Magazine article Science News

Water's Edge Ancestors: Human Evolution's Tide May Have Turned on Lake and Sea Shores

Magazine article Science News

Water's Edge Ancestors: Human Evolution's Tide May Have Turned on Lake and Sea Shores

Article excerpt

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In a cave hugging South Africa's lush southern coastline, Curtis Marean suspects he has cornered a wily Stone Age crew that brought humans back from extinction's brink. These plucky refugees of continent-wide desolation were able to pull off such a stunning evolutionary turnaround because they got lucky. A coastal oasis near the bottom of the world spread its sheltering arms in the nick of time.

Marean proposes that it was there, where the Arizona State University archaeologist now conducts excavations, that humankind's mental tide turned sometime between 164,000 and 120,000 years ago. Seaside survivors learned to read the moon's phases in order to harvest heaps of shellfish--brain food extraordinaire--during a few precious days each month when ocean tides safely retreated.

Tantalizing traces of complex thinking and behavior, including lunar literacy, have turned up at South Africa's Pinnacle Point, a cave-specked promontory that juts into the Indian Ocean. Chunks of dark red pigment and strikingly beautiful seashells found by Marean's team in one cave attest to ancient ritual activities. Stone points unearthed in the same cave sport glossy patches, signs that the rock was heated to make it easier to work with. The finds challenge the long-standing view that Stone Age people did not think abstractly and perform complex rituals until about 50,000 years ago.

People chanced upon Pinnacle Point and its dietary bounty, Marean says, only after global cooling had rendered much of Africa barren and uninhabitable. Several genetic studies suggest that modern human numbers throughout Africa plummeted to a few hundred breeding individuals around that difficult time.

"Our excavations may have intercepted ancient people who shadowed the shifting shoreline and are the ancestors of everyone on the planet" Marean says.

Research on Pinnacle Point's mussel-seeking moon trackers exemplifies a growing scientific conviction that fish and shellfish have played a largely unappreciated role in brain and mind evolution throughout the history of the Homo genus, which appeared at least 2 million years ago and includes people today. Though several East African savanna sites contain butchered animal bones, signaling carnivorous tastes among human ancestors, some scientists now argue that red meat has been oversold as a dietary staple.

At a meeting of the American Association of Physical Anthropologists, held in Minneapolis in April, researchers argued that ancient menus focused heavily on food from lakes, rivers and oceans. New work presented at the meeting pointed to lakeside fishing in East Africa nearly 2 million years ago, the shoreline shellfish harvesting among Homo sapiens at Pinnacle Point starting more than 160,000 years ago and sea voyages to Pacific Ocean islands by an unlikely group of New World settlers around 12,000 years ago.

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Food scientists at the meeting emphasized that nutrients essential for brain growth are much more abundant in fish and shellfish than in red meat or any other food. And grabbing catfish out of shallow waters, not to mention scooping up handfuls of shellfish along the shore, maybe far easier than hunting land animals or scaring predators away from meaty carcasses, says archaeologist Jon Erlandson of the University of Oregon in Eugene.

Shellfish collecting and fishing probably began early among members of the Homo genus, Erlandson says. "These foods later could have provided nutrients that enabled the evolution of fully modern brain size and cognition."

Olduvai gorging

Erlandson suspects that, before Homo sapiens' Pinnacle Point pursuits, fishing was a catch-as-catch-can affair. Consider ancient cuisine unearthed on the eastern shore of Kenya's Lake Turkana. Someone there bellied up to an aquatic buffet nearly 2 million years ago, leaving a mess that only an evolutionary scientist could love. …

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