How many people lived on Earth 2,000 years ago? How can you explain their enormous number?

Math makes it easy, if you want. But it doesn’t explain deaths by disease and other, not to mention average age of death, both make and female.

In ancient Rome, a baby had a 36% chance of dying before the age of one. Life expectancy was 42.

Life expectancy in 1920 was 54.

At 50 years of age 1 in 8 people won’t live to age 65.

In the year 1800 the population of the Earth is said to have hit 1 billion. In 1930, 2 billion. How does that fit into your math??

What does the possible number of people on other worlds have to do with Earth’s population at ANY time?

Sex. That explains their enormous numbers.

https://en.wikipedia.org/wiki/Estimates_of_historical_world_population

There are basic fundamental math & modeling logic errors in the question.

Your assumptions only apply to small groups of people with no common ancestors. But people DO have common ancestors in common. Yes those people had ancestors, but many of their ancestors were the same people – they overlap.

The real way it works should be obvious, if you go forward in time, and multiply that way (and let many people die and not have children).

Your equation is missing an important factor. Every person born, dies.

@jca2 answered your first question, and @LuckyGuy partly answers your second.

I would add that not only does every person born, eventually die…but most of them die young. In Ye Olde Days, if you made it through a year without losing anyone close to you… that was a good year. And something of an unusual year. People had lots of kids for the same reason that insects do – because the mortality rate is such that if you want some to actually survive to have kids of their own, you need a heck of alot more than 2.

You could only support as many people in an area as you had agriculture, and agriculture was alot less productive back then and food kept less well than it does with modern refrigeration and vacuum packing. So anytime a group got too plentiful – famine.

The explosion of the human population is a fairly recent phenomenon. Your math assumes huge numbers of people in the past, but the opposite is true. There are more people living now than ever before at about 8 billion. Note that this is NOT to say that there are more people alive today than have EVER lived…I’ve heard that statistic and it’s bullsh—.

How do we do it? Better medicine, better agriculture, more trade, more productive societies due to market incentives. The reason we avoided the Malthusian trap is that the trap assumes productivity and efficiency never rises. But this is Capitalism’s strength – it relentlessly increased productivity and efficiency. We can complain about some of it’s other features, but it has no peer in that regard, and at a macro level – that’s what matters.

The alternatives are mass die-offs because like a goldfish in a pond, we outgrow our food source.

If you go to old cemeteries (aka historical cemeteries), you’ll find a lot of graves for little babies and toddlers. Also, a lot of women used to die during childbirth. Another big cause of death was infections – people would get a cut or a major wound, and without antibiotics, that was it.

Rhesus negative blood also killed a lot of babies back then. They could not screen for that like they do now.

@kritiper, let me ask you this: What does the possible number of people in Europe have to do with America’s population at ANY time?

I hope you can answer your own question now. :)

@Zaku, your answer neither finds fault in my Maths, nor does it explain anything. People having common ancestors doesn’t annul the fact that EVERY person on Earth had to have a pair of parents, which doubles the number of their ancestors every 25 years on average.

Even if all people now living on Earth had the same father and mother, those two parents would still have to have their own fathers and mothers 25 years ago – and so on – which then brings you back to the calculation that I have made in my question.

You get that, don’t you?

@LuckyGuy, oh….

@jca2, you’re explaining the reverse order of things.

But my question was, how do you explain the order going back in time that I had mentioned?

You are neglecting how many are from Kentucky; i.e. cousins.

@AhYem Another way of understanding @Zaku’s correct answer is to consider how many descendants a man and a woman who lived 2,000 years ago might have today. The number is huge.

Every person who ever lived has two ancestors but as you go back in time more and more of these ancestors are shared common ancestors so the total number of ancestors is not nearly as high as you might think. My great, great, great, great grandfather for example wasn’t just my gggggrandfather he was the gggggrandfather of hundreds of people.

Math is hard but I am fascinated by how people make it look even more harder…

lol!

@AhYem The fallacy of your logic can be explained in just my family. I have three siblings, but the four of us come from one family of two parents. My girlfriends family had one set of parents which resulted in five children and 15 grand children.

