A Portland testing lab and a research team led by the University of Victoria have reset assumptions about the durability of biological evidence.
How durable? Wrap your head around 250,000 years.
Archaeologist April Nowell of Victoria, Canada shipped home a trove of Stone Age cutting tools uncovered during a dig at an oasis in the Jordanian desert. Nowell was curious if microscopic residue on those tools could prove what early humans were butchering and eating. It was an expensive gamble though to send a selection to a private lab for testing.
“Given the age of the artifacts, it was pretty interesting that protein residues were preserved on artifacts that were estimated to be 250,000 years old,” said John Fagan, who runs the Portland lab, Archaeological Investigations Northwest. "Really amazing," he said upon further thought.
Fagan said before this, the oldest blood residue processed in his lab was barely over 10,000 years old. A fraction of the newly examined tools tested positive for blood proteins of camel, rhinoceros, duck, wild horse and cattle.
The Portland lab sampled for animal traces by washing the well-preserved, mostly flint Stone Age tools in an ammonia solution. Next the wash solution was concentrated, residue extracted and then forensically analyzed. The samples were screened for ancient proteins of animals likely to have been butchered by early humans in the Levant.
The researchers from UVic and partner universities in the U.S. and Jordan described their findings this week in the peer-reviewed Journal of Archaeological Science.
Nowell's paper said that 44 tools in all -- scrapers, flakes, projectile points and hand axes -- were submitted for testing. Of these, 17 tested positive for protein residue, i.e. blood and guts.
"It's really huge," Nowell said in an interview. "To my knowledge, the next oldest identifiable protein is about 11,500 years old."
That is why she was dubious when a colleague first suggested they test some of the collected artifacts for biological residues.
"I said, 'They're far too old. No way,'" Nowell recalled. "It just shows you, if you are courageous, if you take a risk, you sometimes have good results.”
Now Nowell is encouraging other archaeologists to test well-preserved ancient tools. "This is really going to change things," she said.
Both Nowell and Fagan said these results show organic material can survive that long "if the conditions are right.”