# Being alive today: the most improbable coincidence?

Think about it; modern humans have been around for at least a couple hundred thousand years.

Yet, your mind, your soul, your very awareness, happens to be "alive" today. If time is a flow, moving forward, and there's really only "now", isn't it an almost impossible coincidence that your lifespan of 70-90 years happens to occur "now"? Why not a hundred years ago? Why not tens of thousands of years ago? Why not a thousand years into the future? No.... Your mind and body are alive today, in the present - the only valid "now".

To me that sounds like too much of a coincidence. In fact, if you take the number of 300,000 years that modern humans have existed, and we take (just for the sake of making this calculation easily understandable) a lifespan of 100 years, your lifespan could have started at any time during those 300,000 years. There's only a chance of 1 in 3000 (0.033%) that the start of your lifespan would coincide with the present. If we add to this a potential/possible 100,000 years of additional "future time" that mankind may have left, then it's even more of a coincidence: 1 in 4000 or a 0.025% chance.

This questions has driven me nuts for years and years. I just can't wrap my head around it.

# EDIT/UPDATE

Just as a general reply; most, if not all of you, seem to focus your response around the probability of me being alive today, and assign the probability of 1 to this; after all, if I'm able to ask this question now, it means I must be alive now.

However, what I'm (even) more interested in, is the coincidence of me being alive today, assuming that time acts like an objective spotlight (gradually passing along, moving into the future) shining at one specific point on the timeline (reaching from the moment of the big bang all the way into at least now, or maybe even the future).

This quarrel, again, assumes that time acts like an objective spotlight, which is important, because, when time would act like a subjective spotlight instead, then (in my mind at least) the probability of a person being alive being 1 whenever he/she asks the question would only make sense if time was not a passing, moving spotlight at all - but instead a fixed dimension, meaning that all time (all moments in history and possibly all moments into the future) would exist all at once, and whatever we're experiencing as the present, is just a subjective representation of this specific moment in time... Which is just something I'm having a hard time with comprehending (which doesn't make it any plausible, of course).

I hope this makes any sense.

Again, thanks for all your contributions.

• This is the ultimate example of the Prosecutor's fallacy (see Wiki). Mixing up two kinds of conditional probability. Essentially, from the fact that the probability that a random birth within last thousand years is you is very low, you incorrectly conclude that the probability for you to be born within last thousand years is also low (but it is 1). Pr(you|time) vs Pr(time|you). – ttnphns Jun 17 '18 at 13:21
• Have you ever had a question why do you even exist? Regardless of time. I think understanding of this is necessary for understanding the answer on this question. – rus9384 Jun 17 '18 at 14:52
• Closely related if not an exact match: Doomsday Argument. – Harry Johnston Jun 18 '18 at 3:05
• Throw 20 dice. Write down the numbers. Show them to me. I'll say I don't believe you got those numbers, because the probability of getting exactly those numbers is smaller then winning the lottery several times over. See the problem? – vsz Jun 18 '18 at 6:16
• This question is also reminiscent of the "anthropic principle" in cosmology. It seems like an amazing coincidence that the fundamental constants of physics created the conditions that allowed life to form. But if they hadn't, we wouldn't be here to contemplate it. Multiverse theories propose that there are many universes that didn't, and this just happens to be one of the lucky ones. – Barmar Jun 18 '18 at 19:57

Your reasoning would be sound if you picked any random human who ever lived and checked whether they would be alive today. This chance would indeed be rather low. (Because today's world population is far higher than ever in the past, the chance is not quite as astronomically low as one might think.)

However, we are not looking at any random human who ever lived. You are looking at R_K (note: R_K is OP's screenname) specifically. Thus, the probability of R_K living today is not an unconditional probability over the entire population in a statistical sense. Instead, this is a conditional probability: we are interested in the chance of R_K living today, conditional on R_K posing the question itself - and a fortiori, this implies that R_K is alive today. And of course, the probability of R_K being alive today conditional on R_K being alive today to ask this question is 1.

This is related to the anthropic principle.

