Life in what is now Tanzania was difficult and dangerous 1.8 million years ago, according to a team of scientists from the United States, Switzerland and Spain.

“Early humans had access to food, water and shady shelter at a site in Olduvai Gorge, Tanzania,” said team member Prof. Gail M. Ashley of Rutgers University.

“They even had lots of stone tools with sharp edges. But it was tough living. It was a very stressful life because they were in continual competition with carnivores for their food.”

Prof. Ashley and her colleagues from the Pennsylvania State University, ETH Zürich, and the Complutense University, reconstructed an early human landscape on a fine scale, using plant and other evidence collected at the sprawling site.

The results were published online February 22, 2016, in the Proceedings of the National Academy of Sciences.

The landscape, it turned out, had a freshwater spring, wetlands and woodland as well as grasslands.

“We were able to map out what the plants were on the landscape with respect to where the humans and their stone tools were found,” Prof. Ashley noted.

“That’s never been done before. Mapping was done by analyzing the soils in one geological bed, and in that bed there were bones of two different hominin species.”

The two species of early humans are Paranthropus boisei and Homo habilis.

“Homo habilis had a bigger brain and was more in sync with our human evolutionary tree,” Prof. Ashley said.

“Both species were about 4.5 to 5.5 feet (1.37 to 1.68 m) tall, and their lifespan was likely about 30 – 40 years.”

Through their research, Prof. Ashley and co-authors learned that the shady woodland had palm and acacia trees. They don’t think the hominins camped there.

“But based on the high concentration of bones, the hominins probably obtained carcasses elsewhere and ate the meat in the woods for safety,” Prof. Ashley said.

“In a surprising twist, a layer of volcanic ash covered the site’s surface, nicely preserving the bones and organic matter.”

“Think about it as a Pompeii-like event where you had a volcanic eruption,” she said.

“A volcano is about 10 miles from the site. The eruption spewed out a lot of ash that completely blanketed the landscape.”

On the site, the team also found thousands of bones from animals such as giraffes, elephants and wildebeests, swift runners in the antelope family.

The hominins may have killed the animals for their meat or scavenged leftover meat.

Competing carnivores included lions, leopards and hyenas, which also posed a threat to hominin safety.

“Scientists have started to have some ideas about whether hominins were actively hunting animals for meat sources or whether they were perhaps scavenging leftover meat sources that had been killed by say a lion or a hyena,” Prof. Ashley said.

The subject of eating meat is an important question defining current research on hominins.

“We know that the increase in the size of the brain, just the evolution of humans, is probably tied to more protein,” she said.

The hominins’ food also may have included wetland ferns, crustaceans, snails and slugs.

“The hominins likely used the site for a long time, perhaps tens or hundreds of years,” Prof. Ashley said.

“We don’t think they were living there. We think they were taking advantage of the freshwater source that was nearby.”

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Clayton R. Magill et al. Dietary options and behavior suggested by plant biomarker evidence in an early human habitat. PNAS, published online February 22, 2016; doi: 10.1073/pnas.1507055113