A new whole-genome analysis of chimpanzees and bonobos reveals that these two great ape species likely interbred several hundred thousand years ago. A better understanding of the genetic flow between humans' closest living relatives could shed light on processes that might have played a recurring role in great ape evolution. While chimpanzees and bonobos are known to interbreed in captivity, the historic genetic flow between the two species in the wild is less clear. To gain better insights into possible historical gene flow between them, Marc de Manuel et al. analyzed the complete genomes of 10 bonobos and 65 chimpanzees. Significantly, more chimpanzees were included in their analysis, and from various regions in Africa, because previous genetic studies have suggested that four distinct species of chimpanzee exist. Following their analysis, the researchers observed clear evidence for gene flow between the two species, occurring between 200 and 550 thousand years ago, they estimate. Central, eastern, and Nigeria-Cameroon chimpanzees share significantly more genetic information with bonobos than do western chimpanzees, they report. What's more, similar to Neanderthal genetic patterns in humans, some background bonobo genetic information has been deleted in the chimpanzee genome, suggesting that some bonobo genes may have been disadvantageous for chimpanzees.
Humans aren't the only species to be influenced by spin. Our closest primate relatives are susceptible, too.
For example, people are known to rate a burger as more tasty when it is described as "75 percent lean" than when it is described as "25 percent fat," even though that's the same thing. And they're more willing to recommend a medical procedure when they are told it has a 50 percent success rate than when they are told it has a 50 percent chance of failure -- again, exactly the same thing.
A Duke University study has found that positive and negative framing make a big difference for chimpanzees and bonobos too.
In experiments conducted at Tchimpounga Chimpanzee Sanctuary in the Republic of Congo and Lola ya Bonobo Sanctuary in the Democratic Republic of Congo, researchers presented 23 chimpanzees and 17 bonobos with a choice between two snacks -- a handful of nuts and some fruit.
In one series of trials, the researchers framed the fruit option positively -- by offering one piece of fruit, with a 50 percent chance of a surprise bonus piece.
In another series of trials, the researchers framed the fruit option negatively. This time they offered two pieces of fruit rather than one, but if the apes chose the fruit, half the time they were shortchanged and received only one piece instead.
Chimps and bonobos were more likely to choose the fruit over the nuts when they were offered a smaller amount of fruit but sometimes got more, versus when they were initially offered more but sometimes got less -- despite receiving equal average payoffs in both scenarios.
The preference for the option framed as a prize rather than a penalty was especially strong in males, the researchers found.
