"What is it that micro- organisms use iron for?"
"For all their basic chemical functions, just as we do. It's wonderfully useful in speeding up reactions. In fact, it's very rare for an organism not to use iron. It's what separates friendly bacteria from ones that want you dead. Friendly bacteria tend not to need iron. Like those in yogurt, which use cobalt and manganese, for instance. Almost everything that is pathogenic, toxic to humans, needs iron. These organisms mine us for our iron."
"About these friendly organisms.... Were the symbiotic relationships between microorganisms the beginning of specialized tissues? Of us? Was that the point at which Nature had a Eureka moment, when life -- complicated life -- came into being?"
"Let me think about that," Sharon says, and there is a long pause. "I'm not sure we'll ever know, given the nature of the complexity. It's hard to reverse engineer and work out. The problem is, the fossil record doesn't preserve tissue. Unless we come across something that's so primitive, or life on another planet that can help us understand how life arose here...We're still missing crucial points of the story. In high school and university we were taught we got two sets of genes from our parents, yet Ethiopians, for instance, will have 13 copies of a particular gene. How? We just don't know how Creation unfolded on this planet."