@Article{Bell:2015a, author = {E. A. Bell, P. Boehnke , T. M. Harrison and W. L. Mao}, title = {Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon}, journal = {P. Natl. Acad. Sci}, booktitle = {}, editor = {}, publisher = {}, month = {}, year = {2015}, volume = {}, number = {}, pages = {}, note = {}, annote = {}, keywords = {}, url = {http://sims.ess.ucla.edu/PDF/Bell_et_al_2015.pdf}, doi = {www.pnas.org/cgi/doi/10.1073/pnas.1517557112}, isbn = {}, 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 $\pm$ 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 $\delta$ 13CPDB of -24 $\pm$ 5$\permil$ 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.}, }