Asked by: Tony Young, Bristol
The DNA of any two strangers never differs by more than 0.1 per cent. But that still gives around 10 million locations in your DNA that can vary.
But genetic variation isn’t the only thing that makes you unique. Identical twins share the same DNA and yet they aren’t the same person. Each of us is also shaped to some degree by everything that happens to us after we are born. If you were born an hour later, some of those experiences would have been different for you. And it’s not just you – everyone you have ever met would also need to have been born at the right time and place so that they would grow up to interact with you and produce the memories you currently carry in your mind.
Remember that big snowstorm when you were a child? That memory is part of who you are too. Think of the chaotic sequence of events that led to that storm occurring on that particular day. Now multiply it by the chances that your mother got distracted at exactly the right moment for you to get lost in the department store that time. When you combine the odds of all of these thousands of formative experiences that define you, the probability of ending up with ‘you’ is effectively zero.