The Brine Revolution

Did lowly shellfish change the world?

Published April 22, 2015
Part of our Ten Best of 2015 series

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Some 110,000 years ago, foragers picked their way across a rocky shore in what is now South Africa, winding between tidal pools and beds of slick, glistening rock. For weeks, the small band had relished the thought of the day’s harvest and the feast to follow. Watching each night as the moon waxed in the sky, they had trekked to this shoreline, taking shelter in an old sea cave on the headland. This morning, as the full moon vanished below the horizon and the waves retreated, they walked out on a rocky realm littered with shellfish.

Moving toward the surf, they scouted expertly for the large, fleshy sea snails that sometimes sheltered in tidal pools, and for the succulent brown mussels that blanketed some of the rocks. Spotting first one dense clump of mussels, then another, they bent to their work, plucking shellfish with quick, calloused hands from the rocks and tossing them onto hide blankets. It was satisfying work, even for the young, but they had to be quick about it. No one wanted to be stranded on the higher rocks when the tide turned. By the time the waves crashed back in, breaking over the shore, they were on the headland with enough food for a small feast.


Early humans adapted to the coast by understanding tidal rhythms and regularly harvesting nutritious shellfish in the intertidal zone when it was safe. At Pinnacle Point, large, powerful waves crash to shore at high tide. Photo by Ilja Herb

Today, discarded shells from that long-ago meal at Pinnacle Point, some 390 kilometers east of Cape Town, are casting light on a key moment in humanity’s past—when our land-loving African ancestors first turned to the sea for their sustenance. At Pinnacle Point, researchers have discovered shells from humankind’s oldest-known seafood meal, as well as evidence that early Homo sapiens mastered the timing of the tides, cleverly exploited coastal ecosystems, and collected colorful seashells for rituals more than 90,000 years ago. Pinnacle Point, says Curtis Marean, a paleoanthropologist at Arizona State University, Tempe, and the site’s principal investigator, “provides an outstanding record of early coastal adaptation.”

Indeed, Pinnacle Point is conjuring up a new, controversial vision of our African genesis. Scientists have long wondered how early H. sapiens expanded so swiftly out of Africa, colonizing the world and outcompeting Neanderthals and other human lineages. Marean thinks the answer, or at least part of it, lies not in advances in hunting big game, but in our ability to adapt to life along the coast and to harvest the wealth of the sea. By systematically reaping protein-rich seafood, he suggests in a recent paper in the Journal of Human Evolution, H. sapiens became more populous, more territorial, and more cooperative in large social groups than other hominins.

“It’s those traits of cooperation,” says Marean, “that allowed us to expand around the world, develop complex civilizations, and ultimately send people into outer space.”

The humble shellfish, agrees archaeologist Jon Erlandson at the University of Oregon, Eugene, may have helped kick-start a human revolution. “When you add shellfish to terrestrial resources,” Erlandson says, “it’s a broader and more stable food base. And that may have helped accelerate population growth and drive that population out of Africa.”


On a damp, drizzly, late-November morning, Marean clambers up a steep slope at Pinnacle Point. Energetic and fit at 54, with close-cropped graying hair and a broad, easy grin, Marean has spent his career studying human origins in Africa. It is a highly competitive field littered with big personalities and larger-than-life egos, but Marean remains both down-to-earth and approachable. Today, although the field season has ended at Pinnacle Point and he is about to fly back to the United States for Thanksgiving, he is taking time out to show a Hakai Magazine photographer around.


Marean’s work at Pinnacle Point conjures a new vision of how early humans expanded so quickly out of Africa, outcompeting other human lineages and colonizing the world. Photo by Ilja Herb

As he explains later, he first got interested in the South African coast in the mid-1980s. Research suggested that early humans had struggled in Africa during a bitter ice age that began 195,000 years ago and lasted about 65,000 years. As the climate cooled and rainfall tapered off in many regions, deserts expanded, bringing starvation to early human hunters. It was against this bleak backdrop, in all likelihood, that H. sapiens emerged in Africa. Marean suspected that at least some of our ancestors pulled through the harsh times in natural refuges along the Western Cape coast, where rain still fell.

Pinnacle Point would have seemed particularly inviting. In a thin ribbon along the coast, a shrub land known as the Cape Floral Region abounded in wild root vegetables. Studies have shown that more than 2,400 plant species in the region possess starchy underground tubers, roots, or corms—potential food sources that hunter-gatherers have long relished. Almost certainly, early human migrants would have found some of the edible varieties around Pinnacle Point, roasting them for carb-rich dinners. And they could have hunted and scavenged large game. Wildebeests and other similar prey may have migrated through the area, and dead whales or dolphins occasionally washed up on the beaches.