• +1 Right on point. There was also an anecdote from Feynman about this, saying something along the lines of "Tonight I was at the movies and I saw a car with license plate 78893. Unbelievable! What are the chances that, out of all the license plates in the world, I would see that one tonight?" – Ant Jun 17 '18 at 19:21
• Well, note that your asking your questions necessitates the spotlight being on you. The relevant conditional probability now essentially is "what is the probability of my being in the spotlight, given that I am in the spotlight?" And again, the answer is necessarily 1. – Stephan Kolassa Jun 17 '18 at 21:27
• Just to add to what's wrong with your analogy: the "spotlight" is coming from you. In a block theory of time, there is no objective spotlight. Every person sees their own parcel of time as "the special one" because that's the one they're in. So your question becomes, "What the chance that I'm alive during this special time that I am alive (aka, the spotlighted time)." Every person in history could ask that, and the answer is the chance is 100% for all of us. – Chelonian Jun 18 '18 at 0:59
• @FooBar: Not sure if that is a deep philosophical question or just that you missed that the OP's name is R_K. ;-) – Chris Jun 18 '18 at 8:46
• @BЈовић Nothing, that's the point. If you go to a movie, you will certainly see some license plate. A priori, it's unlikely that you will see exactly the licence plate 78893 (try going to the movies tonight and check if you see that one!). But you will see something. So a posteriori is not surprising that you saw that license plate, because you would have seen something anyway. Feynman made this point with a joke. As you can see that is the same problem the OP asked about; a priori it's unlikely, a posteriori is certain. – Ant Jun 18 '18 at 10:10

Shuffle a standard deck of 52 playing cards and look at the arrangement you end up with. Assuming your sorting was completely random the probability of you getting that exact arrangement is about 1 in 8 x 10 ^ 67. What an incredible coincidence! Well not really - you had to end up with one of the possible arrangements and they are all improbable, so an improbable event was guaranteed to happen. Similarly you exist, therefore you have to be alive at some point, and therefore you must be alive at one of the periods of time you could be, even though each is individually unlikely.

It is actually much more likely that a randomly chosen person will be alive now than 10,000 years ago. The world population today is over 7 billion, 10,000 years ago it was something like 5-10 million (Wikipedia).

• It is more likely that a random person would be alive now than exactly 10,000 years ago, however it is less likely that a random person would be alive now than 10,000 or more years ago. – Benubird Jun 18 '18 at 8:44
• @Benubird. Actually, it's both. The Population Reference Bureau extrapolated the world population trends back to prehistory in order to estimate the total number of humans who had ever lived. Their estimate was 108 billion, which suggests that even if we did use the prior probability instead of the conditional probability (which we shouldn't, as user33828 and Stephan Kolassa both point out), there would still be a 7% chance of a uniformly selected human being alive today. (And only about 1.1 billion lived before 8000 BCE.) – Ray Jun 18 '18 at 18:02
• @Ray That's only if you don't count all the people who will be born in the future... – Challenger5 Jun 19 '18 at 1:29
• @Challenger5 True enough, as far as the 7% value goes. But the size of the current population relative to that of 8000 BCE would be remain unaffected by the future population growth. (Everyone knows that all the cool time travelers prefer 3000 BCE. :-) ) – Ray Jun 19 '18 at 6:02
• Fun fact: any good randomly shuffled poker hand is more rare than a Royal Flush. There are 4 combinations of cards that classify as a Royal Flush, but only a single combination that equals your hand. – Alexander - Reinstate Monica Jun 21 '18 at 5:08

The first time I recall encountering this argument was in Alan Moore’s Watchmen, where the probability of what you describe is likened to “events with odds so astronomical they’re effectively impossible, like oxygen spontaneously becoming gold”.

I find the argument similar to the gambler’s fallacy. An example:

In a fair coin toss, the probability of landing on heads (or tails) is 50%. Before we start tossing the coin, how likely do you think it is that the coin will land 20 consecutive times on heads? As you’d expect, they are astronomically low. Also as expected, while making the calculations every consecutive toss we add lowers the probability — landing 10 consecutive heads is less likely than landing on it twice.

