Xavier is unresponsive to most social stimuli. he rarely smiles, talks, or makes eye contact with others. he seems indifferent to everyone, including his parents. he engages in solitary, ritualistic behaviors such as constantly flapping his hands. he sometimes goes into sudden tantrums or panics. he also insists on the same familiar food each day. xavier's disorder is most likely:

Humans are believed to have evolved in coastal regions in east africa. the region had an abundant supply of fish for early humanoids to eat. when scientists analyze the fads gene they see an interesting pattern. people whose families have lived in this area of east africa for generation show a high level of diversity in alleles for the fads gene. conversely, people whose families had migrated inland a moderate distance from sources of fish showed a much lower diversity for fads gene alleles. additionally, the fads alleles found in people whose family has lived inland for generation are almost all gene alleles which produce fads proteins with a high level of function and activity. how do anthropologists explain this?