Illustration by Mark Garrison

But the richest, most reliable source of protein at Pinnacle Point was shellfish. The arid conditions of the ice age had little effect on these species, and modern studies show that their densities would have increased, rather than diminished, as ocean temperatures dropped. So even at its coldest and harshest, the Western Cape coast teemed with food. By adding mussels and other mollusks packed with protein and fatty acids to comfort-food meals of starchy tubers, early humans in the region ended up with “an ideal nutrition package during the long, cold glacial,” Marean noted in a book chapter in 2011.

At Pinnacle Point, people began collecting shellfish casually, dining on the flesh and tossing away a modest scatter of shells 162,000 years ago in a seaward-looking cave known as PP13B. It was humankind’s earliest-known seafood dinner. But no one seems to have made a big deal of it: there was no trace of a party, no celebration, nothing that signified that they knew they were onto something important. It was just a good day of foraging, little more, and Pinnacle Point was just one of many brief stops in their restless quest for survival; the foragers had yet to discover the stunning wealth of the sea there.

But as time passed, and as subsequent generations roamed the region, observing even minute changes in the seasons and the tides, they seem to have realized that there was far more to Pinnacle Point than often met the eye. By 110,000 years ago, humans regularly camped in PP13B, a spacious cave measuring 30 meters long and eight meters wide, and harvested large quantities of shellfish—especially the brown mussels that clung to the rocky intertidal zone and the white mussels that burrowed under the sand on nearby beaches. Indeed, these early humans collected and ate so many mussels in PP13B that they paved part of the floor some 40 centimeters thick with shell fragments, creating shell middens there.

How, wondered Marean, did early humans manage to collect such massive quantities of shellfish? What transformed casual beachcombing into a systematic harvest some 110,000 years ago?

REFUGE ZONE - PINNACLE POINT

Marean explains how rich marine resources drew early humans to South Africa’s coast.


During his early field seasons at Pinnacle Point, the paleoanthropologist often walked the neighboring shorelines, mulling over the problem. But he seldom spotted the spiky clumps of brown mussels that early foragers had targeted: these generally lay beneath the breakers. Only during a strong low tide known as a spring tide was an expanse of shoreline nearly one meter below sea level exposed, revealing mussel-covered rocks for as little as 90 minutes. When the time was up, the water pounded back so rapidly that it could trap unwary collectors or sweep them off their feet and into the rocks. “If you go into the zone at the wrong time, it will kill you,” says Marean.

Spring tides take place when the sun, the moon, and Earth are all in alignment like three peas in a pod, a positioning that adds the strong gravitational pull of the sun to that of the moon. The alignment occurs twice each lunar month—the period of time it takes the moon to go through all its phases—and even for people who spend a lot of time on the water today, the spring tide can be tricky to time. A lunar month is about 29.5 days long and the tides advance about 50 minutes each day. “So if you are a fisherman or a surfer, the first thing you do is buy a tide chart,” says Marean. “And those things are so complicated they look like Maya calendars.”


Illustration by Mark Garrison

But South Africa’s early modern humans were expert observers of the natural world, and by paying close attention to the night skies, they eventually noticed that the lowest tides took place on the full moon and the new moon. More importantly, they realized that they could profit from this newfound knowledge. By observing the phases of the moon—a kind of calendar in the night sky—they could schedule their trips to Pinnacle Point to coincide with the lowest tides and the most abundant shellfish harvests. “They made a novel association between a lunar phase and the ocean, and then they made a plan,” says Marean.

All this sounds simple enough to us today, but it was the kind of mental leap that required fully modern cognitive abilities, such as symbolic thought, planning, and a fully working memory—the very thing that allows modern humans to hold and process both old and new information. This was likely a critical development in our history as a species. For years, researchers believed that our ancestors only acquired these abilities some 40,000 to 50,000 years ago, about the time that humans in Europe began arming themselves with fancy new types of bone and stone tools, adorning caves with art, and donning shell-bead necklaces. Marean, however, didn’t buy that theory. At Pinnacle Point, his team had discovered several artifacts pointing to advanced cognition—from tools made of heat-treated, engineered stone to red pigments and pretty seashells likely collected for rituals. These were at least 90,000 years old.

