What Was the Irish Elk? Antlers Four Metres Wide and Whether They Were the Death of It
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Skulls with antlers wider than a car have been dug out of the peat bogs of Ireland since the seventeenth century, and hang in the halls of country houses and the entrance of the natural history museum in Dublin; the animal they came from was a deer two metres at the shoulder, heavier than a bull moose, that carried forty kilograms of antler and regrew it every year. The Irish elk was neither Irish nor an elk, it ranged from Ireland to Siberia, and it has been the textbook example of two opposite things, of an animal that evolved itself to death and of the mistake of thinking so.
The animal
Megaloceros giganteus was a deer, related most closely to the fallow deer, that lived across Europe and northern Asia through the last few hundred thousand years and died out about 7,700 years ago, its last populations in Siberia. Males stood about 2.1 metres at the shoulder and weighed 500 to 700 kilograms, and their antlers, the largest of any deer known, spanned up to 3.65 metres and weighed up to 40 kilograms, shed and regrown each year as all deer antlers are. Ireland has produced hundreds of skeletons because the animals sank in the lakes and marshes that later became bog, where the peat preserved them, and the Irish bogs of the period just before the end of the ice age held a population that was among the last in western Europe.
The antler problem
The antlers were the puzzle. Nineteenth-century naturalists proposed that they had grown, by some inner momentum of evolution, so large that the animal could no longer lift its head or move through forest, and that the species had been carried to extinction by its own ornament, a doctrine called orthogenesis. Stephen Jay Gould settled the question in 1974 by measuring the skulls: across the deer family, antler size increases faster than body size, so that a deer twice as large has antlers more than twice as large, and the Irish elk's antlers were exactly the size that its body predicted. They were large because the animal was, and the animal was large because large males won the fights and the females, which is ordinary sexual selection. What the antlers were for:
- •Display: the broad flat palms faced forward when the head was held up, so that a male showed the whole span to a rival or a female standing in front of it
- •Fighting: like other deer, males locked antlers and shoved, and the palms were reinforced where they would take the load
- •A signal of condition: growing forty kilograms of bone in a few months needs a great deal of calcium and phosphorus, so a full rack advertised that its owner had fed well
The cost
Gould's answer did not make the antlers free. Regrowing them each spring drew minerals from the skeleton, and the bones of Irish elk show the seasonal thinning of osteoporosis, so that a male in a poor year was drawing down his own skeleton to make the display; the animal needed rich grazing on mineral-rich soils, which the open grasslands of the ice age provided and the forests that replaced them did not. When the climate warmed after 12,000 years ago and the grass gave way to trees, the elk's range fragmented, and a large-bodied grazer with an enormous annual mineral bill was among the first to fail; a brief return of the cold around 10,700 years ago, the Younger Dryas, finished it in Ireland. The antlers did not kill it, but the diet that grew them may have, once the land stopped supplying it.
Humans and the end
The giant deer outlasted the mammoth in Europe and survived the end of the ice age in Siberia by three thousand years, and whether hunting contributed to its end is unclear. There are no butchery sites and few images, though the deer appears in the cave paintings of Lascaux and Cougnac with the hump over the shoulders that its skeleton implies, and the last populations died out in the Urals and western Siberia around 7,700 years ago, in country with people in it. The pattern fits the general one, of a large animal squeezed by a changing climate and finished by a new predator, and the Irish bogs that preserved its bones so well are the reason that a species of the whole Eurasian steppe is called by the name of one small island at its western edge.
The takeaway
The Irish elk was a giant deer of Ice Age Eurasia, two metres at the shoulder, whose annual antlers spanned up to 3.65 metres and weighed forty kilograms; Gould showed in 1974 that the antlers were exactly the size its body predicted, grown by sexual selection rather than by a runaway trend, though regrowing them each year cost the animal minerals it could get only from rich grassland. It died out as forests replaced the grass after the ice age, last in Siberia around 7,700 years ago, and Ireland's bogs preserved the skeletons that gave it its name.