The sheep (Ovis aries) is the first animal domesticated for consumption in a historical milestone marking the onset of sedentarisation of human communities at the beginning of the Neolithic. For millennia, sheep were similar to the Asian mouflon (Ovis orientalis), their wild ancestor. The surviving primitive breeds in northern Europe are dark, moult seasonally, have horns in both sexes and produce little wool. The ancestors of the modern breeds arose about 3,500 years ago. They were selected to produce white wool, which grows indefinitely and is collected annually. This process coincides with the invention of iron shears and the discovery of dyes such as purple. Only white wool can be dyed in any colour, making it possible to transfer to the cloth the same symbols that perhaps were used to decorate human bodies with ochre. The sheep, a very manageable social herbivore, added to its values as food supply that of a warm and colour-modifiable fibre, distinctive of those who wear it. A blank canvas on which to transpose aesthetic expressions previously restricted to the body, rock art and portable art. Hence, various mythologies contemplate a special symbolic relationship with them. The aesthetic revolution brought about by the white sheep collapsed in the 20th century with the appearance of new fibres and the cheapening of others. Today, the archetypal white flocks characteristic of Western iconography tend to a mixed colouring as wool is devalued. Other domestic species with fibres that have only recently become commercially appreciated, such as angora goats (Capra hircus) or llamas (Lama glama), follow a process identical to that undertaken with sheep millennia ago to turn them white. We present the aesthetic implications that have stimulated the artificial selection of sheep with white wool from a transdisciplinary point of view. Following a bioevolutionary perspective, which considers our aesthetic behaviour and its manifestations as part of our ethology, we will see how this long process was stimulated by our desire to dye textiles to express an extended phenotype by creating a new social signal. This new signaling, operating at the level of sexual selection, becomes more complicated as our symbolic and technological capacities develop, and it is symptomatic of the causal milieu in which it occurs.