When I searched for this, I found there to be some debate on it (isn't there always?): https://www.pnas.org/doi/10.1073/pnas.1517943113 https://www.pnas.org/doi

When I searched for this, I found there to be some debate on it (isn't there always?): https://www.pnas.org/doi/10.1073/pnas.1517943113 https://www.pnas.org/doi/10.1073/pnas.1517943113 https://arstechnica.com/science/2016/01/why-was-most-of-the-earths-coal-made-all-at-once/ https://arstechnica.com/science/2016/01/why-was-most-of-the-...