When Did Humans Reach the Americas?

By Claire Eamer

Now there's a question that opens a can of worms!

A couple of years ago, I wrote a short news article -- Archaeological Find Puts Humans in North America 10,000 Years Earlier Than Thought -- for Hakai Magazine. It was about a new analysis of bones found 40 years ago in the Bluefish Caves in the northern Yukon by Canadian anthropologist Jacques Cinq-Mars. The magazine followed it up with a lengthy and fascinating piece by Heather Pringle: From Vilified to Vindicated: the Story of Jacques Cinq-Mars.

Doctoral student Lauriane Bourgeon's analysis of the bones, particularly a horse jawbone with cut marks on it, appears to confirm Cinq-Mars's original conclusion -- that human hunters were using the Bluefish Caves at least 24,000 years ago, at the height of the last glaciation. At that time sea levels were much lower than today, and people could have crossed to North America from Siberia on the wide, dry, windswept plains of Beringia, a route now blocked by the waters of the Bering Strait.


At the time Cinq-Mars published his first account of the excavation, the prevailing theory said humans arrived in North America from northeastern Siberia about 14,000 years ago at a time when the glaciers were finally disappearing, but when there was still a dry-land link between Asia and North America. They then followed an ice-free corridor between glaciers that led them south to the rest of the Americas. The problem with that theory is the growing body of evidence that no such corridor existed or was inhabitable at that time, as well as another growing body of evidence that people were living well south of the glaciated lands before the glaciers disappeared.

Cinq-Mars's find and Bourgeon's re-analysis of it support another theory: the Beringian standstill hypothesis. According to that theory, humans moved into the dry region linking Asia and North America 10,000 years or more before the great ice sheets melted and the sea level rose. And there they stayed, making a decent living from the animals -- both large and small -- that shared their giant refuge from the ice.

But what about those people living farther south when the ice was still melting? Current thinking suggests they might have arrived by sea, travelling down the west coast of North America, with its rich resources of shellfish and other coastal foods. A report just released dates a cache of artifacts found in Idaho to 16,000 years ago. A joint research effort by Western scientists and First Nations in British Columbia recently found even more startling evidence to support the coastal theory -- 29 footprints left, probably, by a small family walking along a beach 13,000 years ago.

Unravelling the mystery of humans in the Americas is no easy task. Much of the evidence was ground to dust by kilometres-deep ice or flooded by rising seas as the ice melted. But scientists and Indigenous peoples are working on it. It's still a can of worms, but each worm that emerges changes the picture slightly and makes it a little clearer. And a lot more interesting.

Claire Eamer's most recent book is Out of the Ice: How Climate Change is Revealing the Past (Kids Can Press, 2018).

A Frozen World Returns

By Claire Eamer

The wolf pup cleaned, preserved, and ready for display.
Yukon Government photo.

More than 50,000 years ago, when most of Canada was buried under kilometres-thick ice sheets, a wolf pup was born in one of the few places untouched by the ice -- a dry, grassy plain that extended across most of what is now the Yukon. No more than eight weeks later, the little wolf died, probably buried in a landslip and smothered while it slept in its den. The cold muck froze around it and stayed frozen, summer and winter, preserving the small body.

Just over two years ago, on July 13, 2016, gold miners on Last Chance Creek near Dawson City washed away some frozen sediment and found the little pup. It was frozen and dried but still remarkably well preserved. The miners immediately called in palaeontologist Grant Zazula and his colleagues in the Yukon government's Palaeontology Program. They were delighted with the find. To his knowledge, it's the only ice-age wolf ever found, Zazula says.

Only half of the caribou calf's body was found.
Yukon Government photo.

That was the second spectacular find of the 2016 summer. Six weeks earlier, miners on Paradise Hill -- another famous location in the historic Klondike Goldfields -- had discovered the frozen and mummified remains of a caribou calf. It wasn't as complete as the wolf pup, but nearly all of the front half of the body had survived, with skin, muscle, and hair intact.

Zazula and his colleagues knew they had something special, but they didn't realise quite how special until the results of radiocarbon dating came back. Both animals lived more than 50,000 years ago, the limit for radiocarbon dating. And the caribou calf had been found in association with a layer of volcanic ash that had settled to the ground about 80,000 years ago.

Yukon government palaeontologists Grant Zazula and Elizabeth Hall excavate
the caribou calf from the frozen muck of Paradise Hill near Dawson City, Yukon.
Yukon Government photo

Specimens that old are rare anywhere, and especially in the Yukon where the undulating landscape left few places for dead animals to lie and freeze undisturbed. There was no rush to preserve the bodies, Zazula says.

"We had them kicking around in our deep freeze for a couple of months. They were very well freeze-dried already."

The wolf pup's head before preservation, ice crystals visible.
Yukon Government photo

However, if anyone other than experts was going to see them, more work was required. Yukon Heritage applied for help from the experts at the Canadian Conservation Institute. And they got it. Today, both small bodies have been carefully thawed and preserved in a way that will make it possible to display them to the public. They are currently on display in Dawson at the Dänojà Zho Cultural Centre of the Tr’ondëk Hwëch’in First Nation, in whose traditional territory they were found. Later this fall, they will be moved to Whitehorse and a permanent display at the Yukon Beringia Interpretive Centre.

Meanwhile, scientific interest is building. Zazula is fielding calls from Pleistocene scholars around the world and brainstorming with them and his Yukon colleagues about what kind of questions the little corpses might answer. Is the wolf pup related to the wolves that live in the Yukon today, or did the Pleistocene wolf disappear to be replaced by a new population? Does the caribou calf have relatives living today? If so, which of the many caribou herds do they belong to? And that's just the beginning.

The thawing permafrost and melting ice of the world are revealing more and more clues to the past, both animal and human. That's the subject of my latest book, Out of the Ice: How Climate Change is Revealing the Past. The Yukon pup and calf are too recent to make it into the book, but it contains plenty of other fascinating evidence of lost or forgotten worlds.

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.

The 50 Greatest Inventions Since the Wheel? Maybe....

In the November 2013 issue of The Atlantic, the Editors present a list of their top 50 inventions since, well, the wheel.

A few years ago, I covered this same ground in my book What's the Big Idea? from Owlkids.

Needless to say, the choice presented in my book were not exactly the same as the ones the Atlantic came up with (and there are more of them). That's partly because I selected inventions based on what's most important to kids.

For example, there's the all-important needle.

The needle you say? Why would kids care about a needle?

Simple. The needle is what allowed our ancestors to survive the brutal cold of the Ice Age in Northern Europe etc. etc. They used it so they weren't totally reliant on furs for clothing. And think about it - if you drape furs around you, they can be a little drafty. You really need something to wear underneath them, something close to the skin that you can layer...

Underwear.

Without the needle, there'd be no underwear. And without underwear, we wouldn't have survived the freezy breezy.

So check out the Atlantic list of inventions for sure, but don't overlook, ahem, what's under-represented. Check out What's the Big Idea? for a real EYE-opener. (get it?)

PSST, while you're at it, you might what to check out my current book, Ode to Underwear! Yes, I have a "thing" for underthings!)