If Amerindians had a lot fewer serious infectious diseases than Old Worlders, something else had to limit population – and it wasn’t the Pill.
Surely there was more death by violence. In principle they could have sat down and quietly starved to death, but I doubt it. Better to burn out than fade away.
West Hunter 
I’m not sure why this necessarily follows (though it might indeed be the most parsimonious explanation).
Could various individual serious infections diseases have entered Old World populations over a longer timeframe, giving them more time to readjust and find new steady states (sometimes quite dramatically, e.g. the Black Plague, but even in that case Europe populations recovered over time, right?). By contrast, when an Amerindian tribe was exposed to those infections they got the full suite all at once more or less, on the timescale of decades.
Could other environmental pressures have limited Amerindian birth rates or increased death rates? (Though, hard to square this with the wide range/variety of different types of environments present across the Americas).
We all know pre-20th century Western medicine was pretty pathetic, but perhaps the sum total of medical knowledge in Europe (including customs that might have accidentally led to better health, like drinking beer instead of unboiled river water) helped counteract the impact of illness/death from disease?
In the modern world, we hear about relatively low birthrates among (for example) highly educated Northwest Europeans. Yes, they have access to the pill, but so do other groups with relatively higher birthrates. Presumably it’s at least possible that cultural effects influence relative birthrates?
Or, am I missing some obvious reason why these (and other) explanations are unlikely (or of insufficient magnitude)?
a. Newly introduced infectious diseases hit the Amerindians like a hammer, but that’s not the point: we want to compare Old world mortality & morbidity due to infectious diseases with preColumbian Amerindians.
Did Old world infectious diseases have a big impact on Old Worlders? Yes. Eurasian and African populations must have adapted to some extent to various local diseases, but virulence could be fairly high. In places with good-recording keeping, like Prussia in 1750, we know only 50% of kids lived to 15.
Case fatality rates for smallpox in Europeans were around 30%. Probably at least 10% of children died of smallpox before adulthood. We can estimate the impact of falciparum malaria in Africa, indirectly but accurately, by the prevalence of the sickle-cell mutation: again, high, probably higher than smallpox. And of course there were many more infectious diseases.
b. Other environmental pressures on the Amerindians? Like what?
c. The total effect of Western medicine was strongly negative, but fortunately few people ever visited a doctor. You could think of it as a special tax on the rich.
d. There’s always infanticide.
e. Same for Polynesians.
f. we have more records of organized warfare in Europe… because we have more records. Homicide had to be far higher among Amerindians.
The scale of organized human sacrifice in Mesoamerica always shocked me.
It’s not really surprising considering the level of malnutrition in the region. In Mesoamerica human sacrifice was usually accompanied by cannibalism which is a phenomenon that tends to be only common in really awful environments. Mesoamerica was one of them due to almost absence of other kinds of protein sources.
Beans, turkeys. But people may be tastier.
Sure.
However why wasn’t habitual cannibalism that common in most of Eurasia then?
Without famines and except for a few freaks who are really into it cannibalism was only common in places such as Mesoamerica, Papua New Guinea, Melanesia and certain parts of Sub-Saharan Africa.
Not just Mesoamerica: lots of other Amerindians dabbled in long pig. But sure, a rare thing in Eurasia. I wonder why too. For the Americas, Melanesia and Polynesia, New Guinea – fewer pathogens and therefore safer? That idea doesn’t work in Africa, though.
Overlay an IQ map on a cannibalism-prevalence map. Pretty good correspondence between low IQ and eating your fellow man.
The old turkeys supposedly did not taste the same.
Curious how no other fowl were domesticated. Maybe, a case of one being enough. I wonder if they would have been as cannibalistic if they had had chickens laying eggs 7 days/week.
They also ate dogs.
Aztecs were so starved for animal protein that bred and consumed flies. I don’t know it is true. Vegetarians don’t do it.
Guess I left out the Muscovy duck, which J provided much below. Odd name for a Mexican bird. Guess it domes from “musk.”. They say it tastes like roast beef and is nearly quackless. Why have I not yet eaten this magnificent bird?
Smithie cannot taste Muscovy duck because it is protected in the USA. He could find it in Mexico; ask for “pato mudo”. Gastronomically speaking, I recommend also the “cuy” (alias Guinea pig, although it is neither from Africa nor it is a pig – it is rat). You can taste it in any Andean country. In Ecuador I met a cuy farm of an enterprising German, he was exporting frozen cuy meat to Japan.
