The finding not only throws off some common perceptions of what paleo men actually ate, but also adds some mystery to the fully intact skeleton found in 1996 in Kennewick, Washington.
The ancient human, who stood at 5 feet 7 inches, was found in a region where four-footed game were aplenty. So why wasn't he hunting them?
"The only theory I can suppose for why he chose not to eat local game (which was abundantly available) is that he had some deeply-held belief system that caused him to reject terrestrial meat from his diet," Henry Schwarcz, professor emeritus in the School of Geography and Earth Sciences at McMaster University, said in an email to Discovery News.
"It is hard to imagine how a people could persist in such a belief system as long as these data suggest."
Schwarcz added that his research doesn't exclude the possibility that Kennewick Man also ate plant-based foods like nuts and berries (which happen to also be on the Paleo diet menu).
Another possibility is that the ancient man may have been killed far from his main home. His remains were found some 370 miles inland -- but perhaps his home was closer to the Pacific Ocean.
"Certainly his diet is matched more closely by consumption of marine mammals that live mainly on the coast," Schwarcz said.
Schwarcz, renowned for his research in isotopic analysis of ancient bones, based his findings on his analysis of collagen in a small bone fragment from the famous and controversial skeleton. Hepresented his work at the recent annual meeting of the American Association of Physical Anthropologists in St. Louis.
Previous research has shown that the man died at about age 40. He had lived with an arrowhead stuck in his hip and also suffered from five broken ribs, two dents in his skull and a bum shoulder (probably from throwing so many spears).
"He was a strong, robust man (based on the appearance of his skeleton) who had managed to survive at least one attack by another human," said Schwarcz. "He should have been an able fisherman/hunter."
Kennewick man is one of the oldest and most complete skeletons found in North America. Recent estimates date the remains to between 8,400-8,690 years old. The skeleton became the subject of an eight-year-long lawsuit between scientists who sued the federal government (along with several Native American tribes) to prevent the bones from being turned over to regional tribes for reburial.
In 2004 the Ninth Circuit upheld a ruling that Kennewick Man is not related to any of the present-day tribes and therefore can remain at its current location at the Burke Museum of Natural History and Culture in Seattle. The debate over his ethnicity and origins -- and what should happen to him -- continue today.
Schwarcz's analysis was surprising since Kennewick Man was found by the Columbia River in an area where big game were believed to be abundant.
While the trendy Paleo Diet includes fish on its list of acceptable foods, the diet is also heavy on red meat and other foods like nuts and berries, that our ancestors are thought to have eaten before the dawn of agriculture and animal domestication.
This particular ancient human seems to have missed the memo and stuck to mostly seafood.
Onion, Amanda. 2015. “Real Paleo, Kennewick Man, Ate Mostly Seafood”. Discovery News. Posted: April 3, 2015. Available online: http://news.discovery.com/human/evolution/real-paleo-kennewick-man-ate-mostly-seafood-150403.htm