Language is a hallmark of humans, a species unique in the animal kingdom for its linguistic complexity and flexibility and unbounded capacity for expression. But Cornell psychology professor Morten H. Christiansen challenges the idea that human language stems from a genetic blueprint -- an idea that has dominated language sciences theory for more than 40 years. Instead, he says, the neural machinery used for language likely predates the emergence of language itself.
"We're arguing that language has changed over time to fit the human brain, not the reverse," said Christiansen, co-director of Cornell's Cognitive Science Program and external professor at the Santa Fe Institute in New Mexico. He is the senior author of a study published online in the Proceedings of the National Academy of Sciences (PNAS, 106:3).
The research presents new evolutionary evidence that undermines the theory of "universal grammar," championed most famously by linguist Noam Chomsky. More recently, this theory has been popularized by Steven Pinker, author of "The Language Instinct," who argued that all world languages tend to have similar structures and uses because humans have evolved through natural selection to become "hard-wired" with genes uniquely adapted for language.
Christiansen and his colleagues used computer simulations to show that genes specific for language could evolve only if language does not change.
"There's a general consensus that language would have had to start out as a product of culture," said Christiansen. "However, because cultural evolution is orders of magnitude faster than biological evolution, language would have been subject to rapid change similar to other cultural products. So the fast-changing language is a moving target with which the slow-changing genes can never catch up."
The authors conclude that a language-specific, genetically encoded universal grammar can be ruled out on evolutionary grounds. The paper is co-authored by Nick Chater at University College London and Florencia Reali at the University of California-Berkeley.
In a second paper published in Behavioral and Brain Sciences (Vol. 2008, No. 31) (accompanied by 28 peer commentaries and the authors' responses), Christiansen and Chater argue that language is a culturally evolved system, not a product of biological adaption. This is consistent with the other recent proposals that language arose from humans' unique capacity for social intelligence.
"As Darwin suggested, the evolution of human language may be best understood in terms of cultural evolution, not biological adaptation," Christiansen said. Thus, although this year's celebrations of the bicentennial of Charles Darwin's birth and the 150th anniversary of the publication of "On the Origin of Species" primarily focus on biological evolution, the two papers by Christiansen and colleagues highlight Darwin's additional important contribution to the study of cultural evolution.
The research was supported in part by the Human Frontier Sciences Program, a Charles A. Ryskamp Fellowship from the American Council of Learned Societies (to Christiansen), and a Major Research Fellowship from the Leverhulme Trust as well as grants from the Economic and Social Research Council in the United Kingdom (to Chater).