What concept did Charles Darwin propose regarding species?

Charles Darwin proposed that all species descended from a common ancestor, forming the basis for the theory of evolution through natural selection. This concept emphasizes that species are not fixed and that they share a lineage with others through evolutionary processes. Over time, species adapt to their environments, leading to diversification and the emergence of new species from a common genetic pool. This idea supports the unity of life, where diverse forms of life have evolved and adapted from ancestral connections, rather than being static entities or created separately. The understanding of common descent is fundamental to modern biology and helps explain the diversity of organisms we observe today.