As of 2017, microfossils (fossilised microorganisms) within hydrothermal-vent precipitates dated 3.77 to 4.28 Gya in rocks in Quebec may harbour the oldest record of life on Earth, suggesting life started soon after ocean formation 4.4 Gya during the Hadean Eon.
Answer: Whether the culprit were too much sunlight or not enough, if photosynthesis stopped, plants would stop converting carbon dioxide -- an air pollutant -- to organic material.
