Abstract: Across the vastest scales of time and space, biodiversity reveals staggering variability, with species numbers differing dramatically among otherwise similar groups of organisms. Previous studies have shown that species traits, such as physical characteristics or ecological roles, often fail to explain these patterns. This dissertation explores whether emergent, population-level processes influence species formation and extinction rates, thus addressing a core question in evolutionary biology: how and why did life become so diverse? Specifically, I investigate whether sexual selection intensity (Chapter 2) and population-level persistence over decadal timescales (Chapter 3) or millennia (Chapter 4) drive diversification rates at million-year timescales. I also show how mixing different levels of organization, like species and populations, can severely bias inferences on evolutionary rates across millions of years (Chapter 5). Finally, I present an open-source tool for teaching evolutionary biology through an interactive, data-driven framework (Chapter 6). I conclude that a comprehensive understanding of Earth's biodiversity dynamics demands the integration of evidence across a wide array of disciplines.