What Can a Simple Oil Droplet Teach Us About Life?

I study abstract simple systems that are far removed from biology, yet demonstrate some phenomenology of living systems. Small oil droplets running around in a dish are using purely chemical and physical mechanisms to move, explore, and modify their environment. By moving, the droplets are able to avoid for a longer time a kind of chemical death where they become mired in their waste products, shutting down their metabolism and stopping movement indefinitely. In a way the motile droplets are actively avoiding equilibrium and while doing so appear to demonstrate lively behaviors, such as droplets circling or following each other in a kind of dance. Beyond these life-like behaviors, the droplets bear little similarity to living organisms. Existing natural organisms are not oil based and they do not use the same mechanism of movement. In this sense the droplets could be termed artificial. Such simple non-living artificial systems capable of living properties may be useful as a technology, especially since they do not need to contain DNA and therefore do not have many of the risk and ethical concerns of for example genetically modified organisms. Several diverse types of chemical droplets show self-movement, including models that try to capture an essential aspect of the origin of life. The experiments using a primordial tar as fuel to drive droplet movement is an example of this. It has long been considered that self-assembly of the right recipe of molecules into structures that are essentially living cells are all that is needed for life to spontaneously form. However despite over 100 years of experimentation with self-assembled systems, no one has been able to demonstrate the creation of artificial life. The oil droplet system teaches us that some mechanism other than self-assembly may be necessary for the formation of life, in this case that mechanism is self-movement. By this mechanism the primitive cell (or protocell) enters into an active communication with its environment while it searches for resources while at the same time remodeling its environment, much like living organisms do. Another mechanism to avoid equilibrium could be replication. Only by creating such simple experimental models can one begin to test hypothesis not only about the origin of life but also about the very nature of living systems.