Santa Fe Trail was the most popular route
Physical anthropologist John Hawks and colleagues suggest that evolution is speeding up as population sizes are being continued to mushroom and new mutations which are endorsed.
Human population increased rapidly. The increase began those days of upper Paleolithic which is documented by archaeological evidence.
White fat cells secrete many proteins acting as adipokines such as resistin, adiponectin, leptin and apelin. An average human adult has 30 billion fat cells with a weight of 30 lbs or 13.5 kg.
Primary producer, because it has to make it's own food.
Anaerobic exercise is one situation that would cause a buildup of lactic acid in human muscle cells. As the cells switched over from aerobic respiration to fermentation in order to produce ATP, lactic acid would be produced in relatively large quantities as a byproduct. This allows NADH and FADH2 electron carriers to be oxidized without the electron transport chain and would allow Glycolysis to continue.