How old is thought? I don't know. Maybe thought is so old, it's dying out.

It sometimes seems that way. Here's a headline on the front page of WaPo:



Click through and you get a headline that has one more word — "Ancient teeth show history of epidemics is much older than we thought" — a mere 2-letters without which you have a ludicrous second meaning.

From the article, presumably a worthy article by a man who surely didn't write the front-page teaser:

Scientists and archaeologists now believe... that the plague bacteria, which caused the medieval Black Death that killed up to half of Europe’s population, infected humans roughly 5,000 years ago in the Stone Age. The bacteria, after it had entered the bloodstream and likely killed the host, circulated into the pulp chamber of teeth, which kept its DNA insulated from millennia of environmental wear and tear. In the past decade, scientists have been able to extract and analyze that DNA. The Stone Age plague was, however, an ancestor with a slightly different genetic identity....

Kristian Kristiansen, a University of Copenhagen archaeologist and a co-author of the plague study, believes his group’s research illuminates the causes of a Stone Age demographic transformation, called the Neolithic decline, which archaeologists have long studied. Settlements at the time were disappearing faster than they were appearing, and within a few hundred years, most of the population had been replaced by migrants from the Eurasian Steppe. Researchers had only ever hypothesized that disease may have played a role in crippling the native population before it was overtaken, but now they have evidence, Kristiansen says.

“The steppe migrations would not have succeeded without the plague . . . and [those living in what is now Europe] would not all have spoken Indo-European languages,” Kristiansen said. “Later prehistory has been turned upside down to say the least.”