You see, the great French naturalist George Louis Leclerc, the Count de Buffon had developed what he called his Theory of American Degenercy. The theory basically stated that in America, something about the landscape resulted in the physical (and, in the case of people) mental retardation of growth.
"In America, therefore, animated Nature is weaker, less active, and more circumscribed in the variety of her productions; for we perceive, from the enumeration of the American animals, that the numbers of species is not only fewer, but that, in general, all the animals are much smaller than those of the Old Continent. No American animal can be compared with the elephant, the rhinoceros, the hippopotamus, the dromedary, the camelopard [giraffe], the buffalo, the lion, the tiger, etc"
Jefferson, then, was in search of a moose, the biggest he could find, to shut the Count up.
It would have far easier if he could have built a time machine. Then, all he would have had to do is take Buffon back to the Pleistocene, when America was a rolling wilderness of mammoths, mastodons, rhinoceroses, horses, camels, ground sloths, and an army of predators, including lions, cheetahs, and short-faced bears.
Of course, Buffon never saw such a spectacle. Neither did Jefferson. Neither have we. Yet.
There is no time machine, but a radical group of conservationists have decided on the next best thing. They call it Pleistocene Rewilding. It could also be called "Bring Back the Mammoths."
The reasoning behind Pleistocene Rewilding is simple. It says that most of the world arbitrarily ascribed 1492, when Columbus arrived in America as what America "should" look like. The Rewilders disagree. To them, what Columbus and Co. stumbled across was an already-impoverished America, one in which the first human settlers - the Native Americans - had already wiped out lots of big mammals, leaving us with a land of dwarfs... if one can call an American bison or a grizzly bear a "dwarf." Buffon was right in seeing that there were no giant animals in the Americas... he just didn't understand why.
Now, the problem is that no mammoths, mastodons, etc remain. No problem, say the Rewilders. They advocate using surrogate species - living animals which ecologically resemble their extinct relatives. It's been done on a small scale in other parts of the world. The only difference is that, instead of using Aldabra tortoises to replace the comparable-but-extinct giant tortoises of other Indian Ocean islands, we're talking about Asian elephants replacing mammoths.
It may not surprise you, but the idea has garnered something of a backlash. One of the authors of the original paper was kind enough to let me scroll through some of his hate mail one day, which makes me feel a lot less bad about a few snarky facebook comments from PETA now and then.
Some people just feel the idea is too ridiculous to contemplate (which is never a good argument, in my opinion - anything should at least be contemplated if the goal is saving species). Others deride the impracticality of blocking off huge sections of the west to let elephants and lions roam around. Others still worry about what kind of impact these species might have on native wildlife and the ecosystem. Are proxy species really good enough substitutes? Has the habitat changed too much, and is there enough of it left anyway? Some worry about the distraction, when we should be focusing on animals that we have here now which need saving. And others worry that pulling wildlife from Africa and Asia to restock Arizona or Texas will result in a loss of support for conservation of those same species back in Africa or Asia. Most just think it's too weird.
To an extent, we are already rewilding. We are introducing animals back into the wild, sometimes to areas where they have not been seen for quite a long time, as the case of the California condors in the Grand Canyon goes to show. There are whole herds of African and Asian ungulates roaming the southwest and Texas, courtesy of game ranching. And let's not forget that one of the first species Europeans turned loose in America was the horse... a species which evolved here in the first place, making it something of a homecoming.
Rewilding isn't unique to America, either. It's been attempted in Europe (evidence the recreated aurochs and tarpan of the last century, the reintroduced wisent, the resurgent wolves and bears and lynx), as well as Siberia, where musk-ox once again roam.
Presumably, many of the specimens for rewilding efforts would come from zoos and other breeding facilities. Some proponents of rewilding have argued that these "Pleistocene Parks" could replace zoos for some species. Elephants, big cats, and other large mammals could be bred and maintained in these wildlife reserves, acting as a bulwark against the extinction of their wild relatives.
As far as rewildling goes, I'd just as soon work our way backwards. Let's save the species that we have that are currently struggling against extinction. Then, let's work on repatriating animals which have gone locally extinct within historic times, such as reestablishing jaguars in the southwest. Keep pushing it back. Maybe one day we'll have time for those mammoths.
PS: As far as I know, one zoo alone has taken Pleistocene Rewilding to the extraordinary level of exhibition. San Diego Zoo's Elephant Odyssey is a trail that features that animals (and their proxies) that used to call California home. Besides rattlesnakes and condors, the trail features guanaco, lion, jaguar, secretarybird, tapir, and sloths, as well as the namesake elephants, stand-ins for mammoths and mastodons. Dotting the trail are life-sized sculptures of the species that used to roam California.