Research has shown that “genetic constraints” on language evolution could have caused a “specialized” and “species-specific language module.[8] It is through this module that there are many specified “domain-specific linguistic properties,” such as syntax and agreement.[8] Adaptationists believe that language genes “coevolved with human language itself for the purpose of communication.”[8] This view suggests that the genes that are involved with language would only have coevolved in a very stable linguist environment.