Scientists Reveal Real 'Paleo' Diet of Ancient Skeleton

Researchers baffled by what the famous Kennewick man ate, and didn't eat.

"This guy was apparently living on a diet almost exclusively of marine foods; foods that come from the ocean," Schwarcz said.

The results are surprising because the man was found 350 miles inland along the Columbia River near plains that were teeming with terrestrial wildlife. While he could have been subsisting on salmon swimming upstream, he was likely not venturing to hunt in the fields.

"He was choosing not to eat that wildlife," Schwarcz said.

The geochemist explained that the Kennewick man may have "had a prejudice against eating footed creatures. That’s not really something that we [see.]"

Kennewick said it's unclear why he didn't try to branch out and eat other wildlife in the area.

The time period for the Kennewick skeleton is just under the timeline cited by followers of the "paleo" diet, who aim to eat the same way people ate 10,000 to 2.5 million years before agriculture took hold.

“Whatever angle you chose to look at the diets of our early ancestors, it’s hard to pinpoint any one particular feeding strategy,” Sayers said.

ABC News' Liz Neporent contributed to this article.