/sci/ - Science & Math

>>15873770
It's not that long honestly.
Though to answer your question, I'd wager it was a result of most life ostensibly being confined to hydrothermal vents and other somesuch nutrient sources, thus most life staying around these sources until it developed the metabolism necessary for surviving outside of hydrothermal vents. Then, they'd need to reach the surface and develop photosynthesis. There also might not have been enough nutrients dissolved in the primordial water column (particularly bioavailable carbon) for most life to radiate outside of the deep sea.