Giga-annum

Geophysicists today estimate the earth’s age to be 4.5–4.6 Ga (giga-annums = 1 x 10⁹ years) based on data from lead isotopes (Dalrymple 403).

We report here the sequencing and genomic analysis of the SDR of Ectocarpus, a brown alga that has been evolving independently from plants, animals, and fungi for over one giga-annum.

Possible cyanobacteria from the Apex charts of western Australia, which have been dated at ~3.5 (giga-annums, or billions of years).