Could global warming turn us all into hobbits?

A study of prehistoric horses has found that rising temperatures tend to make mammals shrink. Does that apply to humans too? 

New Line Productions
A new study has found that, as the planet heated rapidly some 56 million years ago, Sifrhippus, the earliest known horse, shrunk to about three-quarters of its size. If this tendency is true for humans, we could be approaching the stature of Frodo and Sam shown here in 'The Lord of the Rings: The Two Towers.'

It's been long known that the Earth's rising surface temperatures portend mass extinction, prolonged droughts, extreme weather, and rising seas. Now we can add a new worry: Humanity could be transformed into a race of hobbits.

New research reveals the extent to which global temperatures can influence the evolution of the size of mammals. Hot weather tends to make them smaller, and cold weather tends to make them grow.

About 56 million years ago, our planet underwent a major temperature swing. Nobody knows what initially caused it – conjectures include volcanic activity, a comet impact, a sudden release of methane from the ocean, and natural variations in the Earth's orbit – but we know that, over a period of about 175,000 years, temperatures increased 9 to 18 degrees Fahrenheit, and then suddenly dropped. 

During this time, an equine creature roamed the forests in what is now Wyoming's Bighorn BasinSifrhippus sandrae, the earliest known horse, doesn't look much like today's horses. For one thing, it weighed only 12 pounds or so and was roughly the size of a small dog. 

And it was destined to get even smaller. A study of Sifrhippus molars unearthed in Wyoming and kept at the Florida Museum of Natural History at the University of Florida in Gainesville found that the animals shrunk to about eight pounds over the first 130,000 years of warming, and then shot back up to 15 pounds during the next 45,000 years as the planet cooled again.

The researchers ruled out atmospheric pressure and aridity, and the animal's diet, and concluded that temperature was causing the species' rapid shrinkage and growth. "This, for the first time, tells us that temperature is what's driving the body size evolution for these horses," said the University of Florida's Jonathan Bloch, who co-authored the study, in an interview with LiveScience.

These findings, which were published Thursday in the journal Science, are consistent with Bergmann's rule, an ecological principle, first proposed by German naturalist Christian Bergmann in 1847, that animals of a given species tend to be smaller in hotter climates. Bergmann's rule holds for about three-quarters of all mammals.

But does that include us? Anthropologists have found that Arctic populations such as the Inuit, Aleut, and Sami peoples, tend, on average, to be heavier than people living closer to the equator. But there are many exceptions to this tendency. 

So what is the likelihood that our species will transform into pint-sized, hairy-footed halflings who, say, favor a quiet bucolic lifestyle yet are nonetheless capable of acts great courage? Probably not that great: As anyone who has walked into a door frame built by our forbears can attest, humans have been getting taller lately. But even if we did wind up with having the stature of Frodo and Samwise, it wouldn't be so bad. Adapting to a changing environment is certainly better than the alternative.  

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to

QR Code to Could global warming turn us all into hobbits?
Read this article in
QR Code to Subscription page
Start your subscription today