With respect to evolution, life is a product of chance. It just so happens that nature selected for tribosphenic molars for therians around the same time as it selected for fruit-bearing angiosperms. Organisms with a particular trait were searching for food, and coincidentally a new food source shoots up from the ground to fulfill this need. The (mostly) independent evolution of two different kingdoms of life managed to align at one precise moment to create mammals as we know them today.
A roadmap for evolution is not included with the timeline of history. Individuals are born into the world with a set of selected traits, but at some point, each one was uncommon. Selection began in response to one of these traits, a chain reaction to create the most fit organisms. Having teeth that both sheared like a butcher’s knife and ground like a mortar and pestle became advantageous for therians at some time, allowing them to tear apart their food and take in nutrients at a faster rate. Nature selected for angiosperms at the right time to cause a spike in the number of therians, and by default those with softer dentitions were selected against.
Most certainly, nature on Earth did not predict the incoming asteroid that eliminated the dinosaurs and a wide variety of mammals. Once again, it labeled a trait for surviving mammals as advantageous and began to improve upon it as a result of evolution. But nature chose these characteristics based on the sudden removal of the top predators.
It is not to say that nature doesn’t play an important role in the evolution of populations; in fact, it is responsible for all of it. But chance events have a strong influence on what traits the world decides to keep for the next generation.
Evolving Organisms 