1900 - 1975
The groundwork that I had to do before I could explore the answers involved acquiring a basic understanding of what is meant by the word "species" and how we would be able to recognize if and when a new species emerged from Homo sapiens. Much of that groundwork was provided by the great geneticist, Theodosius Dobzhansky. His publication in 1937 of Genetics and the Origin of Species provided a framework for evolutionary biology, called the modern evolutionary synthesis, that is still meaningful today.
He pointed out the apparent paradox that if we were able to assemble all of the organisms that ever existed, it would constitute a seamless continuity making it difficult if not impossible to create a classification system of different species. The fact of the matter is that many types of organisms have become extinct—in fact most of them. This has created discontinuities between types of organisms enabling the ability to define species and categorize them.
Nonetheless, evolution is gradual and continuous which complicates my task in defining the answers.
Click on links to other players in my journey below.