Half a century ago, paleontologists and biologists were puzzled by huge strata of "silent" rocks without traces of multicellular life and its sudden - by geological standards - appearance in the Cambrian period (the so-called Cambrian explosion). But then it became clear that the most delicate organisms left marks in the geological record. Scientists who have figured out what and where to look are now actively exploring the "talking" Precambrian - a real "lost world" inhabited by original organisms that are not like modern ones.