What percentage of people are alive today? | Hacker News Reader

What percentage of people are alive today?

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233 pointsjonathanbgood91 comments

Not to detract from the insight but:

Until very recently life expectancy at birth hovered between 20 and 35 years, but in the past century it has risen to 67 years

Most of this increase has been due to a precipitous crash in infant mortality, rather than a soaring increase in the median life expectancy. For example, even in the 1500s it seems a well-to-do Englishman (who lived a somewhat more hazardous life medically than even today's poor) had an average life expectancy of 71 if he made it as far as 21: http://apps.business.ualberta.ca/rfield/lifeexpectancy.htm

Exactly. One of my pet peeves is the misconception that a life expectancy of 35 means a normal adult somehow drops dead at that age. (And leads to arguments like "Oh, don't eat a paleo diet, cavemen only lived to 35").

Socrates lived to 71 in ancient Greece. Yet you know him for being a philosopher, not for living 2.5x the average age (like living to 200 today -- you'd think that'd make a fuss).

And he died condemned to death and executed, too! So he could have lived happily for many more years.

Xenophanes of Colophon supposedly lived to 95. Pyrrho of Ellis lived to 90, and Democritus to 109. On the other hand, Epimenedes is supposed to have lived to the age of 154 or 290 depending on whom you believe, so take these numbers with a grain of artery-clogging sodium chloride.

Yeah, and Noah reportedly died at 950, so I'd definitely take these numbers with a drop of hemlock :)

Go back far enough in history and numbers get even less believable, just think of Methuselah.

It should be noted that there is some difference between history and scripture. Though, history doesn't know everything either.

Zeno of Elea got ever so close to 60 but never quite made it.

I still don't understand why the average is used instead of median (or average of data between the first and third quartile), when people talk about life expectancy. It leads to misconceptions.

(A) It fits into peoples agenda.

(B) Most people know almost nothing about statistics. Even those who use it on a every day base. Honestly, I'm afraid, I'm not really an exception.

I think if you have to guess between human evilness and stupidity the latter is more likely, right?

Most people know almost nothing about statistics. Even those who use it on a every day base.

The same could be said of English.

Not every poster here calls English his or her first language. If you send me corrections, I very much appreciate it.

"on an everyday basis." <shared in the spirit of learning and mutual respect. Not snark>

Aside from the fact that more than half of the people in the world actually don't know anything about English, what does that have to do with..anything?

I do claim to be at least moderately familiar with the language, and have no idea why you're quoting that line.

Because it is the correct measure for the question at hand. In a steady state population, life expectancy at birth times the rate of births gives you the number of people alive, and equally number of people alive divided by average length of life gives you the number (or rather, rate) of individuals born, which is what you need if you want to know how many individuals have ever been born. The maths gets a bit mor complicated with a dynamic population size, but the principle is the same. The median would be completely useless for this.

All true, though, as far as I know, hunters and gathers who manage to survive childhood still die quite early, no? [1] They appear very healthy but thats partly because there are pretty much no grand parents. I might be wrong about this.

Also, a diet high in animal protein might make you very fit but it is thought to be a cause for cardiovascular disease [2]. Actually, afaik, this is the reason why government still gives out these fat making, carbohydrate rich, diet recommendations [3]. They might make you obese, but on the other hand, if you might live a sportive life just to suddenly die of a heart attack.

[1] I can't recall if it was Diamond, Kevin Kelly in "What Technology Wants", Campbell in "The China Study" or someone else, who wrote about this. Can anyone back or correct this? [2] This, Im sure you will find in "The China Study" by Campbell [3] Lustig and also Taubes in "Good Calories, Bad Calories"

Nutrition isn't the only issue. Hunter-gatherers have a much higher chance of a violent death; not just because of the risks of hunting, but because tribal warfare drafts the majority of able-bodied men. Even the ritualized warfare commonly used among present-day hunter-gatherers is likely to cause deaths.

http://en.wikipedia.org/wiki/War_Before_Civilization

Christopher Ryan [1] denies this.

So which of my down voted post above was bullshit? I'd like to learn.

[2] http://www.psychologytoday.com/blog/sex-dawn/201103/steven-p...

