Water's edge ancestors: Human evolution's tide may have turned on lake and sea shores

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.

I started highlighting words and phrases that make or are related to or based on assumptions or layers of assumptions.

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.

Seashells found at a South African cave were probably carried there by early peoples. A. Jerardino and C. Marean/Journal of Human Evolution 2010

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, may be 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.

At a site unceremoniously dubbed FwJj20, a team led by anthropologist David Braun of the University of Cape Town in South Africa unearthed butchered remains of fish, turtles and crocodiles. Remains of animals that don’t live in the water but often reside nearby, such as tortoises, birds, giraffes, hippos, rhinos and antelope, also turned up. Stone tools lay among scraped and fractured shells of tortoises and water-dwelling turtles. Several catfish bones bore tool marks made by individuals who cut off the heads of their catches. Whatever members of the human evolutionary family once dined at FwJj20, they needed only basic implements to put catfish and other lake animals in hungry mouths.

“A large rock is probably all that ancient hominids would have needed to catch fish,” Braun said at the anthropology meeting. Even simpler fishing techniques may extend deep into primate prehistory. Orangutans have been found to snatch catfish from shallow ponds bare-handed and chase the finned snacks out of deeper water with poking sticks (SN: 5/7/11, p. 16).

A steady diet of fish would have nutritionally powered brain expansion in early members of the Homo genus, such as the untidy Lake Turkana crowd, in Braun’s view. access

SOUTHERN BOUNTY The distance between a Pinnacle Point cave labeled 13B and the shoreline changed over time. Shellfish collection probably occurred at times when the coast was within 10 kilometers (highlighted below), though the harvest probably changed with sea level.Africa map: geoatlas/graphi-ogre, adapted by Janel Kiley; receding shoreline map: A. Jerardino and C. Marean/Journal of Human Evolution 2010, adapted by Janel Kiley

The Lake Turkana finds leave a sweet taste in archaeologist Kathlyn Stewart’s mouth. In a 1994 study, Stewart, of the Canadian Museum of Nature in Ottawa, concluded that abundant fish, crocodile and turtle remains at five sites within Tanzania’s Olduvai Gorge represented leftovers from hominid meals. Finds at these nearly 2-million-year-old locations, which have yielded fossils of early Homo and a related lineage called Paranthropus, also include butchered bones of land animals, which have received the lion’s share of scientific attention for more than 30 years.

Game hunting occasionally occurred at Olduvai Gorge, Stewart pointed out at the meeting in April, but aquatic foods provided stable, high-quality nutrition. Pollen data and chemical analyses of fossils indicate that hominids began hanging out in marshy areas, eating grasses and papyrus shoots, more than 3 million years ago, Stewart reported. Papyrus marshes feature a lot of fish, shrimp, snails, mollusks and microalgae, which the gorge residents also dined on. “Lake and river margins provided high-quality food to ancient hominids, especially pregnant and lactating females,” Stewart says.

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