It is 4,000 years or more since the last woolly mammoths, with their spectacularly curved tusks and heavy shaggy coats, roamed the icy wastes of Siberia and Alaska. Climate change and hunting by prehistoric humans are thought to have driven them to extinction.
But the trade in ivory from the tusks of the ancient animals is now booming - and may present a risk to the future of the African elephant, conservationists fear.
The bodies of thousands of woolly mammoths have been found preserved in the frozen Siberian tundra, and the tusks are the best-preserved part of all.
According to a report, as much as 60 tonnes of Siberian mammoth tusks are being exported from Russia every year, mainly to China, where they end up in the workshops of its flourishing ivory-carving trade, being turned into brooches, pendants, figurines and thousands of other ivory objects, and sold around the world.
Conservationists are concerned that this legal trade could be used as a front for the laundering of illegally poached elephant ivory, thereby fuelling the poaching of elephants. The trade in African elephant ivory was outlawed by the Convention on International Trade in Endangered Species, Cites, in 1989, to halt the plunge in elephant numbers.
"Wild elephant populations were decimated by the ivory trade. By the time the 1989 Cites ban came into force, Africa's elephants had been reduced by more than 50 per cent," said Mark Jones, programmes director at Care for the Wild, the international wildlife charity which commissioned the mammoth ivory report. "Poaching continues to threaten wild elephants. Anything that encourages the continued demand for ivory products, whether mammoth ivory or elephant ivory, could potentially exacerbate this threat."
The report, by Edmond and Chrysee Martin, paints a remarkably detailed picture of a flourishing and valuable commerce in extinct animals - worth more than $20m (£12.6m) annually.
It points out that trade in woolly mammoth ivory has been going on in Russia and the rest of Asia for thousands of years, and reached a peak in the 19th century, but during the communist period from 1917 to 1991 business declined sharply.
However, since the early 1990s the domestic and international trade in mammoth tusks has reopened and expanded owing to the freeing-up of the Russian economy, more foreign visitors to the country and greater demand for ivory because of the Cites ban.
"In recent years," says the report, "60 tonnes of mammoth tusks have been exported annually from Russia, mostly to Hong Kong for carving in mainland China." There are also carving industries in parts of Russia, but most of these objects are sold on within the country.
Hunting for the tusks is now a major activity. "Every year from mid-June, when the tundra melts, until mid- September, hundreds if not thousands of mostly local people scour the tundra in northern Siberia looking for mammoth tusks," the report reveals.
"All are Russians, as foreigners cannot obtain a permit to collect tusks. Some tusks are easily seen on the banks of rivers while others are detected on the flat lands. All types of transport are used to transport the tusks: boats, lorries, aeroplanes and even helicopters."
The centre of the trade is the Siberian town of Yakutsk. Once the tusks are accumulated, traders send large planes to pick them up and send them to Moscow. They are paid for by weight. With the average export price of mammoth ivory in 2009 being $350 per kilogram, or $350,000 per tonne, the current trade is worth about $21m per year to Russia. The vast majority of the tusks are sent to Hong Kong, although some also go to Germany and the US. Nearly all are then re-exported to mainland China, where there is a well-established ivory carving trade, and where they are crafted into ivory objets d'art: some stay in China for domestic sale but many are sent back for sale to Hong Kong, and all around the world.
"Many thousands of recently made mammoth ivory items are for sale in Asia, Europe and North America," says the report. "People wishing to buy an elephant ivory object may purchase a similar one crafted from mammoth ivory that is legal and free of cumbersome paperwork. Mammoth ivory items are not for sale in Africa. If mammoth objects were to be offered in Africa, they could be a cover for elephant ivory items."
However, the report's authors fall short of calling for a mammoth ivory ban, saying there is no evidence that the worldwide mammoth ivory trade is yet affecting either the African or Asian elephant.
"For this reason, and because the species is extinct and large quantities of tusks are still available in Siberia, it is the opinion of the authors that a ban on mammoth ivory commerce is not currently justified," says the report.
Yet they sound a cautionary note, saying: "In future, a problem could occur if mammoth tusks of Chinese-made ivory items were brought into African countries, where law enforcement is poor, specifically as a cover for illegal elephant ivory carving and sales."
Although elephants are plentiful in Southern African countries such as Botswana and South Africa, in some countries of Central and West Africa, poaching is now pushing populations to extinction. Chad is thought to have only a few hundred left while Senegal and Liberia may have fewer than 10. Sierra Leone's last elephants were wiped out by poachers in November last year.
In Kenya, whose wildlife protection measures are among the strongest in Africa, the number of elephants killed by poachers rose from 47 in 2007 to 98 in 2008 and 214 in 2009. Reports suggest that at least 15 tonnes of African ivory tusks and pieces - the equivalent of up to 1,500 elephants - were seized in, or en route to, Asia during 2009.
Mammoth facts: The history - and prehistory - of a colossal creature
The woolly mammoth, mammuthus primigenius, sometimes also called the tundra mammoth, is perhaps the best known of the several species of mammoth which existed in prehistoric times, due to the many well-preserved carcasses found in the frozen tundra of Siberia.
Woolly mammoths were no bigger than Asian elephants, though their spectacular curving tusks were in a class by themselves, reaching up to seven feet long and weighing as much as 70kg each - which, at $500 per kilo for the best quality, is a lot of ivory, and a lot of money for the finder.
Protected against the cold in their long, shaggy coats, they roamed the frozen plains of Eurasia during the Ice Age, but declined to extinction about 10,000 years ago, probably because of human hunting, though it is thought that small groups may have survived into historic times.
It is believed that a dwarf subspecies may have survived on Wrangel Island, in the Arctic Ocean, until as late as 1,700BC.
Rumours persist that the animal may still survive in tiny numbers in the taiga, the vast Siberian plain forest, much of which remains unpenetrated - but nobody has ever provided any convincing evidence.