Founder effects identify languages of the earliest Americans
INTRODUCTION Archeological evidence shows that there were human entries to the Americas well before the end of the last glaciation (Dillehay, ; Dillehay et al., , ) and quite possibly by the peak of glaciation c. 24,000 years ago. The linguistic evidence requires entries during or before the last glacial maximum (LGM) (Nichols, , ), enough to give rise to the ~200 independent language families of the Americas and their structural diversity. (Before recent extinctions the Americas hosted close to half of the known linguistic lineages.) Glaciation blocked entry to North America, but recent paleoceanographic data and models show two periods during the terminal Pleistocene when coastal entries were possible: ~24.5–22 ka and ~16.4–14.8 ka (Praetorius et al., ). Overland entries to intermontane North America via the ice‐free corridor between the shrinking Cordilleran and Laurentide glaciers became possible in the same general time frame as the second of these openings (Perego et al., , Anderson & Bissett, :79–80), and movement into the interior via the Columbia and Snake to the upper Missouri drainage and via the Colorado and Gila was always possible (Anderson et al., ; Anderson & Bissett, ). Drawing on these sources, this paper proposes a two‐stratum, four‐opening model for the origin and expansion of the American linguistic population. The first and second openings (~24,000 and ~15,000 years ago, following Praetorius et al., ) resulted in coastal entries south of the ice sheets (i.e. south of the Columbia River). The resultant linguistic populations have mingled in Oregon and California; their descendants cannot so far be clearly distinguished on linguistic evidence, and will be jointly called the early stratum. The third opening was the formation of the ice‐free corridor ~14,000 years ago, resulting in colonization of the North American interior by people from Beringia and unglaciated northwestern Alaska; this produced a later stratum which gave rise inter alia to the Clovis phenomenon and whose linguistic descendants are structurally quite distinct from the early stratum found in California and Oregon. The fourth opening was the retreat of the coastal ice sheet, making possible coastal and near‐coastal settlement of the Pacific Northwest ~12,000 years ago. Descendants of fourth‐opening languages share many of the distinctive properties of third‐opening languages but can be distinguished on other salient properties. Still later came the entries of two known language families: Athabaskan‐Eyak‐Tlingit (AET, a.k.a. Na‐Dene), mostly interior‐oriented, and Eskimo‐Aleut, primarily coastal. Inland Northeastern Asia during the terminal Pleistocene must have been a linguistic spread zone like attested recent arctic and subarctic regions. Relevant modern examples are non‐food‐producing arctic regions (North America; northern Eurasia prior to the introduction of large‐scale reindeer herding) and also non‐food‐producing desert regions (southern Africa, the Australian arid interior, and part of the Great Basin). A spread zone usually has a sparse and often mobile human population and a linguistic population shaped by convergence and diffusion with occasional large spreads altering the genealogical and/or typological profile of the region. In the roughly 8000–10,000 years between the two coastal openings there must have been the normal gradual grammatical and lexical changes in the northeastern Asian languages, and occasional immigration, emigration, or extinction of languages, over time substantially changing the linguistic typological profile of the area. (Note that the linguistic comparative method, used to establish relatedness and reconstruct ancestral states, can rarely reach back more than ~6000 years, so daughters from an 8000‐year‐old split can be as unrecognizably different as two unrelated languages.) A few representatives of the Siberian linguistic population as it changed over time can be assumed to have made viable entries to subglacial North America. With deglaciation after the third and fourth openings, occasional further entries must have occurred. A total of about 12 entries at a mean of 2000‐year intervals, beginning about 25,000 years ago, would generate the genealogical and structural diversity attested in the Americas and allow time for expansion as far south as Monte Verde, Chile, a site with clear evidence of human habitation at over 14,000 years ago (for the expansion rate, Nichols, ; for Monte Verde, Dillehay et al., ; Erlandson et al., ; Dillehay, ). The most recent two postglacial entries are identifiable with specific language families: the AET family, which dispersed in Alaska at least 5000 years ago and has well‐argued likely connections to the Yeniseian family of north central Siberia (Vajda, , , Fortescue & Vajda, ), age of entry unknown but likely early postglacial (Kari, gives some hydronymic evidence) ; and the ~4000‐year‐old Eskimo‐Aleut family of coastal Siberia, Alaska, Canada, and Greenland, whose Eskimoan and Aleut branches split in Siberia, spread eastward separately to Alaska, and later recontacted there (Berge, , ). The AET and Eskimo‐Aleut families are different in structural type from each other and from most of the other families in North America. Geographically, I put them in the Pacific Northwest group. The first entrants to North America expanded the human frontier, and