I have a theory, and the theory is mine.

But I’m willing to share.

The age of an archeological site can be dated by how advanced the car radios are.  Early cars had AM-only.

Then FM was added

Then 8-track and cassette

and CD

and MP3

Now there are satellite

and iPod

and who knows what’s next.

With a slightly different spelling, we could trace the age through door openers and car starters: carkeyology.

(Thanks to Usonian, dsearls, Kaz Andrew, jspaw, Charles Williams, andyp uk, webjones, and bugmonkey for the radio pix, and h-monk, timtak, Caitlinator, 小强@Melbourne, and pmsyyz for the keys)