Okay, so this has been RT into my TL a couple of times this morning and I want to talk about it. This is my field: I'm a geneticist who works in this area, I'm writing a book about it, and I have an article coming out about it in @sciam next month. https://twitter.com/Kisha890/status/1380540320346165249

First: the tweet author is correct. There have been MANY attempts throughout history to portray Indigenous peoples' ancestors as "just another group of settlers" in order to justify colonialism.

Second: the tweet author is (mostly, kind of) correct about the so-called "Bering Strait" theory being outdated. It all depends on what the "Bering Strait" theory means. We don't really use that term in archaeology/genetics.

I *think* the author means the "Clovis First" model for the peopling of the Americas. That model dominated archaeology for a good chunk of the 20th century, and if you're my age or older, it's probably what you learned in school.

This model--which was largely based on then-available archaeological evidence--posited that the very first peoples in the Americas were the makers of the Clovis technocomplex, which appeared in the archaeological record around 13,000 years ago.

(this will be a longish thread, please bear with me).

Under the Clovis First model, people migrated from Siberia across the Bering Land Bridge, moving down a corridor that opened up between the two massive ice sheets that covered much of northern North America. They peopled both continents very rapidly.

This model DOMINATED archaeology for decades. Any sites which were proposed to pre-date Clovis were dismissed, and their proponents mocked. In my book, I describe how I learned this in my introductory archaeology class as an undergraduate.

(By the way, there is a massively racist history of Europeans trying to understand Native American origins that predates this model. I'm not getting into it in this thread, but I do in my book. It's ESSENTIAL that anyone with an interest in this field learns this history).

Back to Clovis First: I don't agree that this model was racist per se (though I recognize my positionality as a white woman working in a colonial field may influence this view). It was, at the time, the best explanation for then-known archaeological data.

However, it HAS been used to dismiss, minimize, and disrespect Indigenous histories. These histories are diverse and ancient. Sometimes they agree with Western scientific models, sometimes they do not.

We researchers in this field MUST be able to talk about our work and scientific models without being disrespectful or minimizing these Indigenous origin histories. (This is a career-long goal for me, and one which I'm always working on, with help from my Indigenous colleagues).

Okay, back to Clovis First. So, sites kept cropping up that were older than 13,000 years ago. And they became harder and harder to dismiss. Finally, the most eminent archaeologists--even skeptics--agreed on the validity of one site, called Monte Verde, in Chile: 14,200 years old.

Brief tangent here: why are these old sites so controversial? It's not because archaeologists aren't good at identifying sites. It's because they can be extremely ambiguous: Is a chipped stone the result of a human working it, or because of natural processes that break stone?

Couple this with the difficulties in dating objects and stratigraphic integrity (I'll leave this to my archaeology colleagues to explain better than I can), and you get a lot of varied opinions about whether some of these very earliest sites (which ARE ambiguous) are legit.

Again: I don't believe that this debate itself is racist (though see my positionality caveat): it's a reflection of how hard archaeology is to do!

Okay, so after Monte Verde, *most* archaeologists agreed that people were probably in the Americas before Clovis. So how did they get here? It's not simple: massive ice sheets blocked any overland route out of Beringia until sometime after ~14,000 years ago (estimates vary).

The alternative model--which, full disclosure, I agree with--is a movement down the west coast by boat. People could have traveled very swiftly and much earlier than the overland route, with access to plentiful marine resources (this is sometimes called the "Kelp Highway" model).

Right now, direct archaeological evidence for that route is not terribly strong. Much of what would have been the coastline back then--and any potential sites--was submerged with the melting of the ice sheets. But INDIRECT evidence (timing, genetics, environment) favors it.

Okay, so let's talk about genetics. First, let me be clear: there is a terrible history of geneticists mistreating and exploiting Native Americans and their ancestors in pursuit of data. We can't talk about this research without talking about how it has been done.

I'm going to really oversimplify this here. A more comprehensive version will be in my article for Scientific American next month, and a book length treatment will be out next year. I've also written several articles previously that I'll link at the end of this thread.

AND let me give one additional caveat: our genetic knowledge is very, very incomplete. It's based on limited genetic sampling. New genomes change our models all the time.

Our coverage is so limited for very complex reasons. Read this to start: https://science.sciencemag.org/content/360/6387/384.long

All genetic evidence--from contemporary Indigenous peoples and their ancestors--show ancestry from a couple of different sources. The major source of ancestry is a population that diverged from the ancestors of East Asians between 36,000-25,000 years ago.

A second source comes from a population that geneticists refer to as "Ancient North Siberians." We have a genome of an individual belonging to this population from the Mal'ta site in south-central Siberia 24,000 years ago.

For those of you paying close attention to the genetics literature, we were also talking about "Ancient North Eurasians" (ANE) as being the Mal'ta population and "Ancient North Siberians" (ANS) as the Yana population.

Following Sikora et al. 2019, I'm just calling them all ANS these days, since they were essentially the same population. Geneticists, we need to have more conversations about naming conventions etc etc.

Genetics models show that these two branches of ancestry came together between about 24,000-20,000 years ago. The resulting population was isolated from gene flow for several thousand years and diverged into multiple sub-populations. (This part is a bit murky and complex).

Exactly WHERE this happened is an area of active archaeological/genetic/paleoecological research. Opinions differ, and include: eastern Eurasia (I don't agree with this), central Beringia, the Siberian Arctic Zone.

These populations were ancestral to the Ancient Beringians (in Alaska, who seem to have no present day descendants), the First Peoples south of the Ice Sheets, and contemporary circum-Arctic peoples and their ancestors (who have additional ancient, complex migration histories).

A third (small) source of ancestry is an ancient population that seems to have also given rise to present day Australasians. So far, we only see this ancestry in South America (but we really don't have many genomes from North America, so it's quite possible that it's there too).

This so-called "Population Y" is a bit of a puzzle for geneticists right now. The best explanation is probably that it comes from a sub-population of the broader ancestral group that gave rise to these peoples.

Current genetic evidence doesn't match what we would predict from a trans-Pacific migration of Australasians

Okay, so: this was a massive oversimplification (please don't "@" me, geneticists and archaeologists). It's complex. Even now, we are arguing about whether the First Peoples were here 15,000, 17,000, 20,000 or even 30,000 years ago.

Yes there are some claims that people were here 130,000 years ago, but they don't really hold up in my opinion (and that of most archaeologists). I'll get into why another time, this thread is already way too long.

BUT, I want you to understand that the original tweet author was not wrong when they said that people are using claims about Native American origins to dismiss their indigeneity. It's true: it has been true ever since European settlers first stepped foot on this continent.

AND, it's true that what we used to teach (the "Clovis First" theory) is not supported by the majority of scientists working in this field these days. (A few still do). This hasn't been the prevailing model for decades, but I think it's still the one that most people know.

AND, it's true that Indigenous peoples have their own complex and ancient histories. What they know about their own origins may or may not agree with what Western scientists believe; that doesn't mean we can't be respectful and acknowledge them.

Please stop harassing and mocking the original tweet author. That isn't cool.