Biosignatures and structures in the geological record indicate that microbial life has inhabited Earth for the past 3.5 billion years or so1,2. Research in the physical sciences has been able to generate statements about the ancient environment that hosted this life3,4,5,6. These include the chemical compositions and temperatures of the early ocean and atmosphere. Only recently have the natural sciences been able to provide experimental results describing the environments of ancient life. Our previous work with resurrected proteins indicated that ancient life lived in a hot environment7,8. Here we expand the timescale of resurrected proteins to provide a palaeotemperature trend of the environments that hosted life from 3.5 to 0.5 billion years ago. The thermostability of more than 25 phylogenetically dispersed ancestral elongation factors suggest that the environment supporting ancient life cooled progressively by 30 °C during that period. Here we show that our results are robust to potential statistical bias associated with the posterior distribution of inferred character states, phylogenetic ambiguity, and uncertainties in the amino-acid equilibrium frequencies used by evolutionary models. Our results are further supported by a nearly identical cooling trend for the ancient ocean as inferred from the deposition of oxygen isotopes. The convergence of results from natural and physical sciences suggest that ancient life has continually adapted to changes in environmental temperatures throughout its evolutionary history.
Access optionsAccess options
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
We thank A. Knoll for his comments on this research, and D. Brooks, F. Battistuzzi, R. Davis, K. Josephson, S. Sassi, R. Shaw, J. Szostak and S. Benner for their assistance. E.A.G. acknowledges support from the NASA Exobiology program. O.G. was supported by a NIH/NCRR grant to A. S. Edison and a National Science Foundation grant to S. J. Hagan. S.G. was supported financially by DNA2.0.
Author Contributions E.A.G. designed the study, performed the evolutionary analyses and circular dichroism experiments, analysed the results and wrote the manuscript. S.G. performed gene synthesis. O.G. performed circular dichroism experiments, fitted the data and analysed the results. All authors discussed the results and commented on the manuscript.
This file contains Supplementary Figures S1-S4 with Legends.