Christopher Ryan's blog post is low on examples, compared with that Wikipedia page about the book...

>>About 90-95% of known societies engage in war. [Etc.]

This is a sensitive subject for people with (political) axes to grind, so I'd prefer better references for the claim that Pinker is totally non serious?

(I was surprised to see that Eskimos had extermination wars?! You would think the population density made organised conflicts impossible?)

Edit: Clarity.

You might be right. I still think its worth reading. I still tend to prefer Christopher Ryan's point of view but this might change. Also, Pinker is afaik not a professional expert on anthropology [1].

[1] http://en.wikipedia.org/wiki/Pinker

Pinker quoted an expert. Or not?

If the research consensus in the field really was different, Ryan would have pointed that out gleefully -- with many more references. Since Ryan didn't do that, he is either dishonest or ignorant. Either way, he can be ignored.

Here are a couple posts questioning the impact of infant mortality on ancient lifespan estimates, http://santafereview.com/chronicle/2011/02/01/ancient-mortal..., http://www.wonderquest.com/LifeSpan.htm both referencing this paper, http://www.animalsimulation.org/index.php?option=com_content....

A few statistics from the paper are the mean lifespans of the Kings of England and Scotland between 1000 and 1600 were about 50. This was also about the mean lifespan of people at court. In a monastic population studied only 5% lived past 45 and excavations of anglo-saxon cemeteries dated at 600-1000 CE found no one older than 45.

Also, there has been much more man to man violence in the past. Its been an exponential decrease since the beginning of man. Stephen Pinker had a TED talk about this http://www.ted.com/talks/steven_pinker_on_the_myth_of_violen....

This back-of-the-envelope calculation appears to be off by a factor of two, which isn't bad.

http://en.wikipedia.org/wiki/World_population#Number_of_huma...

this error is because of assumptions about the life expectancy, right?

Yes, their birth rate assumptions would only yield the population milestones they suggest if the life expectancy was significantly below the reported level.

Am I the only one absolutely terrified by that number?

Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable.

It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.

You are not alone. If you want to get more scared, read http://www.amazon.com/Collapse-Societies-Choose-Fail-Succeed....

Interestingly from the population statistics alone it is possible to make an argument about the total likely future number of humans that will live. There is debate about whether the reasoning is correct, but it is at least suggestive. See http://en.wikipedia.org/wiki/Doomsday_argument for more.

And maybe once you're done with that, you can read a rebuttal of sorts:

http://www.amazon.com/Coming-Population-Crash-Planets-Surpri...

I am familiar with the arguments suggesting that population growth is self-limiting. I am also aware that the spread of birth control is breeding people whose will fail to use it. They may be a small portion of the overall population, but any portion that is on an exponential curve when the rest are not is bound to eventually dominate the population.

Malthus has been postponed for centuries. And may well be postponed for more centuries. But unless resources grow exponentially, Malthus eventually will have the last laugh.

I don't think the Doomsday Argument is that interesting. It may be trivially true, but it doesn't tell us anything interesting or predictive. All it says is that the chronology of human existence is too complicated for us to calculate. That being the case, our working assumption can only be that we're at the midpoint of our species population line. But, keep in mind that this estimate is really, really horrible, it's only virtue being that it's better than all the others.

If someone gave you a trick coin, and you didn't know which side was favored, you'd have to assume 50/50, even knowing that you were certainly wrong. Knowing that one side is weighted doesn't give you any interesting information for one toss.

If you follow the arguments for and against the DA, it's clear this isn't about a well-defined statistical argument, but immediately devolves into qualitative arguments about our survivability. The optimists say, well, based on the average extinction rate it's extremely unlikely we'll die in <100 million years. The pessimists counter that we're creating technologies with extinction level capacities very rapidly. Either way, we don't have a way of gauging the predictive power of these claims. We can't run a controlled study of 100 human species spans.

And that's fine, because we need to argue about and introspect on the longevity of species, but brainteasers like the DA don't further it in any meaningful way.

I don't think the Doomsday Argument is that interesting. It may be trivially true, but it doesn't tell us anything interesting or predictive.

