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I was wondering which year in history was the bloodiest? Is it one of the last two years of WWII? Or are there any other such bloody time in history?

I only wish to include non-natural causes deaths such as from war, disease, or even from accidents.

The number alone is not helpful, so I am looking for a ratio of total number of such deaths to the total human population of given year.

buræquete
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    If you believe the bible is true, and want percentages, it had to be the day of the Flood. If you want pure numbers, it almost had to be 2015, since there were more living on the earth than ever before and therefore, more death.... Now that I've gotten my daily snark out of the way, you'll have to define your request a bit more... death by what? war? famine? natural causes? – CGCampbell Mar 25 '16 at 13:06
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    This may be a more interesting question than it appears. There is a British historian who specializes in measuring violence through history. I believe he concluded that total violence decreases over time, which is counterintuitive. Alas, I don't recall his name. And the one year measurement is going to void the results - statistically there will be outliers and 2015 is the optimal bet - the number of deaths will be proportional to the number of people alive. – MCW Mar 25 '16 at 13:34
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    Just a guess but I would say 1916. It's also quite possible that one of the years during the Holocaust or Mao's Great Leap forward. It could even be 1994 - the Rwandan civil War. I think something like 4 million people died.

    There are a few candidates, but I think due to the nature of these atrocities, the exact data isn't forthcoming. A

     – Anaryl Mar 25 '16 at 13:48
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    @T.E.D oh yes Spanish flu - I forgot about that – Anaryl Mar 25 '16 at 14:05
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    I find curious the definition of "disease" as "non-natural" (unless you count a -yet to happen- GM disease). – SJuan76 Mar 25 '16 at 14:09
  • @SJuan76 I think it should be included, my question was to find the worst year of human recorded history. I think apart from the number, the ratio is also important, so will update my question accordingly. – buræquete Mar 25 '16 at 14:11
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    @SJuan76 - It works for me. Yes, illnesses in general are a normal part of human life, and by and large concentrate on those with weak systems. But pandemic events like happened in 1918 killing off huge amounts of strong healthy people are a whole different kettle of fish. – T.E.D. Mar 25 '16 at 14:14
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    @MarkC.Wallace Are you thinking of Steven Pinker? – Semaphore Mar 25 '16 at 14:54
  • As a ratio of human 'non-natural deaths' to total human population TED would be right in 1918. There have been some pretty large scale events but given the substantially lower global population to very signficant amounts of casualties - the spanish flu probably clinches it. – Anaryl Mar 25 '16 at 15:07
  • @semaphore - I had the name confused with Daniel Pink. But it could also be Beevor. I just can't remember. Old age taking its toll. – MCW Mar 25 '16 at 15:35
  • How far do we go back? If we go back to the time where the first lifeforms we might call "human" evolved, they had a very small population. According to the Toba catastrophe theory there might have been a period when the human population numbered significantly below 10000. Or if someone is a biblical literalist, they might say the ratio being 25% when Cain killed Abel. (of course this is a minority view, as most people would say it's either a completely allegorical story, or there were plenty of other humans around and they were just not contacted or were not regarded as people) – vsz Mar 25 '16 at 15:50
  • If the question is asking for %, not raw #'s, one of the years of the Black Death probably beats 1918. And of course there were probably some tough years in prehistory. – T.E.D. Mar 25 '16 at 15:52
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    The question clearly states in history, so pre-history and Biblical records are out of scope. This question is more precise than we give it credit; it is clearly looking for historical evidence of the bloodiest year on record. Let's save our savage snarking for the questions that deserve it. – MCW Mar 25 '16 at 17:38
  • The Black Death didn't have much of an effect on Subsaharan Africa that I know of and obviously had none on the Americas. Also, it crossed Eurasia in waves and may not have ever been raging in Asia, the near east and Europe in the same year. As such, I suspect the percentage of dead for a given year may be lower than you might think. – Gort the Robot Mar 25 '16 at 21:34
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    @Marc C. Wallace. Perhaps you mean Lawrence H. Keeley, War before civilization. His arguments seem very convincing: violence indeed decreases with time. And in all times, more people die of epidemics than of violence. But I would classify epidemics as "natural deaths". – Alex Mar 26 '16 at 12:33
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    According to this news post, it was WWII, but that goes against all most everything else I've ever read. I get the feeling they blurred the total numbers with some ratios. – Mazura Mar 27 '16 at 00:51
  • If we talking about percentage and unnatural death means war and aggression related , then the Mongol invasion of Eurasia and Timur are the two winners of who could kill more people in very short time ranking. The milage may vary if you calculate year by year, but they beat the wwi and wwii. – Greg Mar 27 '16 at 11:52
  • what is unnatural about death by accident or disease? – Oldcat Apr 07 '16 at 20:28
  • I wanted to build an answer suggesting 536CE https://www.sciencemag.org/news/2018/11/why-536-was-worst-year-be-alive but I cannot find enough online demographics data. We know that the worldwide population dropped a lot in the following years, but most estimations span on decades. – Evargalo Feb 28 '19 at 10:53

3 Answers3

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The actual year would be in prehistory, when the human population were more concentrated.

In terms of recorded history, the initial outbreak of the Plague of Justinian in 541 had an estimated death toll of 25 million. Most estimates of world population gives about ~200 million for the 6th century. The plague thus killed roughly 10-13% of the global population.