But it was one thing to talk about advanced cognition and boosting shellfish harvests by timing the tides, quite another to prove it. Marean needed experimental data. So, in the summer of 2012, he teamed up with human ecologist Jan De Vynck of Nelson Mandela Metropolitan University, anthropologist Kim Hill of Arizona State University, and two other colleagues to measure how much food modern foragers could harvest from the Western Cape coast during different types of low tides and diverse weather conditions. 

De Vynck recruited experienced shellfish collectors—males and females, adults and children—from villages of the Khoe-San people, the aboriginal inhabitants of the region. Then they headed out to various locations on 35 days, during low tides ranging from weak neap tides (when the sun and moon are at a right angle to one another) to strong spring tides, and in conditions varying from calm, flat water to large, foamy waves. In rubber boots and track shoes, the Khoe-San collectors searched for shellfish as long as they wanted and called it quits when they felt that their productivity was dropping off. Back on dry land, the researchers weighed each day’s catch—brown mussels, giant limpets, pearl oysters, turban snails, blood-spotted abalone, and a type of sea squirt called red bait. Later, they calculated the edible portions.

Some on the team were astonished by the results. When conditions were at their worst during a weak neap tide, older female collectors gathered around 100 calories an hour. But when the conditions were best, with a spring tide and calm weather, the foragers could rake in as much as 4,500 calories per working hour. It was a staggering rate of return. By comparison, Ache hunters in Paraguay obtained just 1,329 calories per hour by hunting brocket deer and other game by bow and arrow, while Hadza women in Tanzania reaped just 258 calories per hour from digging wild root vegetables. “The productivity caught us all by surprise,” notes De Vynck in an email to Hakai Magazine.

For Marean, the results revealed just how much early H. sapiens profited from turning to the sea and harvesting the food strewn along its shores in a systematic way. Had other human lineages done the same?

SEA SNAILS - PINNACLE POINT

Marean describes how humans profited from coastal resources just a few thousand years ago.


In 1989, just a city block away from one of the famous beaches of Torremolinos, Spain, a team of archaeologists edged their trowels under bits of shell and fragments of flint tools made by Neanderthals. In the years that followed, archaeologist Miguel Cortés Sánchez at the University of Seville and his colleagues carefully identified and analyzed the many finds from Bajondillo Cave: butchered bones from wild goats and red deer, pollen from evergreen oaks and Aleppo pine, and hundreds of small shell fragments from Mediterranean mussels. The oldest of these fragments dated to about 150,000 years ago. They are the earliest-known evidence of marine use by Neanderthals.

But the occupants of Bajondillo were not alone in their taste for seafood. In caves from Gibraltar to Italy, archaeologists have found pieces of shell in the refuse left by later Neanderthals. For some researchers, including Cortés Sánchez, these table scraps suggest that Neanderthals were just as systematic, just as savvy, just as smart as modern humans when it came to harvesting shellfish. The knack of harvesting food reliably from the sea, writes Cortés Sánchez in a recent paper, may be much overrated as an exclusive behavior of modern humans.

But Neanderthals collected shellfish differently than modern humans did, Marean says. The reports on the Neanderthal sites make no reference to shell middens, much less dense shell deposits. Indeed, at one Italian site often held up as an example of Neanderthals’ ability to harvest food from the sea, our hominin relatives collected little more than two armloads of shellfish over many millennia. And when Marean wrote to the principle investigators of the major Neanderthal coastal sites to see if he had missed something, they confirmed his suspicions. Boston University geoarchaeologist Paul Goldberg, who studied the famous Neanderthal site of Vanguard Cave in Gibraltar, noted, for example, that he saw no evidence for shell middens. “It looks like they brought in a few shells there but that’s it,” Goldberg wrote.

Such evidence strongly suggests that Neanderthals gathered mussels and other shellfish in a casual way, picking up a few here and there when they happened upon a sufficiently low tide. Unlike early modern humans, they seemed to have lacked advanced cognition, and so failed to make the connection between the lunar phases and tidal movements along the shores of the Mediterranean, their home range, and eventually become systematic harvesters of the sea. 

Clever as our near relatives certainly were, Neanderthals seem to have remained strangers to the shore, unable to read its complex rhythms or reap its greatest bounties.

