What are the mathematical odds of me ever being born? Now this question can be interpreted and answered in any way, but my thinking goes like this…only my “exact” father and my “exact” mother could have produced me. No other two person combination in the history of the world could have produced me and no other future two person combination will be able to produce me. Now, I guess you would have to know how many generations my family tree is b/c you would have to factor in the odds of my parents being born, plus the odds of their parents being born, etc, without which I would not even have the chance to exist. Plus the total population of the world during each generation with weighted amount to different people (the chances say my father would have actually married a farmer living in China are remote). An impossible question I’m sure, but any thoughts? Am I really a miracle! 
Well, since you are alive and posting on this board, I’d say that the odds of you being born are just about 1.
I’ll leave it to the more religious of our Dopers to tackle the odds of you being “born again.”
We don’t want to confuse the odds of something happening with the ex post facto reality of that thing having happened. But remember: the odds of being dealt a royal flush in spades are exactly the same as being dealt 2H, 5S, 7D, 8H, 10C.
It’s very difficult if not impossible to define “the odds” in situations like these. Calculating odds, using either the methods of probability or those of statistics, hinges on the notion of an experiment: hypothetically doing X and then measuring the quantity Y. For example, X=“flipping a coin” and Y=“heads or tails?”, or X=“grabbing a person off the street and asking them who they like for president” and Y=“their answer”.
Here, what is the experiment? Is X=“picking a baby being born at random”, and Y=“whether or not that baby is Churnboy”? If so, then the odds are pretty much 0, because you’ve already been born, and so if we pick a baby at random now it’s not going to be you. On the other hand, if X=“checking to see whether or not Churnboy has been born” and Y=“has he been born or not”, then the probability is 1, as silenus has said. (In this sense, the odds of any event that has already happened is 1.)
Perhaps the most interesting possibility is X=“picking a person from the set of all possible human beings” and Y=“whether or not that person is identical to Churnboy”. Then the question becomes, what do you mean by “identical”. If you mean “one and the same person”, then the odds are 1 divided by the number of possible human beings, which is indeed pretty small. But if by “identical” you just mean “identical to within the limits of measurement” or something similar, then the odds presumably go up if only slightly. But I have no idea how you would even begin to calculate such a thing.
Well, if what you want to know is the probability that any given baby is born with your exact genetic makeup (excluding miscarriages, stillbirths, etc.), then the data you suggest are irrelevant to the question.
Although a biologist would know better than I the degree to which genetic makeup varies from one individual to another, I would conjecture that the answer is nearly zero.
To take a purely mathematical approach, you would figure it thus:
Take all the genes in your DNA. For each gene, find empirically the probability that a given human is born with that gene. Most, I think, would be 1. Some might be something like 1/100 or 1/5. Then multiply all those numbers together.
You could write a computer program to do this. Give it your entire genetic sequence, and that of 1,000 other humans for comparison, and let it do the calculations.
I do not know if they have the technology to do this and I am sure the actual process would be quite complicated. Obviously it’s an unrealistic task for a human to do manually. I await the biologists and pertinacious googlers to inform us.
For what it’s worth, I assumed that that was what Churnboy was asking because I have heard other people wonder the same thing, especially when arguing against cloning; e.g., “What are the odds that someday another person will be born who is exactly like me?”
On a related issue, I have personally wondered whether anybody has ever used probability to determine whether the amount time we think life has been on earth is a realistic estimate for how long it would take the simplest life forms to evolve into life as it is today. Anyone know?
I think what Churnboy was asking is what are the chances that his parents should meet and have a child (him), similarly what are the chances that each of their parents should meet and have a child etc, etc, etc.
This is an impossible question to answer because just the probability of his parents meeting is impossible to predict in a scientific manner (I guess it could come all the way down to sub-atomic decisions!) and similarly difficult to predict from some statistical analysis. I suppose you could attempt the second method by trying to calculate the probability of two particular people meeting (at an appropriate time, age, place etc) in a given region. Even this is virtually impossible due to the inordinate amount of possible variables.
Lets take the flower power approach and conclude that we are all miracles in our own right 
Sorry Churnboy, but my take on it is that the odds are so mathematically improbable, that you really don’t exist. But don’t worry (or should I say Don’t Panic™?), nobody else exists either. This follows the Galactic Population Density = 0 logic from Hitchhiker’s Guide to the Galaxy. (Finite population/ infinite space = population density of zero.)
I’ve thought about this in relationship to possible time travel. (I don’t believe time travel is possible, but it was fun to consider the implications.) This follows on with what fezpp posted. It’s even more problematic than the odds that your parents, grand parents, etc. met each other. Consider the consequences for someone who was conceived at a particular moment in time. If you could go back in time and delay the moment of conception - delay one person from getting home by an hour, a phone call at the wrong time - would the same sperm cell fertilize the egg? How minor a change is necessary to have a different sperm cell get to the egg first. Could a few seconds delay in climax for the male, a shift of the hips afterwards for the female, result in a different one of the tens of millions of sperm cells succeeding? So, you being you (or me being me) is not only the result of all our forbearers meeting each other, but that all of them made love at the proper time and in the proper fashion to achieve the current results.
So, that’s why I say it is so infinitesimally impossible that any of us are here, that we may as well consider that we don’t. 
Unless you believe in destiny, in which case the odds are certain instead of zero.
With tongue firmly in cheek ,
Mycroft H.
Well, the way I look at this question is like this:
The odds of your parents meeting falling in love and having sex were roughly 1 in 3 billion (or whatever the earth’s population was at that time). Now, the odds of them having a baby were something else, I dunno, let’s just say 1 in 2. Ok then, so I’m no math guy, but let’s say at the time you were conceived, the odds of that happening were 1 in 6 billion. Let’s assume there were 1800 generations (a number I pulled out of nowhere) between your parents and the first 2 people on earth. Each generation, the odds of any 2 people finding each other and having children goes up (since there are more people on the earth to choose from).
So, ignoring all factors like distance away from each other (I’d assume the odds of your parents having sex would be lower if they lived next to each other than if one lived in England and one in Mexico), using my made up numbers, the odds of your parents having a child (not you, just any child) were roughly:
1 in 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(give or take a few hundred zeros). That’s 17600 zeros BTW.
Now, that doesn’t take into account the fact that everything your mom ate, drank, if she got sick, got punched in the stomach, was on drugs, etc, went together to create you as a person.
I hope there is a math person who can actually provide real numbers to what I’m suggesting, but I’m not a smart man, so I just provide possible solutions, and let others do the dirty work.
I once tried to write a computer simulation that would do the same type of thing, but my populations kept dying off and couldn’t breed fast enough to stay alive.
So anyways, looking at it like that, you’re all pretty dang lucky to be here. And if I’m wrong, at least I gave the smart people something to pick apart
I don’t get why you would ask for the odds of a miracle. If an event has a probability, then it isn’t a miracle if it happens, is it? At best it would be improbable. It isn’t a miracle unless the probability is zero, eh?
What is the probability that you are unique? 1:1
Lastly, you are what you are. Whether you choose to see yourself as a miracle or as something else is up to you. You can’t objectify the subjective and no amount of statistical analysis will change in any way what you are.