Old Fossils, New Knowledge – and the Case of the Misplaced Mastodons

By Claire Eamer

About 18,000 years ago, during the last ice age, the Yukon was a menagerie of exotic animals – scimitar cats, giant short-faced bears, and huge, lumbering woolly mammoths, among many others. Until recently, scientists thought those “others” included the mammoth’s distant cousins, mastodons.

Mastodon, by George Teichmann. Courtesy of Yukon Palaeontology Program.

And they had the radiocarbon dates to prove it. Two mastodon teeth from the Yukon had been reported in the scientific literature as dating from 18,000 years ago and 24,000 years ago, respectively.

But, increasingly, the dates didn’t sit right with Yukon government palaeontologist Grant Zazula. The more scientists learned about the ecology of the Yukon 18,000 years ago, the more puzzling the presence of mastodons became.

You see, mastodons were common in the mid-latitudes of North America, where they roamed the conifer forests, grazing on forest plants and browsing the twigs and needles of the trees. But both reported dates put mastodons in the Yukon at the height of the last glaciation. And there were no trees.

At that time, when most of Canada was buried in ice, the Yukon lay along the eastern edge of a vast, cold, dry, grassy plain that reached all the way to Siberia. It was perfect for grass-eaters, such as the woolly mammoth, but the cold and the lack of trees wouldn’t have suited mastodons.

What were tree-chomping cousins of elephants doing in a landscape virtually without trees? Actually, Zazula wondered, were they there at all? The teeth were the real deal, but what about the dates?

In the years since the teeth were dated, scientists have improved dating technology and learned a lot about the materials they’re working with.

And more mastodon fossils have turned up. A truckload of them, in fact – courtesy of Yukon gold miner Earl Bennett. Zazula met Bennett a few years ago, not long after he started his job as Yukon palaeontologist. Bennett told him he’d found a partial mastodon skeleton in the Klondike goldfields, where so many Yukon fossils have been discovered. The next day, he showed up at the palaeontology lab with a pickup truck full of giant bones.

Mastodon tooth. Courtesy of Yukon Palaeontology Program

So – with more bones and with new approaches to dating them, Zazula set out to see if mastodons really had adapted to life on a dry plain.

First, the original teeth were re-dated, using new techniques. This time, both showed as more than 50,000 years old. Radiocarbon dating only goes back reliably to about 50,000 years, so they could well be older.

To check the new dates, Zazula decided to date as many mastodon fossils as he could find. Altogether, he and his team (there are 15 named authors on the paper reporting the findings) managed to get 53 new dates on 36 fossils. The dates consistently came back near the 50,000-year limit of radiocarbon dating.

Ultimately, the scientists concluded that mastodons last lived in the Yukon about 75,000 years ago, when a warm period between glaciations (called an interglacial) lasted long enough for forests to grow and forest creatures, such as the mastodon, to move into them. Then the ice came back and the forests died – and so did the mastodons.

But how could those first reported dates be so wrong?

It’s easy. The samples were contaminated by carbon from much younger sources – humic (organic) acids in the soil and even the materials museums put on fossils to preserve them, Zazula said in an email interview..

The error wasn’t due to carelessness on the part of the first dating labs. Only recently have scientists developed ways to separate old carbon from new. Zazula’s tests were done with a technique that isolates a single amino acid, hydroxyproline, that occurs in collagen – a protein in bones and teeth.

“Probably 99.9% of the hydroxyproline in the natural world only occurs in collagen,” Zazula said. “So, by isolating this single amino acid, we can be confident that the carbon that is radiocarbon dated, only comes from the fossil itself, not from these darn humic acids from soils which can bind themselves to bone collagen.”

Grant Zazula takes a sample of mastodon bone for dating.

Museum specimens can be contaminated too, he said.

“The problem is that museums have been putting 'stuff' on fossils for centuries to preserve their collections. In most cases, records were not kept in regards to what they actually put on the fossils. So, who knows what is on these bones sometimes?”

With younger specimens, around 10,000 years, it’s not such a problem, because they still contain plenty of radioactive carbon, Zazula said. But by the time a fossil is 50,000 years old or more, there’s almost nothing left to sample.

“Introducing even the smallest molecule containing 'young' carbon-14 into the sample can completely change the radiocarbon date because you are essentially only measuring the contaminant then.”

Separating a few molecules of old carbon from the mass of newer material sounds – and is – technically difficult and frustratingly fiddly. But the resulting information has rewritten thousands of years of history and solved the lingering mystery of the misplaced mastodons.


Here are a couple of news stories on the mastodon research: at CBC and in the Globe and Mail.

You can listen to Grant Zazula talk about mastodons on the Dec. 6, 2014 episode of the CBC radio program, Quirks & Quarks.

Here’s a lengthy and well-illustrated set of posts about Yukon palaeontology and mastodons on the Mostly Mammoths, Mummies and Museums blog: Part 1 and Part 2. Part 3 is still to come, so keep your eyes open!