The exponential growth is not the number of ancestors, but the number of descendants.

As @LuckyGuy said, you have to take deaths into account. The way to look at it is that if every pair of parents has two children then the parents are just replacing themselves and the long term population does not change. To get population growth, the average number of children per two parents must be greater than 2. If every pair of parents has 3 children then each 2 parents are replacing themselves with 3 children, causing a 50% growth rate per generation.

@AnYem “your answer neither finds fault in my Maths, nor does it explain anything.”
– If my answer failed to explain anything to you, I am sorry.

I guess I don’t understand the full scope of your misunderstandings. They seem vast, and to include massive overconfidence in your own supposed understandings.

“People having common ancestors doesn’t annul the fact that EVERY person on Earth had to have a pair of parents, which doubles the number of their ancestors every 25 years on average.”
– If by “the number of their ancestors”, you mean unique ancestors, then you are wrong. Common ancestors are not unique additional people. They’re just ancestor relationships.

For example, take a village where people don’t travel much, as has been the case in most places on Earth for most of the past 2000 years. Suppose it has a population of 100 in the year 1 AD. Over the course of the next generation, suppose the death rate is about equal to the birth rate over that generation, and that it’s been pretty isolated such that we don’t consider people who may have joined the village from outside, and perhaps no one has left and lived to have children elsewhere.

The population of that village, after one generation, will be about 100 still. By your logic, each of the new generation however had two parents, so the previous generation will have been twice as large? No, your thinking is simplistic and has failed to define what it means (in terms of population) to have ancestors. Yes they came from somewhere, and if you ask 100 people who their parents were, you’ll get 200 names. But that doesn’t mean the population was double in the previous generation.

Try a simpler example:

Bob and Jane have two children who survive, Og and Bog. They “each had two parents” but guess what? Both their parents were Bob and Jane. Total: 2.

@flutherother so what? Can’t you see that your statement – although being absolutely true – still doesn’t negate my talk?

@Zaku so what? Can’t you still grasp what I’m talking about?

@LostInParadise your reasoning goes in the opposite direction. I’m not talking about a future increase of population.

My Wikipedia link states this as the answer to your question:

“Published estimates for the 1st century (“AD 1”) suggest uncertainty of the order of 50% (estimates range between 150 and 330 million). ”

You simply don’t get it, do you? :)

You’re all switching to the opposite way of reasoning, by considering a future progress of population.

@Zaku mentioned an example with a village of 100 people, and said that the population of that village will in 25 years remain the same due to no real rise, and by my reasoning it should have been double.25 years ago.

That was not my reasoning. I never said a word about the total number of people on Earth. I said that the number of a person’s ancestors would double every 25 years back in time, which is not just correct, but necessary, because everybody has to have two parents.

If 100 people had the same father and mother, the number of their most direct ancestors several decades ago would not be double, on the contrary, it would be just two of them. Consider that please. I’m talking about the doubling of number of ancestors every 25 years in the past, not of the whole population at that time. It is absolutely irrelevant how many people lived 25 years ago, the only relevant thing is that the number of a person’s direct ancestors will be twice as high.

Try to grasp that, please. If you do that, you’ll get much closer to figuring out the “mystery” behind that calculation.

Ok, let me make it much more simple.

Let’s assume this:

A huge disaster happened in the world, and only one person survived.

That person won’t last very long. Neither will he be able to repopulate the world, since there is no woman left.

So we can’t talk about a future development of things. The only thing we can do is calculate that person’s direct ancestors in the past, by taking 25 years as a parameter for doubling the number of his direct ancestors.

25 years ago 2 parents made him see the light of the world.

50 years ago 4 people beget his two parents.

100 years ago 16 of his direct ancestors lived somewhere on Earth.

200 years ago the number of his direct ancestors was 16×16, resp. 256.

And so further and so on, till we get to the year 1 AD.

25 years ago the number of people in the whole world was about 8 Billion, but that is irrelevant for our calculation here, because we’re only interested to estimate the number of direct descendants of the last person living on Earth now.

