Question

Read the following passage:

Biologists have long debated the evolutionary function of the distinctive black-and-white stripes of zebras. Early hypotheses, championed by Alfred Russel Wallace, posited that the stripes provided camouflage in tall grass, confusing predators like lions. However, later field studies revealed that lions possess visual systems that easily resolve zebra outlines regardless of stripe patterns, rendering the camouflage theory largely obsolete.

A second prominent theory suggests that stripes serve a thermoregulatory function. Proponents argue that the alternating colors create micro-eddies of air across the zebra's body due to differential heating, as black stripes absorb more heat than white ones. While laboratory models demonstrate this effect, empirical measurements of live zebras in their natural habitats have found no significant cooling benefit compared to uniformly colored ungulates of similar size.

Currently, the most robustly supported hypothesis asserts that stripes evolved to deter biting flies, which carry deadly diseases. Experimental evidence indicates that these insects struggle to land on striped surfaces because the high-contrast pattern disrupts their optic flow—the visual motion cue they use to control their approach. Furthermore, geographical analysis correlates the intensity of zebra striping with the historical prevalence of biting flies in their respective habitats.

Despite this consensus, some researchers maintain that stripes also facilitate social cohesion. According to this view, the unique pattern of each individual aids in kin recognition and allows zebras to coordinate movement within the herd during a predator attack. Nevertheless, critics note that horses and other uniform equine species exhibit similar levels of social coordination without such striking markings.

Based on the passage, all of the following are mentioned as evidence or arguments used to evaluate hypotheses regarding the function of zebra stripes EXCEPT: