Double Take

The Chicago Time Capsule was indeed an elaborate production. The greatest of American acting, writing and electronics went into its story of Man, 1960, for future historians. And, centuries later, it was dutifully recovered. Only....
When the Travelers from Outer Space dug into the pile of moldering rock, they found the metal capsule their senses had told them was there. Battered and corroded though it was, the shadow vibrations showed that it had once been smooth and shiny. As smooth, shiny and impervious to wear as Twentieth Century Earth technology could make it.
At the time the Mayor of Chicago had ceremoniously tossed a handful of lake sand into the hole, had his picture taken smiling against the skyline, and had moved away to let the workmen fill the hole with cement and place the marker, the Time Capsule had been bright with the hopes of civilization sending its proud present into the uncertain future.
Time passed....
The tiny radio transmitter in the capsule began throwing out its wide signal at the exact instant planned for it many centuries before. No one heard. Eventually, the tiny powerful batteries gave out. The signal died.
Time passed....
When the Travelers from Outer Space took the capsule back to their ship and opened it, they found the contents in perfect order. Even the reel
of magnetic tape had not succumbed to the centuries.
In due course, the Travelers examined the tape, divined its purpose, and constructed a machine that would play back the recording.
Out of a million evolutionary possibilities in a Universe of planets, the chances of two intelligent races being even roughly similar are astronomically remote.
A being develops sense organs for no other reason than to make it aware of its environment. The simplest primitive being's awareness of its environment centers around food, its means of survival. It develops organs and appendages that will enable it to ferret out, obtain and ingest its food. As the food differs, so, then, does the eater.