200 year ago the number of people living on Earth was several hundred Million, but that’s irrelevant, we’re only interested in those 256 who were that person’s direct ancestors 200 years ago.

I hope this will help you to get a little closer…

https://en.m.wikipedia.org/wiki/Pedigree_collapse

I’m not talking of exponential growth @zenvelo. That is something quite different from what I’m talking about. Exponential growth considers a future development. I’m talking about the development that goes back in time.

You have two parents, don’t you?

They had their own pair of parents, didn’t they?

Your 4 grandparents had a total of 8 parents, didn’t they?

Your 8 grand-grandparents had their own 16 parents in total, isn’t that right?

The number of your direct ancestors isn’t affected by anything. 100 years ago you had 256 direct ancestors regardless if the total number of people in the world was 3 Billion or just 300 Million. Even if 100 years ago only 50,000 people had lived on Earth, the number of your direct ancestors would still be 256.

Neither is that number affected by the number of people living on Earth now. 100 years ago 256 of your direct ancestors would have lived regardless if the actual world’s population is 8 Billion or just 1 Million. Even if you were the only person in the world now, 100 years ago you would still have had 256 direct ancestors. That number is not related to the question if there are other people around you, who would share the common ancestors with you. With or without other people, the number of your direct ancestors 100 years ago will always be 256.

It is true that there has always been that “inbreeding”. But that doesn’t reduce much the total number, because it’s a very rare case, and it doesn’t occur within short periods of time. It can reduce the total number only slightly, so instead of, say, 1024, you may have 822 direct ancestors that lived 250 years ago. The loss of ancestry is almost neglectable, because if it had happened very frequently, most of us would now be mentally handicapped vegetables.

Even if we greatly reduced the number of a person’s ancestors, that number would then not be called Octillions, but maybe “only Trillions”. But as you know well, there were no Trillions of people on Earth 2000 years ago. Not even Billions.

Besides, what none of you has managed to grasp so far is this:

It’s not about the exact number of a person’s ancestors.

It’s rather about the place of their origin.

Maybe it will help you a little, if I asked you to imagine yourself living on a remote island that your grandparents and some other survivors had inhabited after a ship wreck had happened 50 years ago. They settled there and had your parents who then made you be born.

Your lineage will not end after 50 years in the past.

25 years ago your grandparents and your parents were there.

50 years ago only your grandparents were on that island.

75 years ago none of your direct ancestors lived on that island, but you still had 8 grandparents living somewhere in the world.

In the year 1 AD there were neither Billions nor Trillions or Quadrillions or Quintillions of people on Earth.

Just like there were no Billions of people on Earth 1000 years ago.

And if they were not on Earth, where were they then? ;)

@zenvelo, In my last reply I constantly mentioned 100 years in connection with 256 ancestors. I meant 200 years, of course, and I hope you weren’t too much distracted by that careless mistake of mine. :D

Ok. At this point I’m convinced you are just asking these questions to prove you are smarter than any of us. All of the “riddles” you posted here are either just logical fallacy (this question, the investment question) or scenarios with different outcomes that you are convinced only your answer is the right one.

You are not proving your intelligence. You are just making yourself look like a arrogant person with a holier-than-thou vibe.

@Mimishu1995 It’s good to see that you’re not over-pushing yourself. You’re not trying to grasp what you can’t grasp, and that is good. It would be bad if you made your brain “boil” trying to understand what you can’t understand now.

But that is no problem at all. Nobody could follow such complex thinking for as long as they are young. I myself wasn’t able to follow it while I was 20, 25, 30, 35 or 40. My Mind started to become “receptive” for this kind of reasoning only after I turned 45, and that was only the beginning. When I was young, I would have reacted to this question the way most of you did.

There was such a situation several decades ago. And the older person that was trying to make me understand something, said that I would probably need quite a time till I managed to grasp the essence of their talk. And I did need a long time to do so.

It’s not between you and me. It’s between your Mind now and your Mind 20 or 30 years later. :)

@AhYem You just wrote, “It is absolutely irrelevant how many people lived 25 years ago, the only relevant thing is that the number of a person’s direct ancestors will be twice as high.”

