Answer:
Variation
Step-by-step explanation:
Migration into a population from other populations with varying gene frequencies, evolution, or adaptation of heat tolerance is a cause of variation. The allele frequency of the resulting hybrid population would be right in the middle of its original value and the donor population's frequency. In tropical and subtropical ecosystems (Sahara deserts), high temperatures are a significant restriction to human population productivity; they induce morphological and physiological modifications at all times, resulting in significant yield losses but the ability and evolution of human species to cope in this region is as a result of variation.