What Are The Chances That You Would Be Born? • Hacker News Board

Re: What Are The Chances That You Would Be Born?

#41

Post by gus_massa » Sun, Sep 25, 2011, 3:58 PM UTC

altrego99 wrote: post #4

There is another angle through which you could attempt to determine the probability of you existing. It's by dividing number of people on Earth today, by total number of genetic permutations possible. Of course that would remove cultural factors from the equation... but calculating actual probability of cultural factors are pretty damn hard!

It’s more complicated and this is really not my expertise area, but let’s mixes some random numbers from Internet. (Mostly from: http://en.wikipedia.org/wiki/Human_genetic_variation#Measure... )

The total number of bases in human DNA is ~3E9, so there are 4^3E9 ~= 10^2E9 possibilities. But this number includes a huge kind of variations, from humans to cows, to whales, to bats, to cats, to algae, to fungus, to pines, to orange trees, to roses, to petunias, to artichokes and probably even to vulcans, and to unicorns :). (Different species have different number of bases in their DNA, but all the eukaryotic cells have the same order of magnitude, so we will just ignore this fact.)

If we consider only single nucleotide polymorphisms, the difference between two humans is in only 1/1000 of the bases (and let’s suppose that in each case the difference is in the same bases, and that the variations are independent) . So with this restriction there are 4^(3E9/1000)~=10^2E6 "possible" humans. Using that the total number of people that have ever lived is estimated as 10^11, the probability is 10^11/10^2E6 ~= 1/10^2E6.

But, please, don’t take these numbers very seriously.

Re: What Are The Chances That You Would Be Born?

#42

Post by bumbledraven » Mon, Sep 26, 2011, 8:18 PM UTC

The Buddhist parable of the blind turtle is actually a metaphor for how long it takes to be reborn as a human after being reborn as a non-human.

"Suppose a man threw into the ocean a yoke with one hole in it, and then the east wind blew it west and the west wind blew it east and the north wind blew it south and the south wind blew it north; and suppose there were a blind turtle that came up to the surface once at the end of each century. How do you conceive this, bhikkhus, would that blind turtle eventually put his head through that yoke with the one hole in it?"

"He might, Lord, at the end of a long period."

"Bhikkhus, the blind turtle would sooner put his head through that yoke with a single hole in it than a fool, once gone to a lower realm, would find his way back to the human state."

M. 129

[Nanamoli, The Life of the Buddha, p. 250]

As the post says, the probability of the turtle surfacing with his head in the yoke on any one try is about 10^-15. Since the turtle tries once per century, the expected length of time as a non-human is 10^17 years, or 10 million times longer than the amount of time since the most recent Big Bang. It's actually kind of cool to visualize this. Let one penny represent the amount of time since the Big Bang (about 10 billion years). Then here's a picture of the amount of pennies representing the expected length of time as a non-human: http://www.kokogiak.com/megapenny/seven.asp

Re: What Are The Chances That You Would Be Born?

#43

Post by jodrellblank » Tue, Sep 27, 2011, 8:47 PM UTC

xianshou wrote: post #9

jodrellblank wrote: post #5

It's a meaningless "probability" on several counts. 1) It applies to everyone reading it, and it would apply to me if I were different and reading it. It tries to convey a specialness which doesn't seem to exist. If a billion people win a penny each then winning a penny isn't miraculous, even if it is a 1 in 1,000,000,000 chance that you win any particular penny - but the 'particular' part has no significance. 2) I a…

I appreciate point #2: "The probability that I exist, given that I exist, is 1." However, the question addressed by the OP is not "What is the probability that I would exist in this world?" but "What is the probability, across the space of all possible continuations of the world from the dawn of humanity, that the world would end up in a state that includes me?"

I don't understand talking about possibility when discussing the past. Probability reflects our uncertainty about what outcomes will happen. Uncertainty is a property of our understanding, not of macro reality. When looking backwards, we know what happened and what didn't, I happened (probability: 1) and those other worlds didn't (probability: 0). Saying "they could have happened" seems to me a sentence with no real meaning.

Even if you go with a many-worlds view, that only means that all things happened with a probability of 1.

Re: What Are The Chances That You Would Be Born?

#44

Post by jodrellblank » Tue, Sep 27, 2011, 9:12 PM UTC

jimworm wrote: post #31

If you’re reading this, your probability of existing is 1. The probability of all known-to-have-happened events to have happened is always 1. Of course, that assumes that the knowledge is correct; but even the most die-hard skeptic can be absolutely certain that they themselves exist.

but even the most die-hard skeptic can be absolutely certain that they themselves exist.

I could potentially be non-existing or not-me in ways that I'm not clever enough to speculate about, let alone the ways I could speculate about (simulation, Boltzmann brains, Dust theory, dreams).