ARI SHAPIRO, HOST:
In the animal kingdom, humans stand out for their willingness to help each other, to help even total strangers. Scientists have been trying to understand how this unique trait evolved. And as NPR's Nell Greenfieldboyce reports, now they've found a fascinating difference between apes and humans - human babies, to be precise.
NELL GREENFIELDBOYCE, BYLINE: Human babies before they can even talk can watch social interactions and decide who's being helpful and who is mean. Christopher Krupenye says scientists have known this for about a decade after some lab studies had 6- and 10-month-old babies watch simple puppet shows. For example, one puppet - a little circle with eyes - would try and try and try to scale a hill.
CHRISTOPHER KRUPENYE: And he's either helped by the helper who pushes him up the hill or hindered by the hinderer who pushes it down the hill.
GREENFIELDBOYCE: After watching these little dramas, when babies get to choose between the puppets...
KRUPENYE: They're reliably reaching towards the helper.
GREENFIELDBOYCE: Human babies seem to be instinctively drawn towards helpers. Krupenye and a colleague at Duke University, Brian Hare, wondered if the same preference exists in an ape that has a reputation for being particularly social and friendly, the bonobo.
KRUPENYE: Bonobos are one of our two closest relatives along with chimps.
GREENFIELDBOYCE: The researchers designed a series of experiments for bonobos that were very similar to the experiments done with human infants. But the bonobos did not respond like the babies did. They did not reach out towards helpers.
KRUPENYE: Perhaps strikingly, we found exactly the opposite. The bonobos weren't very interested in the helper. Instead they consistently chose the one that was blocking or thwarting the other individual's goal.
GREENFIELDBOYCE: The results are reported in the journal Current Biology. Why bonobos would prefer jerks might not be obvious to most humans. But Krupenye says bonobos seem to interpret non-unhelpful behavior as a sign of dominance, and dominant bonobos control food and mating opportunities.
KRUPENYE: They're attracted to an individual who might be a powerful friend or ally as opposed to someone who's just generally helpful or pleasant.
GREENFIELDBOYCE: He says a next step will be to look at this in chimps. If chimps behave in the same way as bonobos, that would be strong evidence that humans hardwired love of helpers is unique and evolved within the last 6 million years. Nell Greenfieldboyce, NPR News.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.