Determining Divergence Times of the Major Kingdoms of Living Organisms with a Protein Clock

TLDR

The study used amino‑acid sequences from 57 enzymes to estimate divergence times among major biological groups. Protein‑clock estimates place the deuterostome–protostome split at ~670 Ma, the last common ancestor of plants, animals and fungi at ~1 Ga, and the prokaryote–eukaryote split at ~2 Ga; the data also show plants are more similar to animals than fungi, fungi and animals share a more recent ancestor than either does with plants, protists diverged ~1230 Ma, and archaebacterial sequences are closer to eukaryotes than eubacterial ones.

Abstract

Amino acid sequence data from 57 different enzymes were used to determine the divergence times of the major biological groupings. Deuterostomes and protostomes split about 670 million years ago and plants, animals, and fungi last shared a common ancestor about a billion years ago. With regard to these protein sequences, plants are slightly more similar to animals than are the fungi. In contrast, phylogenetic analysis of the same sequences indicates that fungi and animals shared a common ancestor more recently than either did with plants, the greater difference resulting from the fungal lineage changing faster than the animal and plant lines over the last 965 million years. The major protist lineages have been changing at a somewhat faster rate than other eukaryotes and split off about 1230 million years ago. If the rate of change has been approximately constant, then prokaryotes and eukaryotes last shared a common ancestor about 2 billion years ago, archaebacterial sequences being measurably more similar to eukaryotic ones than are eubacterial ones.