Recently, a paper published by Claudio Tennie, Josep Call and Michael Tomasello from the Leipzig Max Planck claimed to show that humans are unique because human culture “has the distinctive characteristic that it accumulates modifications over time.” They say that this is largely because, compared to the cultural learning of other animals, human cultural learning is “more oriented towards process than product.” This may very well be true. Unfortunately, there is no way to reach this conclusion based on the research described in their paper, despite what the authors would have you believe. This is because the authors rely on negative evidence as the foundation of their claim.
They compared apes to human children in their ability to learn a task (tying a loop from string in order to retrieve a reward) by watching a human model the behavior. The authors’ sketch drawing of the task is shown here:
The children were able to perform the task after watching the model; the apes were not. The authors then conclude that since no evidence had been produced to disprove their convictions, their initial claim must be correct: humans are uniquely oriented toward learning the process of solutions. In essence, the authors are making an argument of the form: the ability of apes to socially learn processes has not been proven true; therefore it is false. This is a logical fallacy, and excludes the possibility – very real in the case of negative evidence — that the test wasn’t testing what it was supposed to. For example, the children are dealing with their own species and the apes are asked to imitate another species, so the set up is inherently biased against the apes. See another blog on this website on the issue of fair comparison. Previous experiments at Yerkes Field Station have shown that chimpanzees perform better at a social learning task when another chimpanzee, instead of a human, models the task.
Another example of the problems inherent in this (faulty) logic is illustrated by the creationist website answersingenesis, which currently features the Tennie paper in its News to Note blog as evidence that, not only are we distinct from other animal species in our mechanisms of social learning, but that the very theory of evolution is itself, false. After summarizing the paper, the site observes, “If man and ape are closely related, then one might expect more adeptness in apes’ problem-solving techniques… As creationists, we know that the anatomical similarities between man and ape are the result not of a common ancestor, but of a common Creator.” It appears that using scientific papers to create a God-of-the-gaps argument is a growing trend amongst the creationist community, as an article in Nature by Johan Bolhuis and Clive Wynne received a similar response (see a reply to creationists by the authors in SEED Magazine). I do not know the personal beliefs of Tennie or his co-authors, nor do I have any interest in discussing religious beliefs here, but I have to think that even the authors can see the problem –not to mention irony- in their own logic when it is being used by a religious fundamentalist group to educate against one of science’s most stalwart theories.