@J
I think Brahmin, Buddhist & Jain vegetarians have not deteriorated into cannibalism. So what was going on in the cannibal zones?
I believe muscovy ducks were domesticated in the Amazon basin. In addition, the Inca raised guinea pigs, and you can still buy meals that feature them in Peru.
Presumably fish could be available from irrigation or drainage canals.
Also, “In the September 1989 issue of Natural History, Sokolov follows up on the previous month with an article titled “Insects, Worms, and Other Tidbits” and subtitled “The Mexican diet, before Cortes, obtained high-quality protein from lowly sources.” He emphasizes that “authentic” cuisine “virtually everywhere” is not the immobile tradition that traditionalists wish it to be,” and furnishes an impressive list of foods contributed by the New World to the Old, including potato, tomato, corn, chocolate, squashes, beans and many others. Some of these New World foods have had great nutritional impact, for example, the sweet potato, peanut and the chili pepper in China, and manioc, corn, peanuts and pumpkins in Africa.
Relative to Mexico when Cortes appeared Sokolov notes that the country ” was a major world civilization with a vigorous culture that continues to challenge imported European culture today. [Enough native Mexicans have survived] to carry on local food traditions in tandem with the new ideas and foods from Spain and the Spanish Empire.” Insects of many species are a prominent part of these local food traditions, but Sokolov devotes the most space to the maguey worm, larvae of the giant skipper butterfly, Aegiale hesperiaris, which are also called palomillas del maguey (maguey squabs), champolocos, meccuilines and pecahs. Sokolov paraphrases the account of these larvae in Teresa Castello Yterbide’s Presencia de la Comida Prehspanica (Banamex, 1986), as follows: “Larvae harvesters poke about among the maguey’s lower leaves, looking for the telltale tunnels at the base of the leaves near the outer edges. Working very carefully with a machete, so as not to disembowel the larvae unwittingly, they cut open the leaf. To extract the larvae whole, they use hooks formed by cutting thin strips from the edge of a maguey leaf. Then they remove all its spines except for one at the end of the strip. This they form into the hook they use to catch the larvae by the head. To store the larvae, they make pouches with the skin of a tender new maguey leaf, which is called mixiote (it gives its name, synecdochically, to a dish made of chunks of marinated meat wrapped in mixiote pouches and steamed).
To cook the larvae, people sometimes just put a whole gusano (larvae)-filled mixiote over coals or hot ashes, or they might just put the larvae directly on a bakestone until they swell and stiffen, turning golden brown and crunchy. And this is not some quaint account of a long-forgotten practice. Castello Yturbide nonchalantly mentions that maguey larvae can be obtained in April in the market of San Juan in Mexico City or in Actopan and Ixmiquilpan (two villages of the state of Hidalgo) or in farm hamlets around Mexico City.
Relative to other insects, Sokolov notes that the eggs of water bugs (moscos de pajaro) (Hemiptera) are still harvested in the same manner described by Sahagun. Today, they are toasted, ground up and made into little cakes held together with turkey egg. In the late 18th Century, they were apparently a garnish for the festive dish called revoltijo, served on Christmas Eve and at the vigil of Thursday night of Holy Week. Other insects still eaten include locusts, available year-round at markets in Oaxaco and Atlixco, toasted and eaten with tortillas and a sauce of chili pasilla; mountain chinch bugs, eaten toasted or living; oak-boring beetles which are popular as snacks among Mixtec peasants; ant larvae and pupae (called ant eggs); and in Jungapeo, Michoacan, wasps. Two excellent photographs (one of maguey worms) accompany the article. (Ed.: It can be noted that Dr. Julieta Ramos-Elorduy, who has done extensive research on entomophagy in Mexico, has reported that more than 200 species of insects are still eaten in Mexico [personal communication, 1986]).”
Many diseases could not be transported across the Atlantic or Pacific by slower boats. Iceland suffered periodic epidemics of smallpox when it did manage the crossing from the east, because the disease would burn out and there would be many adults with no immunity, as well as the children. (O’neal perhaps?)
Being of an age where shingles is a concern, I wonder if chickenpox could have traveled to North America with the Vikings, and then the native population contracted the virus from someone with shingles.
Certainly not enough of an issue to counter the original question, but the timing is about the same as the Mayan collapse, per Jared Diamond book Collapse, or the collapse of the Mississippian mound builders for that matter.
