Wow. A study was published calculating the number of living cells currently present on Earth and the number that have ever lived. The paper, titled “The geologic history of primary productivity,” was published in Current Biology, October 11, 2023. Sadly, the full article rests behind a paywall. But the abstract is open access so I will reproduce it here.

The lead author, Peter Crockford, is a geologist at Carleton University.

Abstract: The rate of primary productivity is a keystone variable in driving biogeochemical cycles today and has been throughout Earth’s past. ¹ For example, it plays a critical role in determining nutrient stoichiometry in the oceans,² the amount of global biomass,³ and the composition of Earth’s atmosphere.⁴ Modern estimates suggest that terrestrial and marine realms contribute near-equal amounts to global gross primary productivity (GPP).⁵ However, this productivity balance has shifted significantly in both recent times ⁶ and through deep time.^7 ,8 Combining the marine and terrestrial components, modern GPP fixes ≈250 billion tonnes of carbon per year (Gt C year⁻¹).^{5 ,9 ,10 ,11} A grand challenge in the study of the history of life on Earth has been to constrain the trajectory that connects present-day productivity to the origin of life. Here, we address this gap by piecing together estimates of primary productivity from the origin of life to the present day. We estimate that ∼10¹¹–10¹² Gt C has cumulatively been fixed through GPP (≈100 times greater than Earth’s entire carbon stock). We further estimate that 10³⁹–10⁴⁰ cells have occupied the Earth to date, that more autotrophs than heterotrophs have ever existed, and that cyanobacteria likely account for a larger proportion than any other group in terms of the number of cells. We discuss implications for evolutionary trajectories and highlight the early Proterozoic, which encompasses the Great Oxidation Event (GOE), as the time where most uncertainty exists regarding the quantitative census presented here.

Source: Peter W. Crockford ^6, 7 , Yinon M. Bar On, Luce M. Ward, Ron Milo, Itay Halevy, Current Biology, October 11, 2023, DOI: https://doi.org/10.1016/j.cub.2023.09.040.

An article by Elizabeth Pennisi was published in Science which is a decent summary of the paper. The Science review reports that the number of cells alive today amounts to 10³⁰ cells with most of them cyanobacteria. The total number of cells to ever have lived is estimated to be between 10³⁹ and 10⁴⁰. The article goes further and says that the resources on Earth cannot support more than 10⁴¹ cells.