Pre-Clovis in North America: Myth or reality?

[Antivenin]

I am a newbie, (I hate that word), and I would like some insight on the latest supposed human fossil finds in SC, VA and PA. Are they really 50,000 years old? Who knows for sure? What is the latest on fossil-dating technology?

[TwoTrouts]

Can you provide a link. I haven't heard of this! It sounds very interesting.

[Colibri]

Ever since the Monte Verde site in Chile finally won widespread acceptance a few years ago, there has been little question that people were present in the Americas before Clovis (11,500 BP). So "pre-Clovis" as such is pretty much considered a reality now. The question now is just how far back archeologists will be able to push it.

My sense of the field right now is that dates of 15,000 or so BP in the Americas would not be too controversial to most archeologists. Beyond that, most are still going to require a lot of convincing. I haven't seen much on the finds you mention beyond the news accounts, so it's hard to tell just how solid the evidence might be.

[Squink]

New radiocarbon dates: Evidence puts man in North America 50,000 years ago (http://www.sc.edu/usctimes/articles/2004-11/topper_discovery.html)

First Americans may have crossed Atlantic 50,000 years ago (http://www.csmonitor.com/2004/1118/p01s02-usgn.html)

[Colibri]

Thanks, Squink. I remembered I had seen something on that but had forgotten exactly where.

I'll be interested to see how the Topper results hold up to peer review. I would expect that criticism might hinge on the possibilities that (1) the vegetation that the carbon dates doesn't actually belong to the layer the tools are found in; and (2) as the second link indicates, that the "tools" may not be human artifacts at all but naturally chipped stones.

Personally, I would find dates of 20,000, maybe even 30,000 years BP to not be too far-fetched. Something like 50,000 would be absolutely mind-boggling. But at this point, who knows? Breaking the Clovis barrier has opened up all kinds of possibilities.

[carnivorousplant]

This isn't time measured in relation to British Petroleum, is it? :)

[Colibri]

This isn't time measured in relation to British Petroleum, is it? :)

To clarify for those who might not be familiar with it, BP = Before Present. (Standard for early dates in archeology.) It saves having to do all those mental BC + 2005 years calculations when trying to figure out how long ago something was. Clovis was 9,500 years BC or 11,500 years BP.

[Antivenin]

Can you provide a link. I haven't heard of this! It sounds very interesting.

Here are 2 that I looked at: www.srarp.org/index.html
and www.centerfirstamericans.com

Within a mile of where I live, a friend whom I call Eagle Eye, continues to find artifacts, mostly arrowheads and spear points. That is what has piqued my interest in Those Who Came Before, especially here in the Sandhills of NC.

[Ike Witt]

Here is a previous thread about Clovis and Monte Verde. So is the ''Clovis barrier'' history now? (http://boards.straightdope.com/sdmb/showthread.php?t=167465&). And don't let my friends modesty fool you. He now has a job at a university in west Texas doing his thing.

[Exapno Mapcase]

To clarify for those who might not be familiar with it, BP = Before Present. (Standard for early dates in archeology.) It saves having to do all those mental BC + 2005 years calculations when trying to figure out how long ago something was. Clovis was 9,500 years BC or 11,500 years BP.
Just a technicality. "Present" for these calculations is actually 1950. It doesn't change with the year. This allows dates written in any year to be constant no matter how long after they are read. The error over 15000 years is below the plus or minus amount in all cases, so the difference isn't significant.

[Colibri]

Just a technicality. "Present" for these calculations is actually 1950. It doesn't change with the year. This allows dates written in any year to be constant no matter how long after they are read. The error over 15000 years is below the plus or minus amount in all cases, so the difference isn't significant.

Yes. It's based on the year the calibration curves for radiocarbon dating were established.

Conveniently enough, it's also one year before my birth, so that it's very easy to convert it into years BMe. :)

[toadspittle]

Personally, I would find dates of 20,000, maybe even 30,000 years BP to not be too far-fetched. Something like 50,000 would be absolutely mind-boggling. But at this point, who knows? Breaking the Clovis barrier has opened up all kinds of possibilities.

I still wonder why 50,000 years would be so strange. After all, once you accept the fact that people made it to Australia 50,000 years ago, reaching any other point on the planet doesn't seem that much more difficult (esp. as it doesn't seem like it would be too hard for any seafaring culture--which clearly the early Australians and their ancestors throughout Indonesia, etc., were--would have such a hard time just following the coast of Asia all the way up to the Aleutians and back down south).

