# How many genetically different humans?

**URL:** <https://boards.straightdope.com/t/how-many-genetically-different-humans/737>\
**Category:** Factual Questions\
**Created:** [June 6, 1999, 7:05pm UTC](https://boards.straightdope.com/t/how-many-genetically-different-humans/737 "1999-06-06T19:05:00Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\
**Post date:** [June 6, 1999, 7:05pm UTC](https://boards.straightdope.com/t/how-many-genetically-different-humans/737/1 "1999-06-06T19:05:00Z")

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Can anyone figure out how many gentically different human beings are possible?

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**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\
**Post date:** [June 6, 1999, 9:19pm UTC](https://boards.straightdope.com/t/how-many-genetically-different-humans/737/2 "1999-06-06T21:19:00Z")

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If we knew how many genes there are exactly, and use set theory to figure all the possible subsets, then eliminate combinations that wouldn’t result in a viable person…

The answer is still “no.”

First, we don’t know how many genetic errors still result in a person-- for example, you could calculate the “standard” models, then multiply but two, to account for all pessible people with Down Syndrome. But there might be certain genetic combinations that are fine as “normal” people, but are uncompatible with an extra 23 chromosome.

Then there is the fact that genes are always mutating; even if we did have the knowledge to make valid calculations today, the number would be outmoded tomorrow.

## It’s all moot, anyway, because we don’t know enough about genes.

* * *

–Rowan  
Shopping is still cheaper than therapy. --my Aunt Franny

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**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\
**Post date:** [June 9, 1999, 3:21am UTC](https://boards.straightdope.com/t/how-many-genetically-different-humans/737/3 "1999-06-09T03:21:00Z")

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Well then, suppose you are unique. How many other people in the world would you need to sample to collect all the genes that are in you?

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**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\
**Post date:** [June 9, 1999, 9:39pm UTC](https://boards.straightdope.com/t/how-many-genetically-different-humans/737/4 "1999-06-09T21:39:00Z")

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\>\>Well then, suppose you are unique. How many other people in the world would you need to sample to collect all the genes that are in you? \<\<

Two.

Think about it.

-Bob  
And if anyone starts bitching about spontaneous mutations I’m going to slap you

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**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\
**Post date:** [June 9, 1999, 10:28pm UTC](https://boards.straightdope.com/t/how-many-genetically-different-humans/737/5 "1999-06-09T22:28:00Z")

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Right.

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**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\
**Post date:** [June 9, 1999, 10:44pm UTC](https://boards.straightdope.com/t/how-many-genetically-different-humans/737/6 "1999-06-09T22:44:00Z")

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I’m pretty sure sunbear meant how many people at random.

But the reason I’m writing is that I remember hearing in school that if you take the limiting element for humans on earth (phosphorous, as I recall) and work it out, you get a surprisingly small number of people - a few trillion. (That is, there isn’t enough phosphorous on earth to make more people than that). That’s lots of people, of course, but less than you might think at first.

It’s certainly orders of magnitude less than the number of possible genetic combinations of people. I don’t know if that helps.

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**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\
**Post date:** [June 10, 1999, 3:03pm UTC](https://boards.straightdope.com/t/how-many-genetically-different-humans/737/7 "1999-06-10T15:03:00Z")

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\>\>I’m pretty sure sunbear meant how many people at random.

```
                     But the reason I'm writing is that I remember hearing in school that if you take the limiting element for humans on earth
                     (phosphorous, as I recall) and work it out, you get a surprisingly small number of people - a few trillion. (That is, there isn't enough
                     phosphorous on earth to make more people than that). That's lots of people, of course, but less than you might think at first.

                     It's certainly orders of magnitude less than the number of possible genetic combinations of people. I don't know if that helps.&lt;&lt;

```

I’m pretty sure Lazy meant “How many viable subsets are there of all existing human genes?” not “How many people can be alive at one time?”