Why would evolution—which is supposed to weed out harmful traits and promote helpful ones—allow this gene to persist? That’s what this book is about.
Note: this is the Key Question.
ever bitten down on a raw habanero pepper, you probably felt like you were being poisoned. And you were. That burning sensation is caused by a chemical called capsaicin. Mammals are sensitive to it because it tickles the nerve fibers that sense pain and heat, but birds aren’t—and that goes to show just how clever old Mother Nature can be when she’s doing the evolution dance.
Note: fetlocks
TOXOPLASMA GONDII IS a parasite that can infect just about every warm-blooded animal but can reproduce in a way that guarantees its survival only in cats. T. gondii reproduces by copying itself during the life of its host, but it’s only in cats that it undergoes sexual reproduction,
Note: toxoplasmosis...cat/sheep/horse/monkey
Note: healthy host