[Colibri]

I still wonder why 50,000 years would be so strange.

Modern humans don't seem to have colonized Europe or northern Asia much before 45,000 years ago, so for them to have reached North America even earlier requires revising that date as well. Also, if humans were in North America for so long, it's very surprising there is not more early evidence for their presence, or an indication of their impact on the megafauna or on ecosystems. There is plentiful evidence of the latter post 11,500 BP.

[Antivenin]

Here is a previous thread about Clovis and Monte Verde. So is the ''Clovis barrier'' history now? (http://boards.straightdope.com/sdmb/showthread.php?t=167465&). And don't let my friends modesty fool you. He now has a job at a university in west Texas doing his thing.

I posted to the previous thread you mentioned, Adam. Thanks for directing me. Hopefully I will get it right this time:

Thank you all for the great info--I find it all so fascinating. It is a shame that the Army Corps of Engineers covered the Kennewick site with tons of fill. It is my understanding that the remains until recently were not available for study due to Native American protest. I can certainly understand their feelings, but apparently it is not known for sure the ethnicity of Kennewick. I just wish there had been more time to investigate the whole area.

I am not familiar with the redhead from Nevada. Can you fill me in? Rather, I should say Will you fill me in. I am a humble interested party among the learned.

[Diceman]

What's the current thinking on Kennewick Man's age? I remember hearing that he's pre-Clovis, but I forget how far Before Present he lived. (BTW, I never knew that BP's zero year was fixed at 1950. Cool.)

As for Kennewick Man's ethnicity, the last I heard, they decided that he was related to the Ainu people of Japan, and was almost certainly not Native American.

All of this talk about pre-Clovis Americans has gotten all of the Indian groups up in arms, because it suggests that Native Americans are not the original indigenous peoples in this continent.

[Colibri]

What's the current thinking on Kennewick Man's age? I remember hearing that he's pre-Clovis, but I forget how far Before Present he lived. (BTW, I never knew that BP's zero year was fixed at 1950. Cool.)

The estimates I have seen are mostly around 9500 BP; some sites say 8400 BP. So definitely post-Clovis. But that doesn't mean he could not be the descendent of pre-Clovis colonists. And I am not sure, but I don't think there is any conclusive evidence that Clovis peoples were necessarily the ancestors of modern Amerinds (although they have generally been assumed to be).

As for Kennewick Man's ethnicity, the last I heard, they decided that he was related to the Ainu people of Japan, and was almost certainly not Native American.

All of this talk about pre-Clovis Americans has gotten all of the Indian groups up in arms, because it suggests that Native Americans are not the original indigenous peoples in this continent.

While Kennewick man does not seem to fit an Amerindian type of bone structure, there is no reason he needs to fit into any other contemporary "racial" category either. Some populations at that time might not have been different from any modern groups.

The most intriguing recent info IMO is the suggestion that some early groups in the Americas might have been related to Australoids, or at least have branched off from the rest of humans at about the same time. And that might make sense, if the first colonizations of both the Americas and Australia took place about the same time. However, early Ameri-Australoids don't seem to have left any genetic markers in contemporary Amerindian populations.

Unfortunately, the political ramifications of these finds makes it rather difficult to search for reliable scientific information on the web - it's nearly swamped by polemical articles on both sides.

[DrDeth]

I still wonder why 50,000 years would be so strange. .
Well for one thing, it would ruin the "man is responsible for the Pleistocene Mammal extinctions" theories..... :dubious:

[Colibri]

Well for one thing, it would ruin the "man is responsible for the Pleistocene Mammal extinctions" theories..... :dubious:

Not at all. A recent review (http://www.berkeley.edu/news/media/releases/2004/09/30_.shtml) has concluded that, in many places (including North America) it was the combination of human hunting pressure with climate change that had the greatest impact on most of the megafauna. (In some places there is more evidence for climate, in some places more for humans, but the worst effects were where both coincided.)

Even if humans were in the Americas long before Clovis, one thing we do know is that Clovis was a highly specialized big-game hunting culture, which could have had far more impact on the megafauna than previous cultures did.