Has anyone checked old mummies for chickenpox evidence?
Viking contamination is a possibility.
But is chicken pox serious enough to cause major death in an inexposed population?
There is one disease that didn’t travel to Europe before steamships. Cholera. It’s native to India. At least that’s what I’ve read. It does tend to kill very quickly.
You wouldn’t have thought smallpox could travel by sail from Europe. But it did. You could have a situation where the outbreak didn’t occur until the voyage was well underway. Then it stayed active with new victims for a few weeks.
It isn’t really all that far from Spain to Mexico. The Portuguese journey around the Cape was far longer.
The Maya collapse is ~800, hundreds of years before Leif Erikson.
The Mississippians collapsed in 1400, awfully late for Vikings. Not the fault of the colonists, but maybe contact continued up to 1300, and disease only got through then. But if it were disease from the north, wouldn’t you expect it to also affect the Fort Ancient and Monongahela mound builders?
The book I read on the Maya collapse being caused by several years of drought was well-researched and convincing. (But I’m no expert in the field.)
Apparently they had a technique of storing water that broke down after the drought.
You see unpredictable years-long droughts in Australia.
The book is called “The Great Maya Droughts” by Richardson B. Gill.
I’m not a fan of Jared Diamond ,but once he had an insight that made sense ,he said that in primitively society ,even now 32% of deaths are violent
something has to limit population: in the Old world, increasingly, infectious organisms took that job.
Food supply? I remember reading about how hard farming was without beasts of burden, for example.
Also, domesticated animals were also a food source.
Drought doomed the Maya, according to a book I read.
Both maize and potatoes have very high yields.
They do, and one might add beans to that; but ‘man does not live by tortilla alone’. Protein was always a problem. And the New World (and agricultural parts of New Guinea) never shifted to dairy.
Malthus came to the Americas early and often, and Hobbes followed him.
Especially potatoes. The child mortality in Prussia you mentioned above dropped instantly once potatoes were adopted. Frederick the Great – who promoted the growth of potatoes – is still honored with potatoes by Germans as “Kartoffelkönig”.
Ultimately, food production determines the equilibrium population density. But Greg’s question is, once you’re there, what is actually doing the killing to keep the population in check?
Sure, people could just starve to death, or kill their own babies. But raiding the other guy is the strategy that leads to the most descendants.
Eastern Woodlands Indians were constantly warring amongst themselves. We know Injuns in general have much higher psychopathy than west Eurasians, how’d it get that way? Probably because they lived in an unimaginably violent society, but hey that’s what it took to keep the population to game ratio low enough so that everyone could eat meat. I’d take the risk of being carved to bits alive, tied to a post, over being some stumpy, toothless wretch in a grain-based society. Down with grain!
The Germanics in Tacitus day had something similar in place, where they’d maintain “dead zones” around their primary territory where no humans could live. Basically buffer area with the upside that you had a relatively safe, managed forest at hand.
In another Jared Diamond book, “Collapse” Diamond takes a very politically incorrect view of the Rwanda mass outbreak of killing. He points out that the area was becoming very overpopulated, with people’s plots of land getting smaller and smaller.
There were also other factors too in Rwanda. But overcrowding exacerbated everything.
Have archaeologists found/not found gazillions of died-by-violence remains?
In the Southwest, sure. Good preservation. Often cannibalized.
War before Civilization is a great little book written in 1990’s about prehistoric warfare, although there is no attempt to tie it to Darwin or Malthus or any evolutionary explanation. There is a lot of empirical data, and it is framed as a debate between Hobbes and Rosseau, the author is an archaeologist.
Out of print but a Kindle version available. You don’t usually see that with older books, unless there’s a demand. It’s subtitled “The Myth of the Peaceful Savage.” Looks worth a read.
I is wonderful. I make reference to it a few times a year. You will enjoy his section of Otzi
Could an older weaning age be part of the story, and hence smaller generation sizes? No cow’s milk, after all.
That’s why China never had any population problems.
I assume that this is sarcasm, am I right? You know that China had extreme population problems that regularly resulted in civil wars & widespread depopulation.
Low infant mortality would potentially mean high genetic load. Maybe, that contributed to the dieoff. I’ve wondered whether that could be the case with some of these extinct mitochondrial lines.
Depends on the correlation between infant mortality and load. If it’s just random luck then it doesn’t do much. If it’s just about disease resistance, then you’ll be selecting for disease resistance specifically. If you select too hard on one thing, you’re not selecting on other things, so plausibly high disease burden increases load.
