Technological convergence is a theory which refers to the tendency for technologies that were originally unrelated to become more closely integrated and even unified as they develop and advance. The concept is roughly analogous to convergent evolution in biological systems, such that (for example) the ancestors of whales became progressively more like fish in outward form and function, despite not being fish and not coming from a fish lineage. In technological convergence, a cardinal example to convey the concept is that telephones, television, and computers began as separate and mostly unrelated technologies but have converged in many ways into interrelated parts of a telecommunication and media industry underpinned by common elements of digital electronics and software.