FILE - This Feb. 19, 2013 file photo shows a chimp gathering food at Chimp Haven in Keithville, La. Two different studies looking at why monogamy evolved in some species, pointed at sep

 

              FILE - This Feb. 19, 2013 file photo shows a chimp gathering food at Chimp Haven in Keithville, La. Two different studies looking at why monogamy evolved in some species, pointed at sep
FILE - This Feb. 19, 2013 file photo shows a chimp gathering food at Chimp Haven in Keithville, La. Two different studies looking at why monogamy evolved in some species, pointed at separate reasons. Gibbons are one of the monogamous species among the world’s mammals and chimpanzees are at the other end of the spectrum and wildly promiscuous, said anthropology researcher Kit Opie of University College London, an author of one of the studies. (AP Photo/Gerald Herbert, File)