Under Greg’s hypothesis, you’re selecting on raiding ability.
The Plains Indians were supposedly very tall. One wonders if height was under selection like in Northern Europe, and if the reason in both cases was warfare.
Theoretically, a tall man can run faster and has longer reach, but maybe, he is just a larger target, when it comes to arrows. You would think they would be better known for their running ability. I suppose there was Billy Mills.
Every society manages birth control. Hunter/gatherers do it as well as post-stone-age or modern societies. Plus violence when fighting over scarce ressources. Plus being too few in the first place (the numbers of Indians in large parts of Northern America were tiny). How can you spread diseases when you hardly meet anyone at all? Plus simply being too dumb to do any better.
To quote a geology rule, the key to the past is the present, certainly primatives and indigenous have higher rates of violence and violent deaths now .politically correct or not
Seems to imply less warfare in Africa than America and Australia, then, because more disease? Not totally sure about that.
Or at any rate, at least, adaptation to violence in the opportune circumstances doesn’t seem lesser.
Also: They were lousy farmers. And lousy engineers.
So population was kept in check by collapsing bridges, or something?
Early historical accounts suggest that everyone was pretty much fighting all the time. But I get the same impression from Viking sagas and classical historians. Maybe it’s living in peace that allows the population density to get high enough that you all die of disease.
Charles Mann, if remember correctly, has the wars and violence postdating the disease on the East Coast, as well as in the Amazon basin. Agriculture was widespread and successful in those regions, until society was torn apart by new and frightening diseases.
This wasn’t known until fairly recently because there wasn’t much exploration, or recordkeeping by explorers, during the first century after Columbus.
That doesn’t seem plausible to me. More widespread agriculture before the epidemics, sure, but that doesn’t prevent war.
They were pretty good farmers. That’s why mesoamerica was so populated.
No. They were primitive gardeners. No plows or agricultural machines, no irrigation, no fertilization, no cultivated fruit trees, very few crops and varieties, no domestic animals, no means of transportation (except walking humans), no canals like in China and Europe. .
Of course they had domesticated animals and irrigation. If they had very few crops they sure knew how to pick them.
Yeah, I don’t know what J is smoking here.
The milpa system in Mesoamerica alone was sophisticated, including irrigation and fertilisation. The Andes had terraces and, for transportation, the mountain camelids. Both had aqueducts. Tenochtitlan was famed for its canal system.
The Mesoamerican milpa system is cultivate land one or two years and then abandon it for a decade. Plowing the soil was unknown and flooding for weed control like in China was nonexistent. Tenochtitlan (Mexico city) canals? Maybe Urban Agriculture? or simply drainage? Mexico used to lie in a lake. Llamas and guanacos for transportation? The Israeli army tried that and discovered that they not mules and useless. You are carried away by the current trend of idealizing “the braves”. The biggest problem of the early European explorers was to feed themselves: half the Mayflower people starved, Buenos Aires was abandoned for lack of food. Even today, you cannot find a native community anywhere practicing other than subsistence agriculture.
Dipshit, you claimed that they didn’t have domestic animals or irrigation, and when someone points out that in fact they did have domestic animals and irrigation, you claim that they are “idealizing the braves”.
“Animal domesticates included only two birds (the turkey in North America and muscovy duck, Cairina moschata, from Mexico), a small rodent (guinea pig, Cavia porcellus), and two camelids (llama, Lama glama, and alpaca, Vicugna pacos).” Not very impressive for a whole continent.
Regarding irrigation works, canals watering 60 – 100 acres were discovered in the SouthWest but they were abandoned. Calling them irrigation systems makes one imagine they were comparable to the vast, densely populated Chinese or Mesopotamian or Nile irrigation works. If left alone, they may have developed something in five thousand years. .
“no cultivated fruit trees” seems another ridiculous and moronic part of this statement – no papaya, guava, cherimoya until the Spaniards?
They had irrigation, it’s just not as effective as old world civilizations since mesoamerica wasn’t a river valley. They had a diversity of crops. Much of the veggies we eat today was first cultivated in mexico.
Phoenix, AZ, was named Phoenix because it got its agricultural start by refurbishing, i.e. resurrecting, the irrigation canals developed by the Hohokam native peoples.
People don’t have to submit passively to starvation to experience high mortality, especially infant mortality. All it takes is an inadequate diet over time.
