Have Europeans always had light skin? The answer from paleogenomics is a resounding no. Ancient DNAAncient DNAGenetic material preserved in old remains, often degraded, sequenced with cutting-edge techniques.→ analyses from bones of MesolithicMesolithicThe period between the Palaeolithic and the Neolithic (c. 10,000–6,000 BC in Europe), still based on hunting and gathering.→ European hunter-gatherersHunter-gatherersA way of life based on hunting, fishing and gathering wild resources, without farming or herding; it dominated almost the whole of human history.→ have revealed that these populations, despite having lived in Europe for tens of thousands of years, had dark skin pigmentation. The light skin associated today with northern European populations is a recent evolutionary acquisition, arising mainly during the NeolithicNeolithicThe "New Stone Age": a period marked by farming, herding, settlement and pottery, from around 10,000 BC.→ and Bronze AgeBronze AgeA protohistoric period following the Neolithic, defined by bronze metallurgy (a copper-tin alloy) and the rise of the first cities and states; in Egypt it corresponds to the age of the first pyramids.→, linked to the arrival of new populations from Anatolia and the Pontic steppeSteppeA vast semi-arid, treeless grassland of Eurasia, suited to nomadic herding and the horse; a corridor for the movement of peoples and technologies in later prehistory.→.1

What paleogenomics reveals about European hunter-gatherers

The most spectacular demonstration came from La Brana 1, a Mesolithic skeleton discovered in Asturias (Spain) dated to around 7,000 BCE. In 2014, the team of Johannes Krause and Carles Lalueza-Fox extracted and sequenced its genome with sufficient precision to characterize pigmentation variants. The result sent shockwaves through the scientific community: La Brana 1 carried alleles associated with dark skin (absence of derived variants at the SLC24A5 and SLC45A2 genes), yet paradoxically displayed alleles associated with blue or green eyes (variants at the HERC2/OCA2 gene). A Mesolithic European with light eyes and dark skin - a combination rare in modern humans - was apparently the norm among our Mesolithic ancestors.2

La Brana 1 is no isolated case. Similar results were obtained for Loschbour (Luxembourg, ~8,000 BP), Motala (Sweden, ~7,700 BP), and several other Mesolithic individuals from Western and Northern Europe. All share the same combination: light eyes, dark skin, absence of skin-depigmentation alleles that define today's light-skinned Northern European populations. These Western Hunter-Gatherers (WHG) formed a genetically distinct population whose pigmentation bore no resemblance to that of their modern counterparts.

Biochemistry and histology of different skin types according to melanin concentration
Skin pigmentation is determined by concentrations of eumelanin (brown-black) and pheomelanin (red-yellow) in the epidermis. The genes SLC24A5 and SLC45A2, whose derived variants spread through Europe 5,000 to 8,000 years ago, regulate the production of these pigments. Credit: Gregory S. Barsh, Wikimedia Commons, CC BY 2.5

The genes involved and the timing of their spread

Paleogenomics has identified the principal molecular players. The gene SLC24A5, located on chromosome 15, encodes an ion transporter involved in melanin production in melanocytes. The derived variant SLC24A5*A111T, today present in over 95% of light-skinned Europeans, was virtually absent from Mesolithic Western European hunter-gatherers. The Mathieson et al. (2015) study, covering 83 ancient individuals, showed that this variant only appeared massively in the genomes of European populations with Neolithic farmers arriving from Anatolia roughly 7,000 to 8,000 years ago. These Anatolian farmers already carried SLC24A5*A111T before migrating into Europe, suggesting that partial depigmentation had begun earlier, in the Fertile CrescentFertile CrescentAn arc-shaped region of the Near East (Levant, Mesopotamia) where farming and herding first emerged.→ or Asia Minor.3

A second major gene, SLC45A2 (also known as MATP), whose variants also contribute to reduced pigmentation, followed a similar but delayed trajectory: it only spreads massively in Europe with the migrationsMigrationsLong-distance movements of populations; a major driver of human history (the exit from Africa, the peopling of continents, Neolithic and steppe expansions).→ of Pontic steppe pastoralists (Yamnaya culture and related groups) approximately 4,500 to 5,000 years ago. Two successive migration waves - Neolithic farmers from the Near EastNear EastA region of western Asia (Levant, Mesopotamia, Anatolia, Iran), cradle of the Neolithic revolution, agriculture, the first cities and writing.→, then steppe pastoralists from Eurasia - thus brought the main light-skin genes into Europe, layer by layer, gradually forging the genetic makeup of today's European populations.4

Why light skin was selected for in Northern Europe

The selection pressure that favored these alleles is well understood. At high latitudes, ultraviolet (UV-B) radiation intensity is low, particularly in winter. Yet UV-B is essential for vitamin D synthesis in the skin: it activates the conversion of 7-dehydrocholesterol into previtamin D3 in superficial epidermal layers. Melanin-rich skin, perfectly adapted to equatorial environments where it filters excess UV rays protecting folate and cellular DNADNAThe molecule carrying genetic information, used to reconstruct kinship between species.→, becomes a disadvantage at high latitudes: it reduces UV-B penetration and therefore vitamin D synthesis, exposing its bearers to deficiencies that can cause rickets, immune dysfunction, and pregnancy complications.

Mesolithic hunter-gatherers partly compensated by diet: rich in oily fish, game, and organ meats, their dietary regimes provided preformed vitamin D (animal vitamin D3). With the Neolithic transition to cereal farming - much poorer in vitamin D3 - selection pressure in favor of lighter skin intensified considerably: without adequate dietary supplementation, only individuals capable of synthesizing more vitamin D through lighter skin survived northern winters more successfully. The interplay between diet and latitude explains the global geography of skin pigmentation with remarkable precision.5

Anatomical comparison between Homo sapiens and Neanderthal, two species that coexisted in Europe
Cranial comparison between Homo sapiensHomo sapiensThe present-day human species, which emerged in Africa around 300,000 years ago, the only surviving human lineage after the extinction of Neanderthals and Denisovans.→ and Neanderthal. Ancient DNA studies have shown that NeanderthalsNeanderthalsA fossil humanity of Eurasia, robust and cold-adapted, extinct around 40,000 years before present.→ also carried variants of the MC1R gene potentially associated with red or lighter pigmentation, raising the question of independent evolutionary convergences in low-sunlight environments. Credit: Wikimedia Commons, CC BY-SA 2.0

Blue eyes before light skin: an unexpected dissociation

One of paleogenomics' most counter-intuitive findings is that light eyes preceded light skin in Europe. Mesolithic hunter-gatherers already carried, at high frequency, derived variants at the HERC2/OCA2 gene responsible for blue or green eyes - while still having dark skin. This dissociation rests on the fact that genes regulating eye color and those regulating skin pigmentation are largely independent.

Why were light eyes selected independently and earlier? Hypotheses diverge. Some researchers invoke sexual selection: light eyes may have been a visual signal favoring mate choice in small-population contexts. Others suggest an advantage related to vision in low-light conditions. In any case, the light-eyes/dark-skin combination, rare among modern Europeans, was apparently the norm among their Mesolithic ancestors - confirming that evolution does not always advance in lockstep, and that visually linked traits can have entirely separate evolutionary histories.6