The article setting out the results of the project was “American mastodon extirpation in the Arctic and Subarctic predates human colonization and terminal Pleistocene climate change” in Proceedings of the National Academy of Sciences, Vol. 111 No. 52, which was published online (but behind a pay wall) on Dec. 1, 2014. The full list of authors is Grant D. Zazula, Ross D. E. MacPhee, Jessica Z. Metcalfe, Alberto V. Reyes, Fiona Brocke, Patrick S. Druckenmiller, Pamela Groves, C. Richard Harington, Gregory W. L. Hodgins, Michael L. Kunz, Fred J. Longstaffe, Daniel H. Mann, H. Gregory McDonald, Shweta Nalawade-Chavan, and John R. Southon.

Calling All Citizen Scientists - Check out your Toilet!

By Helaine Becker

You've probably heard it - that water goes down a drain differently on the north and south sides of the equator. But is it true?

The Internet, which knows all, seems to be out on this pressing subject. While there is solid theoretical backing for the difference in spin  - thanks to the Coriolis Effect - there is no solid evidence to back it up. Pardon the puns.

It's time to fill the information void once and for all!

Here's how we play:

You take a video of your toilet flushing, and post it to the comments section here along with your latitude. Eventually, your humble sci-why contributors will watch the videos and tabulate the data. with a large enough (stool) sample, ;) we can determine the truth, once and for all.

So on your marks, get set, flush!

Here is my video contribution, from greater Toronto, Canada (N44):

Winter Whites: How Snowshoe Hares and Ptarmigan Are Influenced by Climate Change & Evolution

By Jan Thornhill

Josée Bisaillon's illustration of Lily wearing her 
"winter whites" in Winter's Coming.

My most recent book, Winter’s Coming: A Story of Seasonal Change, follows Lily, a young snowshoe hare, as she learns about the ways in which other animals prepare for winter’s arrival. While the forest's leaves turn from green to yellow to brown and eventually fall to the ground, Lily is unaware that she, herself, is gradually changing colour from brown to white.

A young snowshoe hare has no idea that it will turn
completely white in the fall. (NPS/Tim Rains)

Snowshoe Hares

Snowshoe hares are one of seventeen northern animals that have adapted to their environments by undergoing a colour change twice a year. In the autumn these mammals and birds grow white fur or feathers so they’ll be hidden against the snow, and in the spring they trade their glorious whites for a variety of muted browns that provide summer camouflage.

Snowshoe hares turn white for the winter (NPS/Jacob W. Frank)

Right now it’s January and winter’s well under way in the northern hemisphere, which means that throughout their range snowshoe hares are safely camouflaged in their “winter whites.” Unfortunately there’s a new glitch in this fabulous winter adaptation: climate change is causing snow cover to arrive later and disappear earlier than usual in many of the areas where snowshoe hares live. 

Snowshoe hare researchers have been keeping track of this shortening of winter for a few years now and, not surprisingly, it’s not a great situation for the hares: for each extra day their coats are mismatched with their surroundings, there is an increase in mortality from predation.

A snowshoe hare in transition. (D. Sikes/Wikipedia)

Unlike people, snowshoe hares can’t just slip on appropriate clothing at will. Their colour changes are triggered by something neither they nor we can control: the changing length of daylight hours. Because of this, as warming trends continue, the snowshoe hare population is going to take a hard hit. The species, however, will likely bounce back as they gradually adapt to climate change. It’s all about evolution: any hares that turn white later than the majority in the fall or that moult earlier than others into their summer browns will have a greater chance of surviving long enough to breed and pass on this advantageous trait to their offspring.

This might be the only chance the species has since, like my character Lily in Winter’s Coming, snowshoe hares don’t have a clue that they spend half the year white and the other half brown. Researchers have found that in the spring, pure white hares do not seek out and crouch in areas where snow remains, but instead choose open areas where they are easily seen. 

Ptarmigan

Soyeon Kim's illustration of a moulting ptarmigan from Is This Panama?

Ptarmigans are another species that turn white in the winter to match their snowy northern surroundings. Although, like the snowshoe hare, the change in a ptarmigan's plumage is linked to changes in daylight hours, researchers have shown that these birds, unlike snowshoe hares, appear to have an awareness of their colour.  

Ptarmigans are camouflaged by white plumage in the winter, and will
also burrow into snow for warmth. (Xander/Wikipedia)

While both male and female Ptarmigans turn almost pure white in the winter, the females' springtime return to cryptic, camouflaging browns happens considerably earlier than the males'. So, while a female in her mottled summer colours is almost impossible to see once the snow melts, the white feathers the male still sports glow like beacons against the greens and browns of their habitat. Which makes them a target for predators such as gyrfalcons. But, apparently, standing out is the whole point: their flashy whites impress the girls, and impressing the girls is more important than hiding from predators. The really interesting thing, though, is that once the females begin egg-laying and are no longer receptive to the males' attentions, the males go out of their way to muddy their white feathers, masking the glaring white with smears of brown dirt for a couple of weeks until their spring moult is complete.

