Did Making Stone Tools Get People Talking? (Where Are We Headed Today?)


prehistoric man

Centuries ago, our hominin ancestors — apes that have been linked to all modern humans via mitochondrial DNA evidence — began a great migration across the African continent, first originating in the deserts before the land became too harsh to support life. According to some recent studies, apes like orangutans and chimpanzees have demonstrated the ability to make plans, particularly migratory journeys in which they must plan for the future, suggesting a common learned memory that may have passed along the species millions of years ago. They display what has long been thought a uniquely human trait.

Among the new evidence that supports the migratory routes of our ancestors across the Sahara are the remains of the Irharhar River to the west, which, according to topography maps analyzing the summers just before the Ice Age 100,000 years ago, had the unusual property of flowing from south to north, providing humid corridors and leading our ancestors to an abundance of food and verdant ground; lush forests that would have sheltered them from predators during their travels.

When seasons changed, the river dwellers moved from place to place — think of it as prehistoric beach property, highly valued depending on the time of year. As they moved, they developed the ability to manipulate the land to create tools, tokens left in the modern-day Olduvai Gorge. As they migrated, they endured, and their brains changed, allowing them to develop the two traits necessary to plan for the future: self-control and mental time travel — the ability to do at least some degree of abstract thinking by anticipating how much time the journey will take; features that are exclusive to only large-brained animals. It need not be just a trek to uncharted lands — simply anticipating what you’ll have for breakfast tomorrow is in itself an example of mental time travel.

Chimps in the wild have also been known to carry small tools to nut-cracking sites — evidence that they plan their activity in advance and show up prepared. Episodic memory must play a role, too — the same function that allows us to remember our own childhoods; specific points in time recalled with the help of the medial temporal lobe. Long after our ancestors braved deserts and floods, we use the same techniques to recall our favorite fishing spots.

This behavior is not only limited to living out on the dangerous plain, as the chimp Santino at Sweden’s Furuvik Zoo demonstrated in 2013. When the zookeepers brought Santino out to his daytime enclosure, he became belligerent with the visitors who came too close to the fence. He searched the boundaries of the paddock and began to stockpile decorative stones off the ground before the zookeepers came to bring him back to his nighttime enclosure. The next day, he turned to his stockpile and hurled the collection of stones at his visitors, using this ferocious display to defend his territory.

Fortunately, the zoo moved Santino to a new fenced-in enclosure before anyone was physically harmed, and he no longer showed signs of aggression. These instances of planning need not happen in isolation, however. Rather, they benefit from collective actions and input taken by a group. Apes such as the wild orangutan Arno have been known to actively plan their travels with other members of the pride — as though mapping out the direction and distance of their destination.

The University of Indonesia recently published a study that followed Arno and 15 other male orangutans, concerning themselves with the loud echoing calls that the animals made back and forth to their families at night. The resonance of these calls was particularly important, as they indicated times of day for travel and when the trek was most preferable. These would be repeated until the orangutans changed calls, indicating a change in their plans of direction, and the calls grew louder — an indication to Arno’s rivals to stay away from his family.

Think of it as the world’s oldest platform of social media — original posts talking about your vacation, with a series of other distinct calls for status “likes.” Twelve hours later, the orangutans would be making similar calls, indicating the directions in which they traveled — suggesting that the researchers completed one of the first successful studies of long-term planning in primates.

Why did the orangutans do this? The researchers who tracked Arno suggested the environmental cues that simpler animals use to migrate may have played a part, alongside associative learning — understanding the association between a behavior and a stimulus. Simple exploration of a given territory would also yield different results at specific times — such as insects or flowers ideal for collecting and eating — and over time Arno and his friends would observe consistent patterns to base their plans around. Planning would also be ideal for the survival of animals, and would therefore be favorable to natural selection. This interaction would also create an environment in which animals would work collectively toward their own survival.

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