Human Adaptability

Maya Blue is a colour that is more than a pigment; it had roles in status, ritual and performance, being daubed onto pots and people before sacrifice. Here researchers use experimental and historical evidence to discover how it was made, including direct scientific analysis of Maya Blue on a pot thrown into the sacred well at Chichén Itzá. The results indicate that the formation of the color was actually part of the ritual.

Archaeological evidence shows that humans began living in the high altitude Andes approximately 12,000 years ago. Andean highlanders are known to have developed the most complex societies of pre-Columbian South America despite challenges to their health and reproductive success resulting from chronic exposure to hypoxia. While the physiological adaptations to this environmental stressor are well studied in contemporary Andean highlanders, the molecular evolutionary processes associated with such adaptations remain unclear. We aim to better understand how humans managed to demographically establish in this harsh environment by addressing a central question: did exposure to hypoxia drive adaptation via natural selection within Andean populations or did an existing phenotype –characterized by reduced susceptibility to hypoxic stress–enable human settlement of the Andes? We genotyped three variable loci within the NOS3 and EGLN1 genes previously associated with adaptation to high altitude in 150 ancient human DNA samples from Peruvian high altitude and coastal low altitude sites in a time frame between ~8500–560 BP. We compare the data of 109 successful samples to forward simulations of genetic drift with natural selection and find that selection, rather than drift, explains the gradual frequency changes observed in the highland populations for two of the three SNPs. Humans residing in the high altitude Central Andes (above 2,500 m.a.s.l.) are directly and indirectly affected by two primary environmental extremes: hypobaric hypoxia and cold. Environments characterized by hypoxic-low concentration of atmospheric oxygen-and cold conditions negatively impact the abundance of resources available to sustain human populations 1. More directly both extremes act as stressors on the human body affecting biological processes, e.g. reproductive growth, basal metabolic rates, morbidity, and mortality 2. Despite these obstacles archaeological evidence shows that humans began to live seasonally in the high altitude Central Andes almost immediately after the first settlers arrived on the Pacific littoral of central South America, and permanent residence is evident by ca. 12,000 to 10,000 years ago 1,3. These early inhabitants laid the foundations for what would eventually become the most complex societies of late pre-Columbian South America, namely Wari, Tiwanaku, and Inca, demonstrating the successful adaptation to the harsh environmental conditions of the Andes. However, the molecular evolutionary processes associated with such adaptations remain unclear. It is unknown if the Andes were initially peopled by individuals genetically predisposed with a reduced susceptibility to altitude stress–assuming that individuals suffering from symptoms of e.g. acute hypoxia would have returned to lower altitudes–or whether the descendants of these early pioneers adapted to the environmental stressor over time 1,4. While prehistoric Andean societies developed behavioral and cultural adaptations to buffer against low biotic productivity and cold 1 , hypoxia constitutes a stress factor acting on human biology that cannot be compensated for by those adaptive mechanisms. Generations of researchers have found that modern Andean populations like the Quechua and Aymara have physiological traits not only distinctive from South American lowland populations