If it is true, it can let us put probabilistic upper bounds on the future of the human race. For instance with 99.99999% likelihood I can tell you that the human race will fail to succeed in expanding colonization of other stars. As much as we may dream of the stars, we will never reach them.

Similarly the odds of our maintaining our current population levels for the next thousand years is something like 40%. That is both interesting and predictive. Its meaning, however, is highly debatable.

Scared? I remember distinctly the book ended with a "cautious optimism".

Yes, it points out a lot of potential problems, and makes it obvious that societies _do_ fail, and that we're not yet above that rule, but I wouldn't call it scary.

I'm putting much more faith in commercial spaceflight programs (Scaled Composites, SpaceX, Armadillo) for advancing space exploration/colonization than I do in NASA. Even their early work shows that their marginal costs are many orders of magnitude less than NASA's funding. This is one of those areas where market forces will beat out the government hands down.

One interesting fact regarding population growth is that worldwide, having children on aggregate is a inferior good: if parts of Africa and Southeast Asia can make some significant gains in the next few decades, we will likely see population peak sometime this century.

Children can't be compared to goods. There's biological things at worth beyond self interest. That is to say, people want children, even though its not in their self interest.

I'd posit, if you were to try to assign children a status as a good in a wealthy culture, they'd be a luxury good. They cost a great deal, are effectively useless, but still desired.

<i>That is to say, people want children, even though its not in their self interest.</i> It certainly isn't in the children's interest either, because they can't be benefited by being brought into existence (they are not waiting in some pre-existence limbo wishing to become existent).

It's in the "interest" of our genes, like many other things we do.

Of course Earth must have some finite carrying capacity, but that's only terrifying if you assume that "The Crunch" is the only way to bring population growth to a halt.

Population growth is already zero or negative in most developed countries if you remove the effects of immigration. If this becomes a consistent rule for all countries once they become fully developed, the real question is not whether we can sustain infinite population growth, but whether we have the resources to support a developed lifestyle for the entire world. Given current technologies and energy sources, the answer is almost certainly "no", but this is a much more tractable problem.

I agree that such a state doesn't (a) seem impossible or (b) seem untenable if we have sufficient technological advances (solving fusion ignition, perhaps).

What kind of trajectory takes us from here to there (or to a place dense with similar stable solutions) without going through war and famine? Or, how does a developed nation survive in relative bounty surrounded by nations undergoing severe war and famine?

The first question is very difficult to answer..the second?

>Or, how does a developed nation survive in relative bounty surrounded by nations undergoing severe war and famine?

Brutality and self interest.

That currently developed nations currently have a negative growth rate only makes sense in terms of our current medical situation. If it were a hundred years ago, they'd all have collapsed by now, and if life expectancy doubled, or if people could halt their aging, population would once again explode, simply because couples like to raise children.

Nature will find far less technical solutions to this problem. War, poverty, disease will provide a ceiling to this growth.

Malthus was wrong in principle. He didn't understand human action or economics, and that misunderstanding remains very common. See:

http://www.fightaging.org/archives/2006/09/overpopulation.ph...

"Common Malthusianism - the idea that a given resource (such as living space or food) will run out in the future based upon extrapolation of present trends - stems from fundamental misunderstandings about economics, human action and change. We create change in response to our environment; our self-interest leads us to constantly strive at the creation of new resources where old resources are becoming scarce and expensive. This is the path to profit for the individual - and progress for all. One needs a certain amount of willful blindness to avoid seeing the process in action now and in recent history."

"Common Malthusianism" is a strange name to apply to a claim Malthus didn't make. Malthus didn't attempt to extrapolate current trends, he merely pointed out (correctly) that there will eventually be a limit to productivity. From "An Essay on the Principles of Population":

We may be quite sure that among plants, as well as among animals, there is a limit to improvement, though we do not exactly know where it is. It is probable that the gardeners who contend for flower prizes have often applied stronger dressing without success. At the same time, it would be highly presumptuous in any man to say, that he had seen the finest carnation or anemone that could ever be made to grow. He might however assert without the smallest chance of being contradicted by a future fact, that no carnation or anemone could ever by cultivation be increased to the size of a large cabbage; and yet there are assignable quantities much greater than a cabbage. No man can say that he has seen the largest ear of wheat, or the largest oak that could ever grow; but he might easily, and with perfect certainty, name a point of magnitude, at which they would not arrive. In all these cases therefore, a careful distinction should be made, between an unlimited progress, and a progress where the limit is merely undefined.

