A global timetree of life (TTOL) was synthesized from 2,274 studies representing 50,632 species, revealing a consistent pattern of diversification. The TTOL shows that species diversity has mostly been expanding, with a constant rate of diversification in eukaryotes. The study identified and avoided potential biases in previous analyses, such as low taxon sampling and small clade size. The TTOL suggests that speciation and diversification are driven by random events, while adaptive change is a separate process. The rate of diversification did not decrease over eukaryote history, and the observed diversification closely matched a simulated pure birth-death model. The TTOL also showed that the time-to-speciation is approximately 2 million years, consistent across different groups. The study found that speciation is influenced by the time two populations are isolated, with genic incompatibilities accumulating over time. The results suggest that diversification is driven by random environmental changes and genetic events, with rate constancy consistent with the fossil record. The study also highlights the importance of avoiding stem branch time in diversification analyses, as it introduces statistical noise. Overall, the TTOL indicates that the diversification of life is expanding at a constant rate, with some small clades showing evidence of decline or saturation in diversification rate. The findings suggest that speciation and adaptation are temporally uncoupled, with adaptive change being a separate process from diversification. The study provides new insights into the mechanisms of speciation and diversification, emphasizing the role of random events and environmental factors in shaping the tree of life.A global timetree of life (TTOL) was synthesized from 2,274 studies representing 50,632 species, revealing a consistent pattern of diversification. The TTOL shows that species diversity has mostly been expanding, with a constant rate of diversification in eukaryotes. The study identified and avoided potential biases in previous analyses, such as low taxon sampling and small clade size. The TTOL suggests that speciation and diversification are driven by random events, while adaptive change is a separate process. The rate of diversification did not decrease over eukaryote history, and the observed diversification closely matched a simulated pure birth-death model. The TTOL also showed that the time-to-speciation is approximately 2 million years, consistent across different groups. The study found that speciation is influenced by the time two populations are isolated, with genic incompatibilities accumulating over time. The results suggest that diversification is driven by random environmental changes and genetic events, with rate constancy consistent with the fossil record. The study also highlights the importance of avoiding stem branch time in diversification analyses, as it introduces statistical noise. Overall, the TTOL indicates that the diversification of life is expanding at a constant rate, with some small clades showing evidence of decline or saturation in diversification rate. The findings suggest that speciation and adaptation are temporally uncoupled, with adaptive change being a separate process from diversification. The study provides new insights into the mechanisms of speciation and diversification, emphasizing the role of random events and environmental factors in shaping the tree of life.