“We cannot live without war. Should we make peace with the Tuscaroras, we must immediately look for some other, with whom we can be engaged in our beloved occupation.”
–Cherokee response to an attempt at brokering peace by Carolinian traders around 1730
Swampr,
Citation please?
It was reported by Chief Seattle. Or Elizabeth Warren. Anyway, someone like that.
Googling the quote, seems it is from “The natural and aboriginal history of Tennessee : up to the first settlements therein by the white people, in the year 1768” by John Haywood (1823).
Full text freely available:
https://archive.org/details/naturalaborigina00hayw/page/n10
Whether or not this quote is strictly accurate, there’s no doubt that at least some Indian tribes looked upon war as a sort of extreme sport.
My heart is filled with gladness when I see
Strong castles besieged, stockades broken and overwhelmed,
Many vassals stuck down,
Horses of the dead and wounded roving at random.
And when battle is joined, let all men of good lineage
Think of naught but the breaking of heads and arms,
For it is better to die than be vanquished and live . . .
I tell you I have no such joy as when I hear the shout
“On! On!” from both sides and the neighing of riderless steeds,
And groans of “Help me! Help me!”
And when I see both great and small
Fall in the ditches and on the grass
And see the dead transfixed by spear shafts!
Lords, mortgage your domains, castles, cities
But never give up war!
When I went to the Koster archeological site in Illinois in 8th grade, they said the village people died average 16 years old when their adult teeth wore out from little stones ground into their cornbread by the mortars.
like elephants…gruesome.
I have heard that ancient Egyptian bread was bad for the teeth as well.
Certainly looks like it from Max Roser’s article on violence in non-state societies based on archeological evidence.
https://ourworldindata.org/ethnographic-and-archaeological-evidence-on-violent-deaths
Let’s test that by averaging his data to smooth differences within continent – https://imgur.com/a/zEmg76u
Seems like Native Americans are the champs, continent by continent, but Africa are the top champs when you remove the effect of the low homicide rates of the !Kung.
I would presume that the Spaniards found America peopled to the land’s carrying capacity. In the Southern pampas, guanaco chasing (on foot) Indians lived a miserable starvation life and population density was very low. In the Andes, all fertile valleys were exploited to the maximum with then available technologies. Mexican peoples, subsisting without animal proteins (except cannibalism), were undernourished. Violence is universal in the human race but never limited population except temporarily. Diseases, like malaria, depopulate vast areas, but there were no such in America. Ergo, population was limited by the carrying capacity defined by the land’s and the technology’s food productivity.
So you’re going with “quietly starved to death”, rather than, say, violent struggle over limited food resources?
I’m going with both, and also Flower Wars and human-sacrifice instituted to cull (and terrorise) the civilians and less-useful soldiers.
Why weren’t there any native killer epidemics before the Spaniards showed up? In Mesoamerica, the numbers were there for a virus to thrive. They had poultry, and a few other domesticated animals. Also many animals in the wild. Why did no animal disease make its way to people? Was it a matter of scale?
Epidemic disease often crosses over from heard animals or bird flocks. Don’t remember many Native Americans heading domestic stock or flocks. Bison traveled in big enough herds to have endemic diseases, but there was much shorter interaction with them at close quarters than with domestic animal herds.
It seems logical, but few of the major infectious diseases of the Old World originated that way.
How do we know there were none? Maybe they had their “own” epidemics.
When the Europeans arrived they brought new ones.
Just saying.
If they had their “own,” then wouldn’t the Europeans, not having been exposed to the Amerindian pathogens until their arrival in the New World, have suffered near extermination by them?
They had fewer.
The cocolitzi might have been indigenous, but local to some Central American valley; transmitted across Mesoamerica by the Spanish.
It wasn’t. It was paratyphoid.
That is what I was thinking, too. “The First Farmers of Europe . . . ” has a pretty good evolutionary analysis of population and carrying capacity. The carrying capacity niche for hunter/gatherers was necessarily low. The population could never be very large and, of course, it was vulnerable to disease and climate changes, disease not being limited to humans since their prey and gatherings were also subject to disease. Killing buffalo brought the plains Indians in fairly quickly. The carrying capacity of an agricultural society is going to be much larger than that of hunter/gatherers and increased calories tend to increase female fertility. It is interesting to note, however, that time and again areas colonized by the first farmers of Europe had a population spike followed often by a plunge in population. It seems a pattern that makes the fall of the Olmec, Toltec, Mayans and others less mysterious.
shared mystery is not the same as an explanation.
