No. 93: May-Jun 1994
Laymen and scientists alike have wondered for millennia why some reptiles possess forked tongues. It seems that we may now have an answer:
Some variations of the forked-tongue theme among lizards and snakes.
"Theory, anatomy, neural circuitry, function, and behavior now support a hypothesis of the forked tongue as a chemosensory edge-detector used to follow pheromone trails of prey and conspecifics [especially the opposite sex]. The ability to sample simultaneously two points along a chemical gradient provides the basis for the instantaneous assessment of trail location."
The framer of this hypothesis, K. Schwenk, adds that the forked tongue and, obviously, the muscles and neural circuitry to use it properly, have evolved independently at least twice, possibly four times.
(Schwenk, Kurt; "Why Snakes Have Forked Tongues," Science, 263:1573, 1994.)
Comments . One can compare the forked tongue to binocular vision. Both require the parallel evolution of impressive infrastructures of data processing "equipment."