as the continent was settled the frontier expanded east and south. Behind the gradually advancing frontier was probably a dynamic and variable ethnolinguistic situation. Though the sociolinguistics of interaction between small, mobile groups in very sparsely inhabited land with an open frontier is unknown, the model sketched here attempts to capture one element of the picture: language viability and spreads from the entry points. In this model an entering group settles in an attractive resource‐rich area (the term of Beaton, is megapatch) not far from the entry point, and there they prosper, adapt to the environment and resources, and expand demographically. By the time another entrant appears the first settlers are well entrenched, more numerous than the newcomers, and in a position to fend off or absorb the small group of newcomers. The newcomers move on, skirting earlier entrants. Offshoots from the first settlement also move away and found new colonies. Thus the early settlement functions as a staging area (using the term of Anderson & Gillam, , Anderson et al., ; those staging areas are archeologically supported while those proposed here are supported by linguistic intangibles). Gradually the human frontier expands far to the south and east, but it continues to be the case that descendants of the earlier settlers remain entrenched in or near the staging area more often than they move on. This paper is an exploratory study showing that there is enough linguistic evidence to support the model and raise research questions and hypotheses. It is intended to help geneticists, archeologists, and linguists formulate research questions and hypotheses relevant to each other's work. Meanwhile, pending larger‐scale and more definitive work, the results are used here as an analytic framework. 

METHOD I survey 16 linguistic structural features that are known or likely to be good markers of families, areas, or underlying types (see Table ). Most of them are complex, with components that are ordered or structured into multidimensional paradigms; such systems are unlikely to recur by chance and are therefore good diagnostics (Ringe & Eska, : 256–280). Some are demonstrably stable (Wichmann, , Wichmann & Holman, , Nichols, ). Surveying published grammars and databases, I determined the frequencies of those markers among 60 well‐described, geographically and genealogically diverse languages of North America. See Figure . The analysis involves frequency comparisons between geographical regions. The geographical breakdown (Table ) is similar to that of Bickel et al., , except for distinguishing an Intermontane region to give a three‐way breakdown into what are called triparts here. , The geographical, and not linguistic, breakdown makes the areal comparisons of linguistic features non‐circular. A non‐geographical grouping is the Penutian languages, a set of language families now found mostly in California that are known to have originated in the southern Columbia Plateau and northwestern Great Basin (Golla, :128–168) and to have moved separately into California and Oregon millennia ago as postglacial desiccation set in. Three of the known or likely ancient staging areas involved in the earliest expansions into North America (Anderson et al., ) host a continued prehistory of language expansion up to the origins of the oldest traceable language families. These staging areas are: (1) In the Intermontane tripart, the Lahontan region around Glacial Lake Lahontan from the northwestern Great Basin to the proglacial lakes of southeastern Washington. It is a likely secondary staging area for the first and second openings, as any initial settlements in the Columbia River delta area are now submerged due to the postglacial sea‐level rise, and earliest sites near the Columbia must have been destroyed in cataclysmic post‐LGM floods from Glacial Lake Missoula (Baker, ). Whatever the geological prehistory, the Lahontan region is the presumable homeland for most of the Penutian language families (Golla, : 128–168 and references there), most of which spread westward as the Great Basin gradually desiccated in postglacial times. It is roughly congruent with staging area 3 of Anderson et al., :197. (2) In the East, the midcontinent Ohio‐Cumberland‐middle Mississippi region, the most likely homeland for the Siouan language family dispersal and for Siouan and other languages that have moved into the Southeast. It coincides with staging area 10 of Anderson et al., :197. Anderson et al. identify the Lower Mississippi Valley as a staging area (their 6), but in recoverable linguistic prehistory it has been not an origin of language spreads but an accretion zone (a.k.a. residual zone: Nichols :21–24, Nichols :369), a region where languages move in more often than they expand out, so that genealogical diversity accumulates. See Kaufman, :29–69 for the Muskogean and Siouan languages there and Brown et al., for Chitimacha. (3) The lower Colorado River, an entry point and gateway for spreads to the Southwest and Southeast and southward to Mexico. The Pacific Northwest must also have hosted spreads of languages and diffusions of language elements into the adjacent Eastern tripart, causing resemblances between descendants of the third and fourth openings (see Results). The 16 structural features were surveyed across all of these groups. The languages and their tripart affiliations are shown in Appendix . 

