Bassem Hassan, Scientific Director and Deputy General Director at the Paris Brain Institute, examines what we all have in common: our individuality.

About Bassem Hassan
"I’m the Scientific Director of the Paris Brain Institute, and my research concerns how the brain develops.

I am a neurobiologist and the Research Director at Inserm, a public scientific and technological institute dedicated to biomedical research. My passion is to understand the fundamental mechanisms of the development and differentiation of the nervous system. My lab studies the genetic mechanisms that regulate the development of the nervous system."

Why we are all different

The idea that our DNA is not the beginning and end of what makes our brains the way they are can be understood through thought experiment, and asking whether the data exists to answer that question. Monozygotic twins in humans and genetically identical individuals in any other animal species, for example shrimp-like species, literally have exactly the same DNA. Yet, remarkably, despite the fact that monozygotic twins or clones of a certain species of animal are more similar to each other than they are to everybody else, they’re not actually identical, even in their external appearance. They have the same DNA but they are not identical to each other. That alone tells us that our DNA encodes our development and much of what happens to us in life, but it does not determine it. The alphabet encodes all the words in a different language but it doesn’t determine what those words are – and new words appear and disappear all the time in different languages.

This tells us that even if you have an immutable set of instructions to play with, the forming elements, and then the instructions that those elements form, are not deterministic. They are not predictable with 100% accuracy. So that’s the difference between encoding and determining something. A blueprint determines, say, the electrical wiring circuit of an apartment. If I give you the blueprint, you will make an electrical circuit of that apartment exactly the way it is now. The blueprint of DNA encodes the information necessary for the brain wiring programme to run itself.

Key Points

• Our DNA encodes our development and much of what happens to us in life, but it does not determine it.
• Many of the processes that are encoded in the DNA have randomness built into them.
• Our innate tendencies shape the environment we choose to live in, and the environment we live in then feeds back on our innate tendencies in this ever-continuing interactivity.