How many humans have lived on Earth?

[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...

 

[Jimmy Snyder]

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.

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

Bingo!

 

[mgb_phys]

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

When scientific measurements, such as radiocarbon dating, are made, the Flying Spaghetti Monster "is there changing the results with His Noodly Appendage.

 

[Jimmy Snyder]

Here is a report from the Smithsonian/NASA Astrophysics Data System

This study evaluates the accuracy of U/Th dates for young (< a few thousand years old) reef corals, both living and fossil, and explores strategies for refining those dates.

Apparently it does not take millions of years to create a fossil. Dryness isn't necessary either it seems.

 

[DaveC426913]

Here is a report from the Smitsonian/NASA Astrophysics Data System



Apparently it does not take millions of years to create a fossil.

I don;t think that's quite the same thing. Corals are already a framework of mineralized organic material.

 

[mgb_phys]

Apparently it does not take millions of years to create a fossil. Dryness isn't necessary either it seems.

Fossil just means 'preserved remains' (it's latin for dug-up) - the bones-turned-to-rock process is properly called mineralisation.

 

[DaveC426913]

Fossil just means 'preserved remains' (it's latin for dug-up) - the bones-turned-to-rock process is properly called mineralisation.

Yes, that was going to be my other comment. When they're talking about corals, I really doubt they're using 'fossil' in the common sense anyway (even if it did mean bones-to-rock).

 

[Jimmy Snyder]

I don;t think that's quite the same thing. Corals are already a framework of mineralized organic material.

Are you saying that the corals were already millions of years old before they died less than 1000 years ago? You have a tenacious hold on this idea that it requires millions of years to create a fossil and that is why I am convinced you can post a citation in support of that idea.

 

[DaveC426913]

Are you saying that the corals were already millions of years old before they died less than 1000 years ago?

What? I never said anything of the sort. They don't need to be millions of years old to be formed of a mineralized framework. They build this while they're alive.

Actually, they build on top of the framework. The living parts of coral are the top few inches formed over a calcified framework of older coral that's been built up over tens of thousands of years. But that's not fossilisation, that's just a calcified remnant structure. Sea cucumbers and sand dollars do a similar thing (just not in giant communal structures). It's basically their skeleton left behind.

 

[Jimmy Snyder]

What? I never said anything of the sort.

If the coral are not millions of years old then fossils don't take millions of years to form. Cite if you will. If not, then your methods are no different than those of a creationist. You believe and so it is true.

 

[DaveC426913]

If the coral are not millions of years old then fossils don't take millions of years to form. Cite if you will. If not, then your methods are no different than those of a creationist. You believe and so it is true.

Jimmy, are you having me on?