Well, your question here is: “How many people lived on Earth 2,000 years ago? How can you explain their enormous number?”

That seems to me like the number of people who lived in the past is relevant, since it was your question.

You don’t seem to have considered what I was saying in my previous answer. Just think of a small village through several generations, which like many places, due to historical rates of death and the tendency of people to stay in the same general area, has not really increased its population. Say about 100 people live there, after 10 generations.

You say everyone has two parents (true), so each person has 2 to the 10th power ancestors after 10 generations (also true). 2 to the 10th power is 1024. 10 generation ago, were there 1024 people in the village? No, probably not. In many cases, as in my example, there were about 100. How can this be possible? Well, because many of the ancestor slots will be filled by the same people.

It’s possible to breed a whole village or town from a handful of people (even from 2 . . .). Just because they all have parents doesn’t mean the 10th generation before wasn’t just a handful of people.

Example:
4 people (A, B, C, and D) meet and start a village.
A and B have children, and C and D have children.
One of the children of A&B has children with one of the children of C&D.

In the next generation, those children will have children with… oh, well, their choices from the previous generation are now ALL people who have all of A, B, C and D in their ancestry. Their children will all have their 8 great-grandparent slots filled twice with each of A, B, C, and D.

@AhYem , Here is the fault in your reasoning. You have each previous generation as being twice as large. That would mean that each succeeding generation is half as large. That is not right. The 2 parents came from 4 grandparents. The 4 grandparents would have formed two couples, resulting in the 2 parents plus 2 aunt/uncles that you have left out. An aunt and an uncle would produce 2 cousins in addition to the 2 children. Each time that you double a previous generation you have to also double the current generation. That would leave us with some power of 2 original ancestors producing that same number in the current generation. That is mathematically possible, but it is much more likely that there were only two original ancestors who produced larger populations by having more than 2 children per pair of parents.

@AhYem there you go. Arrogant holier-than-thou.

I already engaged with your questions twice, and I realized that it’s no use engaging with a riddle made by someone who intentionally set it up to be a game of guessing the right answer from the “enlightened” asker. I come here to discuss actual questions, not to be told to have an undeveloped mind when I don’t say what you want to hear.

It’s ironic one of your question is tagged “philosophy” yet you are dead set on one answer and demean my intelligence when I don’t agree. That is no way to conduct a philosophy discussion.

You are right. I’m not pushing myself with you anymore. I prefer to push myself with an actual discussion.

@LostInParadise, are you really that much lost in Paradise?

Or haven’t you read some of my replies here that explain it all?

Whatever be the case, it’s on you to grasp the whole thing – provided you can do that at all. I have written enough, even gifted children could understand this concept if they read what I wrote in this thread so far.

@Zaku, same goes for you. You either don’t read my explanations, or you can’t process them properly. When I say “every one has to have 2 parents” I’m not referring to “every one living at one moment of History”, but on “every one back in time”. You have to have two parents. Your two parents had to have 2 parents each. Their parents had to have 2 parents each” – and so on. That has nothing to do with the number of people living each 25 years back in time. The doubling doesn’t apply on them but on your direct ancestors. It’s only your direct ancestors whose number doubles every 25 years on average.
I explained the thing about that 100-people-village, you should just read it and grasp it.
If you can’t understand that, nobody will be able to help you, unless your own Mind 20 years later than now.

@Mimishu1995, I’m sorry I can’t help you. But Time will. Just give it chance.

@AhYem I think the limit on me processing your explanation happens at the point where you stop making sense to me. That’s the point where I see clearly that you’ve made mistakes in your logic.

I’ll try being concise:

Your question reads, “How many people lived on Earth 2,000 years ago? How can you explain their enormous number?”

Your logic is about doubling of “ancestors”, but when you double ancestor relationships, you don’t necessarily double the number of people you’re talking about (because people have children with people who have some of the same ancestors), nor the number who lived on earth in the past, because your ancestors start overlapping. When people have children with even very distant cousins, the same ancestors start appearing more and more filling more and more of those ancestor slots.

So the answer to your question is, *“About 231 million people lived on Earth 2,000 years ago. That doesn’t require any particular explanation.”