But now let’s say we’ve already made 19 tosses that all landed heads. What’s the probability the next toss will also land on heads? The gambler’s fallacy is thinking the previous math applies and the odds are astronomically low. They are not — they are once again 50%. This is because the coin doesn’t care how many times it landed on the same side. It’s not self aware and won’t try to “correct” itself to (what we call) a fair/balanced result. Every toss is statistically independent from another, individually they all are 50/50. Looking at past tosses gives us no information of future results. Statistics apply when the tosses we want to predict are all in the future.

The same happens here.

If centuries ago one asked “what’s the probability of the specific person R_K being alive on the specific time of June 17 2018”, the odds might indeed be astronomically low. But no one asked that question, so the fact you’re alive at this moment is as (ir)relevant as you being alive at any other point in history. They’re all as probable as you having never existed in the first place. If you (or me, or anyone else) had not existed, no one would have known or cared. You are a person, some person, not the specific person someone else was predicting or waiting to exist in a point in time.

The probability of an event X happening, GIVEN THAT IT HAS HAPPENED, is always 100%.

I hear thinking like you give used in many flawed arguments. For example, I once got into a conversation with someone who claimed that the Gospels in the Bible must be frauds, because the people who it is claimed wrote them would have been like 70 years old at the time they were written, and very few people in those days lived to be 70. So if the probability of someone living to be 70 was 20 to 1, then the odds are 20 to 1 that this person could never have written this book. Except, umm, while FEW people in those days lived to be 70, SOME did. Obviously the ones who didn't live to be 70 couldn't have written this book. But no one is saying that he did. We're saying that it was written by someone who DID live to be old. (This doesn't prove that the Bible is true, of course, and that's not my point in this discussion. Just that this particular argument is flawed.)

Look at it this way. The odds against winning the lottery are like 20 million to 1. (Depending on which lottery.) So if you read in the newspaper that Fred Smith won the lottery yesterday, would you say that this story is virtually impossible because the odds against Fred Smith winning were 20 million to 1? No, because we are asking for the probability that Fred Smith will win, GIVEN that he won. That probability is 100%. If you asked me the day before the winning number was chosen what the odds are that Fred Smith will win, I'd say 20 million to 1. But once the numbers are chosen and we see that they match the numbers on Fred Smith's ticket, the odds aren't 20 million to 1 any more. They are now 100%.

Likewise, if you had some master list of all the human beings who have ever lived, and you picked one at random and asked, What is the probability that this person would be alive in 2018?, depending on what estimates you're going to use for world population over history etc, I'd say the odds are pretty strongly against. But if you take a list of people who are alive today, and ask what the odds are that they are alive today, while clearly that's 100%, because we're picking from a pool of people whom we already know are alive today.

• This answer is preposterously unlikely. But my comment is just as unlikely. – Wildcard Jun 18 '18 at 20:22
• @Wildcard Exactly! What is the probability that someone randomly bashing keys on a keyboard would come up with exactly this combination of letters? I haven't bothered to calculate, but probably quadrillions to 1 or more. And yet ... there it is. – Jay Jun 19 '18 at 17:58

First, in your question you are assuming that the passage of time is an objective feature of reality. That is, in order to give a full description of the world, you need (perhaps) to describe what occupies every point in spacetime, but that's not enough: you also need to provide a concrete location for the objective now. This is a variety of what is known as the A-theory of time. Most philosophers and physicists, on the other hand, endorse a B-theory of time, according to which the passage of time is subjective: for every inhabitant of spacetime, their time is "now". The paradox that worries you does not arise if the B-theory is correct.

And, second, your argument depends on what is known as self-locating beliefs: beliefs about where (or when) one is. Reasoning involving self-locating beliefs is notoriously slippery. One illustration of ways in which they may lead us astray is the Sleeping Beauty problem.

• I'm not seeing the connection to the SB problem? – Cloud Jun 18 '18 at 7:32

Right now I am looking at a pair of scissors laying on my desk. What are the chances of that?!?? Think about it: that pair of scissors had to be created; the desk had to be created. The house that this is all in had to be created. What are the chances a house was built right at the location it has been? And that a desk was brought in, standing in the location that it is in. And that a pair of scissors would be laying on that desk, laying in the position that it is in ... all exactly on June 17, 2018?!? From this perspective, it is an absolute miracle that I am indeed looking at a pair of scissors right now! Indeed, for pretty much every truth with any kind of detail, it is a complete and utter miracle that that truth came to be!

