About 10,000 years ago, a remarkable evolutionary change took place in the vast, snow-rich and sunless landscapes of Northern Europe, which had a lasting impact on the appearance of part of humanity: the emergence of blue eyes. Originally, all modern people had brown eyes, as a high concentration of the melanin pigment in the iris offered optimal protection against the intense UV radiation in the African regions of origin. However, when human populations moved north in the course of the migrations, environmental conditions changed radically. In the ice age and post-ice regions of northern Europe, sunlight was scarce, and the landscape was covered with snow and ice for months. In this specific environment, the strong sun protection lost its biological urgency. Scientific research shows that the development of blue eyes is due to a single, specific genetic mutation that occurred on the so-called OCA2 gene. This gene controls the production of melanin in the iris. The mutation acted like a biological dimmer that did not completely stop melanin production - which would have led to albinism - but throttled it exactly so far that the eyes appeared blue. Since this mutation is genetically traced back to a single common ancestor, the trait spread rapidly in the isolated, small groups of people in the north. For survival in deep snow and under cloudy skies, bright eyes offered a subtle but decisive advantage in everyday life. Since fewer pigments block the incident light, blue eyes can perceive fine contrasts and contours much better in the dark Scandinavian winter landscape than darkly pigmented eyes. This greatly improved orientation and hunting efficiency in low-light conditions. At the same time, this characteristic probably co-evolved with a lightening of the skin, which was necessary in the north to synthesise enough vital vitamin D despite the low sunlight. In addition to this purely practical benefit of improved residual light utilisation, sexual selection played a driving role in the evolution of this eye colour. In the genetically isolated communities characterised by harsh winters, the rare, glowing eye colour was a visual signal preferred when choosing a partner. Because people with blue eyes were perceived as potentially more attractive or healthier partners, they passed on their genes more successfully to the next generations. Thus, the mutation solidly solidiss in the gene pool of the northern European population over the millennia. What began as a random copying error in the genetic material of a single person in an icy environment, developed into one of the most striking evolutionary characteristics of the European population through the interplay of changed vision requirements in the snow, the need for biological adaptation to the lack of light and the psychological factor of partner choice, which to this day makes the genetic diversity of our species visible. #viral #fy #nature #blue #eyes - @educationaldude