How do organisms communicate honestly despite conflicts of interest? Over the past quarter-century, the "costly signalling" hypothesis -- that signal honesty can be ensured by appropriate signal cost -- has emerged as the dominant explanation for this puzzle. First proposed by Zahavi [1, 2] and...

In an influential paper, Grafen (1990) provided a mathematical demonstration of the validity of Zahavi's handicap principle . Grafen showed how an honest signalling system is stabilized through costly signalling: cost stabilizes the system when the cost of lying is greater than any benefit...

How did human language arise, and what accounts for its present structure? Over the past decade, there has been great interest -- and impressive progress -- in using evolutionary theory to address to these and related questions. In particular, a number of studies have shown that several key...