OK, so then does that mean anything? No. It is all just a complete fluke. I guess that is how you should think about it. Just like we don't (and of course shouldn't!) get all bent out of sorts because we see a pair of scissors laying on a desk in front of us, you also should not read anything into the fact that you and I are here. We're here because it's all just a fluke.

• +1 because scissors example opens up the existential (not mathematical) dimension of the question. If the scissors were like one of stars on that black sky canvas one might indeed feel lost and anxious facing them (like facing all those thousands of lives in history before us). Because stars are difficult grasping as useful, adjutant. With them, we are, most of the time, futile too. But these scissors on my table in front of me is likely to bear the mark of usefulness, they are in labour under the sun. Most of the time I don't reflect on that they are randomly chosen from the many ones. – ttnphns Jun 17 '18 at 18:23
• Not only that, but a society has to be formed with a language that calls one object a pair of scissors! – pipe Jun 17 '18 at 18:51
• This borders on nihilistic, it is indeed a miracle that you are reading this comment :) – Cloud Jun 18 '18 at 7:36
• @Cloud Well, given that you posted it under my Answer, not so much. But the fact that I am reading it this very second is :) – Bram28 Jun 18 '18 at 11:55
• A fluke? Hardly. No naturalistic explanation for existence is credible. The only credible explanation is the existence of God, but many people, philosophers or not, don't like to go there. – Ham Sandwich Jun 20 '18 at 22:51

Dead or unborn people don't ask themselves : "Why am I not alive today?".

You can ask yourself the above question, it means you're alive.

• But he can't prove he actually exists though. lol. – Mohammed Joraid Jun 19 '18 at 22:46
• @MJoraid He can't prove to you that he actually exists (though he can provide evidence that should put it beyond reasonable doubt), but everyone can prove to themselves that they themselves exist by questioning whether or not you exist, because the fact that you are able to question your own existence means you exist in some fashion (you might still be wrong about the nature of your existence though). – Cubic Jun 20 '18 at 10:57

Your question is, why does your lifespan occur now rather than at some other time? But if it did occur at another time, then that would be your "now" and you would be asking the same question. Sometimes I get myself wrapped around the question "Why am I me and not someone else?" But of course the answer is that if I were someone else, then that would be my "me". The probability that you are alive at some specific time is low. But "now" is relative to your own consciousness, so asking why you are conscious "now" is a tautology.

• Do you have any references to strengthen your answer perhaps of philosophers who have discussed this issue and came to a similar conclusion as you did? This would give a reader somewhere to go for more information. – Frank Hubeny Jun 18 '18 at 20:31
• Sorry, I am not well-read enough in philosophy to give a reference. Others here have shown that by using conditional probabilities the probability of the original question is 1 and not a very small number. I was trying to come at it from a language/logic approach to show that the probability is 1 by definition. Proposition: The definition of "Now" is the moment in time when your consciousness is aware and forming questions and inferences. Given: You are conscious and forming a question. Inference: Therefore it is "now". – JGH Jun 18 '18 at 21:36

A reason why you might find it surprising/improbable, is having a view that you (i.e. "your mind, your soul, your very awareness", and your body) is a self that's independent of its present circumstances -- so you're remarking on an allegedly improbable coicidence between this self and its location.

A different view suggests that this self is a product of (it is conditioned by) its environment -- it's not unique (thus not identifiable), among the set of human beings for example, except as a product of its environment (including its genes, society, education, food, possessions, past actions, etc.).

For example, look at a house in Paris and say, "Isn't it remarkable that that house is in Paris!"; one might reply, "No, it's the fact that it's in Paris that defines it, it has no existence independent of its location in Paris: it's by looking in Paris that you found it; and Paris made that house what it is."

To think that the house has an existence that's independent of Paris would be a kind of a "conceit".

One shouldn't privilege the view of Paris either: it's no more existent than its houses -- it's merely an aggregate of components.

Perhaps this explanation corresponds to the Buddhist view of anatta or anatman (i.e. "without self" or "no thing should be seen as an independent soul"), and sunyata (i.e. "no thing has its own independent existence").

Even "very awareness" (of anything) is conditioned by contact with the thing (or idea) it's aware of.

