Maybe you've never seen any space aliens, but recent polls indicate that up to 6 percent of Americans claim to have been abducted by them. The experience doesn't sound pleasant. The extraterrestrials are often said to take their captives to their saucers, lay them out on a table and extract sperm from the men and impregnate the women.

If you're familiar with UFO lore, you know there are a couple of common explanations for these breeding experiments. One is that the aliens are in a reproductive bind on their home world: They can no longer successfully procreate and so have come to Earth to use humans as incubators to spawn alien offspring. The other is that the aliens are producing hybrid beings that will somehow help them take over our planet.

Scientists, of course, are dubious of such claims. After all, there's never been any good evidence that the abductions are taking place. No one ever seems to bring along a cellphone to take photos or to pocket an artifact from the saucers.

But an instructor at the University of Oxford in England believes the abductions are real. Young-hae Chi, who teaches Korean at the university, also claims to know what the aliens have in mind. In lectures given at the university, he says they're creating alien-human hybrids as a hedge against climate change. To support his unorthodox theory, Chi notes that for several decades the number of reported alien abductions has risen. He bases this statement on the work of David Jacobs, a retired Temple University historian who has published several books on ufology and who runs the International Center for Abduction Research.

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Jacobs has interviewed more than a thousand people who claim to have been abducted, using hypnotic regression that apparently allows them to recall their unearthly encounters with aliens. (Mind you, this too is controversial, and Jacobs himself admits that people should be skeptical of these recollections.)

Chi takes the claims at face value, and links the growing number of abductees cataloged by Jacobs to the increase in atmospheric greenhouse gases. He doesn't imply a cause and effect: The abduction experiment is not responsible for global warming. Rather, it's a reaction to it. The extraterrestrials are producing hybrids that can better withstand the rigors of a toastier planet. By producing a new model of Homo sapiens, this project would eliminate the need for difficult climate accords or elaborate geoengineering projects. It would also help the aliens themselves — who are said to be living among us — by preserving the part of their DNA that's carried by the temperature-tolerant hybrids.

Of course, human-alien hybrids, no matter how well adapted to a warmer world, don't address the crux of the climate change problem. Even unimproved humans can handle hotter temperatures; after all, they already live in a plethora of steamy environments including the Congo, Amazonia and downtown Tucson. Rising sea levels could be dealt with too, by building dikes along the seaboards and writing off Miami Beach.

But it's the other inhabitants of the planet that are problematic — crops and critters that will either migrate toward the poles or disappear altogether. These, after all, are essential to both our environment and our food supply. Does the Oxford instructor presume that these other earthly residents are also being re-engineered by the aliens?

In addition, Chi's argument rests on the fact that two things have simultaneously increased in the past several decades: the number of reported abductions and the concentration of atmospheric carbon dioxide. Of course, many other things have risen during this time, too — including the price of bacon and the number of TV channels. It's a big jump from a coincidence in timing to an alien project to produce a climate-resistant species.

Eventually, this weird theory will be vindicated or vanquished by observation. Chi says the reason we don't see the aliens is that they are largely unrecognizable. "The first generation hybrids still have physical features distinctive to aliens'" he told NBC News MACH in an email. "But from the second generation ... they have almost indistinguishable bodily features from those of humans, although they may still carry at least one fourth of alien genes."

The inability to discern anything odd about the appearance of the hybrids is both convenient and unconvincing. They live among us, but we don't notice. And meanwhile, the concentration of atmospheric carbon dioxide continues to climb. It seems unlikely that humanity will ultimately find this situation less threatening thanks to an alien re-build.

But still, you might want to check your 23andMe results. Maybe you're already a hybrid.

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