Select the scenarios that are likely due to positive assortative mating. purebred dachshunds have a higher incidence of degenerative disc disease compared to mixed breed dogs. short, muscular males from a native indigenous tribe preferentially select the tallest and slimmest muscular wives that do not resemble their own physique. a livestock breeder carefully selects cows that produce the most milk to mate with his bull. tall, slender males from a native indigenous tribe preferentially select the tallest and slimmest wives that resemble their own physique. in a large population, the frequency of the aa genotype increases over many generations. grasshoppers randomly select mates based on proximity and breed with as many other grasshoppers as possible.