How many humans have lived on Earth?

[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.. let's 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!

 

[Phrak]

define 'this'

 

[Zdenka]

define 'this'

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.

 

[Phrak]

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.

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

 

[cragar]

i don't know 10 billion

 

[Pythagorean]

42, the rest are just their trolls.

 

[Jimmy Snyder]

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

 

[Dadface]

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

 

[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.

 

[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 got to take my daughter to horseback lessons. See yer tomorrow.

 

[Redbelly98]

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.

 

[maze]

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.

That is a common myth.

 

[humanino]

I remember reading somewhere that over half of all humans that ever lived are still alive today.

Probably this has been debunked.
Fact or Fiction?: Living People Outnumber the Dead

 

[Redbelly98]

That is a common myth.

Probably this has been debunked.
Fact or Fiction?: Living People Outnumber the Dead

Thanks for the correction!

So earlier growth rates were a lot slower, about 0.1% per year according to the sciam.com article humanino linked to.

 

[humanino]

So earlier growth rates were a lot slower, about 0.1% per year according to the sciam.com article humanino linked to.

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.

 

[arildno]

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

 

[humanino]

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

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 ?

 

[turbo]

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

 

[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.

 

[WiFO215]

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

 

[arildno]

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 ?

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

And THAT is extremely silly to begin with.

 

[Jimmy Snyder]

But how many people have lived AND died on Earth in the past up to this moment?

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

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

 

[maze]

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

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.

 

[DaveC426913]

This is quite a defeatest attitude. The problem is nontrivial, but not impossible.

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'.

 

[Phrak]

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

 

[maze]

I think within a factor of 2 would be possible

 

[Zdenka]

Okay, the answer is 98 895 312 455 humans have lived on this Earth up to yesterday at exactly 12.00am. +/- 1 human of course because I believe that there is an Alien among us that once was human.

 

[Vanadium 50]

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 ?

Relatively little. The key line in the article is "the living will never outnumber the dead". That means that most of the dead are recently dead, so adding a few hundred thousand more or less in the distant past won't make a difference.

Also, if you add more people in the past, you are increasing the number of the dead. Since there are already more dead than living, the conclusion still holds.

 

[Zdenka]

Relatively little. The key line in the article is "the living will never outnumber the dead". That means that most of the dead are recently dead, so adding a few hundred thousand more or less in the distant past won't make a difference.

Also, if you add more people in the past, you are increasing the number of the dead. Since there are already more dead than living, the conclusion still holds.

The Key to solving the problem is fossil record. If we can find and add up all the fossils of the dead together with the current population (also factoring in the dynamic deaths and births right this moment as I type), then we can arrive at a realistic figure. Maybe not within +/-1 human but extremely close to it.

 

[redargon]

Okay, the answer is 98 895 312 455 humans have lived on this Earth up to yesterday at exactly 12.00am. +/- 1 human of course because I believe that there is an Alien among us that once was human.

I call ********. Show us your calcs. I don't come up with a "it's too detailed to put in this forum"

 

[neu]

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

Pop it in Philosophy then

 

[Alfi]

Okay, the answer is 98 895 312 455 humans have lived on this Earth up to yesterday at exactly 12.00am. +/- 1 human of course because I believe that there is an Alien among us that once was human.

amazing! exactly the number I was going to guess.

 

[DaveC426913]

The Key to solving the problem is fossil record. If we can find and add up all the fossils of the dead together with the current population (also factoring in the dynamic deaths and births right this moment as I type), then we can arrive at a realistic figure. Maybe not within +/-1 human but extremely close to it.

This is a joke.

You do realize that, even in principle, you can't dig up significant numbers of bodies. All but a tiny fraction of dead carcasses are completely destroyed over millennia. Only a very, very,very few are preserved to be later recovered. (BTW, you're not going to find many of them fossilized anyway. Fossilization takes millions of years, not thousands.)

 

[Jimmy Snyder]

Fossilization takes millions of years, not thousands.)

I don't understand that. What keeps the unfossilized tissue around during those thousands and millions of years. It seems to me that bones in the ground are gone in a few decades.

 

[DaveC426913]

I don't understand that. What keeps the unfossilized tissue around during those thousands and millions of years. It seems to me that bones in the ground are gone in a few decades.

