Since Europeans began to travel the globe, hundreds of cultures have disappeared. Diversity is not greater but diminished since the competition started. If I took a breeding pair of each of these kinds and placed them in a large preserve and allowed natural selection to work unhindered for 50 years, I would not, in fact, have more types of dogs at the end of my experiment. Yes, for the concept does explain how certain species can come to predominate. No, it resulted in less.
Natural selection works in a negative fashion to actually limit diversity.
A few days ago I heard a report on public radio describing the alarming loss of native languages occurring throughout the world today. The host stated that 95 percent of the languages present today will become extinct during the next 100 years. Chinese, English, Spanish, and French have come to dominate because of world trade and the universal availability of the radio. Also, modern governments try to unify their countries by teaching one language in the schools. Parents who speak a language with few speakers teach their little ones a tongue that is widely recognized so that more opportunities will be open to them.