RESULTS Frequencies of features per area are shown in Tables and . Pan‐North American features are noun plurals, frequent across northern Eurasia, and inclusive/exclusive pronouns, frequent in the eastern parts of the world (Americas, Australasia); both might well have been brought in by any language entering via Siberia. Statistically significant differences among the triparts involve n‐m pronouns (a western, near‐exclusively Californian feature that marks the early stratum and probably the second opening as discussed below), polysynthesis, and noun incorporation (the latter two are structurally related and mark the later stratum and both third and fourth openings). That is, they primarily cluster not in whole triparts but in subparts of triparts. Frequency differences between subparts of triparts can sometimes be associated with particular strata and openings. The early stratum, in addition to high frequencies of n‐m pronouns, is marked by the high overall number of statistically significant frequency differences involving California‐Oregon (Table ) and also the well‐known high diversity of language families in California and western Oregon. This picture is consistent with a long diversification time in situ. The later stratum is marked by polysynthesis (100% frequency in the Pacific Northwest and the Northeast), head marking, and noun incorporation, and more generally by the near‐absence of significant differences between the Northeast and either the Pacific Northwest or the Southeast. The distinguishing features are less frequent in the Southeast, where a handful of isolates and small families identified by Kaufman, as anciently indigenous, with no evident linguistic or archeological connections elsewhere, lack polysynthesis and resemble languages of California more than eastern ones. It is possible, but hypothetical, that they descend from early entrants via the Colorado. Other Southeastern languages come from families with known or likely external connections, chiefly to the north: Caddoan (southern to central plains), Siouan (Ohio River valley); Iroquoian (New York), and Muskogean (Southeastern but earlier possibly Southwest to Mexico). No features likely to be unique to the first opening have been found; it appears to be a well‐mixed, diverse set of languages. The second opening is marked by n‐m pronouns and the Penutian languages (nearly all of which have n‐m pronouns). n‐m pronouns are found densely in different families (Penutian and other) of Oregon‐California, but only once north of the Columbia in the small Tsimshianic family. Since personal pronouns are among the most stable of vocabulary items (Wichmann & Holman, ) and structural properties, especially paradigms, are stable, resistant to borrowing, and strong diagnostics of family membership (Wichmann, , Nichols, , Ringe & Eska, :266–267), they are unlikely to have spread by contact and more likely to be an archaism where they occur. They may have been an innovation of a second‐opening group. The third opening is distinguished by later‐stratum features and simple consonant systems; the fourth opening is similar but is saliently marked by complex consonant systems and numeral classifiers. Numeral classifiers are found in clusters in coastal Southeast Asia and the Pacific (Gil, ; Nichols & Peterson, , ). They are prone to spread in contact but in the Americas are barely attested outside of the Pacific Northwest, consistent with a relatively recent entry. Verb complexity (Table ) is higher than noun complexity in most areas (strongly so in the East), but the picture is reversed in the Pacific Northwest. Languages of the fourth opening fit typologically with some of the Paleosiberian languages of eastern Siberia and the whole set defines a North Pacific Rim linguistic population (Fitzhugh & Crowell eds. , Miyaoka ed. , Matsumae et al., , Fortescue & Vajda, ). The AET languages from a later entry to some extent fit typologically with the descendants of the fourth opening, and both AET and Eskimo‐Aleut have North Pacific Rim affinities. A Neighbor Net cluster diagram based on the morphological features is in Figure . There are three large clusters: at the top, mostly polysynthetic languages of the Pacific Northwest (plus Navajo, southern Intermontane but in origin from Alaska); at lower left, head‐marking and often polysynthetic languages, mostly eastern; and at the right, a disparate cluster of mostly Penutian languages (upper right) and a mix of others at lower right, including most of the isolates of the Southeast. Briefly, the left part spans mostly the Northwest and the East, including members of the large interior families (Siouan, Algonquian, AET); and the right spans mostly languages of California‐Oregon and the isolates of the Southeast. The left contains the sample's polysynthetic languages. Most generally, the left contains languages from the later stratum, separately clustered as Pacific Northwest and Eastern (most Northeastern in origin), while the right contains the best candidates for languages of the early stratum, separately clustered as central to northern Californian (mostly Penutian) and a mix of isolates and small families from California and the Southeast. Thus, the graph captures formative events and fissures over the entire North American population history. 

