For all their cognitive prowess, chimpanzees will never build four-stroke engines, stone pyramids, or even a simple wheel.
Technological innovation and improvement seem to be uniquely human traits, despite culture and ample tool use in chimpanzees and other animals. New research on children and chimpanzees might explain why.
“For culture to accumulate – to become more and more complex – requires innovations and one of the first ways in which hominins clearly went beyond chimpanzees was in making stone tools,” says Andrew Whiten, a psychologist at St Andrew’s University, UK.
Most three- and four-year old children, by contrast, had no trouble jettisoning the less efficient approach for a better solution.
Experiments such as these may be far removed from the African jungles where chimpanzee culture flourishes and the urban jungles where we humans innovate. Yet they provide hard data to questions once addressed with just-so stories and speculation, the researchers contend.
Testing different theories of culture in real animals – be they chimp or child – has also brought the two once-disparate camps into closer sync, if not total agreement. “I think we’re both converging on how things are,” Whiten says.
He and researchers in Germany argue that this difference comes down to the distinct ways in which humans and chimpanzees learn new tricks from others.
Eyes on the prize
For chimpanzees, culturally transmitted skills tend to focus on food, whether cracking nuts with rocks, or fishing insects out of the dirt with sticks.
Overwhelming evidence now suggests that chimpanzees pass these traditions onto their brethren. For instance, individuals in Taï National Park in Ivory Coast feast on nuts, while chimpanzees in Gombe National Park in Tanzania ignore them. Less clear is what chimpanzees learn by watching another animal demonstrate a new trick.
Claudio Tennie and Michael Tomasello, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, contend that chimps focus on the outcome of a demonstration – a cracked nut – rather than the bodily actions that produce the treat. Yet humans imitate the sequence of body movements: raising a stone or hammer above their shoulder before slamming it down.
This difference, Tennie argues, helps humans learn feats they never would have come up with, left to their own devices. Chimps, instead, adopt only new technologies that they might stumble on. Seeing another chimp perform the action sparks a sort of “a-ha” moment, after which it seems obvious.
Learning to lasso
Tennie’s team recently tested whether several species of apes and four-year-old children could learn to fold a piece of string into a loop to tug on a block with a nail in it, behind a cage. If successful, the apes got access to grapes, the children got stickers.
His team intended the task to be complex enough that neither children nor apes could instantly solve it, but not so complicated that it demanded extensive dexterity or memory.
Indeed, when playing around with the string, none of 24 children, seven chimpanzees, six gorillas, eight orang-utans and five bonobos made so much as a loop. Even after Tennie’s team showed half the children and apes that the block could move, just one child managed to pull the stickers within reach.
However, after the researchers demonstrated the entire trick to the other 12 children, 9 managed to make a loop and 4 succeeded in obtaining the prize. After watching five demonstrations, none of the apes ever made a loop.
Because apes focused on the outcome, rather than the process of creating a loop and bringing the block closer, they did not – and will never – transcend their inability to discover the solution on their own, Tennie says.
Whiten thinks things are a little more complicated. “I don’t think that simple dichotomy works,” he says.
Student and teacher
In 2005, Whiten’s team published work suggesting that chimpanzees learned specific movements and passed them onto others. Beginning with two chimpanzees from different groups, Whiten taught each a different way to get a treat out of a special box.
One approach relied on poking a stick into the box to make the treat available. In the other method, the chimp learned to pull on a lever on the outside of the box that releases the treat – same outcome, different actions. Not only did the two chimps learn whichever approach they observed, but they also passed on the trick to other members of their group.
This would suggest that chimpanzees can pay attention to – and imitate – the actions of others, Whiten says. He favours more nuanced explanations for the culture gap between humans.
For one, children imitate step-by-step actions with far more fidelity than chimps, particularly when some of the steps are superfluous. “We are such a cultural species that it pays children to copy everything that adults do,” he says. And second, children seem more willing than chimpanzees to upgrade their approach to solving a problem.
Recently, Whiten and colleague Sarah Marshall-Pescini taught 11 young chimps to scoop honey from inside a box by dipping a stick into a hole in the box. Five of them either figured out this approach on their own or learned it after watching a demonstration.
Next, Whiten’s team showed the same five chimps how moving the stick around the hole releases a latch that opens the box. This offered up all the honey at once, plus peanuts that were previously hidden. Yet, none of the apes adopted the more efficient approach.
“They didn’t get it. They didn’t show any kind of cumulative cultural evolution,” Whiten says. “There’s something rather curious going on in these non-human species, where they get stuck on simpler techniques.”
Via New Scientist