|DIANA A CHERNIKOVA|| at 11:00
A late origin of the extant eukaryotic diversity: divergence time estimates using rare genomic changes
Accurate estimation of the divergence time of the extant eukaryotes is a fundamentally important but extremely difficult problem owing primarily to gross violations of the molecular clock at long evolutionary distances and the lack of appropriate calibration points close to the date of interest. These difficulties are intrinsic to the dating of ancient divergence events and are reflected in the large discrepancies between estimates obtained with different approaches. Estimates of the age of Last Eukaryotic Common Ancestor (LECA) vary approximately twofold, from ~1,100 million years ago (Mya) to ~2,300 Mya. We applied the genome-wide analysis of rare genomic changes associated with conserved amino acids (RGC_CAs) and used several independent techniques to obtain date estimates for the divergence of the major lineages of eukaryotes. Our estimates suggest a young LECA, with an age of about ~1,000-1,300 Mya. The inference of a "young LECA" is compatible with the latest of previously estimated dates and has substantial biological implications. If these estimates are valid, the billion years of evolution of eukaryotes that is open to comparative-genomic study probably was preceded by approximately the same duration of evolution that might have included extinct diversity inaccessible to comparative approaches.