The O allele is unusually frequent in the Americas. What does this pattern suggest about the evolutionary history of these populations?

Populations from the Americas started from a founding population with a high frequency of the O allele

Explanation:

Human blood type is determined by three different codominant alleles: IA, IB, and, which are named A (IA), B (IB), and O (i). Each person has two blood type alleles, i.e., one allele inherited from the mother and one from the father. The frequency of the O blood allele is very high in indigenous populations, and in Central and South American populations this allele may reach a frequency of 1 (100%). In consequence, the predominance of the O blood allele in Native American populations suggests that these populations descended from a founding population that had a high frequency of the O blood allele. A founder effect may even cause the fixation of one allele within a population, and this phenomenon is known to be associated with the loss of genetic variation.

endo:

regulates body hormones, aldosterone, vasopressin

neural:

signal, regulates body using electric signals, reflex

endo has to do with hormones; aldosterone and vasopressin are both hormones. i also had this question and got it right : d