DISCUSSION This paper has presented a two‐stratum, four‐opening, multi‐entry model for the American settlement prior to the later entries of AET and EA. The strata define large language and language‐family populations and large human populations with separate origins and entries. The early stratum was coastal in origin and primarily maritime in subsistence and material culture, and entered during the first and second openings, when sea ice conditions permitted coastal canoe travel and entry south of the continental ice sheets. In the ~8000 years between the two openings, the languages of coastal eastern Siberia must have evolved and the language population must have lost members and acquired members, causing changes in frequencies of linguistic structural types there. Sorting out, in this linguistically diverse population, descendants from the respective openings is a challenge for further research, but one possibility was mentioned here: n‐m pronouns appear have been a second‐opening feature. The later stratum is primarily inland (East tripart, from the third opening) but also includes the Pacific Northwest from the fourth opening, when sea‐level rise was reducing Beringia and direct overland Asia‐Alaska connections were shrinking. Settlements in the first and second openings necessarily occurred south of the continental ice sheet, which reached nearly to the Columbia River in the LGM. Temporary landfalls in coastal refugia may have occurred earlier, but what is necessary to begin populating the continent with languages and their speakers is a durable settlement with year‐round proximity to good resources and possibilities for expansion. Any direct evidence for the earliest coastal settlements has been obliterated by the postglacial sea‐level rise, but even inland there is so far no evidence of first‐opening human presence in the north (one of the earliest nearby is Paisley in southern Oregon, ~14,000 years ago: Gilbert et al., ). The two coastal openings, though brief, were exploited by what must have been a mobile, canoe‐using population with wide‐ranging subsistence strategies (deep‐sea fishing, coastal fishing and gathering, inland hunting) and when necessary obtaining stone from considerable distances (Davis & Madsen ). For such a population, any productive river delta would have been discovered soon after access opened up and might have served as a local staging area for further coastal exploration and movement into the interior. Productive deltas probably included the Klamath, San Joaquin (San Francisco Bay), and especially the Colorado, a staging area for inland entry. Three recently dated ancient archeological sites fit the time frame that is expected for a pattern of movement that reached Monte Verde, Chile by over 14,000 years ago: White Sands National Park, New Mexico with preserved human footprints possibly dating to 21,000–23,000 years ago (Pigati et al., ; Bennett et al., ; but see Davis & Madsen, ; Oviatt et al., ); the Hartley mammoth site in northern New Mexico dated at 36,000–39,000 years ago (Rowe et al., ); and bones in the oldest depositional level of Coxcatlan Cave, Puebla, Mexico dated to 28,000–33,000 years ago (Somerville et al., ). The entrenchment of first settlers has implications for language structure and complexity. Ordinarily, when one society absorbs another, many incoming adults learn the absorbing population's language, and learn it imperfectly, often speaking with an accent and a simplified grammar (Trudgill, ). As a consequence, expansive languages tend to be lower in complexity than their neighbors and any sisters remaining in the homeland. But in the case of the North American founder languages, the intervals between founding events would have allowed the entrenched population to become larger than the immigrant one, so that a few incoming speakers with imperfect command of the language would have no appreciable impact on it. Thus, the entrenched language continues to develop on its own with little or no external input that might hinder further complexification (Dahl, ; Trudgill, ). Though that initial sociolinguistic situation must have changed considerably over time, especially as languages spread out, it is suggestive that languages of the Pacific Northwest, from the Columbia to eastern Alaska—likely landfalls or entry points for all four openings—exhibit notably complex morphology and phonology compared to the rest of the hemisphere, and complexity levels in the Americas are high overall relative to world averages (Donohue & Nichols, ). Both the n ‐ m pronouns of the early stratum and the polysynthesis of the later stratum have what can be called click distributions (Nichols, ): features that are very rare worldwide but well‐installed and stable in a large cluster of languages in one place (so called from the click consonants of southern African languages, which exhibit such a distribution in its most clear‐cut form: absolutely unique to Africa). Numeral classifiers have