Your notion that there were 1.21 Quintillion people, because that’s the number of points on family trees, is an error of understanding. However many ancestor relationships there were, at 2,000 years back, they’re all filled by some fraction of those 231 million people (the fraction who still have living descendants today).

@Zaku , That double counting argument is a good one.

I give up on this question. @AhYem , if you want to believe there were over a quintillion people 2,000 years ago, go ahead.

So, now I’ll make an end to this question that almost no one here was able to process, by telling you how the whole thing works.

You have two parents. They had two parents too. They again had two parents themselves.

That means that 75 years ago you had 8 direct ancestors living somewhere on Earth.

You have two brothers and 3 sisters. They too had two parents each. And their parents had two parents, as well as these had their own parents.

That doesn’t mean that 75 years ago you all had 48 direct ancestors.

It’s not the number of the ancestors of all people living now that doubles every 25 years, but it is only your own ones. Your ancestors are multiplied by two each 25 years.

Your brothers’ and sisters’ direct ancestors did double as well every 25 years, but that is irrelevant, because your direct ancestors are the same as theirs.

Your reasoning always goes wrong because you don’t stick to what I have proposed in my question.

In the example of the village with those 100 people whose number remains the same over a longer period of time, you’ve made the same mistake, by thinking of the total number of people who were living 25 – or more – years back in time, instead of focusing on the number of a person’s direct ancestors there. A person of that village had 2 parents 25 years ago and 4 grandparents 50 years ago, regardless the fact that the total population of that village hasn’t changed for decades. That same person had 8 direct ancestors 75 years ago, resp. 16 direct ancestors 100 years ago, despite the fact that the number of people in that village was 100, 100 years ago. 175 years ago, when the number of their direct ancestors would surpass the number of 100, at least one of her direct ancestors must have been outside their village – which is very likely, because it’s very plausible to think that once in 175 years at least one person may “enter a closed circle”. If you go further back in time, you will in most cases realize that that village didn’t even exist say 300 years ago, so its distant population was a part of another large community somewhere else in the world. There have been oh-so-many examples for that, just think of all those early communities in North America or Australia or Africa or South America. Or of the numberless migrations of large groups throughout history.

The number of people that live or lived in a community is irrelevant. 20 people can have just one father and one mother, and each of them will have 2, 4, 8, 16… direct ancestors each 25 years back in time. But they still won’t have 20 times those numbers, because those 20 people share the same mother and father, granfather and grandmother and so on. So, that multiplication doesn’t reflect the number of all people that had lived back in time, but will only reflect the number of one person’s direct ancestors.

If you somehow and somewhen manage to grasp that, it will occur to you that the number of their direct ancestors is even fixed, and cannot be decreased as a result of inbreeding. Inbreeding can occur between two or more people’s family lines but not within one particular person’s family tree. Your grandfather could have been my grandfather too, because he incidently had sexual intercourse with my grandmother while he was a soldier in my country, but he could have never been your grandfather on both – your father’s and your mother’s – sides.

If you want to give up on this, just do that, because it will probably be the best you can do now. But if you want to spend some more time thinking about it, think harder.

Have a nice time, every one! :)

@AhYem I gave you the answer, above, cut and pasted from Wikipedia, with the Wikipedia link for further reading. Was that not accurate, to you?

@jca2, I did read your reply, but I didn’t respond to it, because my question was not about what wikipedia thinks about it, but what you do.

Anyway, thanks for your comments, I’m glad to see people corresponding, regardless if we agree or not. :)

@AhYem You just reformatted my answer which you discredited yesterday. So don’t act like you just exposed everyone else’s mistake.

@zenvelo, I just gave you a GA as a sign of my apology, in case I really did something wrong there.

I was (mis)lead by the fact that you were talking about an exponential growth, which refers on future development, where as my calculation goes back in time.

But chances are that I don’t have the best understanding of the term “exponential growth”, ‘cause English is not my native language and I don’t understand every single word or term or phrase there. So I really apologize if your comment was at least partly identical with my last explanation here.

