universetoday.com
Early Earth Had Toxic Oceans
Researchers from NASA have confirmed that it would have been impossible for advanced life forms, like fish or mammals, to live in the Earth's early oceans because it was such a toxic environment. The scientists studied ancient rock formations, and found evidence of photosynthetic bacteria living as recently as 1.6 billion years ago. This bacteria would have required both sunlight and an environment rich in hydrogen sulfide - this environment would have been quite toxic for air breathing creatures.
Fraser Cain