The principle of parsimony

In November, a SARS outbreak occurs in an area around a wild animal market in a giant city in southern China. The city is more that 1000 kilometers from the bat caves where SARS viruses are believe to originate. It is believed that the virus went from bats to mammals sold in the market, who then infected human workers and shoppers.

Of course I’m describing the 2002 SARS-1 outbreak.

And also the 2019 SARS-2 outbreak. And yet for some bizarre reason, most people view these two events as being completely unrelated. An alternative “lab leak” hypothesis has gained majority support, despite precisely zero pieces of evidence in favor of that hypothesis. Consider:

1. The first cases all cluster around the Wuhan animal market, not the Wuhan lab which is a 40 minute drive away, and across one of the world’s largest rivers. If lab workers brought the virus into the vast Wuhan metropolitan area and created a “super spreader” event, what are the odds that it would have occurred in that specific place? Wuhan is a crowded city (I’ve been there), with hundreds of similar places where the public congregates in large numbers. What’s the most parsimonious explanation for the location of the outbreak?

2. There are newly released environmental samples of the virus in the specific part of the animal market where the most suspect animals were sold. Keep in mind that the market is huge, the size of two football fields. Some of those Covid samples contain genetic material from raccoon dogs but not humans. What’s the most parsimonious explanation?

3. Two variants of Covid (A and B) crossed over to humans near the animal market in November or December 2019. Do people really believe that lab workers brought both of those variants to the market? Isn’t the most parsimonious explanation that the virus mutated in the animals (say raccoon dogs), and then spilled over a couple times to humans in the market?

4. Lab leakers wonder why no animal hosts have been found. But we now know that the Chinese are attempting to cover up evidence pointing to the animal market hypothesis. This is a pretty clearly established fact (even if the lab turns out to be the source of the pandemic.) This should be a major scandal! But the Chinese government is getting off scot-free due to the media’s obsession with an alternative narrative that is supported by no evidence.

(I suspect the Chinese government doesn’t know where the pandemic originated, and to play it safe is denying both the lab and the animal market.)

5. Lab leakers continue to propagate false evidence. There are claims that the virus “looks engineered”. False. There are claims that the Wuhan lab took a database offline in September 2019. (This is not true.) But if it were true, what were they covering up? The virus crossed over into humans in November 2019. There have been false claims of Chinese reports of an “emergency” at the lab in November 2019. But then what about the September 2019 timeline? Lab leakers just keep throwing mud at the wall, hoping something will stick. But there’s still zero evidence for a lab leak. None.

I understand there’s still no “proof” that it was the animal market. But come on people, what’s the most plausible explanation here? Ever heard of the principle of parsimony?

For those of you who rely on Fox News for your information, check out this video if you want to expose yourself to some actual evidence.



31 Responses to “The principle of parsimony”

  1. Gravatar of Adam Adam
    27. March 2023 at 02:24

    Some of those Covid samples contain genetic material from raccoon dogs but not humans. What’s the most parsimonious explanation?

    Well the researchers removed DNA of humans. It’s in the paper.

    The A and B variants is only an issue for zoonosis since it requires two spillover events since most of the market had the b variant. The lab leak proponents suggest well b evolved from a and this market is a super spreading event. I don’t see any evidence that suggest either one is falsified.

    The database thing
    Shi Zhengli explained in emails, in interviews, and to the WHO joint mission, that the database had been put offline after the pandemic started, because of hacking attempts…

    Anyone in IT knows how inane that comment is. Hacking attempts on a database. I wonder how any company, government with private data operates if “hacking” takes down a database. The research was supposed to help prepare for the next pandemic. Then we have a pandemic and now we can’t access the data.

    The market sampling is sampling bias. You have Chinese cdc sampling data where they think it occurred. That’s econ 101. Why are they not using %positive.

  2. Gravatar of Thomas W Colthurst Thomas W Colthurst
    27. March 2023 at 08:13

    “despite precisely zero pieces of evidence in favor of that hypothesis.”

    Please see for example for a summary of the evidence for and against the lab leak hypothesis, including estimates of the Bayesian strength of each.

  3. Gravatar of foosion foosion
    27. March 2023 at 09:24

    Scott, you are ignoring the most common thing underlying the lab leak theory: (1) China is evil, therefore (2) lab leak. What other evidence could possibly be needed?

