I was wondering if researchers have given any thought to the idea that in the same way that disease devastated human populations after the European discovery of the Americas, perhaps disease was a contributing factor in the demise of much of the fauna of the Western Hemisphere. Could domesticated animals traveling with the humans, or maybe wild animals making use of the same pathways, have carried pathogens so alien to the native populations that they perished?

Bob Stewart
Florence, Mass

Couldn’t most of the life-threatening damage have been caused by excessive radiation? That is, larger animals would have taken bigger doses—especially with forests dwindling—while smaller animals could more easily have found shelter.