To see a World in a Grain of Sand
And a Heaven in a Wild Flower,
Hold Infinity in the palm of your hand
And Eternity in an hour
[William Blake, Auguries of Innocence]
Memory works similarly at the very largest and the very smallest scales of life. For both the microcosm and the macrocosm structure is memory.
Viruses are able to attach to and gain entry into living cells because they are encapsulated in a protein coat possessing a predetermined structure and shape which can latch onto particular proteins found on the outside of a cell much as a key fits into a lock. The virus's genetic material can then be injected into the cell hijacking its replication process creating ever more of the virus.
In multi-cellular animals body cells are defended by an immune system which learns to recognize the outer protein structure of invasive viruses and other microorganisms. Once identified, its structure is physically recorded for future use as needed. Subsequently the immune system can produce endless attack cells which possess this prerecorded structure in the form of an adaptive layered defense against the invading pathogen. This is how vaccinations create immunity to diseases for example.
The key insight is that pathogens learn how to gain entry into cells by "learning" the optimal protein structure to do so. Once this learning occurs it is passed down to all descendants--all possess the same successful structure.
An infected organism's immune system subsequently "learns" to recognize these invasive pathogens by memorizing the shape of their outer protein coat. The organism then stores this learning in the form of template cells, which when needed can be replicated in vast numbers to overwhelm an invading pathogen. "Learning" in life's microcosm involves developing and recognizing particular structural configurations.
For the largest structures created by human societies, nation-states and the overall international system, learning also involves structural adaptation. A society's learning and memory are encoded, in part, for long-term storage and usage in the form of institutions and laws which encode the adaptive learned responses of individual level decision-makers into the structure of the political economic system.
For example, at the nation-state level, in the USA, adaptive learning deriving from the experience of the Great Depression was encoded into our political system in the form of newly created institutions such as the Securities and Exchange Commission (SEC) which was created by Congress in 1934 to regulate the stock market and to prevent trading abuses. There were regulatory laws such as the Glass-Stegall Act of 1933. This act regulated the permissible activities of savings and investment banks.
At the global level, adaptive learning from the experience of WWII was incorporated into the structure of the international political economy by the creation of the United Nations. All members of this institution are required to sign its charter which then becomes legally binding upon the signatory nation.
This process allows for the transfer of hard learned knowledge from the minds of the learners into the very structure of society. As those who possessed this knowledge directly pass away, their learning remains viable, potentially forever to benefit futurity.
Thus at both life's microcosm level and at its macrocosm level, learning is encoded structurally. This is for identical reasons: initial learning occurs at the individual level. However, for learning to be passed down through successive generations, it must be encoded in some manner. Encoding learning in structure is a robust technique for long-term informational storage. So both microbes and men (people) have learned to exploit this technique.
Storing information in this manner has both positive and negative implication for large-scale organized human complexities. A clear positive implication is that past learning can be maintained to the benefit of all long after the individual learners have passed from the scene. A negative implication is that the learning may decay over time.
Decay can occur in at least two ways:
1) Forgetfulness. Over time, structurally encoded past learning may simply be forgotten. This might happen because the circumstances to which it is adaptive, seldom or never recur, over a sufficiently long period of time. If eventually the circumstances did recur, the appropriate adaptive response would have been "forgotten" through prolonged disuse.