    You might deny the premise or the connection, but that doesn’t mean it isn’t the underlying notion.

  4. Gravatar of Capt. J Parker Capt. J Parker
    27. March 2023 at 12:33

    Dr. Sumner Said: “There are newly released environmental samples of the virus in the specific part of the animal market where the most suspect animals were sold. Keep in mind that the market is huge, the size of two football fields.”

    a) The marker wasn’t randomly sampled. More intensive sampling was done in areas where animals were sold
    b) The highest rate of positive samples for the virus was exactly where the toilets were.

    Intelligent debate won’t settle this issue. There is too much conflicting and highly technical information to adjudicate.

    If prediction markets can be useful for complicated task of NGDPLT they should also be useful for determining the origin of SARS CoV 2

  5. Gravatar of c8to c8to
    27. March 2023 at 14:42

    A possible data point is bats might bite and infect animals all along that 1000Kms – are there any other markets cities along that route.

  6. Gravatar of ssumner ssumner
    27. March 2023 at 16:16

    Adam, “Well the researchers removed DNA of humans. It’s in the paper.”

    You are misinterpreting that, please listen to the video.

    Your A and B variant theory is possible, but way less likely if it started in a lab than if it started in the animal market.

    As far as the database, this is becoming a game of whack-a-mole. Fist is was September, then February. It’s an infinitely elastic conspiracy theory—will fit any facts.

    You don’t seem to understand that the Chinese have been trying to cover-up the animal market as a potential cause of the pandemic. The previous Chinese study reported human DNA but no suspicious animal DNA. They don’t want us to think it was the market.

    Thomas, Lot’s of misinformation there. Whoever did that is in way over his head. Watch the youtube video I link to.

    Capt, It’s not just “animals”, it’s the specific types of animal that are most likely to be a problem.

    foosion, I’m not missing it—it’s so obvious I didn’t think it was worth mentioning again.

    c8to, There are other cities, but a major outbreak is most likely to occur in a very big city (as was the case with SARS-1)

  7. Gravatar of Student Student
    27. March 2023 at 17:03

    That is an excellent video. The figure they present showing the spatial distribution of the covid positive swabs is phenomenal. However, while they do admit the weakness of not having negative swab data, they don’t explain why if a problem very well. If they took 1000 swabs near the raccoon dog pens and 100 were positive and they took day 20 in other places with ten being positive, that figure could be misleading. That all said, this was the best explanation of this study that I have yet seen.

  8. Gravatar of Sara Sara
    27. March 2023 at 18:45

    Occam’s razor is the more accurate description. It’s a tool that one can use in philosophy to guess. It’s not meant to be used as proof. Not to mention one might easily argue the simplest explanation is that it came from a lab.

    I’ll play the devils advocate.

    1. You’ve been told already, by a Nobel prize winning scientist: namely, Luc Montagnier, that the virus began in a lab.

    2. You have no idea where the first cases “clustered”. You only know what you’ve been told by a totalitarian regime.

    3. The virus does look engineered to many virologists, and that’s precisely the reason Montagnier reached his conclusion. You, as an economist, are not in a position to argue with Luc Montagnier. I doubt you could achieve an “A” in college level biology, never mind win a Nobel Prize in biology. You are not even in the same ballpark.

    4. You then claim the database was not offline, but could be offline when you state it is unequivocally “untrue” but “even if it was true”, lol….

    Well, what is it Scott. Is it true or untrue, because it cannot logically be both. This is the idiocy research that you engage in daily.

    You are correct about one thing: there is no hard evidence of a lab leak. There is also no hard evidence that Trump is Hitler, that Putin is trying to take over the world, that everyone is engaged in false flag operations to secretly and covertly destroy the west, that a one world NATO will be the wonderful utopia you imagine, that cloth masks stop nanoparticles, that a bunch of unarmed people are domestic terrorists hell-bent on destroying democracy, etc, etc. All things you’ve promulgated….

    Hopefully, you will learn how to be impartial — not just when it comes to your beloved CCP, and standing up for their interests which you do regularly on this blog, but also when it comes to American domestic and foreign policy.

  9. Gravatar of ssumner ssumner
    28. March 2023 at 07:56

    Student, Alas, the lab leakers don’t want to consider the evidence, so they won’t watch the video.