For reference, the 1918 flu pandemic killed perhaps 50-100 million. The global population at the time was about 1,860 million, however, so the ratio works out to be 2.7-5.4% of the total population.

A.D. 541 also have additional "advantages" in terms of higher infant, maternal, and child mortality were far higher in some parts of the world, relative to the industrialised nations of 1918.

Semaphore
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    the Plague of Justinian in 541 had an estimated death toll of 25 million -- what is the source of this claim that 25M died in the single year of 541 from the plague? Right now the linked Wikipedia page says "deaths of an estimated 15–100 million people during two centuries of recurrence", but I'm unable to find any source that claims that 25M died in the single year of 541. –  Apr 01 '23 at 04:50
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70,000 BC

Analysis of the human genome has suggested that there was a choke-point in human history where the number of humans was drastically reduced.

Some believe that this was due to a single volcanic eruption occurring 70,000 years ago give or take.

According to this theory human population may have been reduced to just a few thousand breeding pairs.

Not sure if this meets your definition of 'non-natural' or of 'history' but no other event will have made the same ratio.

AllInOne
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    History and prehistory; that said, this such a good answer that I can't bring myself to cavil about a difference of a few tens of thousands of years. – MCW Mar 25 '16 at 18:56
  • I remember hearing about this. But wasn't that just for one line? IIRC, you get very different findings when you check the Y Chromosome (inherited only from father to son) and Mitochondrial DNA (inherited only from the maternal line). – T.E.D. Mar 26 '16 at 15:45
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    I'm pretty sure that volcanoes going off is a natural thing. On the other hand, the question classes disease as non-natural so who knows? – David Richerby Mar 27 '16 at 23:10
  • Recent criticism about this theory: https://www.bbc.com/news/science-environment-22355515 – Evargalo Feb 28 '19 at 13:10
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A bit of quick research tells me the worst in absolute terms almost has to be 1918.

There was a worldwide influenza epidemic that killed about 40 million people that year. That's the single biggest recorded death toll for a global pandemic in a single year in human history1.

There also happened to be one of the bloodiest wars in human history (in terms of sheer number of combat deaths) going on at the time. For most years, roughly 3 million combat deaths would be a huge deal. That year it wasn't even 10% of what the flu did.

Barring some new fast-moving pandemic, or a disaster of extinction-event proportions, that is liable to be the worst the human race will see for quite some time2. The number of deaths due to war is actually decreasing globally.

1 - The Black Death probably killed more people; perhaps as many as 200 million in Eurasia. But it took 6 years to work its way around Europe.
2 - Everyone reading this please go find some wood to knock on.

T.E.D.
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    As for some putative European contact year, the problem with that is even by the most ridiculously generous estimates there were no more than 100 million pre-Columbian Americans. For it to beat 1918, those would have to be correct, and most of the deaths would have had to happen in a single year. Communications and travel weren't that fast on that continent at that time. For example the medieval black death took 6 whole years to work its way through all of Europe. – T.E.D. Mar 25 '16 at 14:11
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    If the Black Death killed 200 million people in 6 years, you have an average of 33 million/year if you assume equal distribution. So it's at least conceivable there's a year close to the end that had more than 40 million. And of course, the percentage of total population was much higher at that time. – Guntram Blohm Mar 26 '16 at 05:46
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    @GuntramBlohm - Yes, but you're taking the highest estimate (which is quite likely to be an overestimate), and then giving it a boost on one year, for a supportable reason, but mostly because it helps arrive at a number you'd like it to. One should avoid doing that with multiple pieces of information.This is the exact kind of logic that Columbus used to argue Japan was 3,000 miles west of the Canaries, when it was more like 20,000. Far better to use averages so wrong estimates even out. – T.E.D. Mar 26 '16 at 15:32
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    If 200m people died of Black Death over 6 years then there must be at least one year when at least 33m people died of Black Death. Assuming equal distributions would lessen the worst year. Taking a lower estimate of 75m for the Black Death over 6 years with population at 450m shows its worst year killed at least 2.7% of the world population, c.f. 2.2% for the flu using 40m / 1.8b. So the Black Death answers the question in terms of ratio. And whether it breaches 40m in a single year is probably known as well. – djechlin Mar 26 '16 at 23:53
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    The book referred to above regarding the historical trend of violence is "The Better Angels of our Nature" by Steven Pinker. A weighty tome but very interesting appraisal – michaeltooth Apr 01 '16 at 03:31
  • For those wondering, AIDS has killed approximately 35 million people, and that was over decades. – Golden Cuy Dec 17 '17 at 11:41
  • Population of Europe at the time of the Black Death was about 80 million. There's no way it killed 200 million people there in 6 years. It may have killed that many over the course of a few generations – C Monsour Feb 28 '19 at 22:14
  • @CMonsour - The very first sentence of the WP page linked in this answer currently reads: "The Black Death, ... resulting in the deaths of an estimated 75 to 200 million people in Eurasia". Sadly for Asians (and North Africans), the disease wasn't racist enough to just kill Europeans. Its a decent point that this is the high estimate so it shouldn't be taken as gospel, but rather an upper limit. I made the same point in my comment dated March 24, 2016. – T.E.D. Feb 28 '19 at 22:19
  • @CMonsour - In general, I don't like adding a lot of detail to superscripted footnotes in answers, because multiple lines of those don't read well. However, in this case I could clarify the confusion with two words, and it still fits on a line in my browser, so I've done so. Is it clearer now? – T.E.D. Feb 28 '19 at 22:43