Irish elk
The size of Irish Elk antlers is distinctive, and several theories have arisen as to their evolution. One theory was that their antlers, under constant and strong sexual selection, increased in size because males were using them in combat for access to females. It was also suggested that they eventually became so unwieldy that the Irish Elk could not carry on the normal business of life and so became extinct. This is simply nonsense, because no species survives that long if it is not effective in its habitat. Also, many other Pleistocene megafauna went extinct within a few thousand years of the end of the ice age. The Irish Elk is no different in that respect.