Africa is a continent of remarkable diversity, including a wide range of skin colors. A team of geneticists led by Sarah Tishkoff, a Penn Integrates Knowledge Professor, has demonstrated a huge amount of variation of skin color within Africa, ranging from skin as light as some Asians to the darkest skin on a global level. While skin pigmentation is one of the most strikingly variable and strongly selected phenotypes among human populations, there are other factors that influence skin tone among African tribes.
Striking skin pigmentation variability among African populations has been underappreciated in genetic studies. Despite being home to the greatest range of pigmentation globally, remarkably few genetic studies of pigmentation have been published to date in continental Africans. Instead, the genetic basis of skin color has primarily been studied in Eurasians and admixed African Americans.
This article explores the genetic, environmental, and cultural factors that contribute to the presence of light skin in certain African tribes, such as the KhoeSan and Fulani, and the Igbo people of Nigeria.
How Could So Many Skin Colors Come from Adam & Eve?
The KhoeSan: Light Skin in Southern Africa
Light skin pigmentation is observed in the far southern latitudes of Africa among KhoeSan hunter-gatherers and pastoralists in and near the Kalahari Desert. The KhoeSan are unique in their early divergence from other populations, likely dating back at least ~100,000 years ago. They exhibit extraordinary levels of genetic diversity and low levels of linkage disequilibrium (LD).
Previous work points to southern Africa as the point of origin for modern humans, but it is unknown whether moderate to light skin pigmentation in the different KhoeSan groups is an example of convergent evolution with northern Europeans and Asians, or reflects the ancestral human phenotype.
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A recent evolutionary and genetic study of skin pigmentation included a total of 465 genotyped KhoeSan individuals (278 ‡Khomani San and 187 Nama), with targeted resequencing at associated pigmentation loci and matched quantitative spectrophotometric phenotype data. The ‡Khomani San are traditionally a N|u-speaking hunter-gatherer population living in the southern Kalahari Desert, while the Nama are traditionally a Khoekhoe-speaking semi-nomadic pastoralist group of KhoeSan ancestry.
Skin pigmentation is lighter in the KhoeSan than the majority of other African populations, with baseline upper arm M index = 57.57 ± 10.12 (mean ± sd) in the ‡Khomani San. Baseline upper arm pigmentation in the Nama is slightly lower, with M index = 52.12 ± 8.93. The ‡Khomani are on average significantly darker than the Nama (p=3.6e-10, Figure 1C), but the variance is not significantly different (p>0.05).
For comparison, quantitative skin pigmentation was aggregated across 32 globally diverse populations (4,712 individuals) assayed with a Derma Spectrometer (DSMI or DSMII). Only four African populations are available for comparison; among these only the Ghanians represent an equatorial African population with minimal recent admixture. Skin color is substantially darker in equatorial Ghanaians, where M index reaches a mean of 96.04 ± 10.94; M index for Cape Verdeans, who have ~40% European admixture on average, have slightly lighter (55.39 ± 13.00, p=5.6e-3) and considerably more variable pigmentation (p=1.9e-6) than the KhoeSan.
The ‡Khomani San and the Nama have both experienced admixture with neighboring darker-skinned Bantu-speaking groups beginning ~450 years ago, as well as with lighter-skinned European settlers who first arrived in the Northern Cape during the late 18th century.
A Khomani San family. Source: Wikimedia Commons
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Genetic Factors in KhoeSan Pigmentation
Approximately 15 genes have been directly associated with skin pigmentation variation in humans, leading to its characterization as a relatively simple trait. However, by assembling a global survey of quantitative skin pigmentation phenotypes, we demonstrate that pigmentation is more complex than previously assumed with genetic architecture varying by latitude.
Researchers have hypothesized that variable exposure to ultra violet radiation (UVR) creates opposing selective forces for vitamin D production and folate protection, resulting in variable melanin production and global pigmentation differentiation. Skin pigmentation differences at similar latitudes and UV exposures indicate that additional evolutionary forces, such as assortative mating, drift, and epistasis, are also likely to have affected global skin pigmentation.
Strong positive selection acting on skin pigmentation has resulted in large effects that explain a large fraction of heritable variation. For example, a previous study in recently admixed Cape Verdeans with European and West African ancestors showed that only 4 loci explain 35% of the variation in skin pigmentation.
In a multivariate mixed model with the significant European and Bantu admixture components, European and Bantu ancestry are strongly correlated with light (β = −18.09, p=2.9e-03) and dark skin (β = 25.60, p=1.8e-09), respectively. Together, we estimate that fixed admixture effects explained 34% of the variation in skin color (adjusted R2); by comparison, 44% of pigmentation variation in Cape Verdeans is explained by admixture effects.
The Fulani: A Complex History and Wide Distribution
The Fula, Fulani, or Fulɓe people are an ethnic group in the Sahara, Sahel, and West Africa, widely dispersed across the region. Inhabiting many countries, they live mainly in West Africa and northern parts of Central Africa, South Sudan, Darfur, and regions near the Red Sea coast in Sudan.
Read also: Genetic diversity insights from Cameroon, Congo, and Bantu groups.
The approximate number of Fula people is unknown, due to clashing definitions regarding Fula ethnicity. A significant proportion of the Fula-a third, or an estimated 7 to 10 million-are pastoralists, and their ethnic group has the largest nomadic pastoral community in the world. The majority of the Fula ethnic group consist of semi-sedentary people, as well as sedentary settled farmers, scholars, artisans, merchants, and nobility.
