Memory is one of our most treasured capabilities. We build our identities and our cultures with it. Human memory and the things we do with it can be extraordinary, especially when we have not had too much to drink. Yet if we have a broad view of memory as the ability to retain information for later use, it is not exclusive to human beings, but foundational to life itself.
The first living systems, perhaps those hypothesised for an RNA world, would have been distinguished by (among other things) precisely this: an ability to record in their chemical codes, and reproduce later, those properties which enabled them to thrive. And all organisms alive today retain subsystems that were first encoded during the early days of DNA-based life roughly four billion years ago. Every moment your cells are replaying routines that ran in the Archaean aeon. Most of the ‘memory’ in the world continues to be entirely unconscious and does not even require a brain. The immune system is a good example: it ‘remembers’ the viruses, bacteria and other nasties that you’ve encountered during your lifetime: if you encounter the same pathogen again, the ‘memory’ cells will recognise it and your body will be able to mount a faster immune response. Plants do this as well as humans and other animals.