DECODING THE TRACE OF LIFE IN THE PRECAMBRIAN STRATA

Abstract

Major events concerning the early evolution of life have occurred in the pre-Cambrian era. Quality and quantity of the fossil records with important information regarding the early evolution of life have been insufficient. The introduction of geochemical methods and the recent discoveries of well-preserved fossils that have provided high resolution data for the discussions on the early evolution of life are reviewed. The major events of the early evolution of life are the emergence of life, photosynthetic bacteria, and Metazoa. Studies on the early evolution of life with fossil records began with discussions on the 1.9 Ga fossil bacteria. Currently, oldest fossil records are traced back to 3.5 Ga. Recent controversies on these fossils have been made on the basis of several geochemical approaches. Some interesting attempts for the detection of the photosynthetic activity from sedimentological setting of the strata-containing bacteria fossils should be noted. Ediacaran fossils are regarded as ancestors of Metazoa, but some researches proposed that apparent difference exists between those fossils and Metazoa. Recent discoveries of well-preserved three-dimensional Ediacaran fossils will provide insight into the evaluation of such unique organisms.