[Diceman]

The estimates I have seen are mostly around 9500 BP; some sites say 8400 BP. So definitely post-Clovis. But that doesn't mean he could not be the descendent of pre-Clovis colonists. And I am not sure, but I don't think there is any conclusive evidence that Clovis peoples were necessarily the ancestors of modern Amerinds (although they have generally been assumed to be).
Huh. I thought I heard that he was pre-Clovis. I saw something on TV where they said that a study of his skeleton revealed that he was more similar to the Ainu than anyone else. In any case, he is not Native American, but the local Indian tribe got his remains because the law assumes that any remains that pre-date white settlement must be Native American.

[Colibri]

Huh. I thought I heard that he was pre-Clovis.

Time-wise, that's not true. But as I said, it's entirely possible than he belongs to a population that colonized the Americas pre-Clovis. And if you assume that Clovis = Amerindian (which is commonly believed, but probably not true), then if he's not Amerindian he must be a descendent of pre-Clovis people.

I saw something on TV where they said that a study of his skeleton revealed that he was more similar to the Ainu than anyone else.

Quite possible, but that doesn't mean there is any direct relationship. The Ainu may retain characters present in ancient populations that have been lost in other modern ones, but may not be any closer to Kennewick in terms of genetic relationship.

In any case, he is not Native American, but the local Indian tribe got his remains because the law assumes that any remains that pre-date white settlement must be Native American.

Actually, the tribe (fortunately) never "got his remains." Scientists won the rightin court to study the bones last year. They are currently held by the Burke Museum in Seattle. Appeals are continuing.

This site (http://www.kennewick-man.com/kman/news/index.html) has news reports with updates on the controversy.

[Diceman]

Actually, the tribe (fortunately) never "got his remains." Scientists won the rightin court to study the bones last year. They are currently held by the Burke Museum in Seattle. Appeals are continuing.
Glad to hear it. At the time the TV show was filmed, the tribe had won the early court battles.

[DrDeth]

Not at all. A recent review (http://www.berkeley.edu/news/media/releases/2004/09/30_.shtml) has concluded that, in many places (including North America) it was the combination of human hunting pressure with climate change that had the greatest impact on most of the megafauna. (In some places there is more evidence for climate, in some places more for humans, but the worst effects were where both coincided.)
.

In fact your site does show that the "man is responsible for the Pleistocene Mammal extinctions" theory. is incorrect. "Contributed to" and "the primary or sole cause of" are way different.

"In the forensic quest for who done it, many have pointed fingers squarely at humans.

But in a review appearing in the Oct. 1 issue of Science, Barnosky and his colleagues conclude that climate change also played a big role in driving these extinctions."

and "There's been a lot of talk about people causing the extinction of the megafauna by killing everything they saw, like a blitzkrieg," said Barnosky, professor of integrative biology and a curator in UC Berkeley's Museum of Paleontology. "But if you look at all the evidence, it's clear that while humans had a major role in these extinctions, in many cases climate change was a key part of the recipe."

As the article says- many blamed the extinctions only or primarily on human hunting. The article disputes this- saying that in many cases climate changes are more important, and in some cases it was man- but indirectly, by long-term habitat alteration.

The point being- many thought that human hunting was the sole cause of such extentcions- and your cite strongly disputes this.

[Colibri]

In fact your site does show that the "man is responsible for the Pleistocene Mammal extinctions" theory. is incorrect. "Contributed to" and "the primary or sole cause of" are way different.

. . .

The point being- many thought that human hunting was the sole cause of such extentcions- and your cite strongly disputes this.

Nonsense. You are just setting up a straw man. Few scientists have ever contended that humans were the sole cause of Pleistocene extinctions. And many other scientists have argued that climate change was the primary or sole cause of the extinctions. The article strongly contradicts the latter position as well.

The fact of the matter is, the evidence strongly suggests that without the impact of human hunting, much of the megafauna would not have become extinct even in the face of climate change. Most of the species had survived several equally severe climate changes through most of the Pleistocene. It was humans that tipped the balance the last time.

[DrDeth]

Nonsense. You are just setting up a straw man. Few scientists have ever contended that humans were the sole cause of Pleistocene extinctions. .

Your cite says otherwise: "In the forensic quest for who done it, many have pointed fingers squarely at humans."

"There's been a lot of talk about people causing the extinction of the megafauna by killing everything they saw, like a blitzkrieg,..."

"Those blaming humans ascribe the extinctions to human hunting, either through overkill - hunting that could have led to extinction in about 1,500 years - or through a "blitzkrieg" of hunting that could have knocked off a species in less than 500 years."

"Barnosky and his colleagues found sparse evidence outside Australia that humans were the sole cause of extinction."

