brown-eyed individuals share a large area in their DNA controlling melanin production, blue-eyed individuals have only a small region. By examining mitochondrial DNA of people from multiple countries, Eiberg and his team concluded blue-eyed individuals all share a common ancestor. In 2018, an international team of researchers from Israel and the United States announced their genetic analysis of 6,500-year-old excavated human remains in Israel's Upper Galilee region revealed a number of traits not found in the humans who had previously inhabited the area, including blue eyes. They concluded that the region experienced a significant demographic shift 6,000 years ago due to migration from Anatolia and the Zagros mountains (in modern-day Turkey and Iran) and that this change contributed to the development of the Chalcolithic culture in the region. Bronze Age to Medieval Era Resistance to malaria is a well-known example of recent human evolution. This disease attacks humans early in life. Thus humans who are resistant enjoy a higher chance of surviving and reproducing. While humans have evolved multiple defenses against malaria, sickle cell anemia—a condition in which red blood cells are deformed into sickle shapes, thereby restricting blood flow—is perhaps the best known. Sickle cell anemia makes it more difficult for the malarial parasite to infect red blood cells. This mechanism of defense against malaria emerged independently in Africa and in Pakistan and India. Within 4,000 years it has spread to 10–15% of the populations of these places. Another mutation that enabled humans to resist malaria that is strongly favored by natural selection and has spread rapidly in Africa is the inability to synthesize the enzyme glucose-6-phosphate dehydrogenase, or G6PD. A combination of poor sanitation and high population densities proved ideal for the spread of contagious diseases which was deadly for the residents of ancient cities. Evolutionary thinking would suggest that people living in places with long-standing urbanization dating back millennia would have evolved resistance to certain diseases, such as tuberculosis and leprosy. Using DNA analysis and archeological findings, scientists from the University College London and the Royal Holloway studied samples from 17 sites in Europe, Asia, and Africa. They learned that, indeed, long-term exposure to pathogens has led to resistance spreading across urban populations. Urbanization is therefore a selective force that has influenced human evolution. The allele in question is named SLC11A1 1729+55del4. Scientists found that among the residents of places that have been settled for thousands of