A female willow ptarmigan is well camouflaged in the spring after
she grows her cryptic breeding plumage. (Jan Thornhill)

Male ptarmigans keep their conspicuous white feathers longer than
the females in the spring to attract the girls. (Jan Thornhill)

To prove that this feather-soiling activity wasn't just a coincidence, during a 17-year study, Bob Montgomerie of Queen's University and his team purposely dirtied the white feathers of males early in the mating season with markers when the females were still receptive. This sullying of the birds showy "winter whites" so disturbed the amorous males, that they went to work, primping and preening, making their handsome white feathers once again immaculate within 48 hours.  

Soyeon Kim's illustration of a moulting ptarmigan from Is This Panama?

References:

Zimova M, LS Mills, PM Lukacs and MS Mitchell (2014). Snowshoe hares display limited phenotypic plasticity to mismatch in seasonal camouflage. Proceedings of the Royal Society B: 281(1782).
Mills LS, et al. (2013) Camouflage mismatch in seasonal coat color due to decreased snow duration Proceedings of the National Academy of Sciences of the United States of America 110(18):7360-7365.
Montgomerie, Robert; Lyon, Bruce; Holder, Karen, 2001: Dirty ptarmigan: Behavioral modification of conspicuous male plumage. Behavioral Ecology 12(4): 429-438


Kids' Resources:

Shameless plug for my two most recent books, Winter's Coming: A Story of Seasonal Change (illustrated by Soyeon Kim), and Is This Panama? A Migration Story (illustrated by Josée Bisaillon)

Reply to an editorial

Readers expect to read facts in a newspaper -- maybe not the whole story, but as much of it as is practical, and all facts. Only on the editorial pages do we readers find opinions being presented as opinions. It's a good idea for opinions to be backed up by facts and science, but that doesn't always happen.

It didn't happen anyway in an opinion piece that appeared in the Victoria Times-Colonist newspaper, where a student of geography at the local university wrote a column titled "No Need to Fear Genetically Modified Crops." Here's a link to her piece. It was clearly written but there's no books or research quoted to support her opinion.

The best thing about newspapers is how people can not only read them, but write for them. We can read opinion pieces and letters to the editor -- and we can write them ourselves as readers expressing our opinions. It's a good idea to support opinions by facts and science, in practical ways. You don't need to be a food scientist to have reasons for your opinions about food!

So I wrote a reply to the column, explaining why there is a need for more thorough testing of GMO crops. And it appeared in the editorial pages a few days later. You can click here to read my reply in the newspaper, or click here and scroll down to read it as a guest post on my partner's blog Farm Gate.

The fun part is that the book I quote from is at the public library. Most of the science I learn is from books written for everyone to understand -- real facts, written in plain words. I'm proud to find science books I've written in libraries, too. But reading my own opinion piece in the newspaper was like having a conversation on science with my neighbours.

Neuroplasticity - Can We Upgrade Our Brains?

By L. E. Carmichael

My husband came back from a work trip recently, excited about a documentary he'd watched on the airplane.* It's an Australian production called Redesign My Brain, and if you can find all three episodes, it is well worth a watch. The host of the show offers himself up as a human guinea pig - over the course of three months, he spends 1 hour per day doing exercises (everything from memory drills to juggling) to see if he can change the way his brain functions. The exercises are designed by neuroscientists and other experts, who also conduct a number of in-depth physiological tests (such as functional MRIs) to measure his brain activity before and after the training. And the results are amazing. With a relatively modest investment of time - about as much as an adult is supposed to spend physically exercising each day - the host manages to dramatically increase his focus, memory, creativity, and mind-body connection.

The series is absolutely riveting, and I spent most of it thinking how badly I wanted to try this myself. My grandfather died of Alzheimer's a few years ago, after all, and in the last ten years I've often felt that I'm not as quick or as focused as I was when I was a kid. My knowledge has increased, but I suspect my intelligence has actually declined. I know my attention span has (I'm looking at you, social media!).

So I did some digging, and managed to track down an online brain training system that, near as I can tell, mimics the one modelled in the show.** A year's subscription is only $8 per month, and in the spirit of scientific enquiry (and jump starting my own brain) I'm thinking very seriously of making this my New Year's Resolution. If I do, I'll keep you posted on how it goes.

What about you? Have you noticed a change in your focus and thinking as you've aged? Have you ever tried a brain training system? If so, how did it work for you?

--

* Yes, he's the kind of guy that watches the documentaries. Me, I go for movies. And also novels. I think it's because I spend so much time reading nonfiction for book research that I want my entertainment to be free of learning.

** BTW, producers of Redesign My Brain, this is info you really should have included in the show itself - or at the very least, on your website.