This is largely inspired by two questions that @dsollen has asked over the past year or two. The first: Would ritual cannibalism of the dead lead to issues with disease? The second: Cultural beliefs, practices, and prejudices of tribes practicing ritual cannibalism.
EDITING NOTE: This question originally emphasized the biological sciences over science as a whole, which I've come to view as too narrow a focus. Also, the question as originally written didn't make very clear the importance that I believed secondary/residual consequences of the ritual would play in the larger effects on the civilization over a very long period of time. Hoping to rectify these and other minor concerns I had over the clarity of the question, I've since made significant edits.
Imagine a society that participates in passive ritual cannibalism (they eat people who have died rather than killing others for the purpose of eating them). They don't eat the dead as their primary source of food, but simply as a supplement to the domesticated flora and (possibly) fauna that forms the basis of their diet. Additionally, the culture has a strong taboo against waste and values the re-use/reclamation of just about anything of potentially practical use. Every time someone dies, their corpse is inspected to determine what can be salvaged for any of various possible uses, including consumption.
If it helps you to visualize the scenario, imagine that, at some point in their distant past, some horrible event (perhaps a natural disaster of one sort or another) wiped out all other sources of food in the location where they had settled. Then, while they either searched for a new place to settle or tried to start-up again in the same location, the inevitable famine struck them and, in order for some to survive, they resorted to (passive) cannibalism. This sudden, catastrophic loss of everything but their fellow survivors and the subsequent horror of the famine was forever imprinted into their cultural/institutional memory as the previously mentioned taboo towards wasteful behavior.
Setting aside the health concerns of engaging in the ritual (addressed in a separate section, below), would that society have a potential advantage in regards to scientific advancement over a second civilization that is identical to them in every other way, but doesn't eat, examine, or otherwise "usefully use" the corpses of their fellow men. This second civilization, instead, simply disposes of the bodies postmortem (e.g. burial, cremation) and sees any other "uses" of the bodies as taboo. Also, for argument's sake, the two civilization aren't in contact with one another, so neither can mooch off of the advancements of the other.
Here are a few assumptions I'm making that might be important:
- If every dead body is a potential food source, then it will likely go through as extensive an examination process as they are capable of, given their level of advancement, at any particular point in their history
- The absolute necessity of identifying who died of a relevant illness could easily lead to a more clinical basis for identifying the sick and their specific illness before they've died, which would create a better foundation for medicine from the start
- Because every single corpse is going through a sort of proto-autopsy, at the very least, I would imagine that they could gain a grasp of certain cause-and-effect relationships to certain causes of death quicker than other civilizations
- In the earliest stages of engaging in this ritual, by virtue of observation of the consequences from eating particular portions of the corpses, they would quickly learn what practices were and weren't safe
- In part because the transmission of diseases would be more prevalent, they may more quickly develop medical understanding of both causes and treatments, and the citizens that place a higher value on sanitation would be much more likely to survive, promoting sanitary practices and potentially affording an earlier understanding of the underlying science
- If cannibalism can account for as much as 10% of human dietary protein (see Viability section) and if the same butchers that handle the preparation of livestock can also handle corpses, some workers that would otherwise be busy raising livestock would be freed-up to do other, more specialized work
- If cannibalism has a more compatible nutritional profile for the human diet (see Viability section) and a portion of the nutrition consumed by the dead is passed on to the person consuming them, a lesser amount of crops might be needed to feed the citizens and some more workers might be freed-up for specialized work
- With the lower amount of livestock, as well, even fewer crops would be needed and even more workers would be freed-up for specialized work
- The larger the portion of society is that's available for specialized work, the quicker they develop and expand to more specialized careers, such as doctors, law enforcement, politicians, lawyers, and so on
- The earlier that laws can be created, enforced, and adjudicated, the earlier that the civilization becomes more civilized, a situation under which further advancements can flourish
- The more settled/civilized a civilization is, the more likely they are to develop a formal education system that could more pointedly ask the questions that lead to greater advancement of the society
- The earlier that an educational system is in place, the earlier an educated class of medical specialists can systematically examine various issues that might expand beyond the immediately practical medical purposes and into the biological sciences at large
- Medical advances would not only increase the expected lifespan, which would increase the amount of embodied knowledge in society available from the elderly, but also reduce mortality related to childbearing, childbirth, and general childhood mortality, therefore increasing the population and the number of specialists
- Although a population boom might lead to temporary famine, the initial deaths from the famine would actually become a food source that would decrease the likelihood of further deaths (a negative feedback loop) than would be seen in a society that refuses to eat the dead or that only resorts to cannibalism in extreme circumstances (and therefore doesn't know how to properly handle/prepare the corpses)
- At some point, the vast number of specialists would expand to include nutritionists, who, unlike their real-world counterparts, would be able to study the effects of a particular diet not just on the person who ate that diet, but on the person who ate that person; if people are more likely to eat people with a similar diet as themselves, then there would be a positive feedback loop that I imagine creates a rather convenient natural experiment
- The educated class wouldn't be limited to biological sciences and may stumble upon other advancements that end up reducing the burden on workers, not only aiding their health, but also freeing-up more people for specialized work
I feel like going any further would be complete overkill, but I think you should understand the point that I'm making. It isn't that the ritual would give them one giant leap ahead in understanding, but that it might give them a head start over other civilizations and then, in a positive feedback loop, keep steadily increasing the force that's pushing on the accelerator. So, just like a small initial difference in two bank accounts can make a huge difference with compounding interest down the line, what is a small advantage at any one given point of time potentially accumulates to something much, much larger over a few millennia.
