found fragment

From the 'drafts' folder of my work email, addressed to my gmail address but unsent:

The co-evolution of dragons and humans is analogous to the arms race between weapon and armor makers of various nations. Just as plate armor is invented to deflect weapons that were deadly to the users of chain hauberks, so did the genetic code of dinosaurs invent new ways to defeat their proto-hominid enemies. And vice versa. Both genus draco and genus homo evolved cognition and metacognition (i.e. magic), though the potentialities for the two lines are different. Some dragon species seems to have a greater capacity for rational thought than their human [fragment ends]

I have absolutely no memory of writing this passage. Does it look familiar to any body? Maybe I cut and pasted it from somewhere else. That "And vice versa." as a separate sentence looks like something I would write, but I'm not entirely sure.