He then observed the tendency of humans to reproduce until the limits of their environment are reached and concluded that poverty will be the terminal state of humanity.

Malthus was merely wrong on this empirical point - humans are willing to voluntarily stop reproducing under certain cultural and economic circumstances. These circumstances involve modern levels of economic productivity, technologies (birth control) invented 100 years after his death, and western cultures. He wasn't wrong on principle, he merely lacked the data we have today.

> he merely pointed out (correctly) that there will eventually be a limit to productivity

I don't understand this point. Why would there be a limit to productivity, especially with machines and computers to leverage our efforts thousandfold and more?

And how could anyone know that such limit exists, even if it is actually reached one day? That would require predicting any possible innovation of the future.

I don't understand this point. Why would there be a limit to productivity, especially with machines and computers to leverage our efforts thousandfold and more?

There are limits to what you can do with matter. It's unlikely the economy (our productive capacity) will continue to grow much for 100,000 years after all mass we can get at is weird ass artificial quark composite computronium.

As long as the measure of productivity corresponds to something physical (which even bits on a harddisk are), then an exponential increase in productivity (as we have seen in the past) would eventually require humanity and its products to form a sphere whose radius grows faster than the speed of light.

Do you agree that that is a pretty hard limit?

I think you may have skipped some steps... Could you fill in the middle a bit? I'm confused.

Let's suppose the amount of physical goods produced increases 1% each year. Let's add that as physical objects they take up some space minimum amount of time. Now let's add that humanity is spreading out in all directions at the speed of light. If humans cover 1 light year of space they can expand faster than the new amount of stuff. However Volume = 4/3 pi * radius ^ 3 so what happens when humanity covers 1,000 light years. Well, next year they need to put 1% more stuff into 1002^3 / 1000^3 = 0.6% more space which means they need to increase the density which at some point means you have a black hole.

PS: 1% growth per year seems slow and sustainable but in 20,000 years your talking about 2.7 with 86 zeros after it. Start with 1 atom for one second and compare it with every atom in the earth for a year and your only at 4.2 with 57 zeros. So if the total economic output of humanity was 1 atom we could not sustain 1% economic growth per year for 30,000 years.

Edit: This assumes that the economy is based on physical goods, if we assume intangibles can take up 99.99...9% of the economy then 1% growth is possible for long periods of time even if it's somewhat meaningless.

In out three-dimensional space, volume grows with radius at r^3. If something physical grows exponentially (2^t), then the radius of its volume needs to increase over time at an accelerating rate, which means the growth of that radius will eventually surpass c.

Yes, I think a limit on productivity amounts to a limit on knowledge. Does knowledge have a limit? There's no evidence for it; all our present mathematics of complexity suggests not (but it's possible one will be discovered...)

However, energy needs do seem to increase with productivity, and there's limit on how much energy we can get from the sun (a dyson sphere encloses the sun, capturing all its energy). But there's some assumptions here: that we can't discover ways of being productive that require less energy (and wouldn't that enhancement itself be "productive"?); that we can't discover other sources of energy (e.g. room temperature fusion micro-suns - or something better).

Once you factor in the unknown (i.e. knowledge that we don't yet have) it's hard to know what the limits are. I guess the entire universe is a limit on matter... if we can't discover a way to make more matter... or more universes.

There are actually mathematical limits to the amount of information that can be stored within a given volume, the Bekenstein bound, which is a lot like a limit to knowledge.

Well... if we can make new universes, the volume isn't limited.

Actually we know for a fact such a limit exists. There are physical limits on how much energy can be extracted from a certain mass.

Historically, colonization has had little impact on the size of the population that sent them. And even if it improved the lives of the people who left, it had no impact the lives of the people who stayed.

The vast majority of natural populations that I've looked into have s-shaped population growth without any particular unpleasantness; as population nears its carrying capacity, birth rate naturally tapers off, leading to near-zero population growth. Humanity appears to be in the tapering-off stage of this already (since around 1980), and I don't see any reason to presume there will be unusually high levels of conflict or tragedy as that tapering-off process continues.

