Public-domain compression algorithms are a good, fast way at calculating the complexity and redundancy of some dataset (the more redundancy, the better the data compresses). It turns out that true fossils have really different compression characteristics from rocks that only look like fossils.
Although biological stromatolites and non-biological stromatolite-look-alike structures appear similar to the human eye, the biological origin of stromatolites makes them more ordered, more highly patterned. And it is this patterning that, while hard for the human eye to discern, is readily detected by the compression algorithm. Non-biological stromatolite-like structures are more random, less patterned and therefore less compressible.
(via /.)
