Read the following passage.
For over a century, evolutionary biologists have debated the primary adaptive function of the zebra’s distinctive black and white striping. Early naturalists overwhelmingly subscribed to the crypsis hypothesis, arguing that the stripes serve a camouflage function by disrupting the animal’s morphological outline in the tall grass of the savanna, thereby confounding the visual processing of apex predators. However, subsequent field observations challenged this view, noting that lions—the primary predators of zebras—have relatively poor visual acuity at a distance and hunt largely by scent. Furthermore, zebras frequently graze in open plains where they remain conspicuously visible regardless of their coat pattern.
Seeking alternative explanations, later twentieth-century researchers proposed the thermoregulation hypothesis. This camp suggested that the alternating light and dark bands absorb and reflect solar radiation at different rates, generating localized micro-eddies over the skin that physiologically mitigate extreme heat stress. Yet, recent comprehensive thermal imaging studies have contradicted this, finding no significant surface temperature differential between zebras and similarly sized, solid-colored ungulates inhabiting the same environments.
A third faction, composed primarily of behavioral ecologists, emphasizes intra-species social dynamics. They posit that the stripes act as a complex biometric marker system, enabling individual differentiation and facilitating social cohesion within large migratory herds. While this theory elegantly accounts for the high degree of phenotypic variation in stripe patterns among individual zebras, it struggles to explain why many other highly social, closely related equids survive successfully without such distinct markings.
Presently, the most robust consensus has coalesced around the ectoparasite deterrence model. Proponents of this view point to compelling empirical data demonstrating that the visual systems of tsetse flies and horseflies—which transmit fatal diseases—are optically disrupted by high-contrast striped patterns. Consequently, these disease vectors are significantly less likely to land on zebras than on solid-colored equids. While no single theory may entirely exclude the others, the ectoparasite model currently provides the most comprehensive resolution to the ecological paradox of the zebra's coat.
Based on the passage, match each group of researchers to the primary evolutionary function they attribute to the zebra's stripes.
- Early naturalistsObscuring the animal's physical boundaries to evade predatory detection
- Later twentieth-century researchersGenerating physiological relief from extreme environmental temperatures
- Behavioral ecologistsFacilitating group cohesion through unique individual identification
- Ectoparasite deterrence proponentsConferring a survival advantage by confusing the visual systems of disease vectors