I’m not trying to compete with you, nor to “teach” you, let alone “diminish” you or anyone else here. I’m trying to make you understand something. If you can do it, it’s very good and I’m glad to see it, If you can’t, Time will help. If you do understand it, and I wrongly assume that you didn’t, I apologize.

That’s it, my friend. :)

@AhYem , I don’t see how you answered the question. According to you:
It’s not the number of the ancestors of all people living now that doubles every 25 years, but it is only your own ones. Your ancestors are multiplied by two each 25 years.

In that case, to determine the number of ancestors I had 2,000 years ago, I divide 2,000 by 25 to get 80 generations, which comes to 2**80 ancestors, or about 10**24 or about a septillion.

What am I missing?

Judging by the way how you wrote your answer, you’re not missing anything, apart from the number of Septillion. But maybe you’re right there, and my own calculation was wrong, that ended up with 1.21 Quintillion.

However, it’s not the exact number that is of relevance there, but rather the fact that such a high number is irrational. Which again means, that something is wrong with the official historical record concerning the Earth’s population throughout History. Or with the age of the Earth. Or that there has been a development of things (i.e. a massive migration between various worlds, the Earth included) that has never been officially told.

And exactly that was the purpose of my question.

One absolutely last time showing why you are wrong.

In your scenario, each pair of parents has 2 children. Therefore everyone in the current generation has one sibling. We can group these siblings into pairs. Suppose there are n such pairs of siblings. The total size of this generation is therefore 2n. We can now match each pair of siblings to a unique pair of parents. There are therefore n such pairs of parents, accounting for the entire preceding generation, whose size must also be 2n. Therefore each previous generation has the exact same size as the current one.

Correction. You did not specify how many children each set of parents has. I covered the case of where each pair of parents has 2 children. Using the same logic, we can show that if the average number of children per pair of parents is greater than 2 then the preceding generation is smaller than the current one. If the average number of children per parent is less than 2 then the preceding generation is larger. The key factor that relates generation sizes is number of children per pair of parents.

@LostInParadise, why do you always think about the total number of people – be it in the past or in the present or in the future?

I’m not considering the total number of population in any way, be it in the past, in the present or in the future. The total number is irrelevant, because it has nothing to do with what I have been talking here.

You had 256 direct ancestors 200 years ago regardless if the total number of people living now was 8 Billion or just 1 Million, regardless if the world’s population 200 years ago was I Billion or just 200,000, and regardless if those 256 direct ancestors of yours were living in one small village of 500 people or in 50 different countries. It all doesn’t make a difference.

Maybe you will understand it better if you think of the fact that your 256 ancestors lived on several continents, whereas the 256 ancestors of a Pygmy lived in a small area in central Africa. See, their habitat doesn’t make a difference, you and a Pygmy had 256 direct ancestors 200 years ago, regardless where those people lived at that time.

You have only one or two siblings, while a Pygmy has between 5 and 15, but that doesn’t make a difference either. The population of your country has increased greatly during those 200 years, while the population of the Pygmys has maybe decreased during that time, but that still doesn’t make a fucking difference, because in either cases you and that Pygmy had 256 direct ancestors 200 years ago.

Is it possible for you to just focus on the number of your direct ancestors back in time?

If it is, you’ll figure out that that irrationally high number of people 2,000 years ago stands not only for your direct ancestors, but for mine, too, as well as for that pygmy’s. Those Quintillion or Septillion of people that lived 2,000 years ago was all. That number didn’t increase by 2 because of me or by 3 because of me and that Pygmy or by 8 Billion because of the 8 Billion now living people. That number is all there was at that time. That’s why I was urging every one to just focus on it. if you figure out the approximate number of your direct ancestors, you will have automatically figured out the number of all people’s direct ancestors that lived 2,000 years ago.

Have a nice day or evening or night, @LostinParadise :)

Consider the special case where each pair of parents has 2 children. I showed that each previous generation would have the same number as the previous generation. Suppose the current latest generation has 5 billion people. Then each previous generation would have 5 billion people. There is no way that you could get to a septillion. If your logic fails in this special case then it fails in every other case, Population growth depends only on the average number of children per pair of parents.