Matteo Mariani

For over a century, evolutionary biology has explained genetic variation largely as the result of random mutations, filtered over time by natural selection. This view has been extraordinarily successful. Yet, when we look closely at the molecular life of the cell, a more nuanced picture begins to emerge—one in which the past may play a more active role than we usually imagine.

Inside every cell, DNA is not simply a static record. It is continuously read, copied, and transformed through interactions with RNA and a variety of molecular processes. Some of these processes can copy RNA back into DNA, while others allow cells to recognize and align similar sequences across the genome. Together, they create a dynamic environment where genetic information is not only stored, but also revisited and rearranged.

This raises an intriguing possibility: what if cells can, in a limited way, reuse fragments of genetic information that proved useful in the past?

A useful metaphor is that of writing. If evolution relied only on random mutation, it would resemble a text modified by accidental typos—letters changed here and there, most of them meaningless, a few occasionally improving the sentence. But what if, instead, the system sometimes works more like an editor with memory? Instead of random letters, it reuses words, phrases, or variations that have already been tested, selecting alternatives that “fit” within an existing context—more like choosing a synonym than introducing a random error.

In this view, the genome may contain not just active instructions, but also traces, fragments, and echoes of past solutions—molecular “notes” that can be revisited, recombined, and tested again under new conditions.

My research explores this possibility. The central idea is that mechanisms involving RNA activity and sequence similarity may allow cells to draw on this deeper layer of information, shaping how new genetic variation arises.

If such processes play a role, even occasionally, they could extend our understanding of evolution. Variation would still involve chance, but it might also reflect a form of molecular memory—where the past quietly informs the possibilities of the future.