We – society – frequently overstep the importance of DNA. “It’s in our DNA” and similar phrases are used every day in conversation. These phrases are so integrated within natural language that they have their own dictionary definitions. But as geneticists, we don’t challenge this enough. DNA is not our destiny; many factors come into play when it comes to how we look, how we act, what diseases we get or don’t get, and ultimately, who we are as people.
The entirety of our DNA – our genome – has all the information required for our cells to make everything that is needed for us to live. The remarkable process of a single fertilised egg can make a whole human but this is only the beginning; the environment, in all its complex manifestations, in which we then find ourselves plays an equal if not greater role in determining who we are. When we speak about the environment this doesn’t just mean the climate we live in or the quality of the air we breathe, but also the societal differences we encounter – the people we interact with, the opportunities we receive, and the choices we make etc – that will have an enormous impact on shaping our future.
We’re all – mostly – the same
Two aspects of DNA need to be considered here; the majority of our DNA that is constant for all humans, and then the very small part of our DNA that varies from person to person. This variation can cause both important differences, for example in disease risk, or superficial variations, for example in hair and eye colour. Sometimes these differences are fixed early on and cannot change, but often they can change during a lifetime due to environmental factors.
The degree to which genetic variation affects an individual is also very different depending on what you look at. For example, what defines your height is predominantly genetic with around 80% of determinants found in your genetic code and the rest depending on environmental factors such as diet. However, more complex outcomes such as an individual’s chance of getting schizophrenia, is estimated to depend on ~50% of genetic determinants, and even this assignment to variance depends considerably on precisely which people are considered and how the estimation happens. In short, most things we are interested in are complex, and genetics is only part of the story.
Genes are only a contributing factor
Taking the example of performance in education (eg, exams), our environment plays a huge role in determining the outcome. If a child is born with genes advantageous for intelligence, this doesn’t guarantee them better opportunities than anyone else. Many environmental factors – and of course luck – help to steer them on this path. The nurturing they receive as a child, attending school everyday and an enjoyable learning environment will all play a big part in what they achieve in later life.
Our genes affect everything we do, from our education to our health, but the reality is that they are only one of many contributing factors. Our environment, including choices made for us by our parents and the choices we make – where we live, how much we eat etc – have similar if not greater impacts on who we will become.
DNA is a fundamental source of information in biology, and variation in DNA is a tool that can be used to understand how this information unfolds in both humans and other organisms. But DNA is not your destiny, nor your core being. For building our identity and behaviours, variation in our DNA can play a role and can influence some of our choices one way or another but ultimately DNA is not defining us. We are.