By Jim Maceda
NBC News

Dmitry Solovyov/NBC News

Siberian sunset.

It’s hard to imagine, looking out at the frozen expanses of Yakutia, in North Eastern Siberia, that 30,000 or so years ago, so many animal species, now extinct, roamed the Pleistocene grasslands. From 12-foot tall, five-ton wooly mammoth bulls to tiny rodents, an Ice Age hunter would have found as many as 100 animals in each square mile he tracked, at least according to Sergei Zimov, our Ice Age expert, geo-physicist and guide during our recent visit.

Today, Siberia’s thick icy crust, or permafrost, which has held the remains of predators and herbivores alike in an epochal deep freeze, is beginning to melt. And the bones of prehistoric rhinos, bison, reindeer, horses – and yes, mammoths – are rising to Yakutia’s surface at an amazing rate. One literally trips over bones on a short stroll along the banks of the Kolyma River. The downside, of course, is the attendant release of so much CO2 – a greenhouse gas - as this melting permafrost exposes a 150-foot thick layer of plant and animal remains. But there is an upside: a burgeoning cottage industry in the finding and selling of prehistoric bones.

Zimov says that 30 years ago, only a handful of Russian "bone" men – serious businessmen - were attracted to the adventurous lifestyle, spending their summers combing Pleistocene beaches and valleys. Today, at least 1,000 bone hunters work throughout Russia, with several dozen focusing on Siberia’s permafrost zone, where the best prizes are to be found.

Dmitry Solovyov/NBC News

One of Zimov's prized mammoth tusks.

Professional hunters like Feodor Shidlovsky and Alexander Votagin are at the top of the bone chain. Shidlovsky has arguably the biggest mammoth bone collection in Russia, displaying them in his own natural history museum in Moscow. The money he makes from the sale of mammoth bones goes into his exhibitions, the funding of artists who fashion jewelry from the ancient bone, and scientific expeditions.

Every summer, Votagin leads his team to Dvarii Yar – or Windy Cliffs – a remote stretch of Kolyma riverbank that has given up the richest finds of prehistoric bones over the past decade. Located about 400 miles north of Zimov’s isolated science station in Cherskiy - Yakutia’s main airport and hub - the so-called New Siberian Islands (all underwater in Pleistocene times) are now a treasure trove of bones. Local hunters collect more than 20 tons of mammoth, rhino and bison bones a year, selling most of them to local dealers in Cherskiy – presumably to sell them to tourists like us, though the Russian government bans the export abroad.

And here’s why: prehistoric bones can be a very lucrative catch. While fishermen and hunters now augment their meager incomes with up to $10 per mammoth tooth or ivory shard, the more professional - and lucky – hunters can fetch more than $80,000 for a pair of mammoth tusks in good condition. Zimov keeps such a pair in the living room of his science station cum abode – but isn’t tempted to sell them.

Dmitry Solovyov/NBC News

Prehistoric bones along the beach.

"These are like my family," he told us. "Would you sell your brothers for $80,000?" In fact, Zimov has never sold any bones he’s collected over his decades of combing Yakutia for clues to global warming. On one such outing, he and his son Nikita collected some 1,200  bones – which he thinks is a world record - all which remained of a pack of mammoths and all within a few hundred yards of beach. For amusement, they arranged their bone hoard into the shapes of mammoths, horses and bison.

Until the mass, mysterious extinction of so many Ice Age animals took place - triggered, probably, by extreme change of climate and habitat - the so-called "Mammoth Steppe Eco-system" chugged along like a glacier, both efficient and self-sustaining. Mammoths knocked over heat-absorbing trees, grasses grew, and dozens of herbivore species not only grazed on those grasses, but fertilized them too.

Though that eco-system died some 15,000 years ago, mammoths and other Pleistocene throwbacks are helping to maintain today’s human population, with a $5 prehistoric bison jaw here, a $10 wooly rhino knee bone there or $1,000 piece of wooly mammoth tusk, buried right under your feet.