If an Irish elk stag responded to a lack of food the way red deer do today, their antlers would shrink down to the size of moose antlers or less. Feeding stags extra food can double the size of their antlers. Antlers can get small even without an evolutionary shift–if red deer suffer overcrowding and run low on food, their antlers can lose almost a third their weight. They point to red deer that have adapted to living on predator-free islands, where they shrank to half the size of their mainland ancestors. Worman and Kimbrell argue that even with the advantages that some with a fancy set of antlers, the Irish elk could have easily shrunk them if they didn’t have enough food. There, they take aim at the notion of the doomed antlers. It turns out he is a devotee of Megaloceros giganteus as well, and he sent me his new paper with Tristan Kimbrell in the journal Oikos. Recently, though, a University of Florida graduate student named Cedric O’Driscoll Worman noticed this picture of an Irish elk proudly displayed on the front page of my web site. This always seemed a bit odd to me, but I didn’t see much research from scientists that took a critical look at the idea.

Sexually selected suicide, in other words. As the shrubby woodlands in which the Irish elk lived began to shrink at the end of the last Ice Age, the animals could no longer get enough food to fuel those giant antlers, and they died. Each year they lost these monstrous growths and regenerated them the following year. The antlers got bigger and bigger as the Irish elk stags advertised their quality. Playing the role of orthogenesis now is the relentless power of sexual selection. The funny thing about this story is that hypotheses about the extinction of Irish elk have come back to those doomed antlers again. Today there’s a lot more evidence supporting the idea that antlers are driven by sexual selection, not natural selection or orthogenesis. Big antlers in living deer are a sign of a high-quality male–a male that can fight off other males for territory, and that may be able to attract females. When Gould wrote his essay in the mid-1970s, scientists were just beginning to recognize that antlers had important functions of their own beyond just warding off a wolf. A big body helped Irish elk survive, and the bigger antlers were just an unavoidable–but manageable–inconvenience. Its antlers simply evolved to be bigger at a faster rate than its body. The Irish elk was not a victim of some mysterious inner momentum. Orthogenesis fell apart in the early 1900s, as scientists began to learn how genes make natural selection possible. (For more, see this essay by Stephen Jay Gould.) The poor Irish elk ended up burdened with massive headgear that got them stuck in thickets and drove them extinct. While they may have been useful at first for keeping away predators and such, orthogenesis could not be stopped. Evolving from small ancestors, they grew to be giants. The Irish elk was a prime example of this straight-line evolution known as orthogenesis. In the late 1800s, many scientists believed that evolution proceeded in straight lines, with too much momentum to be steered off course by natural selection. The antlers of the Irish elk have long obsessed zoologists, bored or otherwise. After they’re gone, people will look back at pictures of them the way we look at pictures of the Irish elk, and imagine they were just made up by a bored zoologist. And the way things are going, orangutans and river dolphins may not be long for this world. Of course, for the people who lived alongside the Irish elk in Europe and Asia before its extinction 7000 years ago, it probably didn’t seem terribly ridiculous at all–no more ridiculous than an orangutan or a river dolphin look to us today. Irish elk grew the biggest antlers ever recorded, stretching over ten feet across and weighing about 90 pounds.

The reaction probably has something to do with the fact that we are all familiar today with deer, moose and other animals that look for the most part like the Irish elk, except for that extravagant rack. I can’t help finding the Irish elk wonderfully ridiculous.

Large antlers in male elk quizlet