In many hairy vertebrates, such as apes, dogs, and rats, the involuntary erection of hair acts as an efficient means of thermoregulation. the erect hairs trap an insulating layer of air against the skin, keeping the animal warm. humans also display hair erection when cold, though humans are not hairy enough for this reflex to have a significant effect on body temperature. which statement is true regarding this reflex?
1) it reflects the common ancestry of humans with hairy vertebrates.
2) it suggests humans are less evolved than other hairy vertebrates, because they are not adapted to maintain body temperature.
3) the loss of hairy bodies is an evolutionary disadvantage to humans.
4) the reflex is actually a voluntary response humans manifest during infancy.