# How many humans have lived on Earth?

1. Mar 28, 2009

### Zdenka

Here's a brain teaser (or brain-wrecker!) for everyone! Anyone who can answer this question with an accuracy of +-1 human deserves a Nobel prize in my books! I already know the answer. ;-))

Okay, we all know there are 6+ billion people on earth currently living at this moment. But how many people have lived AND died on earth in the past up to this moment?

Ideally to answer this question we must have some criterias..

1. A living human being is defined as an organic entity that has come out of a Vagina and still breathing. Or even a cizarian. Therefore those that died in the womb should not be factored into the equation. Half human-animal breed do not count, assuming some females have breeded with an animal in Earth's history.

2. How long ago were the first humans were actual humans? This is a difficult thing to classify because, are homo Sapiens really human? I think the best way is start at a point in time.. lets say EXACTLY 1 million years ago was when the first humans started being born. Anything before that is NOT considered a human being. So therefore we should work our answers from this point.

3. You have until exactly midnight this Friday12.00AM universal time to answer the question.. ie how many humans beings have lived up to this EXACT point in time.. Please tell us what formula you have used, as this is a tremendously challenging question, I know! Good luck!!

Last edited: Mar 28, 2009
2. Mar 29, 2009

### Phrak

define 'this'

3. Mar 29, 2009

### Zdenka

Phrak what do you mean? Maybe I should state "How many human beings have graced the earth starting from exactly 1 million years ago to yesterday at 12:00pm" This should give us a range to work on.

4. Mar 29, 2009

### Phrak

I see. Then I'm out of time. Oh well, better luck next time.

5. Mar 29, 2009

### cragar

i dont know 10 billion

6. Mar 29, 2009

### Pythagorean

42, the rest are just their trolls.

7. Mar 29, 2009

### Jimmy Snyder

Can we do Saturn? I know the answer to that one. Also, are solipsists allowed to play?

8. Mar 29, 2009

There were three....Gert and Daisy and some geezer whose name I forget.
(It's a nice question and needs some thought)

9. Mar 29, 2009

### maze

I looked into this at some point. If I recall correctly the answer is somewhere around 100 billion, which was quite a bit higher than my first guess.

10. Mar 29, 2009

### Chi Meson

This is what I'd do, if I didn't have a full day of errands to get to, starting in 15 minutes, ending with me mum's birthday tonight...

find a decent graph of the known human population curve, determine the function it approximates (starting with 100 years ago, and going back), extrapolate to 1 million years ago, divide the "years" axis by 15 or 20 years (assumed historical life span), integrate (count up the "area under the curve"). Then add the population of the last century, which has been following a different function.

Is the method valid?

Now I gotta take my daughter to horseback lessons. See yer tomorrow.

11. Mar 29, 2009

### Redbelly98

Staff Emeritus
I remember reading somewhere that over half of all humans that ever lived are still alive today. Makes sense for our recent history at least, since average life expectancy (about 70 years?) is a lot longer than the time it takes the population to double (about 30 years).

If that's true, the answer is less than twice the present population.

12. Mar 29, 2009

### maze

That is a common myth.

13. Mar 29, 2009

### humanino

14. Mar 29, 2009

### Redbelly98

Staff Emeritus
15. Mar 29, 2009

### humanino

It seems to me to be a pretty complicated problem actually. SciAm article and wikipedia provide very little details about Haub's calculations, we only can assume he has the correct population growth rate. What I am wondering about is, in his model he starts from just 2 people, his "Adam and Eve". This initial condition is crucial, and I don't quite understand what justifies it. What would result if instead he used two couples ? Maybe twice more total number of people ? Unfortunately, it is difficult to obtain an estimate in this method of the current world population. It seems he can only say "100G humans ever lived" without further reference point to justify the model.

16. Mar 29, 2009

### arildno

The question is largely meaningless, due to the impossibility to gain relevant data to any significant extent.

17. Mar 29, 2009

### humanino

I'm not sure what you mean. Is it that we can reproduce the experiment many times, like in cosmology ? Or is it that we can not gather more than old remnants of the experiment, like in cosmology ? :uhh:

18. Mar 29, 2009

### turbo

A: All of them. Now, where's my prize? I want to retire.

19. Mar 29, 2009

### DaveC426913

Yeah, it reads to me like a trick question. There are details and restrictions that make no sense in light of the fact that it's all gonig to be guesswork and estimation anyway. We have no idea what population growth rates were, etc.

20. Mar 29, 2009

### WiFO215

:rofl:

21. Mar 29, 2009

### arildno

It is several orders of magnitude sillier than "studying" the Drake equation.

And THAT is extremely silly to begin with.

22. Mar 29, 2009

### Jimmy Snyder

I have it on good authority that Mark Twain is not really dead.

23. Mar 29, 2009

### maze

This is quite a defeatest attitude. The problem is nontrivial, but not impossible. We know, for example, when certain populations lived in certain areas due to archaeological evidence. This can be used to give lower bounds. We also know how many people can be supported at a certain level of technology in a given area, so this can give upper bounds. You can do statistical analysis of DNA of people currently living to track back common ancestors. You can apply the same sort of analysis that people currently use to estimate species population. (They don't actually go around and count every single africanized honey bee to figure out how many there are in the americas...)

If you derive a bounds using one method, you could test it by calculating using a different method. This would actually make a very interesting study.

24. Mar 29, 2009

### DaveC426913

Depends on how you set your success criteria. If you're expecting accuracy of better than an order of magnitude, or possibly two, then it's not defeatist, it's realistic (i.e. virtually impossible). (In fact, without asking for a level of accuracy first, there's no way you can claim it is possible. )

Certainly though, in the context of a brain-teaser, and with the (albeit perhaps tongue-in-cheek) request for an accuracy of +/- 1 person - yeah, I'm comfortable with 'impossible'.

25. Mar 30, 2009

### Phrak

The challenge is to get the count to "+- human". Good luck.