So my question isn't if simply dissecting something would give an advantage, or if the slaughtering/consumption of a member of your own species offers some added benefit, or whether any ritual would give some sort of an advantage, or if this one specific cultural consideration could potentially be overwhelmed by any number of other cultural/situational factors that might come into play. It isn't any of these things individually and it isn't some of them at all.
What I'm concerned with is if the consquences of the ritual (and the consequences of those consequences, ad infinitum) would create an advantage over the course of a few millennia, cumulatively. Are any of my assumptions conclusively wrong? Are any of them, on the basis of research/evidence, very likely to be wrong? Are there other considerations that I didn't consider which mitigate the effects that I did correctly identify?
[As an example, @JBH told me that cannibalism might not be able to sustain a high enough portion of the human diet to actually reduce the burden on the workforce. That is a perfectly valid concern that would clearly throw a huge wrench into my thinking. I'd appreciate some form of relevant research to back up the speculation, but it's something that I hadn't thought of (though I should have) in my initial brainstorming.]
SIDE NOTE: This is my first time asking a question on any Stack Exchange site, so I apologize if I've done anything I'm not supposed to or haven't done something that I should have. Hopefully this isn't too broad of a question, either. I've mostly been just occasionally lurking before now and I know I still have a lot to learn. Thanks for your patience/help.
The answers to @dsollen's questions largely addressed the health risks associated with such a society, such as:
- Prion disease transmission (e.g. Kuru) through consuming nervous tissue, the spinal cord, or the brain, although some evidence has been found of genes that protect against similar prion diseases among populations with a long history of cannibalism
- Transmission of infectious diseases (e.g. flu) through the respiratory system or GI tract
- Bloodborne disease transmission (e.g. HIV, hepatitis, hemorrhagic fever) through any portion of an infected person
Those answers also offered many ways to make the ritual safer, such as:
- Remove the GI tract from the body as quickly after death as possible to prevent cross-contamination
- Do not consume the riskiest portions, such as the brain/nervous tissue, GI tract, lungs
- Avoid opening up internal organs and, if possible, limit consumption to muscle tissue
- Clean the corpse thoroughly and cook at an internal temperature above 160° F
- Consume the corpse as quickly as possible after cooking or cure it through smoking/salting
I also found some interesting information in this SciShow video from YouTube about a month ago:
- "There's archaeological evidence that in some societies, human was a part of the original paleo diet, accounting for as much as 10% of the protein people ate"
- "Human flesh might actually have more nutritional value than other kinds of meat" because we have about the same amount of calories as other animals our size (e.g. a small deer) and "the more closely related your meal is to you, the more closely its nutrient profile will match your needs"
- "Studies in all kinds of animals have found that carnivores are healthier when they're fed members of their own or closely related species"
- "Elderly Fore who survived the Kuru epidemic had genetic changes that probably made them resistant to prion diseases"
- Similar genetic changes have been found around the globe, suggesting that cannibalism was common in our evolutionary history
- "Despite the number of cases of human and animal cannibalism we've found fewer examples of it causing disease outbreaks than we'd expect"
- "According to a review paper published in the American Naturalist 2017 [...] cannibalism could actually protect people from catching dangerous diseases because it gets rid of some of the microbes that spread them"
[Now, if you'll excuse me, I need to go shower after jumping down this particularly gruesome rabbit hole.]