In fact, according to your cite, it was primarily in NA (and not in Alaska) where "North America, in particular, is an example of a place where humans speeded the process of climate-caused extinction, in many cases by overkill."

I know of few that doubt that human hunting had an impact. Fact is- we'll never know exactly how much of an impact. The "humans killed them all off by hunting" camp had one "big arrow in their quiver of arguments"- that the extinctions and the arrival of humans more or less co-incided. That was their strongest argument, and now it's gone.

[Colibri]

Your cite says otherwise: "In the forensic quest for who done it, many have pointed fingers squarely at humans."

Try reading the general literature, and not a single cite (and a non-technical one, at that). In the primary literature, there are few scientists who attribute megafaunal extinctions solely to humans. Most accept a role for climate change.

"Barnosky and his colleagues found sparse evidence outside Australia that humans were the sole cause of extinction."

But widespread evidence that they contributed.

I know of few that doubt that human hunting had an impact. Fact is- we'll never know exactly how much of an impact.

Barnowsky indicates it was significant in several regions.

The "humans killed them all off by hunting" camp had one "big arrow in their quiver of arguments"- that the extinctions and the arrival of humans more or less co-incided. That was their strongest argument, and now it's gone.

Once again, nonsense. You persist in trying to oversimplify a complex situation. The argument, of course, is not "gone." It still applies for some regions. The extinction event in North America may not have coincided with the arrival of humans, but as I said it did coincide with the rapid spread of the big-game hunting Clovis culture.

[DrDeth]

Try reading the general literature, and not a single cite (and a non-technical one, at that). In the primary literature, there are few scientists who attribute megafaunal extinctions solely to humans. Most accept a role for climate change.


It was your cite, not mine- I can only assume you chose it because you generally agreed with it and admired it. And you called my statement a 'strawman", which if so, was a strawman used no less than 4 times by the very cite you provided.

Simply put- there is no proof that humans (by hunting) caused any extinctions of any successful species during the Pleistocene. Those who said that humans did "cause the extinction of the megafauna by killing everything they saw, like a blitzkrieg" had only one argument in their belt, and that's gone. Sure- Clovis man was a successful hunter. But he didn't kill off the "Irish elk... the straight-tusked elephants... grizzly-like Arctodus simus, mammoths and others" ("This is a very clear case of climate-caused extinction without the significant input of humans," Barnosky said."), and he didn't kill off the Bison, either. In fact- before the white man, there were uncounted millions of them. Much easier to kill than the mastodons or the saber-toothed cat- why wasn't even a dent put in the population of the Bison?

No doubt that hunting played a part. That human changes to the evironment played a part. But also that climatological changes played a part too. AND, there may have been other significant factors that we don't know about- disease, maybe. Pointing a finger at any one cause is "oversimplification" and "nonsense".

[Colibri]

It was your cite, not mine- I can only assume you chose it because you generally agreed with it and admired it. And you called my statement a 'strawman", which if so, was a strawman used no less than 4 times by the very cite you provided.[quote]

That's an interesting contention - that because someone cites an article, they necessarily agree 100% with every single statement in it. In case you haven't noticed, that's a press release, not a scientific article, and hence it states things in a highly simplified way for the general public. I'd link to the Barnosky article itself, but I don't think it's available for free. I do agree with Barnosky's basic point, that both human activity and climate played a role in the megafaunal extinctions, and that's why I linked to it.

And even so, the article doesn't say anywhere what you said:

[quote=DrDeth]The point being- many thought that human hunting was the sole cause of such extentcions- and your cite strongly disputes this.

Emphasis mine. Nowhere in the article does it say those who blame humans think they were the sole cause. If you read the original articles by the scientists they are referring to, you'll find few that would take that position.

No doubt that hunting played a part. That human changes to the evironment played a part. But also that climatological changes played a part too. AND, there may have been other significant factors that we don't know about- disease, maybe. Pointing a finger at any one cause is "oversimplification" and "nonsense".

I agree with this. Who are you arguing with?

[Colibri]

Coding fixed for clarity:


It was your cite, not mine- I can only assume you chose it because you generally agreed with it and admired it. And you called my statement a 'strawman", which if so, was a strawman used no less than 4 times by the very cite you provided.