    Sara, You said:

    “You have no idea where the first cases “clustered”. You only know what you’ve been told by a totalitarian regime.”

    LOL. That’s a pretty deep conspiracy! (Even the lab leakers accept the data.)

  10. Gravatar of Student Student
    28. March 2023 at 08:12

    We live in a time of particularly strong priors. And no, they def won’t watch it, certainly not consider it.

  11. Gravatar of sean sean
    28. March 2023 at 10:05

    The two variants does seem like a significant data point. The rest is just speculation and not the easiest Baysian logic to throw probabilities on.

    There also were numerous scientists who when they looked at it said lab leak and looks engineered. That seems like a key data point. Including Anderson but many others came out later.

    If you start with an assumption it looks engineered then its fairly easy to use that as a strong probability and it was just chance that the animal market was the first spread event. The 2 lineages though seems to be signficant.

  12. Gravatar of Student Student
    28. March 2023 at 14:47

    The furin cleavage site initially looked engineered to some but that has since been thoroughly debunked and there is a lot more to in than that. Note there is a portion of the video where they discuss this.

  13. Gravatar of Student Student
    28. March 2023 at 14:52

    From the POV of parsimony or a well founded prior though, zoonotic has always been more likely. How many times has this happened before covid? With respect to even coronaviruses, it’s happened two times already this century (SARS1 and MERS). Plus there was no cluster near the lab. Come on peeps. It could have been a lab leak but the evidence is starting to pile up and even initially ones prior ought to have been this thing followed the pattern of that which has happened many times before.

  14. Gravatar of Ricardo Ricardo
    29. March 2023 at 00:21

    Who cares where it started.

    It’s quite interesting that whenever we hear any negative news towards China: whether it’s trade, lying about their treatment of Uighurs, or their organ harvesting practices, or in this case possible lab leaks, Sumner immediately defends China as if someone is paying him to do it.

    Most people read the news about some genius virologist claiming it came from a lab, like Montagnier, or they hear about intelligence operatives claiming they have evidence, and then they go back to work, take care of their kids, and forget about it: because it’s nothing they can control. If you woke up tomorrow and the lab leak was confirmed, people would say “fuck the CCP” as 7B people already do, and then they’d go on with their day.

    But Sumner doesn’t appear to be very normal does he. Like a propaganda machine he begins to rebut any narrative that might be even remotely critical to the CCP. One must ask “why?” why the need to come to the rescue all the time? Is it money? hmmm….

  15. Gravatar of Student Student
    29. March 2023 at 05:39

    Now they don’t care where it started. This has been happening about every 8 years or so over the last few decades. Just bury your head in the sand because your pet theory is becoming less and less likely. Suggesting Scott is a Chinese propagandist… do you even read this blog? Lol.

  16. Gravatar of Capt. J Parker Capt. J Parker
    29. March 2023 at 07:27

    You said “Who cares where it started… If would you woke up tomorrow and the lab leak was confirmed people would say F the CCP… and then go on with their day.”

    I think if it becomes known beyond any reasonable refutation that SARS CoV 2 was a lab manipulated virus that escaped then there would be huge blowback against not only any kind of gain of function research but a whole spectrum of biotechnology. The blowback would take the form of funding cuts and legislative prohibitions on research and development, probably to all of our economic detriment.

    Fear of this blowback has motivated many experts in the fields of virology and genetic engineering to argue against the lab leak theory even though they actually believe it to be the likely source of SARS CoV 2. This has been proven by the release of some of Fauci’s emails:

    So, the fact that the very people who are in the best position to infer the origin of the virus also have a motivation to not favor the lab leak theory means that consensus on the origin will be a long time coming, if ever.

    As for Dr. Sumner’s motivations – I read his blogs because his fundamental motivation IMHO is finding out the truth. I think he is wrong about the origins of SARS Cov 2 but I don’t see that as a reason to question his motivations.

  17. Gravatar of ssumner ssumner
    29. March 2023 at 07:46

    Sean, The best explanation I’ve heard for the initial confusion was that scientists were misusing probability theory. Certain features are somewhat unlikely, but then you have sampling bias because you are examining the one out of billions of genetic variations in viruses produced by evolution that happened to lead to a highly unusual global pandemic. Survivor bias. (Someone correct me if I’m misinterpreting this issue.) I would add that one of the two suspicious features was later found in the wild in Laos, so that greatly weakened that argument.

