Stone tools, particularly projectile points and scrapers, are the primary evidence of early human activity in the Americas. Crafted lithic flaked tools are used by archaeologists and anthropologists to classify cultural periods. Scientific evidence links indigenous Americans to Asian peoples, specifically eastern Siberian populations. Indigenous peoples of the Americas have been linked to North Asian populations by linguistic dialects, the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA. 8,000–7,000 BCE (10,000–9,000 years ago) the climate stabilized, leading to a rise in population and lithic technology advances, resulting in a more sedentary lifestyle.