Can't we teach other intelligent animals "complex" languages?
Many researchers into animal language have presented results of studies as evidence of linguistic abilities in animals. Many of their conclusions have been disputed (Jannedy, Poletto, &amp; Weldon, 1994; Wallman, 1992).
It is now generally accepted that apes can learn to sign and are able to communicate with humans.
The Smithsonian Institution talked about apes communicating and the following are YouTube videos of a gorilla communicating through sign language
A Conversation With Koko
Koko signing with Robin Williams (with translation in subtitles)
References
Jannedy, S., Poletto, R., &amp; Weldon, T. L. (Eds.). (1994). Language files: materials for an introduction to language &amp; linguistics. Ohio State University Press.
Wallman, J. (1992). Aping Language. Cambridge University Press.