Figure 7.

An analogy between the history of trains and biological evolution, presented in a form resembling Figure 2. Due to the many major transitions in train development, it would be a challenge to examine a modern-day Shinkansen and deduce in a “top-down” manner the components of the first train. While the materials that trains are built from have changed over time, their purpose and functions have remained constant. By analogy, the biological components that life uses today may be different from the biological components at life’s emergence, but the processes—the four pillars of lyfe—have been conserved. Shinkansen image: Daylight9899 (Wikimedia Commons).