According to the biological species concept, when the new species no longer can interbreed with the ancestral species, or with the population that it has been geographically isolated from long enough to have allele change significantly enough to prevent interbreeding.
Over time species evolve into new species.
Organisms can evolve into new species over long periods of time through the process of natural selection and adaptation to their environment. This can result in the development of new characteristics and the divergence of populations into separate species.
No, he recognised that species evolve into new species.
Not only can aliens evolve into different species but they can make us into a new species but they may only do that with the correct technology. So the question is how will they do it and how much time will they have?
they evolve to fill new niches
Punctuated equilibrium theory proposes that species evolve rapidly during short periods of significant change, followed by long periods of stability with little evolutionary change. This contrasts with gradualism, which suggests that evolution occurs steadily over long periods of time.
Flies will likely continue to evolve for another 1.1 billion years before extinction. The current species will have gone extinct (replaced with a new species of Fly) long before then.
No one knows what humans will look when they become a new species. It will depend on the type of species that humans evolve into that will determine what they look like.
Probably the toughest thing about discovering a new species is being familiar with the ones that are known well enough to tell if a new example belongs to a new species. So, I would say yes, it is difficult, just because it takes a long time to learn about whatever species you are studying, and get to know it well enough.
New species can evolve through natural selection over long periods of time. However, the process is complex and can take thousands to millions of years due to the gradual accumulation of genetic changes and adaptations. The formation of new species also depends on various factors such as environmental changes, genetic variation, and reproductive isolation.
That depends on what you mean by 'immediate'. Drastic rates of evolution are possible in many species, where mutations are either relatively very common or where the environment results in harsh selection. But nothing will make one species "immediately" evolve into another in one generation, or even two or ten.