Share this story Close X Switch to Desktop Site  How the dance
of predation upends ecology models  Not all predators are equal,
and neither are prey. When lots of genetic variety allows two
species to co-evolve rapidly, reports a new study, both their
population numbers and their evolutionary fitness levels
fluctuate, defying traditional ecological models.  A female
Canada lynx heads for the woods after being released near South
Fork, Colo. in 1999, a year before the species would be declared
a threatened species.  AP Photo/Jack Smith  About these ads  The
primordial two-step of predation and predator-avoidance has
driven evolution since long before our hominid ancestors
abandoned knuckle-walking for the upright posture that let us
scan the savannas for dangerous cats, who were meanwhile
learning more effective ways to flatten themselves and stalk
prey.  A hundred years ago, when ecologists began to study how
predation shaped populations, they found that many relationships
followed a logical cycle: rising pre