanders, Saamis and Skolts, the age of the subjects are between 20 and 59 years (anthropological age). Western Finns are young adults (male conscripts and female students). The results for Kökar (Åland) are based on all subjects aged over one year. Consequently, the Kökar data may have small negative biases. Note that the proportion of dark irises is higher among Saamis than among Skolts. The differences between females and males are insignificant. Pigmentation among Skolts is markedly higher than among Finns in Western Finland, Southern Finland (Åland Islands) or in the Saami population situated west of Inari lake.

What was the result of our pigmentation studies of the Saamis? To our knowledge, population studies of the translucency of the iris have never before been conducted. Nobody has before us studied changes in the pigmentation of the lashes, the eyebrows and the eye ground throughout life.
After considering all of our results, we believe that the benefit of the darker pigmentation in Saamis is negligible. The Saamis are darker than the other Nordic peoples because they very likely got their pigmentation genes from the other populations in northern Eurasia.

FIGURE TEXTS.

Table 1. Correlations between the pigment variables iris, translucency, choroid, retina, eyelashes (lashes), eyebrows (brows). The number of observations varies between 172 and 189. The empty cells contained insignificant correlation coefficients. Strongly significant correlation coefficients (P < 0.01) are bolded, and the rest of the presented correlation coefficients are significant (P < 0.05).

Figure 4. Comparison between the proportions of dark irises (Fisher-Sallers scale 5-8) in Skolts according to sex and age.

Figure 6. Comparison between the proportions of dark irises (Fisher-Sallers scale 5-8) in neighbouring populations. The Skolt data were obtained in this study. The other data were presented in Eriksson and Forsius (1991). For Åland islanders, Saamis and Skolts, the age of the subjects is between 20 and 59 years (anthropological age). Western Finns are young adults (male conscripts and female students). The results for Kökar (Åland) are based on all subjects aged over one year. Consequently, the Kökar data may have small negative biases. Note that the proportion of dark irises is higher among females than males, but the difference is insignificant.