A research team has tested a hypothesis in paleo-ocean chemistry, and proved it false. Many researchers attribute the delayed diversification and proliferation of eukaryotes to very low levels of zinc in seawater. But after analyzing marine black shale samples from North America, Africa, Australia, Asia and Europe, ranging in age from 2.7 billion years to 580 million years old, the researchers found that the shales reflect high seawater zinc availability....