The typical Mathusian "overpopulation" argument (based on a shallow misreading of Malthus) is not that we'll have an S-shaped population growth curve, but an A-shaped one -- that we'll have population grow out of control, and then come crashing back down through some massive tragedy (akin to the Kaibab Deer population [0]). The A-shaped scenario is reasonably unlikely for humans.

[0] http://depts.alverno.edu/nsmt/youngcc/research/kaibab/story3...

>Am I the only one absolutely terrified by that number?

No, unfortunately there are plenty of other irrational sensationalists.

>Malthus wasn't wrong in principle, just in timescale.

He has been horribly wrong in principle, as has every other pessimist who cried wolf for the past 3000 years. Saying 'the timescale was just wrong' is not an adequate defense by any means. Timescale is what matters and is the essence of all predictions.

Ask a trader: a prediction that oil will go up in the long run is completely useless if you don't define when that event will occur, and subsequently loose everything on a big short term dip that you were blind to.

Additionally, if your prediction is allowed to take "infinity" duration to come true, then it can never be disproven. And what can't be disproven is usually categorically not worth the thought.

To discuss particulars, the current evidence is technology allows us to produce TOO much food TOO cheaply, which is compounded further by domestic farm subsidies. Efficiency gains are so successful in keeping up with demand, that in Mexico City they buy corn from Iowa, even though they have cheaper farmland and local labor that could be utilized.

Additionally, many economists are currently considering the possibility of efficiency gains being so strong a factor that they lead to structural unemployment. This picture of runaway efficiency gains is the exact opposite of what Malthus had envisioned (constant\linear resource utilization massively outstripped by population growth rate)

>It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.

All the nations economically developed enough to have a space program are rapidly decreasing in population. China, Russia, Japan are all on the decline, the US is only increasing due to immigration. It's economics 101: wealthy people have more economic freedom to invest in birth control and their time in things other than family. Additional children switch from being an asset into a liability when you have to pay substantial amounts for them to be educated and the opportunity cost of taking time to raise a child becomes higher. The S shaped curve has been in full swing in developed countries like the US and Russia where the vast majority of the land is deserted, without anything resembling a Malthusian scenario.

> It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.

The politicians who authorized the current pension structures for California state employees undoubtedly had similar data, so I imagine defunding NASA would be comparatively trivial short-term thinking.

i'm sure there is a more accurate prediction out there (explained in papers) by researchers who have spent way more time and effort into this subject. for us common folks, there's even a wikipedia answer: http://en.wikipedia.org/wiki/World_population#Number_of_huma...

Super fascinating. Definitely would never have guessed it was anywhere even close to 12%. Wow.

I've always wondered this! I thought it was probably relatively high, but 12% is pretty insane.

I had heard it was over 50% which i found very hard to believe so the 12% number seems a lot more reasonable.

I've always wondered something about evolution (or rather, speciation): how many generations removed could an ancestor and descendant be and still be theoretically able to mate?

I'm sure the ability to mate isn't exactly the definition of a "species," but it seems like a decent way to get a grip on the extremely gradual genetic changes predicted/described by evolution. This article made me ask the question: How would you be able to recognize the "first human"?

Since it's speculated that Neanderthals and early humans inter-bred, then it stands to reason the gap can be pretty far apart.

There are exceptions like those with dogs where one dog may be physically too small or too large to breed with another. I'm kind of irritated that some claim species cannot be created when a chihuahua and a Newfoundlander could not possibly inter-breed. If dogs like that were stumbled upon in the wild they would obviously be classified as entirely different species.

This is an important computation. It's even scarier if you suppose that you are not in any way special. It is likely that you are not one of the first 5% of humans to ever live. Thus, given that such a great proportions of all humans who have every lived are alive now, the implication is that the human race hasn't got long to go even if the population remains constant! Or you could just assume you are special.

By that calculation, no human should assume they are in the last 5% so the human race is immortal.

It sounds like nonsense; the people actually in the first 1% are not more special than the people in the 43rd 1%, but you have to be somewhere in the distribution.