That's one of the reasons why only one-in-a-zillion carcasses are ever fossilized. It's only the ones that are buried in a way where they are protected (tar-pits, river-beds, very fast sedimentation, etc.) from decay due to weathering, bacterial consumption, scavenging and a whole host of other destructive forces.

 

[Zdenka]

I call ********. Show us your calcs. I don't come up with a "it's too detailed to put in this forum"

meh, too tired. I've been counting fossils for the last 10 years

 

[Zdenka]

This is a joke.

You do realize that, even in principle, you can't dig up significant numbers of bodies. All but a tiny fraction of dead carcasses are completely destroyed over millennia. Only a very, very,very few are preserved to be later recovered. (BTW, you're not going to find many of them fossilized anyway. Fossilization takes millions of years, not thousands.)

But what about dinosaur bones? I mean human bones should also last a long time too, although they're not as dense of bones of dead beasts.

 

[Jimmy Snyder]

That's one of the reasons why only one-in-a-zillion carcasses are ever fossilized. It's only the ones that are buried in a way where they are protected (tar-pits, river-beds, very fast sedimentation, etc.) from decay due to weathering, bacterial consumption, scavenging and a whole host of other destructive forces.

But what do you call a bone that has been around for a ten thousand years? That's not enough time by your definition to be called a fossil. If it hadn't fossilized wouldn't it have decayed by interal destructive forces?

 

[DaveC426913]

But what about dinosaur bones? I mean human bones should also last a long time too, although they're not as dense of bones of dead beasts.

Did you know that there are only five Tyrannosaur skeletons in existence? 99.999999999...% of ancient skeletons disappear without a trace.

Even if that weren't the case, how do you propose to find all the ones that do exist? Are you planning to scrape the entire Earth's surface to a depth of 100 feet, then sift through those megatons of dust, separating out every human skull you find?

This is ridiculous even for GD.

 

[DaveC426913]

But what do you call a bone that has been around for a ten thousand years? That's not enough time by your definition to be called a fossil. If it hadn't fossilized wouldn't it have decayed by interal destructive forces?

My definition? No. Fossilized bones are bones whose volume in the rock has been replaced by minerals. They are rock.

And yes almost all bones decay by internal and external destructive forces. Which is why Zdenka's idea is ridiculous.

 

[Jimmy Snyder]

My definition? No. Fossilized bones are bones whose volume in the rock has been replaced by minerals. They are rock.

And yes almost all bones decay by internal and external destructive forces. Which is why Zdenka's idea is ridiculous.

So just after death they are bone and millions of years later they are rock. I'm asking what are they in between. If still bone, how do they survive the internal destructive forces to become rock. If rock, why aren't they fossils?

 

[DaveC426913]

Zdenka, come clean with us. Is this a brain teaser that you made up yourself that sounds plausible based on your own understanding of the fossil record?

Because unless there's something you're not telling us, this is just way off the reservation.

 

[DaveC426913]

So just after death they are bone and millions of years later they are rock. I'm asking what are they in between. If still bone, how to they survive the internal destructive forces to become rock. If rock, why aren't they fossils?

You're asking me to teach a basic lesson in paleontology, and I'm no paleontologist, but...

In very rare circumstances, carcasses are buried in ways that prevent decay of the hard structures. Flesh decays quite rapidly of course. Bones, less so, they're a network of calcium afterall; bacteria don't really dissolve them. Decay can be prevented in environments low in oxygen or very cold. If a large animal sinks to the bottom of a very cold lake, or into a tarpit, then its bones will survive long enough for the surrounding sediment to turn to rock. Then, over millions of years, minerals dissolved in water seep through the cracks, dissolve the soft bony materials and carry them away. The cavity left behind can get deposited with new minerals. Eventually you've got a fossil in the shape of the original set of bones but made of rock.

Note that all of this requires that the bones are not disturbed or destroyed by weathering, quakes, or other forces over the entire length of the fossilization process.

You can see that we're very lucky that there are any fossils at all.

 

[Evo]

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

Actually, this is the correct answer. I am not aware of any humans that meet the OP's criteria that have not lived and died on earth.

Asking for a specific "number" is not possible, since as it has been pointed out we don't even know of civilisations that might have lived and been eradicated without any record, and since they were wiped out, they have no present day decedants.

