Cells are living nanocomputers
The cell is the fundamental unit of biological systems. Complex life begins from a single embryonic cell that divides into two, then four, and so on. Divisions continue according to the program until the entire body plan is complete. These cells communicate across space and time, sharing information and specializing into distinct roles. Neurons for thinking, muscles for movement, and immune cells for defense. Cellular division and differentiation create a distributed network in which each node can receive, process, and transmit information.
Cellular computation shares some similarities with digital computers. Every cell contains two copies of the DNA genome, which store all the information needed for life. When cells activate a specific program (a gene), they make RNA copies from the corresponding DNA template. This is the famous central dogma of biology: information flows from DNA to RNA, and then the RNA is translated into a protein. Similarly, in computers, information flows from the hard disk to RAM, to the CPU. In both systems, computations can result in new requests for information from storage.
How can mixtures of molecules perform computation? When two molecules are required to achieve an outcome, this implements AND logic. If two molecules are valid substitutes for each other, this implements OR logic. Some molecules can modify others to switch functionality, similar to NOT logic. Unlike digital circuits, molecular circuits operate in the face of significant thermodynamic noise: different copies of a single molecule can be in different states at one time, so the output emerges through equilibrium. These principles apply across thousands of components and finely tuned feedback loops, enabling cells to implement robust behaviors and programming at scale.
Biology has developed a remarkable distributed computing system for billions of years. We have only begun to decipher and harness the power of these systems for our benefit!