No, a shared mystery is not an explanation. But if a mysterious event happens multiple times there is hope it will not always remain a mystery. Certainly violence is a factor since there is ample evidence of it. But I would guess that early farmers who were able to scaffold their way toward civilization still did not have enough variety in their support structures to survive sudden changes from violent neighbors, ordinary crop failures, disease, or social experimentation. Basically they were fragile and could not always bear the weight of change though the fatal change need not be the same thing in every instance.
Is it IQ? Else their population would have been massive?
Nope. When a continent is that isolated IQ is not really the decisive factor. A large part of Sub-Saharan Africa had better tech compared to pre-Columbian Americas.
Sometimes quite extraordinary rates of violence.
“Examination o f Peruvian crania from four central highlands
populations – San Damian, Cinco Cerros, Matucana, and Huarochiri –
indicates a very high frequency of healed cranial injuries, mostly depressed
fractures from violent confrontations: 55.7% o f males, 31.6% o f females,
and 26.9% of juveniles are so affected” (Verano & Williams, 1992).
Does it matter that war mostly kills males? If you still wind up with the same amount of women around, it doesn’t seem like this does much to limit population long-term.
Only if men don’t matter for any purpose but contributing DNA. Someone still has to help provide food, shelter, security, etc.
I didn’t get the impression the Amerindians were quite so discriminating
What was the population density of the MIssissippi valley prior to the 16th century?
The large structures that still survive were surely not constructed by small bands of hunter-gatherers.
https://infogalactic.com/info/Mound_Builders
Margeret Mead had some ideas on the population and culture of Samoa. It would be interesting to hear Greg´s view of her work. Surely she was a gigantic scientist.
Completely wrong,
Only joking, amazing that she had an influence, the reason imo people want to believe in nice things, have no interest in what is true or what is reasonable.
Criticism is vital but does not make you popular.
Parts of Australia also has good farming potential … yet the Aborigines did not develop farming … and there is evidence of lots of inter-tribal war.
The early English convicts and free settlers found it difficult to farm, they had the crops and the animals but soils are poor in general and the unpredictable droughts and floods didn’t help. Eventually with a lot of effort, breeding, technology and eventually fertiliser the country became the farm it is today. The most profitable early farmers were graziers sheep and cattle. The flocks and herds could roam vast areas and so not deplete limited enclosed farmland.
Why Melanisians from PNG didn’t settle in far north Qld is a bit of a puzzle, they only lived a stones throw from Cape York and they had settled on the Torres Strait islands but nothing on the mainland. Maybe the aborigines were too violent and the land not fertile enough.
Violence is the likelier explanation, but don’t discard the Pill. Lots and lots of tropical poisonous, abortifacient plants in South America.
Some people used them, some didn’t…
And up here in the Turtle Island too. Gary Jennings in “Aztec” mentioned the barbasco. A web search yields up that the Mesoamericans did indeed believe this “wild yam” had contraceptive qualities. (Besides that Jennings was an old dirty pervert he had done his homework.)
Do we have good estimates of either Eurasian population densities in the Neolithic before bronze and the wheel or New World population densities just before 1491? If not, do we have other reasons to believe that Amerindians were more or less warlike than other late stone age farmers or hunter gatherers?
This argument should be general: call it “Epidemic and Peace”.
Some researcher theorized that left-handedness is an advantage in more violent societies, because righties aren’t as used to dealing with southpaws, but southpaws, being in the minority have lots of practice versus righties. Native Americans had the highest rate of left handedness.
I can see there being situations where voluntarily limiting family size could be selected for. If having fewer children meant more resources per child, so they grow up healthier and better able to hunt, gather, fend off interlopers from other tribes, and agress against others. Maybe nature red in tooth and claw favored those who kept their numbers low without intragroup selection favoring the more fecund.
What population figures for the Americas do people have in mind? I have seen estimates as low as 10 or 20 million people and as high as 112 million. Since the population estimate for Europe in 1500 is only 90 million, and since the Aztec and Incan empires seem to have been fairly densely populated, are the differences really that great? Once again, depending on the population estimates that people accept, do we need any more of an explanation than lack of animal protein?
Rust never sleeps-
Does it have to be a thing? Population stable when birth rates = death rates. What caused them to die? Probably lots of things: violence, famine, some disease. Perhaps violence was a big component. What is known about fertility rates? Infant survival?