In her new book, Hannah Critchlow, Science Outreach Fellow at Cambridge’s Magdalene College, tackles two of the great unanswered questions: whether nature or nurture has the upper hand, and whether human beings can be said to have free will.

Presenting her account of the current state of neurological and genome research, she enthusiastically reports that “the latest neuroscience breathes new life into the concept of fate by situating it at the core of what we increasingly believe makes us who we are: the brain."

Her findings might initially make depressing reading, as they suggest that, by the time we’re born, our DNA has already decided on the kind of person we’re going to be. Predispositions to such conditions as depression, obesity and addiction are basically hardwired into our brains. The decisions we make will be strongly influenced by characteristics inherited from our parents, as well as the unconscious preferences common to our species (such as the ability to smell a mate with a contrasting immune system, giving offspring broader resistance to disease).

Given the mammoth amount of work it does every second, the brain doesn’t like to expend precious energy creating new neural pathways, preferring instead to interpret new information in terms of our established biases. So, thanks to “a combination of species-wide biological constraints and our own idiosyncratic blend of genetic inheritance and cognitive biases”, our beliefs and actions are rooted in a perception of the world which is not under conscious control and which varies from person to person. It’s a restriction which can keep people stuck in a cycle of self-destructive behaviour as easily as it can prevent us updating our opinions in response to new evidence.

Critchlow is at her most compelling in the chapters dealing with belief, which are based on “the most awe-inspiring results” in current neurological research. But it would be a mistake to think that our paths through life are completely fixed. Environmental and socioeconomic factors can mitigate our genetic destiny, at least to an extent. There is enough flexibility in the brain for “disordered” or negative ways of thinking to be coaxed in a healthier direction, particularly when it’s taken into account that, as we have seen, “reality is not an objective and immovable concept”. Critchlow notes especially positive results for MAP (mental and physical) training to combat depression.

Although immersed in the microscopic world of DNA, neurons and synapses, Critchlow is most concerned with society as a whole, arguing that “we need a compassion-based mindset more than ever”. Towards the end, she asserts that, based on what she’s learned, societies can be “collectively nudged” towards healthier, more altruistic behaviour. And this isn’t just an opinion from the crank fringes: the UK Government set up a Behavioural Insights Team which thinks along the same lines.

For a book that drives home what slaves we are to our dopamine receptors, and explores the extent to which our “fate” is governed by unconscious forces over which we have only limited control, it’s an unexpectedly upbeat and welcome conclusion.