Darwin was troubled by elaborate male traits observed in many species that are seemingly maladaptive for survival, the peacock's tail being the most iconic of all. He wrote "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick" because it challenged his theory of evolution by natural selection for adaptive traits. The extreme length of the tail may render a peacock more vulnerable to predation and therefore maladaptive for survival. He hypothesized that peahens may find the tail attractive thus enhancing male mating success. This idea led to the theory of sexual selection, wherein, traits that directly enhance mating success may be selected for, either through male-male competition for mates or through female-mate preference for elaborate male traits.

Male and female elephants in the proboscidean evolutionary radiation have had tusks and show extreme exaggeration in size and form. However, tusk in the Asian elephant (Elephas maximus) is sexually dimorphic as it is expressed only in the males, hinting at a possibility that opposing selection (sexual selection advantage to males and natural selection disadvantage to females) may have been the processes behind this pattern of tusk expression. Intriguingly, tuskless males (male dimorphism with respect to tusk) also occur at fairly high frequencies in some Asian elephant populations.

I hypothesized that sexual selection and artificial selection
(selective removal of tusked males from wild populations) on elephant tusks as possible mechanisms leading to the observed patterns of tusk dimorphism. I used mathematical models of population genetics, population dynamics, demography data and behavioural observations of wild Asian elephants in Kaziranga National Park, Assam, in an attempt to understand the evolution of tusk dimorphism in elephants.