Why do snakes have forked tongues? And why do they flick them? Is it because snakes are naturally deceitful, ready to whisper lies into passing ears?
Actually, it's to aid a snake's vomeronasal systema sensory system in snakes that is akin to smell. Snakes have forked tongues so that they can "smell" in stereo.
What Exactly Does This Mean?
What does it mean to sense anything "in stereo?"
If you listen to music holding only one side of your headphones to your ear, the whole orchestra sounds like it's crushed into one, tiny speaker.
If you put your headphones on correctly, using both ears, the music becomes more three- dimensional. Likewise, it's easier to judge the depth of a scene with both eyes open than with only one.
Detailed, Three-Dimensional Whole
The key herewith both ears and eyesis that your brain combines two different perspectives to make a more detailed, three-dimensional whole. Because you have two separate eyes and two separate ears, you can see and hear in stereo.
A Snakes Tongue...
When a snake's tongue flicks out, the two tines of the fork spread as wide as they can. The tines flick back into the snake's mouth, and whatever chemicals each tine encountered in the environment are delivered to the snake's two, separate vomeronasal organs on the roof of its mouth.
This gives the snake a directional perspective on the chemical traces in its environmenta kind of stereo smell. Like your two ears help you identify which direction a sound comes from, the two tines of a snake's tongue tell the snake whether its prey ran left or right.