By Victoria Gill Science and nature reporter, BBC News In the test, two animals had to work together – each pulling on a rope in order to tug a platform towards them. Elephants’ apparent grasp of the need to co-operate shows, scientists say, that they belong in an “elite group” of intelligent, socially complex animals. Researchers from the University of Cambridge built the apparatus, which was originally designed for chimps. The team published their findings in Proceedings of the National Academy of Sciences.  Researchers have documented elephants in the wild helping each other Study leader Dr Joshua Plotnik from the University …