If you want to go even deeper into the formation of an embryo, millions of sperm are released each time someone ejaculates. Let's take this number as 400 million (400,000,000).Source The average human male ejaculates 7500 Source times in his life time.

400,000,000 * 7500 = 3,000,000,000,000 (3 trillion sperm)

Add this variable to your thinking. The odds become even less likely.

Just because the odds are less likely doesn't mean it could never happen. It could happen, because you are here.

• It would be good to provide references for the number of sperm and ejaculations just in case someone questions them. It would strengthen the answer. – Frank Hubeny Jun 17 '18 at 13:10
• I made an edit for grammar and corrected the calculation. You are welcome to roll this back or continue editing if you wish. – Frank Hubeny Jun 17 '18 at 13:18
• 400,000,000 sperm? This is in odds with the info I have. In either way this does not provide an answer but only forces the question. – rus9384 Jun 17 '18 at 14:35
• Only 7,500 times? For an 80 year life that's once every 3.9 days... did you get this data from monks? xD – Cloud Jun 18 '18 at 7:38
• @cloud That is an impressive 80 year old who has been ejaculating at a consistent rate from the moment he was born until the day he goes into the grave! In reality the rate is actually zero for the first decade (ish), probably peaks somewhere in the teens/20s, and then declines over the remainder of the lifespan. Add to that the fact that it's an average (so we're including less sexually active people in the numbers), and it doesn't sound so unreasonable. – JBentley Jun 19 '18 at 12:12

The question is essentially, "I am alive right now, and I am alive at the exact same time that I am alive. Isn't that impossibly unlikely?" No, it's a tautology. It's the same as saying "Isn't it impossibly unlikely that the current room's temperature is equal to the current room's temperature?" Nope, it's 100% guaranteed, because it is a tautology. "What are the odds that Super Bowl X would be held on the exact same day as Super Bowl X?" 100%. That's not a coincidence, because it is the exact same event repeated twice. It isn't a COincidence at all if the two events are not at least distinct (and also possibly unrelated, depending on how the problem is worded).

If you randomly selected a person born in all of Earth's history, without any sort of selection bias that might prefer or guarantee a person who is currently living, then it would be remarkably coincidental that they were born on the same day as you. But it is not a coincidence that a particular person is alive at the same time as a particular observer, who also is that same person by design.

• It seems like there must be more to this question, but expressing what that is may be difficult. – Frank Hubeny Jun 18 '18 at 23:21
• How does this add anything that hasn't already been written in other answers? – Philip Klöcking Jun 20 '18 at 10:24
• It's shorter and to the point, which it hammers home; that this has nothing to do with philosophy and everything to do with logic. And it contains the words tautology and selection bias - it's no wonder there's a 'coincidence' if you're guilty of either of the former. We don't really need the anthropic principle; just an axiom: it wouldn't be if it wasn't. and no one knows why IT is - so stop asking ;) – Mazura Jun 21 '18 at 3:41

Causation punctures the paradox of coincidence

You take into account only two, apparently unrelated, things : (1) your being alive and (2) time t1 (now). Given data as bare as this, there is a coincidence and even if you like an improbable coincidence between (1) and (2). But isn't there a causal link betweeen the two ? You are alive now as the latest state of affairs in a causal chain which connects you to your past. Keeping the biology simple, let's say that you are alive now and not 200 years hence or 200 years in the past because of (if I may put it so) a causal interaction between two persons that resulted in your conception and existence. You are alive now because of a precisely datable causal interaction that occurred in the past (t minus-1). Equally the two persons whose causal interaction at t minus-1 resulted in your conception and existence were themselves each the result of causal interactions that occurred at times t minus-2 and t minus-3 (unless the respective causal interactions that resulted in their conception and existence were simultaneous). Causal interactions are datable. Where's 'the most improbable coincidence' in (1) your being alive now and (2) time t1 (now) ? The improbable thing, given the causal nexus, would be if you were not alive now rather than at some arbitarily different time.

