Key points are not available for this paper at this time.
Evidence from Precambrian sediments appears to indicate that nucleated (eukaryotic) organisms had become well established and relatively diverse about 850 +/- 100 million years ago and that eukaryotes were probably extant, and may have first appeared, as early as 1400 +/- 100 million years ago.
Schopf et al. (1976) studied this question.