Archaeologists who study early hunter-gatherer societies are discovering that even the simplest cultures altered their environments, whether they meant to or not.
For example, aboriginal people in Australia burned huge areas to change the landscape so they could hunt animals more easily. Perhaps the most famous example is the way mastodons and giant sloth and other ice-age animals were killed off by roving bands of hungry humans.
Torben Rick, an archaeologist at the Smithsonian Institution in Washington, says the notion of hunter-gatherers living in perfect harmony with their environment is going the way of the dodo. He says he's discovered that indigenous people even altered America's coastlines, thousands of years ago.
In a big, sunny laboratory at the Smithsonian, Rick pulls a palm-sized shell out of a plastic bag to show what he means.
"These are red abalones," he says. "This one is 6,500 years old." He says people living on the islands of California dumped these shells after eating the abalone and, unknowingly, became "dune-builders."
"So there might have been a five-foot dune there at one time right above the beach," Ricks says, "and a group of hunter-gatherers came in, lived on top of that dune, dumped their refuse there and left. And this creates a pavement there that anchors that sand."
Small dunes eventually became big ones, built up like a layer cake, with trash dividing each layer.
Then there were intentional changes that people wrought, like the clam gardens of the Pacific Northwest.
People built rock walls into the ocean shallows.
"What these rock walls do," says Rick, "is they create behind them an area of sandy substrate that's really good for clams. You can kind of think of them like a terraced garden."
Rick has also found layers of sea otter bones thousands of years old in California's Channel Islands. The layers above just had sea urchin remains. He thinks people killed the otters because they ate too many shellfish. Since otters also prey on sea urchins, the urchin population exploded. All those urchins ate up the kelp forests, creating what Rick calls an "urchin barren."
Changes Can Lead To Disaster
Rick says intentionally or not, hunter-gatherers altered the environment for a long, long time, long before agriculture emerged. University of Nebraska anthropologist Raymond Hames, who studies how people interact with their environment, says they had no choice.
"The take-home point to some extent is that humans do things to make their life easier," Hames says. "It was really hard to make a living back then, so you know, you took advantage of the knowledge and skills you had in order to make the environment useful to you."
Hames says sometimes in early human history, changing the environment led to disaster.
"The problem is that your successes lead to population growth, which then leads to more pressure on the system to produce more resources," he says. "Your successes can set you up for even greater failures."
Many archaeologists argue that societies like the Easter Islanders and the Mayans suffered after over-exploiting their forests and land.
Rick notes that human activity is now threatening places like the Everglades and the Chesapeake Bay. Scientists are trying to restore them, but to what condition? He says archaeology can provide snapshots of what these places looked like at different moments in time, and how much people had altered them.
Rick's research on coastal exploitation appears in the journal Science.