Primitive technology gives them away.
"We dint mean no harm," said Bert Stench. "We was just wipin our hands off after supper and that there rock was all we had."
He was referring to the recent kerfuffel in the scientific community over whether evidence of Neanderthals had been found in North America.
The site? A small cave near Colorado's famous Weepen Hovel National Monument, which is well-known for harboring evidence of peoples from the Paleo-Archaic period. This far-distant time reaches back as far as 12,000 years.
Until recently this was considered pretty darn early for North America.
But one day that suddenly changed, or seemed to, when anthropologists from Colorado State University entered this unnamed and previously-unknown cave during a routine survey of the area.
"We found hand prints similar to but cruder than those from Spain, which date to over 45,000 years ago," said CSU's Dr. Thaddeus Specter.
"My first thought? No way! And then, on closer inspection I thought...Way! My hair literally stood on end, and I'm almost bald, so that says something right there."
"Stone Age artists were painting red disks, handprints, clublike symbols and geometric patterns on European cave walls long, long ago. But in North America evidence of human presence generally goes back only a few thousand years, and there's nothing like this at all. Nothing. We were stunned. This resembled Neanderthal work, but is decidedly more primitive."
Mr. Stench and his buddy Merton Thredbare, both backpackers, were not intending a hoax, according to them. They were simply doing what backpackers do.
The cave looked like a good stop for the night. A few stray twigs gave them fuel for a cooking fire. But there was no water, and so no way to wash up after their meal. Hence the greasy, sooty handprints on the cave walls.
But how could scientists have made such a mistake?
"We used a new uranium-thorium dating technique," said Dr. Specter. "It gave us a date of 78,400 years, B.C.E. Obviously that was wrong. Either our technique was off or their food was stale. Right now we suspect the latter."
The backpackers admit that the food they got at an Army-Navy surplus store in 1992 did taste a little funny, "but when your out backpakin you allays end up hungry so you dont mind none a that," Mr. Thredbare volunteered. "I tasted worse, plenty worse. It staid down, an thats OK," he added.
"I guess we shoulda stuck to wipin off on bushes," said Mr. Stench, "but we dint have none, so it was the cave wall or go to bed dirty."
"Yeah, right," Mr. Thredbare confirmed.
As for the scientists, they have retracted their earlier claims about the antiquity of the "cave art" but are attempting to get DNA samples from the two backpackers.
"I'm no medical expert," Dr. Specter continued, "but although the handprints these two left are clearly modern, we now suspect that the backpackers themselves may be, in fact, a previously unknown remnant of a pre-human species, and we want to get a closer look at them. We have promised to treat them with respect and release them back into their native habitat once we run a few simple tests."
"Huh," was Mr. Stench's reply.
"Diggity," agreed Mr. Thredbare.