    Ricardo, LOL, this post is really a “defense” of China!! Read point #4.

    Captain, You said:

    I think he is wrong about the origins of SARS Cov 2 but I don’t see that as a reason to question his motivations.”

    And just to be clear, I’ve consistently made the following two arguments.

    1. For policy purposes, we should assume lab leak. It might have happened, and that’s scary enough.
    2. In an ethical sense, the animal market is far worse.

  18. Gravatar of anon anon
    29. March 2023 at 19:56

    FWIW, anything wrt China that ssumner writes – I take it with a big pinch of salt. Now that out of the way,

    virus – was it engineered, intentionally/unintentionally? seems no. is this refuted beyond reproach?

    spill over to humans – direct in non-lab setting (zoonotic)/in a lab setting (lab leak) – don’t know. But having seen the “establishment” science vehemently vilify those that say there is a probability of lab leak, even possible, one can aver that there are vested interests that would want to suppress any discussion and continue their grants/research/whatnot for true-science/nefarious/cya benefits. and/or CCP stooges.

    pandemic – originated in a wet market (though why would a wet market be a china’s embarassment is beyond me. it is a chinese cultural thing and they want to operate it, so be it?). seems established. One way it could be an embarassment is that nothing is local to geo anymore, that local wet market impacted all life and commerce in the 3rd rock from the Sun

    Is that the state of affairs today?

  19. Gravatar of ssumner ssumner
    30. March 2023 at 10:59

    anon, You said:

    “though why would a wet market be a china’s embarassment is beyond me.”

    Yes, I can’t imagine anyone would criticize markets that China claimed to get rid of and which most other countries don’t even allow, which brutally mistreat wild animals and caused multiple global pandemic.

    It’s a real puzzle.

  20. Gravatar of Matthew Moore Matthew Moore
    31. March 2023 at 01:13

    I often see the claim “Bit too much of a coincidence to believe this outbreak *just happened* to occur near this lab” with no acknowledgement of the fact that the lab was placed in this site precisely because of the prevalence of these viruses in nearby animal populations.

  21. Gravatar of ssumner ssumner
    31. March 2023 at 06:47

    Matthew, Yeah, lots of Americans know little about China. Wuhan is one of 3 or 4 cities where the outbreak was most likely to occur (Along with Guangzhou, Chongqing and Chengdu.)

    Guangzhou was the site of the previous SARS outbreak.

  22. Gravatar of John Thacker John Thacker
    31. March 2023 at 11:07

    1. “The first cases all cluster around the Wuhan animal market, not the Wuhan lab which is a 40 minute drive away”

    There are multiple Wuhan labs.

    “I often see the claim “Bit too much of a coincidence to believe this outbreak *just happened* to occur near this lab” with no acknowledgement of the fact that the lab was placed in this site precisely because of the prevalence of these viruses in nearby animal populations.”

    “Wuhan is one of 3 or 4 cities where the outbreak was most likely to occur (Along with Guangzhou, Chongqing and Chengdu.)”

    Huh? Wuhan is very far away from the bat population. Chongqing, sure, absolutely, that’s near the mountains. Sure, it’s a place where you might expect some outbreaks of viruses that had spread to humans, but not “these viruses” in the sense of bat coronaviruses in general (absent transmission through other animals.)

    The bat caves are a thousand miles away. Why isn’t the most parsimonious explanation that low paid employees (not always wearing the best protective gear) who went out to bat caves to harvest viruses and bring them back to Wuhan had poor sterile technique and spread the virus in that fashion (without it necessarily getting to the lab in the first place)? There have indeed certainly been leaks in other countries before too.

    It certainly seems quite convincing that the wet market was a super spreading location. That doesn’t means that it’s the place where the virus first entered Wuhan.

    I don’t doubt that China would have difficulty at this point determining the origin, even if different levels of the government wanted a full investigation and transparency. But it doesn’t really make one particular explanation more parsimonious.

    The bat population in which these coroviruses are native is a thousand miles away. You would expect infection to start somewhere closer to the caves, whether first going directly to humans or to other animals. In the absence of that, a researcher or collection worker traveling to bat country to harvest wild viruses accidentally bringing a wild virus back to Wuhan seems parsimonious.

