ABSTRACT
When Darwin published the Origin in 1859, his thesis was straightforward: Plants and animals vary in their abilities to survive. The fittest pass on key traits to more offspring than the rest. So even slight advantages spread. As variations accrue, useful traits are elaborated and accentuated, and new species arise: “If a variety were to flourish so as to exceed in numbers the parent species, it would then rank as the species, and the species as the variety; or it might come to supplant and exterminate the parent species; or both might co-exist, and both rank as independent species.”1