 

[Jimmy Snyder]

You're asking me to teach a basic lesson in paleontology, and I'm no paleontologist, but...

In very rare circumstances, carcasses are buried in ways that prevent decay of the hard structures. Flesh decays quite rapidly of course. Bones, less so, they're a network of calcium afterall; bacteria don't really dissolve them. Decay can be prevented in environments low in oxygen or very cold. If a large animal sinks to the bottom of a very cold lake, or into a tarpit, then its bones will survive long enough for the surrounding sediment to turn to rock. Then, over millions of years, minerals dissolved in water seep through the cracks, dissolve the soft bony materials and carry them away. The cavity left behind can get deposited with new minerals. Eventually you've got a fossil in the shape of the original set of bones but made of rock.
.

I'm sorry Dave, but a casual glance at a piece of petrified wood is enough to see that this is not the process.

 

[mgb_phys]

But what do you call a bone that has been around for a ten thousand years? That's not enough time by your definition to be called a fossil. If it hadn't fossilized wouldn't it have decayed by interal destructive forces?

Bone is a bit of a special case. If you remove the organic material you are left with a mineral (calcium phosphate / calcium carbonate) that is pretty stable. Assuming it is buried in a non-acidic dry ground it can last an awfully long time as bone without becoming a fossil.
A lot of remains found in caves and tar pits are not strictly fossils because the bone has not been replaced by minerals - it is the same chemical bone that was in the living animal.

Ironically the incredibly well preserved bodies from peat bogs that preserve the skin and hair contain no bone which is dissolved by the acid very quickly.

 

[Jimmy Snyder]

Bone is a bit of a special case. If you remove the organic material you are left with a mineral (calcium phosphate / calcium carbonate) that is pretty stable. Assuming it is buried in a non-acidic dry ground it can last an awfully long time as bone without becoming a fossil.

But then how does the bone become mineralized? It seems to require water and once water is supplied over a period of millions of years so that minerals can replace the calcium phosphate, where is the necessary non-acidic dry? I think that even if it takes millions of years for bone to become mineralized, something else must happen quite rapidly to stabilize the bone. Whatever that else turns out to be, it should be suffient to make the bone last millions of years even without mineralization. In other words, fossilization should take place within decades, even if mineralization takes millions of years. By the way, why should it take so long to mineralize? I wonder if there is a non-sequitur going on. Many fossils are millions of years old so they must have taken millions of years to form.

 

[mgb_phys]

The classical model of fossilization (you should really call it mineralization - fossilization is used loosely for any old preserved remains) :
Organic matter (the meat on the bones) is destroyed and the remains are buried.
Fine clay/silt etc covers the bones and permeates into all the cavites where the cells once were. You can have negative fossils where the process stops here and you have a mould of the animal body part - this is especially common for plants.
Or with the right conditions you can then have water laden with minerals permeate through the clay and dissolve the original bone replacing it with deposited minerals.
This gives you a classic fossil where the bone is replaced by an exact replica in rock.

The time this takes depends on the geological conditions, there are places with very heavy mineral loaded water where you can coat an object in limestone in a few years. Some are among the first tourist attractions (Petrifying wells) where you could hang up a soft object in the dripping water and it gets coated by rock.

 

[Jimmy Snyder]

Thanks mgb_phys.

 

[DaveC426913]

The classical model of fossilization (you should really call it mineralization - fossilization is used loosely for any old preserved remains) :
Organic matter (the meat on the bones) is destroyed and the remains are buried.
Fine clay/silt etc covers the bones and permeates into all the cavites where the cells once were. You can have negative fossils where the process stops here and you have a mould of the animal body part - this is especially common for plants.
Or with the right conditions you can then have water laden with minerals permeate through the clay and dissolve the original bone replacing it with deposited minerals.
This gives you a classic fossil where the bone is replaced by an exact replica in rock.

The time this takes depends on the geological conditions, there are places with very heavy mineral loaded water where you can coat an object in limestone in a few years. Some are among the first tourist attractions (Petrifying wells) where you could hang up a soft object in the dripping water and it gets coated by rock.

Of course, this is all just rationalization. God did all this 6000 years ago...