As an ethnic group, they are bound together by the Fula language, their history and their culture. Many West African leaders are of Fulani descent, including the former President of Nigeria, Muhammadu Buhari; the first president of Cameroon Ahmadou Ahidjo; the former President of Senegal, Macky Sall; the President of Gambia, Adama Barrow; the President of Guinea-Bissau, Umaro Sissoco Embaló; the prime minister of Guinea, Bah Oury; and the Prime Minister of Mali, Boubou Cissé.
While their early settlements in West Africa were in the vicinity of the tri-border point of present-day Mali, Senegal, and Mauritania, they are now, after centuries of gradual migrations and conquests, spread throughout a wide band of West and Central Africa. The Fulani People occupy a vast geographical expanse located roughly in a longitudinal east-west band immediately south of the Sahara, and just north of the coastal rain forest and swamps.
There are generally three different types of Fulani based on settlement patterns, viz: the nomadic-pastoral or Mbororo, the semi-nomadic, and the settled or "town" Fulani. The pastoral Fulani move around with their cattle throughout the year. Typically, they do not stay around for long stretches (not more than 2-4 months at a time). Settled Fulani live in villages, towns, and cities permanently and have given up nomadic life completely, in favor of an urban one.
Distribution map of Fula people. Source: Wikimedia Commons
Cultural and Historical Influences
The Fula, living on the edge of the Sahara, were among the first sub-Saharan groups to adopt Islam. Armed with horses and weapons from the north and inspired by Fula, Berber and Arab clerics, Fulani political units would play a central role in promoting Islam in West Africa through peaceful and violent means.
Throughout the 19th century, Sokoto was one of the largest and most powerful empires in West Africa until 1903, when defeated by European colonial forces. The Sokoto Caliphate included several emirates, the largest of which was Adamawa, although the Kano Emirate was the most populated.
The Fulani, migrant Arabs and Hausa people have taken some influences from each other's cultures. Upon the success recorded in the 1804 Fulani War of Usman dan Fodio, many formerly nomadic Fulɓe subsequently joined the ruling classes of the many emirates of the Sokoto Caliphate.
Paul Riesman, an American ethnographer who resided among the Jelgooji Fulɓbe of Burkina Faso in the 1980s, states that the Fulɓe are tall, slim, and light-skinned; they have thin straight noses, and their hair tends to be long and curly.
The Igbo People of Nigeria: Examining Skin Tone Variations
The question of why some Igbo people have fair skin is a common one, but is it even accurate? And if so, why are there so many fair-skinned Igbos compared to other African ethnicities? Amongst Africans from the continent, determining whether someone is deemed dark or light skinned is based on whether or not their skin complexion is lighter than the average skin tone of the others around them. This is the definition we’re referring to in this article.
First and foremost, it’s important to note that the Igbos are not the only African ethnicity with significant numbers of lighter-skinned individuals. In fact, many West Africans have brown or light brown skin. Nigeria’s three largest ethnic groups are the Hausa, Yoruba, and Igbo. These groups are often what people think of when they hear the word Nigeria. In comparison to the other major ethnic groups, the Igbo population tends to have a greater number of light-skinned individuals.
Africa is the most visually diverse continent when it comes to skin color, with variations attributed to factors such as sun exposure, temperature, natural selection, migration, and mixing.
Since different parts of the world have different levels of sun ray exposure, it makes sense that people’s skin adapts to suit their environment over time.
Igbo People. Source: Igbodefender.com
Environmental and Evolutionary Factors
As demonstrated below, much of South-Eastern Nigeria lies within the ‘rainforest’ regions of the world. In these regions, plants provide protection against sunlight, with only 2-15% of the sun’s light reaching the ground. From an evolutionary perspective, it may be logical to assume that less melanin would be required to protect the skin in these regions.
In addition to the environment and climate, several complex and nuanced evolutionary factors may influence regional variations in skin colour.
Social Preferences and Genetic Variation
It has been suggested that a societal preference for lighter skin may be a factor contributing to the higher numbers of fair-skinned Igbos. In situations where societal preferences for a specific trait exist, groups of people with that preferred trait tend to occur in more concentrated areas.
However, amongst the Igbo people, skin tone variations appear to be random. It’s widely recognised that drastic variations in skin tone can even occur within a single nuclear family. So, while it’s possible that societal preferences play a role in skin tone perceptions among the Igbo people, it may not to be the driving force behind the prevalence of fair skin.
Historical Interactions and Admixture
When it comes to the Portuguese and their involvement in the transatlantic slave trade, their impact on the genetic makeup of the Igbo people was limited. While the Portuguese arrived on the shores of West Africa in the late 1400s and began trading with the Bini Kingdom in 1485, they didn’t venture far inland due to illnesses like yellow fever and other difficulties.
The transatlantic slave trade between the British and the Igbos in the 1700s had a limited impact on the genetic makeup of the ethnic group. According to historians, British slave traders did not venture deep inland where the Igbos resided. Instead, they relied on negotiating with native rulers along the seacoast, who then worked with Igbo middlemen to bring enslaved people down to the coast.
Interestingly, a significant number of fair-skinned Igbo individuals were among those who were enslaved and transported to Jamaica. Due to their light skin tone, they were referred to as “red eboe” - a term that combined the English word “red” with the name of their ethnic group (Igbo).
Ultimately, genetics determine how much melanin a person produces, and this can vary significantly even amongst siblings with the same bloodline. It’s crucial to note that one’s skin complexion does not make one more or less Igbo than someone with a different skin tone.
Conclusion
The presence of light skin in African tribes is a complex phenomenon influenced by a combination of genetic, environmental, and cultural factors. While specific genes play a role in determining skin pigmentation, factors such as UV radiation exposure, historical interactions, and social preferences also contribute to the diversity of skin tones observed across the African continent. Further research is needed to fully understand the intricate interplay of these factors and their impact on the evolution of skin color in different populations.
