Individuals with the ability to digest lactose had a 4% higher chance of producing offspring, a significant evolutionary advantage conferred by a genetic mutation that spread across Europe around 5,000 years ago, eventually impacting over three-quarters of the population. Around 8,500 years ago, the first farmers from the Fertile Crescent in the Near East made their way to Europe, partially replacing the hunter-gatherer populations. A second wave occurred about 5,000 years ago with the arrival of herders from what is now the Caucasus region. A mutation from 6,000 years ago was discovered in present-day Ukraine, and by 4,500 years ago, it was found in 5% of the European population. This mutation enables the production of lactase in adulthood, an enzyme that breaks down lactose, thereby aiding in milk digestion.