Evidence for earliest life on Earth

[Cypress]

Extraordinary that life possibly existed on the proto-Earth more than 4.1 billion years ago.

Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon

Abstract
Evidence of life on Earth is manifestly preserved in the rock record. However, the microfossil record only extends to ∼3.5 billion years (Ga), the chemofossil record arguably to ∼3.8 Ga, and the rock record to 4.0 Ga. Detrital zircons from Jack Hills, Western Australia range in age up to nearly 4.4 Ga. From a population of over 10,000 Jack Hills zircons, we identified one >3.8-Ga zircon that contains primary graphite inclusions. Here, we report carbon isotopic measurements on these inclusions in a concordant, 4.10 ± 0.01-Ga zircon. We interpret these inclusions as primary due to their enclosure in a crack-free host as shown by transmission X-ray microscopy and their crystal habit. Their δ13CPDB of −24 ± 5‰ is consistent with a biogenic origin and may be evidence that a terrestrial biosphere had emerged by 4.1 Ga, or ∼300 My earlier than has been previously proposed.


https://www.pnas.org/doi/10.1073/pnas.1517557112

 

[Cypress]

The remarkable thing to me is that it took 3.5 billion years for single celled life to evolve into complex multicellular life, but the isotopic evidence suggests life was present on Earth almost since the very beginning of when the planet became habitable.