a transcontinental click distribution around the entire Pacific Rim. (Worldwide maps of both: Gil, and Nichols & Peterson, ). Click distributions can be excellent population markers, but if (as with numeral classifiers) the population they mark is larger than the survey population, they are of little use in identifying subpopulations. The two‐stratum, four‐opening model proposed here has several essential properties: strata and openings are reflected in linguistic distributions; the early first opening allows an early start for the formation of a structurally and genealogically diverse population and for expansion to all of South America; languages reflect both early coastal and post‐LGM interior entries; the geographically patterned structural typology of North American languages is consistent with the different openings during a long time frame; and North Pacific Rim affinities are evident in the latest opening. The results here appear to be incompatible with the Beringian Standstill proposal of Tamm et al. ( ) and not obviously compatible with the shorter standstill of Pinotti et al. ( ). These are single‐origin and perhaps single‐entry models; others are Rasmussen et al., ; Li et al., . The standstill is understood as a single well‐blended and thus presumably undifferentiated population seeding most or all the linguistic diversity of the Americas (except for the more recent EAT and EA families). At a high latitude, such a population would be likely to speak a single language at any given time, with occasional unifying sweeps of one dialect maintaining low diversity (Nichols, , ). Such a population would be unable to export the structural and genealogical diversity of founder languages required to generate the attested American diversity. The only way a uniform standstill population could give rise to the sharp structural differences between the early and late strata is by change over time, and it is doubtful that the great typological distance between the radical head‐marking, polysynthetic type and the radical dependent‐marking type that represent the extremes found in the Northwest and California respectively could be reached in anything like 10,000 or even 20,000 years without external input. Additionally, a single origin (especially if accompanied by a wave‐of‐advance model of spread) cannot easily account for the geographically patterned distribution of structural types in North America. The results also appear inconsistent with the three‐stage models of Hamilton & Buchanan and Mulligan et al., . Both posit a post‐LGM initial settlement (too late, though that is probably not essential to the model), followed by the second stage with a long period of isolation and little growth, then rapid growth and expansion in the third stage. The isolation and minimal growth seem incompatible with the early expansion across South America. Post‐LGM population growth would probably fit any model. None of the stages appears to explain the geographically patterned structural distributions. The results are compatible with the two‐origin analysis (Two Main Biological Components, or 2MBC) of Walter Neves and various colleagues (Neves & Pucciarelli, ; Neves et al., ; Hubbe et al., ; Hubbe et al., , and several others; overviews in Rothhammer & Dillehay, ; Hubbe, ; von Cramon‐Taubadel et al., ), which infer a distinction of early versus later populations in South and Central America from craniometric data; the early population has Australasian/Melanesian affinities while the later one has Siberian affinities. Skoglund et al., find South American genomic evidence for two populations and the same affinities. These findings are a good match for the distinction here of early versus late strata. Whether the physical diversity matches the linguistic diversity is not yet clear. The start times implied are too late, but this is probably not essential. The geographically patterned structural distribution is not addressed as Neves and colleagues deal only with Central and South America, and Skoglund et al., find too little data for North America. Pitblado, reviews other evidence for two origins. Thus the modern facts speak for a structurally differentiated linguistic population in ancient Siberia. Its descendants entered through a chronologically and geographically sequenced series of openings beginning in the peak LGM, first coastal and then inland, rapidly moving well to the south and well inland. Whether the early and late South American populations continue the North American early and late strata, and whether the North American geographical patterning continues to South America, warrant further work. 

Johanna Nichols: Conceptualization (lead); data curation (lead); formal analysis (lead); investigation (lead); methodology (lead). 

OPEN RESEARCH BADGES This article has earned an Open Data badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://onlinelibrary.wiley.com/doi/full/10.1002/ajpa.24923 . 

Data S1. Supporting Information. 