  23. Gravatar of John Thacker John Thacker
    31. March 2023 at 11:11

    I certainly grant that because Wuhan is a large and wealthy city, there could have been outbreaks among people or animals in smaller cities before the disease was noticed in Wuhan.

    There are some viruses that I might expect would first outbreak in Wuhan, but (absent a lab studying them) not bat coronaviruses, where I would expect the first outbreak to be closer to the bat population, even if it spread through another animal population.

    The virus has spread *from* humans to other animals as well; once humans start being infected, that doesn’t mean that other animals were the original source (look at the Danish mink slaughter.)

    That the Wuhan night market was an early identified super-spreading location doesn’t mean that it was the original location; just as that Wuhan is the place where we first identified the virus doesn’t automatically demonstrate that it is the location where it first jumped to humans. It could well have affected some smaller town or village first – and such evidence would be useful (but agreed, China would suppress it too.)

  24. Gravatar of John Thacker John Thacker
    31. March 2023 at 11:15

    Why was it noticed in Wuhan first?

    1) A wild-type virus was brought back directly to Wuhan from caves a thousand miles away, by a worker from Wuhan who was sent to explore those caves and bring viruses back directly to Wuhan, and it spread in Wuhan (whether to humans first or through another animal, who knows) because of poor sterile technique.

    2) A wild-type virus from caves a thousand miles in Wuhan spread from the bat caves via other means, traveling long distances to get to Wuhan, likely infecting other locations along the way (whether in farms or not).

    In the absence of evidence of infections in humans or animals in intermediate locations between Wuhan and the caves, it seems reasonable that the action that involved going into the far away caves and directly bringing back samples to Wuhan is the parsimonious explanation.

  25. Gravatar of ssumner ssumner
    31. March 2023 at 13:33

    John, I don’t think you are well informed on this issue. SARS-1 also began in a city almost 1000 miles from Yunnan (Guangzhou). That proves nothing. The way these things usually work is that there is an intermediate host (often a small mammal), which is brought to the wild animal markets that you see in big cities. There’s no big mystery here; it’s happened before. Lots of pandemics have begun in southern China

    “There are multiple Wuhan labs.”

    But that completely undercuts the entire raison d’etre of the lab leak hypothesis, which is that one specific Wuhan lab was special. Sure, any major Chinese city will have several research labs, but they aren’t doing this specific sort of research. The one that was doing this research was not particularly close to the outbreak.

    “Chongqing, sure, absolutely, that’s near the mountains”

    There are bat caves near Wuhan, and indeed throughout almost all of southern China.

  26. Gravatar of Student Student
    1. April 2023 at 07:43

    John doesn’t seem to understand how many thousands or millions of odd things need to happen for a jump to occur. It’s not one human catches a virus from a bat and then spreads it. It requires thousands or millions of mutations and many people and animals interacting in close quarters for these things to happen. It’s hundreds or thousands or whatever number of interactions, mutations, pseudo jumps for a pandemic to occur. These are why these things tend to happen in cities where people and animals are clustered together for dozens or years. It takes many jumps and mutations bouncing around in close quarters (hence the two lineages) for everything to fit together in just the right way for a pandemic to happen.

    It’s like a box of marbles with a tiny marble sized hole in it. As marbles bounce around inside of it, it’s quite unlikely that one of them hits the tiny hole just right so as to bounce out of the box. But as you increase the number of marbles to thousands of them and shake them up violently and they bounce around in increasingly complex and random ways… it becomes more likely one of them happens to hit that hole just right and escape.

  27. Gravatar of ssumner ssumner
    3. April 2023 at 11:08

    Student, Good points.

  28. Gravatar of myb6 myb6
    14. June 2023 at 15:22

    This hasn’t aged well.

  29. Gravatar of ssumner ssumner
    14. June 2023 at 19:55

    myb6, I disagree.

  30. Gravatar of myb6 myb6
    15. June 2023 at 07:13

    I’ve been reading for 13 years and won’t stop because you’re unreasonable on a tangential issue or three, but damn I’m genuinely surprised at the obstinacy.

  31. Gravatar of ssumner ssumner
    15. June 2023 at 08:09

    All the recent evidence points to the animal market. The lab leak rumors are a set of lies, unsubstantiated guesses by people over their heads, and people who don’t understand science. Please wake me up when there is some reputable information supporting lab leak—not nonsense like that story in the Times.

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