Bedbugs have been tormenting us for a long, long time. But a new find indicates they may have been feasting on the blood of humans for much longer than initially believed.

The discovery in an Oregon cave with the earliest evidence of human habitation in North America also has some remains of insects from the genus Cimex, the same family as bedbugs (Cimex lectularius).

The species found (Cimex pilosellus, Cimex latipennis, and Cimex antennatus) were all parasites of bats, which also made their home in the Paisley Caves, near the namesake town, according to the study in the Journal of Medical Entomology.

The three species of bugs were as old as 11,000 years, the researchers found. The previous oldest specimens of Cimex dated to just 3,500 years ago, found in Egypt in 1999.

The bedbugs which torment humans were believed to have made the jump from bats during cohabitation in caves in the Eastern Hemisphere.

It’s not clear why the ancient Oregon insects did not successfully harness humans as a food source, the researchers said.

“Given that Paisley Caves was only a seasonal occupation area for human hunter-gatherers, did the humans move around too much, or were the bugs not able to withstand the environment outside the caves for very long?” said Martin E. Adams, Entolomological Society co-author of the study. “Or, were there other constraints involved? I’m working on these last few archaeological questions right now.”

Bedbugs have been known to have evolved right alongside humans for a long time. But much has yet to be understood about their resilience – especially since their resurgence in many places with the decreased use of the pesticide DDT, which nearly eliminated the critters from human habitation after World War II. A New York City study of the lineage of bedbugs from the 1970s showed them to be stubborn survivalists last year, in work commissioned by the American Museum of Natural History.