Miss Marmelstein —
disclosure: educated years ago in physiology, genetics, general life sciences.
Please note that “species” is an important word. In general terms the ‘boundary’ of a species is what species A can sexually reproduce with and produce fertile offspring. Cats cannot mate with dogs, and get pregnant ... because they are different species. Simple.
Darwin correctly noted that WITHIN a species, natural selection does cause the most viable members of a species’ population in a given environment to produce the most viable, surviving offspring, generation over generation — because the offspring won the genetic lottery over time/generations, and had the longest necks, best eyes, longest fur, etc. But even these seemingly unique offspring could still mate with and produce fertile offspring with other members of the SAME species who has short necks, weak eyes, and short hair. Darwin MISSED it when trying to demonstrate the evolution of new SPECIES due to environmental pressures on a population. Even modern science/genetics ‘knows’ that environmental stress does NOT cause species A to give birth to Species B.
Look at it this way: Darwin observed the phenotype and reached conclusions about the genotype. WHAT??? He looked at feathers, beaks, tails, colors and decided these were new species unique to Galapagos. Nope; not in genetics. The weird birds of Galapagos could still have mated with their peers no the mainland. *IF* one were to apply Darwin’s metrics and criteria for identifying and segregating species to humans, then a tall blonde swede with blue eyes would be a different species than a dark-skinned, short, black-haired, brown-eyed Amazon pygmy. Nope — all humans.
I’d suggest you read Darwin ‘knowing’ that he was wrong, and he even doubted he was right.
*IF* you are a genetic nerd or deeply interested in this topic, I suggest you read. “The Language of God” by Dr. Francis Collins. He is a triple PHD who was raised atheist, led the project to decode the human genome (successfully to a narrow depth), and exited the project understanding that what he had previously believed about the origins of life and species was all wrong.
https://www.amazon.com/dp/B000NY12E6/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1
I have always loved genetics. Thanks for sharing.