To describe this new state of life, I suggest a contraction of the term "anima-materials" -- "animats." This term has previously been used to describe adaptive or cognitive systems capable of robust action in a dynamic environment. The goal of these systems involves the creation of higher levels of cognition from many smaller processes. Many scientists who work in this field appear ready to dismiss chemical sentience as smaller and simpler than anything they would consider smart. But we must not assume that minds are built from mindless stuff. Chemical intelligence can manifest as the ability to catalyze a single chemical reaction. It is a dangerous, and possibly terminal, error for the children of carbon to dismiss the power of pure electron fire. Much of our fear of bioterror is based on the power (chemical intelligence) of a single molecule that allows it to block a single metabolic reaction inside the human body.
Better to heed Bertrand Russell's prescient warning that "Every living thing is a sort of imperialist, seeking to transform as much as possible of its environment into itself." Russell goes on to use the term "chemical imperialism" as the driving force for biological life. The obvious corollary to this warning is that chemical imperialism spawned human intelligence, not the other way around. Therefore, the definition of an animat as a living material should have primacy over any definition involving more complex cognitive functions. If we accept this logic, the creation of the first BTM interface by nanobiotechnology will require a new operational definition for the living state.
To expand the chemical franchise of the living state we must first deconstruct biology. The Human Genome Project sold us the concept that DNA is the chemical basis of life. But, in fact, that is not true. DNA is the result of life, not its cause. Our genetic code is the crowning achievement of biochemistry, not its progenitor.
It is crucial to keep this distinction in mind when considering the concept of animats. Life is not defined by DNA but by a continuous chemical struggle against entropy. The second law of thermodynamics tells us that all natural systems move spontaneously toward maximum entropy. By literally assembling itself from thin air, biological life appears to be the lone exception to this law. The gaseous molecules snared by plants during photosynthesis were once free to roam the entire atmosphere of Earth. Plants -- Earth's primary producers -- fix gas molecules from the air and minerals from the water into sugars and proteins. Humans eat the plants, or we eat the animals that eat the plants. Now those molecules that were free to roam the skies and waters must be where you are, go where you go, and do what you do. Clearly, the atoms in your body have experienced a radical reduction in entropy. But thermodynamics takes the full measure of the physical world. What little biology can build is barely visible against the chaotic horizon generated as the sun exfoliates into space. Like a tiny windmill in the solar hurricane, the wheel of life is turned by a unique set of chemical reactions that capture and channel the least part of that storm of dissipating energy into further cycles of replication. Biological life is a tiny stowaway on the entropy-powered craft of our solar system.
Life, then, is not based on DNA but on a chemical programming language spoken by a discrete set of biomolecules. This language directs the set of operations necessary to assemble the next generation of biomolecules. DNA or RNA, the genetic material, stores the directory of available biochemical operations but does not execute them. The program steps for replication are executed by a set of protein catalysts collectively known as enzymes. It is probable that the first biological life forms were RNA molecules capable of both catalytic replication and data storage -- so-called ribozymes. Through evolutionary time, RNA generated two biochemical subroutines, proteins and DNA, to carry out some of the operations of replication and data storage with greater efficiency. Yet a cursory look at the molecular biology of the cell proves that RNA retains its central role. If life is viewed as a discrete set of chemical operations, then nanofabricated components that directly interface biological and materials chemistry must create the possibility of new life forms. These nanofabricated components are, in fact, the next generation of self-replicating systems: not enzymes but animats.
One could argue that it is too early to be talking about animats. It is easy, and reassuring, to dismiss even the most advanced nanobiotechnology systems of the near future as mere devices. But if biological evolution is any guide, that viewpoint is both specious and potentially catastrophic. During the 3-billion-year operation of the algorithm called evolution, revolutionary new adaptations often began as trivial events. A small genetic mutation resulting in a slightly altered protein that provides an incremental, almost trivial, enhancement to catalytic function.
Thermal tolerance is a classic example. A mutation to the DNA sequence translates into a modified physical structure for an essential protein. This new structure has enhanced thermal stability, which means it retains enzymatic function at a higher temperature than the original. As a result, the mutant is capable of 100 percent catalytic efficiency in climates a few degrees hotter than normal. This change in protein structure will only involve the rearrangement of a few atoms, making molecular evolution the original nanoengineer.
Over time, the heat-tolerant progeny of the original mutant may be able to migrate into a warmer climate: say, move down the Sierra Nevada into Death Valley. But it takes thousands of reproductive generations or more for this migration to actually occur. The original mutation will not become essential for a hundred thousand, or even millions of years. Evolution covers enormous distances one angstrom at a time, which means it is almost impossible to catch an adaptation at the exact moment, or even in the exact generation, that it becomes essential for survival. Likewise, it is highly probable that the BTM interface will evolve from smart material to living material. This means that, in order to find the moment when the first animat appeared on Earth, we will have to backtrack from the future. Or be watching the present very, very carefully.
Based on this evolutionary model, it is highly unlikely that animats will spring fully grown upon the Earth. It is much more likely that animats will initially evolve as part of a larger biological system. In order to identify the first true manifestation of a living nonbiological material, we must develop a definitive test to distinguish an organism that is at least part animat from one that carries a smart material designed simply to assist or enhance life function.
This brings us to the Third Law of Nanobotics: The carbon barrier will be eliminated when humans create the first synthetic molecular device capable of changing the state of a living system via direct, intentional transfer of specific chemical information from one to the other.
This law formalizes the concept of animats and leads directly to the "Animat Test," which is designed to identify the moment in time when life on Earth evolves to include both biological and nonbiological materials -- the date when we break the carbon barrier.
Next page: The test: Can all critical information be stored in an entity's DNA and RNA?