Lifeboat Africa

Blacklight Helps Archeologists Study the Origins of Modern Human Behavior

Picture an endangered species. Climate change has forced it into a small refuge. The population has crashed to thousands or fewer. Survival is by no means ensured.

This grim scenario may have happened. To us.



More amazing, not only did the human species survive its great population crash, we emerged from it with unparalleled, complex behaviors. This change allowed us to adapt our surroundings to suit us rather than the other way around. It made us “modern,” able to live in virtually everenvironment on the Earth.

“Humans cooperate with nonkin at spectacular levels of complexity,” says Curtis Marean of Arizona State University. “So what we want to know is what are the contexts of evolution for those special features of humans? When did they arise, and why did they arise?”

To answer these questions, Marean and colleagues at Arizona State and in South Africa, Australia, Israel and France, have been studying the archeology of the Cape Floral Region of South Africa. They believe this region may be where the human species emerged from near-extinction to global domination.


Judging from the interrelatedness of every human being, everyone on Earth today may descend from 15,000 or even fewer survivors of a great population crash. Based on genetic mutation rates, this crash happened an estimated 100,000 to 300,000 years ago.

Eastern excavation group photo4During the last glacial maximum, Africa experienced a long dry phase that could explain why the human population crashed. At that time, the Cape Floral Region of South Africa is one of the few on the continent that shows any evidence of human habitation. Also at this time, people began displaying a number of behaviors that separate “modern” from “early” humans. They began to carry out complex thermal treatments of stone to make better tools. They started to engrave geometric patterns in ochre and bone.

“It seems very, very likely that the modern human lineage evolved…during a glacial stage when Africa was mostly dry and uninhabitable,” Marean says. “We not only have a big brain, it’s wired in a way that allows us to think in complex analogies, plan for the future, understand mathematics. We know that proclivity is imbedded in our genes. If we’re trying to understand the process of that event, which leads to all modern humans, we need to understand the environment at that time.”


One archeological finding in particular caught the research- erseyes. The Cape Floral Region is rich in shellfish, with a long, rich coastline, as well as tubers—plants with fleshy roots. Humans need a source of both protein and carbohydrate to survive, and this combinationof foods would certainly do the trick. But were they there—and available enough to humanson foot—to sustain the human remnant at the time?

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The researchers’ final supercomputer simulations will incorporate climate, natural resources and human behaviors.

“Our project began as a straight archeological dig,”says Marean.We were interested in looking for evidence of modern human behavior, when it occurred, what types of behaviors are indicated, and so forth. And we were very successful at that.

Then I realized that we needed much better climate and environmental contextual data to understand the archeological record we were excavating.After a few years of working on commodity computers, the Arizona State researchers decided to “up the ante” btaking their models to PSCs Blacklight. An SGI Altix®UV 1000 shared-memory system, Blacklight offered a unique combination of large memory (up to 16 terabytes of memory available for a single job) and parallel processing(4,096 cores total) that served the requirements of two simulations that Marean and collaborators needed to run.The first was a “paleoclimate”model to see how currents and wind movements during the glacial maximum may have affected the local climate in the Cape Floral Region. The otherwill be an “agent based” model that simulates plants, animals and humans, making each grow, move and interact in a realistic way.

Thanks to Blacklight and support from PSC staff, the paleoclimate model was the first to simulate the Cape region during that period at a level of detail sufficient to shed light on whether the region was warm and wet enough to sustain sufficient shellfish and tuber populations—a major accomplishment in the field. Even better, the initial results suggest that the climate would indeed have supported the food sources humans needed, at a time when virtually no place else in Africa did.

Next the scientists will run the agent-based model, and explorthe role of this environment in the emergence of modern behaviors. The project promises enough predictive power for the models and the archeological evidence to be tested against each other, another first.

We certainly have debates over exactly how small the modern human population was at this point,” Marean says. And other people have argued that the progenitor population was in North Africa, or the Maghreb area … It’s going to be a while before we can say one way or another; but I think right now the Cape Floral Region hypothesis is a strong one. And like all good hypotheses, it’s generating an enormous amount of good science.

Archeaology / Human Origins