Image of the Elk

One hypothesis is that the female elk's shitty choice in mates resulted in the entire species dying off. Females preferred mates with the largest antlers. With natural selection, the antlers continued to grow with each generation until they became a hindrance to survival (e.g. the rack of antlers got stuck in trees).

http://www.ucmp.berkeley.edu/mammal/artio/irishelk.html