The size of Irish Elk antlers are 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 has also been suggested that they eventually became so unwieldy that the Irish Elk could not carry on the normal business of life and so became extinct. It was not until Stephen Jay Gould's important 1974 essay on Megaloceros that this theory was tested rigorously.