No point is special in the sense that you have a stronger than usual reason to assume you aren't there and are more likely elsewhere.

Not really. You shouldn't assume you are in the last 5%. Statistically, by definition, it is most likely (though not certain) that you are not.

That's the sort of analysis I'm questioning - it's also 95% likely that I'm not in the second-last 5%, and the same for the third-last 5% and for any 5% slice.

How can we usefully reason anything from a start like that?

They never say how they estimate births_t.

We use the world population and average life expectancy to calculate births in a year. To connect these point estimates at the varying times in history we use a bounded exponential growth model for births.

I'm still not completely getting it. Let's say in some year there are a billion people alive and the average life expectancy is 50 years. How are these two pieces of information sufficient to determine how many children were born in that year?

You also need the previous year's population. With population and life expectancy, you can approximate the per capita death rate, and then it's a straightforward linear equation.

What about infant mortality? If a million babies are born in the year 234BC, and die before 233BC rolls around, they won't be counted in the population for either year.

That's what I'm wondering about. The infant mortality rates in pre-industrial times were astoundingly high, but I don't see anything that tries to explicitly account for them. I guess they get rolled in with life expectancy (bringing the mean way down), but it would be nice to see an explicit formula for births_t.

This is great info if there ever is a zombie apocalypse. Eight heads each people.

Now if we could get every person educated and productive, we could solve tens of billions of problems. Unfortunately, most people are just trying to survive.

We'd also have to give them problems to solve outside of 'how do I raise my children' or 'feed myself' or 'entertain myself'...or is that what you meant by productive?

It's an ugly thought but I think more people than ever are trying to create a biological retirement plan - having multiple children to take care of them later on.

Trying not to make a moral judgment call on that and hoping I am just being too cynical. But think about how many people you know with children and then count the number that have conscientiously chosen to have only one.

I fail to understand why this is of interest. The number doesn't tell you anything. If only 600M people were alive to today, the number would be a factor of 10 smaller. So what? You can't distill any meaning from the number. It doesn't predict anything, doesn't spell out opportunities, doesn't explain anything. It's a synthetic numerical fact, as constructed and unrelated to anything Real as the fact that the length of my thumb is exactly 1.5% of the height of the Eiffel tower.

What 200,00 BC mean, 200,000 BC?

The author made that error 3 times (cut&pasted wrong chart).

Thanks for pointing it out - we fixed this to 200,000 B.C.

I'm pretty sure I'm alive today, although some may have their doubts on Moday morning...

I thought that 'humans', as in, you would see one and say, "yeah, that weird looking guy over there," went back about 2.2 - 2.3 million years.

http://en.wikipedia.org/wiki/Human_evolution

Populations would have been small, but an extra 2.1 million years is a long time.

There have been catastrophic events in that time that some believe acted as population bottlenecks, in particular the Toba eruption 70,000 years ago: http://en.wikipedia.org/wiki/Lake_Toba

Of course, there is much debate about the effect this had.

[edit] In a recent Seminar About Long Term Thinking, a biologist said that there is evidence the human population was reduced to a few thousand by the Toba event. That is the extent of my knowledge on the subject.

Quote from that link:

"There is some evidence, based on mitochondrial DNA, that the human race may have passed through a genetic bottleneck around this time, reducing genetic diversity below what would be expected from the age of the species. According to the Toba catastrophe theory proposed by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign in 1998, human populations may have been reduced to only a few tens of thousands of individuals by the Toba eruption."

From that, The dominant view among scientists concerning the origin of anatomically modern humans is the "Out of Africa" or recent African origin hypothesis, which argues that Homo sapiens arose in Africa and migrated out of the continent around 50,000 to 100,000 years ago, replacing populations of Homo erectus in Asia and Homo neanderthalensis in Europe. Scientists supporting an alternative multiregional hypothesis argue that Homo sapiens evolved as geographically separate but interbreeding populations stemming from a worldwide migration of Homo erectus out of Africa nearly 2.5 million years ago.

The difference is that the species that we call Homo sapiens - us - is on the order of 100,000 years old.

Wikipedia lists the total number of people to ever live at about 115 billion, which means 6% of all people are still alive today. 12% is too much.

Funny, that they have a cloud in their logo.

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