Last week my brother asked my friend a common question, “If you could go back in time and kill Hitler as a baby, would you?” After asking, he pointed out that killing Hitler might not save the world from the kind of hardship Hitler created. Perhaps if the world hadn’t learned the lessons it learned during WWII, it would have been forced to learn them some other way. I told him I followed his argument, but I made an additional point and said that neither he, nor any of his friends would be here today if he were to go back and kill Hitler. I went on to say that no one under the age of 60 would be here today if Hitler had not existed. My brother and our friend disagreed with me on this point. Sternly. It didn’t sound right to them. But after a few minutes I was able to convince them otherwise. Let’s see if I can convince you.
To start we have to discuss the nature of stochasticity. Stochastic processes are processes where there are so many moving and interacting parts that it is impossible for a human to observe a starting state and make a precise prediction about how things will end up. They are the purview of thermodynamics and chaos theory. They involve phenomena that appear to vary in a random or chaotic manner and include processes like the growth of a population of bacteria, an electrical current fluctuating due to thermal noise, and the movement of a molecule of gas. Many processes are stochastic. Stochastic models are used in chemistry, physics, biology, computer science, economics and many others.
You have heard of the “butterfly effect” right? The idea is that one flap of a butterfly’s wings can alter wind current and atmospheric pressure in a way that could potentially be responsible for a storm on a different continent. Now adding a butterfly wing beat in South America is not going to change the weather in Africa a second later. However, as more time passes, the butterfly’s tiny push will have effects that ripple outwards into the environment. As you can imagine the existence or nonexistence of WWII would have profound and far-reaching ripples.
Most of what goes on inside our cells is stochastic. Our brain activity, and our reproductive biology are also highly stochastic. This means that the butterfly effect comes into play whenever we make a decision, and whenever a person is conceived. So a major change in the Earth’s sociopolitical timeline is going to have significant repercussions that reach down to cellular and molecular scales. It is pretty clear to see that miniscule changes in stimulus reception by the brain have cascading effects on downstream biological outcomes. Outcomes like mate choice, fertilization, and conception.
Consider this. A healthy man’s ejaculate contains hundreds of millions of sperm. That means that even a slight perturbation during the act of sex (a small change in the force of thrust, or a fraction of millisecond change in timing) could easily result in a different sperm fertilizing the egg. That sperm decides 50% of the DNA and determines whether the offspring is male or female. It is very clear that tiny variations at a molecular level can have profound consequences.
If you were comparing two timelines, one where you friend says a single extra word at parting, and another one where he doesn’t, that difference will alter your trip home to see your spouse. That word may have delayed your departure by less than a second, but nevertheless it could result in a chain of causal events that will slightly throw off the time you arrive home. This in turn could throw off a reproductive event. But the act of sex aside, miniscule variations in perceived events play roles in how the information in our brain is processed. Since our brains process stimuli stochastically there is no telling what kind of difference a single word can make. It could cause a person to make different decisions, pursue different interests, and even develop a different personality.
I have heard people talk about WWII for as long as I can remember. I have heard the word and related words thousands of times. I have taken semester long history courses on the topic. I clearly would not be the same exact person I am today if none of this had occurred. But even more to the point, everyone I have been exposed to has had the same experience. Our personal identity is very fragile. It is a tiny twig at the end of a tremendous branching structure that has branched innumerable times since our birth. Taking a slightly different branch at age four could create irrevocable changes to who we are as a person that are then compounded over time.
Now you may point out that there are hunter-gatherer groups that have been relatively isolated from the rest of the world, that they would not have been affected much by WWII, and that people born within such groups would still be alive today if WWII had never occurred. But I disagree. The world wars altered plane and boat schedules dramatically and spotting planes and boats would have affected the lives of hunter-gatherers when they saw them. Add to this that there is no tribe on earth that has been completely isolated from outside contact, and that a single visit, or even just a small change in timing in such a visit, would have grossly altered the cascade of neurological and reproductive causality for the people of the tribe.
If the 1940 had played out differently, I would not be here for one million reasons. Let me give you a few straightforward ones. A few minutes after my paternal grandfather left his station abord a Navy ship to check his mail during WWII, a bomb destroyed his deck and most of the men that worked there with him. If he had not decided to check the mail on a whim, I would not be here. He then met my grandmother after the war. If the war had never occurred, they likely would never have met or gotten married. As another example, my father got to know my mother due to chance. He noticed that she was talking while walking along an elevated rocky surface and that the rock looked slippery. He went below her, and when she fell, he caught her. They got to know each other because of this uncommon, relatively improbable interaction. Many couples meet under improbable circumstances.
Now there are people that were born before World War 2 that are still alive today. So it is not possible to generalize this concept to everyone alive in 2021. However, I would take the general line of reasoning expounded above to conclude that if a prominent historical figure who lived before the 20th century (Shakespeare, Napoleon etc.) had never been born that absolutely no person living today would still be alive because of the far-reaching nature of stochastic processes. That is not to say that the world would not be incredibly similar to the way it is today. It is just to say that people who look identical to us, with our names, our DNA, and our personal identities would not be here.
I posted the question that this blog entry addresses on Quora. I received a few different answers from people with advanced degrees. They seemed to believe that if Napoleon Bonaparte had never been born, that they, their friends, and everyone else would still be alive today. I’d like to think that if they read this blog entry that they would be convinced otherwise. Specifically, I asked:
If a prominent historical figure who lived before the 20th century (Shakespeare, Napoleon etc.) had never been born would anyone living now still be alive today given the nature of stochastic processes?
A man with a Ph.D. in statistics answered:
“That’s a strange question. I wouldn’t expect the absence Shakespeare to have much effect on whether you or I would be here.”
So far we have asked how much an important person would alter history. A similar question would ask if an unimportant person can appreciably alter history. One might ask, “would I be alive if the least causally important adult person were erased from history.” If that person lived more than 1000 years ago, then I believe that I would not be alive. It might be impossible to know, and you might need a computer the size of (identical to) our universe to run a proper model of it to test the prediction.