Darwin referred to the origin of species as "that mystery of mysteries," and even today, more than 150 years later, evolutionary biologists cannot fully explain how new animals and plants arise. For decades, nearly all research in the field has been based on the assumption that the main cause of the emergence of new species, a process called speciation, is the formation of barriers to reproduction between populations. But now researchers are questioning the long-held assumption that genetic reproductive barriers, also known as reproductive isolation, are a driving force behind speciation.

Source: Genetic reproductive barriers: Long-held assumption about emergence of new species questioned