the most brilliant and diversified. The practical function of striping in zebras has been debated and it is unclear why the quagga lacked stripes on its hind parts. A cryptic function for protection from predators (stripes obscure the individual zebra in a herd) and biting flies (which are less attracted to striped objects), as well as various social functions, have been proposed for zebras in general. Differences in hind quarter stripes may have aided species recognition during stampedes of mixed herds, so that members of one subspecies or species would follow its own kind. It has also been evidence that the zebras developed striping patterns as thermoregulation to cool themselves down, and that the quagga lost them due to living in a cooler climate, although one problem with this is that the mountain zebra lives in similar environments and has a bold striping pattern. A 2014 study strongly supported the biting-fly hypothesis, and the quagga appears to have lived in areas with lesser amounts of fly activity than other zebras. A 2020 study suggested that the sexual dimorphism in size, with quagga mares being larger than stallions, could be due to the cold and droughts that affects the Karoo plateau, conditions that were even more severe in prehistoric times, such as during ice ages (other plains zebras live in warmer areas). Isolation, cold, and aridity could thereby have affected quagga evolution, including coat colour and size dimorphism. Since plains zebra mares are pregnant or lactate for much of their lives, larger size could have been a selective advantage for quagga mares, as they would therefore have more food reserves when food was scarce. Dimorphism and coat colour could also have evolved through genetic drift due to isolation, but these influences are not mutually exclusive, and could have worked together. Relationship with humans Quaggas have been identified in cave art attributed to the indigenous San people of Southern Africa. As it was easy to find and kill, the quagga was hunted by early Dutch settlers and later by Afrikaners to provide meat or for their skins. The skins were traded or exploited. The quagga was probably vulnerable to extinction due to its restricted range. Local farmers used them as guards for their livestock, as they were likely to attack intruders. Quaggas were said to be lively and highly strung, especially the stallions. Quaggas were brought to European zoos, and an attempt