By BILL KOVARIK and KEN WARD JR.
A young Virginia Tech scientist is standing up in a canoe, gesturing at the river around him. "Imagine this," he says. "It's 300 million years ago. There are no trees – just giant ferns. There are no birds or flowering plants. There are no dinosaurs – they won't show up for many millions of years. Everything about the landscape is utterly different. But in the river – the fish – are the same then as they are today."