That's an interesting contention - that because someone cites an article, they necessarily agree 100% with every single statement in it. In case you haven't noticed, that's a press release, not a scientific article, and hence it states things in a highly simplified way for the general public. I'd link to the Barnosky article itself, but I don't think it's available for free. I do agree with Barnosky's basic point, that both human activity and climate played a role in the megafaunal extinctions, and that's why I linked to it.

And even so, the article doesn't say anywhere what you said:

The point being- many thought that human hunting was the sole cause of such extentcions- and your cite strongly disputes this.

Emphasis mine. Nowhere in the article does it say those who blame humans think they were the sole cause. If you read the original articles by the scientists they are referring to, you'll find few that would take that position.

No doubt that hunting played a part. That human changes to the evironment played a part. But also that climatological changes played a part too. AND, there may have been other significant factors that we don't know about- disease, maybe. Pointing a finger at any one cause is "oversimplification" and "nonsense".

I agree with this. Who are you arguing with?

[Spectre of Pithecanthropus]

This sort of thing is fascinating. While I was a senior in high school, I got to my anthropology class one morning when the teacher said instead of our usual classwork that day we were going to go over to a place on campus where a Native American grave had been accidentally unearthed. We went over to look, and there was the skeleton of a small adult, with two small soapstone bowls. Radiocarbon dating eventually showed it to be from 8000BP, and the bowls were similar to those of a Channel Islands culture of that time. I have mixed feelings about this. This person's loved ones buried their deceased relative with ceremony and care, obviously expecting that he would remain there in peace. On the other hand, to be present when something like this comes to light, seems to connect us with those people of long ago in a unique way.

There must be any number of similar graves in the neighborhood. There are springs on the grounds of the school which always flow abundantly, no matter how dry the Southern California weather gets. Father Serra is supposed to have camped there while travelling from San Gabriel to San Fernando. No doubt, it was a meeting place for the aboriginal population for thousands of years.

[Blake]

I still wonder why 50,000 years would be so strange. After all, once you accept the fact that people made it to Australia 50,000 years ago, reaching any other point on the planet doesn't seem that much more difficult (esp. as it doesn't seem like it would be too hard for any seafaring culture--which clearly the early Australians and their ancestors throughout Indonesia, etc., were--would have such a hard time just following the coast of Asia all the way up to the Aleutians and back down south).

Yeah, it’s a lot more difficult.

The point to remember here is that the longest water journey made by people colonising Australia was probably only a bit over 40kms. At the time humans arrived sea levels were such that island hopping was quite easy. Moreover because of the patterns of ocean currents and winds and the migration patterns of birds even that one ‘huge’ half day, over-the-horizon sea journey wasn’t a leap into the unknown. Those people would have or at least should have been fully aware that there was land there. In reality they probably had a fairly good idea of where the land was and how big it was. Moreover the journey was reasonably safe and routine. Water and air temperatures were mild and in winter the storms were rare.

Added to that with the exception of boats these people were able to use the same basic level of technology as they had when they left Africa. Tropical subsistence is fairly standard. That’s probably a large part of the reason why both H. erectus and later H. sapiens colonised SE Asia so rapidly and completely while Europe and central Asia took much longer to be even partially settled.

That’s very different any hypothetical journey along the east coast of Asia through Siberia and down Alaska. At the best of times the temperatures were unpleasant and the weather unpredictable with fogs, storms etc. Moreover I don’t know of any evidence that migration patterns or ocean currents (even in periods when the oceans weren’t frozen) would have provided evidence of land across the horizon. It was a leap into the unknown. And the lifestyle was radically different to the African savanna style and presumably required a radically different toolkit. No longer could the colonists simply live as tropical hunters. Now they needed to rely exclusively on fishing and hunting seals etc along with changes in shelter and behaviour that a frigid climate dictates. Basically to make the leap across the straits by sea would have required the first people to become fully fledged Eskimos. That’s quite a cultural and technological leap from the African lifestyle they left behind just a few tens of millennia earlier.

Note that none of this means that they couldn’t have done it. It just means that it was much more difficult than the short island hops from tropical Asia to tropical Australia.

[Oslo Ostragoth]

(popping in without having read the entire thread) A book (http://www.amazon.com/exec/obidos/ASIN/0618352104/qid=1115787825/sr=2-1/ref=pd_bbs_b_2_1/104-9888683-7981554) that is very relevant to this discussion.

[Spoke]

It would be very hard to argue that climate change killed the mammoths, I think. Mammoths were very adaptable animals, their remains having been found as far south as Florida on the east coast, and even as far south as Guatemala. What sort of climate change could have wiped out an animal which could so obviously handle widely varied environments?

