Discounting rocks (unless they’ve been shaped into a tool). Fossils are fine. Just anything that shows some evidence of life, really. What’s the oldest thing that’s been found?
If fossils are allowed, this is the ultimate winner.
“The cyanobacteria have an extensive fossil record. The oldest known fossils, in fact, are cyanobacteria from Archaean rocks of western Australia, dated 3.5 billion years old. This may be somewhat surprising, since the oldest rocks are only a little older: 3.8 billion years old!”
Well I guess those rocks would win, then.
[sub]looks around, sees question was answered[/sub]
OK then, what is the oldest thing to be lost?
If peculiar isotope ratios are allowed, the graphite microparticles in Greenland’s Itsaq gneiss formation provide evidence of earthly life dating back 3.65 to 3.85 billion years.
The fossil bones of Peking Man (the name then given to specimens of what is now called Homo Erectus) were several hundred thousand years old. They vanished in the chaos of the Japanese invasion of China in the late 1930s. Casts and photographs of the originals are still around but the actual bones themselves are gone.
The oldest rocks themselves. Although the Earth is about 4.5 billion years old, the oldest known rocks are only about 3.9 billion years old (although tiny zircons have been found that were part of the oldest rocks that are possibly 4.4 billion years old).
Also, the remains of the very oldest life forms, and their pre-life precursors, have also been lost.
Fred Flintstones keys.
We lost Grandma at the flea market once. She was a hundred and two!