But in the long run, what difference did it make, this special ability of our human ancestors to harvest mussels, limpets, or sea snails in bulk? As achievements go, this seems modest at best—a far cry from carving a chunk of smooth mammoth ivory into the figure of a woman or piercing the wing bone of a vulture to make a flute. And yet, if Marean is right, our ability to harvest mollusks en masse and eventually to fish the seas may have had a huge impact on humanity. It may have made our ancestors more populous and more territorial, and may ultimately have led them to work together at key times in teams, becoming more interdependent as they scouted and colonized the far corners of the world. Such cooperation may not sound like a huge behavioral shift, but it had enormous consequences. 

WHALES - PINNACLE POINT

The oldest evidence of humans dining on seafood is at Pinnacle Point. Marean explains how our early human ancestors managed to make meals of some of the largest marine mammals—whales.

Marean says the idea jelled as he read comparative ethnographic studies of more recent hunter-gatherers. The studies, based on historical accounts and anthropological observations and interviews, showed that traditional societies who lived off the bounty of the sea were different in many ways from their interior counterparts. To begin with, the coastal dwellers often attained far higher population densities. The Nuu-chah-nulth people in coastal British Columbia, for example, had an estimated density nearly twice as high as their Nlaka’pamux counterparts in the British Columbia interior. Farther south, along the California coast, the Chumash achieved the highest population density of any known hunting and gathering people—an estimated 21.6 persons per square mile.

Such high population densities, moreover, increased the likelihood of technological innovation, through a process that anthropologists call “cultural ratcheting.” Humans, by their very nature, build on the knowledge of others, taking an old idea taught by their elders and giving it a new personal spin, gradually adding one small improvement to another over time. When humans live in large groups, someone is more likely to come up with a really inspired tweak, significantly advancing a technology until the group ends up with something new and very complex, such as heat-treating stone to improve its knapping qualities as they did at Pinnacle Point, or making clam gardens, intricate fishing tackle, and deep water boats, as later groups did along North America’s west coast.

“Like viruses, cultural innovations need very particular social conditions to spread—most notably … large connected populations who can ‘infect’ one another,” noted archaeologists Fiona Coward and Matt Grove in a paper published in PaleoAnthropology in 2011.

In addition, since coastal dwellers tended to focus on dense, predictable, and highly desirable foods such as mussels, herring roe, or salmon, they often packed into the most productive areas. And this, says Marean, had important consequences. Unlike terrestrial hunter-gatherers who ranged over vast areas, coastal groups could easily patrol the boundaries of their home turf and defend them from outsiders intent on stealing food or usurping resources. And in these circumstances, “things like cooperation between individuals and between groups begin to have big payoffs,” Marean says.

By working together, alerting others to danger and coming to their rescue when needed, cooperative humans could have excelled at fending off intruders and protecting valuable food resources. Moreover, groups with many cooperative individuals would likely have outcompeted those with few or none, and this advantage, Marean says, could have resulted in the spread of collaborative behavior in modern humans.

Marean thinks that this process began along Africa’s Western Cape coast between 110,000 and 90,000 years ago, or possibly earlier. As our ancestors began combing the shorelines and systematically harvesting the wealth of the sea, they were less inclined to follow the old hominin way of moving restlessly to hunt and gather across vast stretches of land. And as modern humans began defining their territories along small stretches of coastline and fighting over resources, individuals with a natural propensity to cooperate began teaming up and working together, making common cause as no other hominins had in human history. Such cooperative behavior, writes Marean in a 2014 paper in the Journal of Human Evolution, “was perhaps the final addition to the assembly of traits that produced our unique species.”

It is a compelling argument, but, as Marean concedes, more evidence is needed to back up these contentions. Although archaeologists working in the region have found clear indications of increasing populations and increasing territoriality during this critical period, evidence for conflict over resources is fragmentary. But Samuel Bowles, an economist at the Santa Fe Institute who has mathematically modeled the origins and evolution of altruism, says Marean’s scenario makes a lot of sense. Indeed, Bowles calls the paleoanthropologist’s new research “an extraordinary piece of scholarship.”  

For Marean, however, the quest for evidence continues at Pinnacle Point. He and his team are now excavating in a second large cave along the headlands there and analyzing finds from a later period, hoping to add new details to the picture. Through his research, we are catching glimpses of our early African ancestors as we have never seen them before—timing the rhythms of the sea, feasting on shellfish, and becoming thoroughly modern human beings.

PROJECT MANAGER - PINNACLE POINT

Directing a big, complex archaeological dig has its own peculiar pleasures; hear it from a master, Curtis Marean.