[Antivenin]

I have been out of commission for a few days due to sciatica (rough!)
I appreciate the links, especially the extensive one on Kennewick man. As far as the extinction theories go, I saw something interesting on the Science Channel, and I wish I could remember where the archeology sites were--either pretty close to Canadian border or in Canada--At any rate, there seems to be some evidence that Man somehow ran the big boys off the edges of cliffs in big numbers, which they postulated due to finding bone beds at the base of cliffs where there were mammals of all ages and some spear points.

However, according to the people on the TV show, it could have also been evidence of something catastrophic (act of God) that killed a bunch of dinos in the same area, because they were herd animals. Then again, they had never seen fossils of meateaters all together, and they were presumed to be solitary in nature.
I wish I had the exact references, because I know this info is vague, and my memory isn't perfect (could be due to the mega Percocet I had to take for the sciatica in order not to jump off a cliff myself and end the misery.)

[Spoke]

I saw something interesting on the Science Channel, and I wish I could remember where the archeology sites were--either pretty close to Canadian border or in Canada--At any rate, there seems to be some evidence that Man somehow ran the big boys off the edges of cliffs in big numbers, which they postulated due to finding bone beds at the base of cliffs where there were mammals of all ages and some spear points.

That would be the descriptively-named Head-Smashed-In Buffalo Jump (http://www.pc.gc.ca/progs/spm-whs/itm2-/site6_e.asp) in Alberta.

I believe there are other similar sites where this hunting technique was used.

[Spoke]

It is a possibility to consider that man existed in America for some time fishing, gathering and trapping small game before making the technological leap (of which the Clovis point may be a part) which enabled them to become big game hunters (and subsequently drive several large species to extinction).

I'm more inclined to believe that it was a numbers thing. Man may have been here before Clovis, but in numbers too small to do significant damage to game populations. There may have been a population explosion around the time of the Clovis point, or perhaps a new wave of immigrants who brought technology with them and who overwhelmed the earlier (and more primitive?) inhabitants.

[Antivenin]

That would be the descriptively-named Head-Smashed-In Buffalo Jump (http://www.pc.gc.ca/progs/spm-whs/itm2-/site6_e.asp) in Alberta.

I believe there are other similar sites where this hunting technique was used.

I thought you were just funning me, but what a surprise I got. Great site!

[Oslo Ostragoth]

I have been out of commission for a few days due to sciatica (rough!)
[off-topic but hopefully helpful: I had a bad case a few years ago. Several trips to a chiropracter later, I was cured.]

[Blake]

It is a possibility to consider that man existed in America for some time fishing, gathering and trapping small game before making the technological leap (of which the Clovis point may be a part) which enabled them to become big game hunters (and subsequently drive several large species to extinction).


That’s pretty improbable and unsupported by any evidence. The biggest problem is that humans already had the toolkit needed to be effective big game hunters by 80, 000 years ago, well before any possible ventures into the Americas and possibly before any humans had left Africa.

Now there is a possibility that the earliest people in the Americas suffered the same fate as the Tasmanians in that they suffered a serious population decline and as a result lost almost all technology from the ability to make fire to the knowledge of clothing and hafted weapons. Note however that this is merely possible. There’s no evidence for it and moreover the massive size of the Americas makes it unlikely that the technology wouldn’t be rapidly reinvented as the population recovered and grew into the hundreds of thousands or millions.

I guess that’s related to your idea about human populations remaining low, however I can’t see any particular reason why anatomically and mentally modern humans would remain in low densities and technologically deficient on a land mass as massive as the Americas. Sure it’s not as large as Europe/Asia/Africa but it still should be more than large enough to support critical human growth.

[Spoke]

I can’t see any particular reason why anatomically and mentally modern humans would remain in low densities and technologically deficient on a land mass as massive as the Americas.

And yet, if the archaeology is correct, there were people here before Clovis, but apparently not in large enough numbers to be archaeologically ubiquitous. So if that's the case, we have to figure out why their numbers (apparently) remained low until Clovis.

My post was only speculation, so of course it's not supported by evidence. I'm open to other ideas.

As to why numbers may have remained low, well, North America was a predator-rich environment. If the earliest inhabitants were technologically deficient (speculation, of course), those predators, combined with more limited food options, may have been enough to keep numbers down.