Due to total human population being the largest its ever been its more probable that a human being would live now than at any previous time in human history. The world's current human population is over 7.6 billion people and this is expected to reach over 11.2 billion by the end of the Century. World Population Growth

Historically total human population was far less than this. An estimate during medieval times is a total of around 0.35 billion in 1400 AD. In prehistory humans numbered far less than this. An estimate at the time of Ancient Egypt is 100 million. So this is approx 1% of a 10 billion figure we can expect to see this Century. Therefore the chances of existing at the time of Ancient Egypt would be about 1% of how likely it would be toward the end of this Century. Historic world population estimated

A human population bottleneck occurred as recently as 70,000 years ago. At this time the total number of humans alive dropped to as low as 1,000 to 10,000 individuals. This explains why genetic studies show a lot of relatedness between people who are geographically very distant. Being a human alive when there were the least humans on the planet would be the most improbable time to exist.

• This is a nice distributional analysis but has nothing to with the "probability" of being alive today. Probability is an estimator for future events. You are talking about absolute frequency. Probability is derived from the frequency of events already happened (and counted), but not the same. Also, there is no such thing as "material probability", i.e. the probability of anything that is isn't defined. The event "you are one of the humans living today" has no probability. The event "choosing exactly one out of the humans alive today, that one is you" has one. Until you did the choosing. – Philip Klöcking Jun 20 '18 at 10:30
• I think you're actually agreeing with the analysis but you don't like the conclusion. The chance of an object being in existence is directly related to the volume of things that exist. ie. If there were a total of 100 billion people (estimated purely for arguments sake) that ever existed and 20 billion people lived in the 20th and 21st Century then the chance that a human being existed in those Centuries would be 20% that's just basic mathematics. It'd like looking at a bell curve and realizing that the majority of people fit in the big bulge of the curve and very few out by the thin edges. – Stevernator Jun 20 '18 at 23:16
• "Due to total human population being the largest it's ever been, it's more probable that a human being would live now than at any previous time in human history." — Extrapolating the probability distribution in both directions leads to an even more disagreeable conclusion: if there were really going to be even more billions of people on Earth two centuries from now, wouldn't you expect to be one of those people instead of one of us? This is known as the Doomsday Argument. – Quuxplusone Jun 22 '18 at 1:34

I just farted two seconds ago.

What an incredible coincidence! Out of all the possible times in my lifetime (and after death, by the way) I could let out a three-point-six-two-second fart -- and that's such a precise number there are only a handful of times I can let out that specific fart -- what's the probability of it having been precisely two seconds ago?

Being surprised has nothing to do with a low probability. The probability of almost any event (specified to fullest detail) occurring is zero. So what? Our surprise has more to do with the kind of event that occurred -- e.g. meeting a person with blue skin is more surprising than meeting a person with a very specific shade of brown (even though the first may very well be more likely), and a fart of length 3.14 seconds is much more surprising than a fart of 3.65 seconds.

Just as a general reply; most, if not all of you, seem to focus your response around the probability of me being alive today, and assign the probability of 1 to this; after all, if I'm able to ask this question now, it means I must be alive now.

To be fair, you specifically referenced the probability of the event. It’s both in your title (“the most improbable coincidence?”) and text (“only a chance of 1 in 3000 (0.033%)”).

However, what I'm (even) more interested in, is the coincidence of me being alive today

Merriam-Webster defines coincidence as “the occurrence of events that happen at the same time by accident but seem to have some connection”. Events. Plural. You being alive today is a single event, so there’s no inherent coincidence in that. It’s the same as saying “I’m holding an apple”. Single event, no coincidence.

The only way you being alive today could be considered a coincidence would be if there were another unrelated event that seemed to have some relation to your current existence. As stated previously, if no one predicted your existence before it occurred, there is no coincidence to you being alive now, as it’s as likely as you being alive at any other point or not at all. And as others have stated, if we ask about you being alive during/after the fact, then the probability is 1 because we already know the event is true.

assuming that time acts like an objective spotlight (gradually passing along, moving into the future) shining at one specific point on the timeline (reaching from the moment of the big bang all the way into at least now, or maybe even the future).

The given answers were already compatible with that scenario. It doesn’t matter where the spotlight currently is, since questions can be made about any point in time but only in the point in time the spotlight is shinning on. If the spotlight is not on you, there’s no way to ask anything. Previous reasonings still apply.