It’s St. Patrick’s Day! To celebrate, let’s take a look at an absolutely massive animal: the Irish elk (Megaloceros giganteus).
The Irish elk is one of the largest deer ever, clocking in at around 7 feet tall at the shoulder (the height of an average door frame). Unfortunately, you’ll never be able to see this magnificent creature – the Irish elk has been extinct for the past 11,700 years. Ancient hominids knew about them, though; some cave paintings from 20,000 years ago have images of these elk with their characteristic antlers.
And even if we’ll never see a live one, Irish elk played an important role in shaping how we understand evolution.
Let’s start with some basic facts: the Irish elk is not exclusively Irish and not an elk.
Irish elk were found throughout Eurasia, not just in Ireland. They get their Irish name because the first specimen was found in Ireland. Plus, most of the fossilized remains have been found in Irish bogs (they’re an excellent place for fossilization)!
The Irish elk is also not an elk but a deer. After seeing the large fossilized antlers and body size, early scientists assumed it was an elk. But they were wrong! Research today suggests that the closest living relative for the Irish elk is the fallow deer, not moose.
We obviously can’t know for sure how Irish elk lived, but we can make some guesses based on the lifestyle of fallow deer and other deer species. Irish elk probably dropped their antlers every spring and regrew them in the summer. Males and females also probably lived separately during the year, coming together just for mating season. Like deer today, males probably competed with each other for the ability to mate with the females.
A theological issue
The description of the first Irish elk skeleton in the late 17th century caused a slight problem for early scientists. Even though it was much bigger than other deer or elk, it had to be an existing species. Early scientists flat-out denied the possibility of extinction.
You have to remember that, at the time, science and religion were very much intertwined. So, European scientists believed that the skeleton had to be from a living species. God spent all this time creating animals; He would never let his perfect creation die out. Animals currently known only as fossils were still alive on Earth somewhere, just in an unexplored area.
In the words of Thomas Molyneux, who first described the Irish elk: “That no real species of living creatures is so utterly extinct, as to be lost entirely out of the world, since it was first created, is the opinion of many naturalists; and Ôtis grounded on so good a principle of Providence taking care in general of all its animal production that it deserves our assent.”
It wasn’t until 1812 that the Irish elk would be correctly identified as an extinct species.
By the late 1800s, Irish elk presented another problem: how did their antlers get so big? At this time, many scientists believed in ‘orthogenesis,’ which is the idea that evolution proceeds in straight lines. Like a runaway train car, traits would continue to grow and grow, gaining too much momentum for natural selection to stop. The Irish elk must have originally had small antlers that kept getting larger and larger until they were so big that the elk would get caught in thickets and die.
Reader: this is not true. Also, orthogenesis is not how evolution works.
By the early 1900s, orthogenesis began to fall apart as scientists learned more about natural selection and the power of genetics. The Irish elk was not the victim of some runaway, large-antler-evolving momentum. Instead, antlers evolve at a faster rate than bodies. In other words, as Irish elk evolved larger bodies, their antlers grew, too, just at a faster pace.
A huge rack
Let’s talk a bit more about these antlers.
The Irish elk’s antlers are its most noticeable characteristic. The largest antlers of any known deer, these babies can weigh in at a whopping 90 pounds and measure almost 12 feet across. Unlike modern deer, Irish elk have antlers that are massive sheets of bone with pointed projections coming off of them.
Based on the sheer size of these antlers and what we know of the ancient geography of Ireland, we think that Irish elk preferred to live in more open areas. This way, they wouldn’t get their antlers stuck on tree branches and bushes.
Why were their antlers so large? Scientists think they served as a way for male Irish elk to impress females and secure mates. As they signaled a healthy and virile male, bigger antlers were more desirable to the females. Big antlers could also have been intimidating to other males; in fact, how their antlers are shaped means that you would see the maximum area of the antlers if a male looked at you face-on.
Intimidating other males with their antlers would help keep actual fighting (and potential injuries) between males to a minimum. But don’t worry – the antlers could be used for fighting, too. Males would interlock the lower parts of their antlers and then shove each other. The winner would get to mate with the females.
So what happened to them?
Until we invent a working time machine, we won’t know for sure what happened to the Irish elk. But of course, we have some hypotheses!
One hypothesis comes back to the large antlers. Remember, large antlers advertised a high-quality male. According to sexual selection (a type of natural selection driven by mating choices), female Irish elk would always prefer to mate with the male with the biggest antlers. This choice would continually drive the size of the antlers larger and larger. But remember: Irish elk lost their antlers every spring and had to regrow them for the fall mating season. Regrowing such large, mineral-rich antlers takes a lot of energy. But the amount of available food decreased as the Earth moved into an ice age around 8,000 years ago. Males no longer had enough food to make their antlers, so the species eventually died out.
There are a few issues with this story. First, if large antlers were really an issue, Irish elk could have started evolving smaller antlers. There’s precedence for this: red deer on predator-free islands have shrunk their body and antlers compared to the mainland red deer. Red deer can also shrink the weight of their antlers if the population is overcrowded and low on food. Plus, even if all the big-antlered males died off, there should have been plenty of small-antlered males to mate with the females. After all, a single male can father many offspring in a population, so you really only need a few males to keep the species going.
A more popular explanation is that the female Irish elk were a victim of climate change. With less available food as the ice age began, females would have trouble raising their young. Nursing is energetically expensive, and females need a lot of food to successfully nurse their calves. Even after weaning, the young would need ample vegetation to eat. The Irish elk may have gone extinct because they couldn’t raise enough young to keep the species going.
And, of course, there’s always a chance humans played a role. Neolithic settlements were expanding into the Irish elk’s habitat when the Irish elk went extinct. It’s very possible that human hunters targeted Irish elk (they had lots of meat on their bones, after all!) or that expanding settlements disrupted the natural vegetation the Irish elk thrived on.
Even though I’ll never see a living Irish elk, I can dream of their magnificence. And create an image of St. Patrick riding one across Ireland.