How do languages evolve?

Language evolution has two aspects. Culturally, languages change over time like biological species (a "descent with modification" in tongues). Dialects diverge geographically, sound shifts occur, grammar and vocabulary drift, and through contact/borrowing languages transform and split into families. For instance, Latin diversified into the Romance languages. Biologically, humans have evolved neural adaptations (e.g. FOXP2 gene changes) that enable speech and language learning, but specific languages are culturally inherited. In essence, cultural evolution creates language diversity: communities pass on linguistic conventions which gradually change. These changes accumulate, so "Latin" gradually became Spanish/French, etc. Meanwhile humans' evolved brain capacity for complex language made this possible.