(Phys.org)—A very public argument has erupted between researchers involved in attempting to understand why monkeys cannot speak—in the pages of respected journals. The argument traces its roots back several decades when a group led by Philip Lieberman conducted research on rhesus macaques to better understand why they cannot speak in a human-like manner. They concluded that the vocal abilities of the monkeys were far too limited to allow the monkeys to talk anything like humans—even if they had the proper brain wiring.