Randomness in Speciation and Darwin's Theory of Evolution

Since school days, it has been taught to us that natural selection is the primary reason for the origin of species. Only 'fit' individuals survive in a particular environment. That is, it means that that there are certain characteristics needed for survival in a particular environment. So, if natural selection had played its role well, there can be only one species in a given environment - one species of bacteria, one species of a plant, one species of a spider, one species of a mammal etc. But this doesn't seem to be the case. Often several species cohabit an environment. So, it becomes obvious that natural selection cannot explain the 'origin' of species. This has been a contentious issue among evolutionary biologists since long and a recent study probably has revealed the underlying 'fact'. See the nature article. Or, read this New Scientist article which explains the issue in layman terms. According to this study, the origin of species is a random event. A rare event triggers change and a group of individuals in a particular species become reproductively isolated. These isolated group of individuals then gradually change, adapt by natural selection and form the new species.

I think this completes the theory of evolution. A rare event triggers the formation of a new species. This species then adapts to the environment and forms a new species. It seems like randomness is an important aspect of life! Nothing can be predetermined as some claim.

ஏனோ வெளிநாடு சென்று புகழ்பெற்ற இந்தியர்களை தலையில் தூக்கிக் கொண்டு "இந்தியர் அறிவாளி" என்று கொண்டாடும் பெருவாரியான மக்களை இன்று காண்கிறோம்.
சற்று சிந்திப்போமே ஏன் அவர்கள் இந்தியாவிலேயே சாதிக்கவில்லை என்று.
சற்று சிந்திப்போமே ஏன் இந்தியாவிலேயே வசிக்கும் 100 கோடி மக்களில் பெருவாரியானவர் சாதிக்கவில்லை என்று.
அல்லது ஏன் தான் நாம் மற்றவர் நம்மை அடையாளம் காணும் வரை பொருத்து இருக்கிறோம்?

English translation: There are great many number of people today, who cite examples of Indians who have achieved in foreign nations and claim the intelligence of Indians. Let us think why these people did not achieve it in India. Let us think why, of the 100 crore people, there are not many achievers. Or, why do we at all wait until a foreign organization identifies the talent in the Indian talent pool?