Why don’t humans use colourful tails like the peacock to attract mates? A new study explains this in terms of smaller social groups. The paper is published in Behavioral Ecology.
Creatures throughout the animal kingdom have been endowed with special ways of attracting mates – some of these are more conspicuous than others. But, why are others unable to make such ‘public displays of affection’? For instance, why don’t humans have the male-peacock equivalent?
This is because the social groups in which the species that do not use such ‘quality signals’ were smaller such that the individuals of the population were acquainted with what the others were like, explains one of the authors, Michael Sheehan, assistant professor of neurobiology and behavior.
Sheehan explains in a news release of Cornell University that animals that are constantly interacting with the same individuals have a greater chance at understanding them – in this manner, they get to learn more about their ‘rivals’.
Throughout evolution, quality signals (external) have been antagonistic to facial recognition which was favoured by small social groups. For instance, the alpha male in a group of baboons is well-known by all. However, the one among Gelada monkeys has a bright red patch on its chest which serves as indication of the strength of the male to unfamiliar rivals. Also, Sheehan adds that knowing the social system of an animal might help to predict their signalling type.
Both forms of signalling – the visual external signs and the one pertaining to social recognition – require energy, a cost. But, for either to work for its particular species, the cost has to be outweighed by its benefits. This explains why some animals will have colourful traits which will have required investments of its own and why others will not have such designs, states Sheehan.
Furthermore, these types might vary within a social group as well. For example, songbirds will establish their territory through quality signalling. On the other hand, following this, they will learn about their neighbours to eventually depend on individual recognition and not on quality signals.
As for humans, it may have been the other way round: we started off with social interaction, and ended up incorporating quality signals into our culture, such as military uniforms or the number of windows in an office.
The authors also include a word of caution that this way of thinking remains untested.