Where Does Language Complexity Evolve?

I'm not entirely sold on this article's conclusion about the circumstances in which language complexity evolves, at least not based upon the data presented, even though there is good evidence that large numbers of language learners tend to reduce grammatical complexity.

Polysynthetic languages are very common in the New World and just across the Beringian land bridge from it (which could also be connected to the Paleo-Siberian cases), suggesting that most instances of it could be derived from a common source creating a Founder effect. 

Also, while these languages are small and isolated now, this hasn't always been the case. Athabaskan-Eyak-Tlingit and Nahuatl, for example, historically were quite expansive and had lots of contact with other language families.

The second cluster is from Aboriginal Australians and Papuans who derive from the first wave of modern human migration Out of Africa and into Asia around the time of the Toba eruption. 

There is a third cluster in the Caucuses, involving just one of the language families there, which are associated with early migrants from the first wave of Fertile Crescent agriculture in the highlands of West Asia. 

There are apparently other instances in South Asia and East Asia.

A handful of major language expansions, none of which happened to be polysynthetic make up a huge share of all languages spoken today. These include the Indo-European language family, the Afro-Asiatic languages, the Bantu language family, the Dravidian languages, and the arguable Altaic language family. European and Chinese colonial empires further reduced the size of many languages (long after their features were well intact), for reasons unrelated to language complexity. 

There are polysynthetic or borderline polysynthetic languages listed in the following major language families: the Sino-Tibetan languages (seemingly all in the Tibetan-Burmo branch), the Austroasiatic languages (3 Munda languages in Northeast India), the Austronesian languages (5 borderline seemingly Formosan languages) 

If only a minority of pre-expansion languages were polysynthetic, it wouldn't be surprising if the main expanding languages didn't end up including them.

Significance

A global test reveals statistically robust support for the hypothesis that complex word forms are more likely to develop in isolated languages. Polysynthesis, where words are built from many units to convey complex meanings, is more likely to occur in smaller populations and less likely to occur with many languages in contact. By building a global database of polysynthetic languages and analyzing in a phylospatial framework, this study highlights the potential for macroevolutionary methods to test hypotheses about language evolution and contribute to long-standing debates in linguistics.

Abstract

Evolution of complexity in human languages has been vigorously debated, including the proposal that complexity can build in small, isolated populations but is often lost in situations of language contact. If it is generally true that small, isolated languages can build morphological complexity over time, but complexity tends to be lost in situations of language contact, then we should find that forms of language complexity that have evolved multiple times will tend to be associated with population size, isolation, and language age. 

We test this hypothesis by focusing on one particular form of morphological complexity, polysynthesis, where words built from many parts embody complex phrases. By assembling a global database of polysynthetic languages and conducting phylospatial analyses, we show that languages with highly complex word morphology are more likely to have small population sizes, less likely to occur with many other languages in direct contact, and have a greater tendency to be on long phylogenetically isolated lineages. 

These findings are consistent with the hypothesis that languages that evolve in isolation for long periods may be more likely to accrue morphological complexity. Polysynthetic languages also tend to have higher levels of endangerment. Our results provide phylogenetically informed evidence that one particular form of complex language morphology is more likely to occur in small, isolated languages and is prone to loss in contact.

Lindell Bromham, Keaghan Yaxley, Oscar Wilson, and Xia Hua, "Macroevolutionary analysis of polysynthesis shows that language complexity is more likely to evolve in small, isolated populations" 122(24) PNAS e2504483122 (June 12, 2025) (pay per view; but open access supplemental materials).

The languages counted as polysynthetic and borderline, according to the Supplemental Materials, are below the fold.

The Huns Were Paleo-Siberian, Not Linguistically Turkic (Also Slavic Origins)

A new paper makes a strong case that the Huns, a group of "barbarians" (in the eyes of Roman historians) who made multiple attempts to invade the Roman empire, spoke a Paleo-Siberian language (to which the Na-Dene languages of North America, such as Navajo, are distantly related), rather than a Turkic language, as conventional wisdom in historical linguistics prior to this paper had wrongly believed.

The Xiōng-nú were a tribal confederation who dominated Inner Asia from the third century BC to the second century AD. Xiōng-nú descendants later constituted the ethnic core of the European Huns. It has been argued that the Xiōng-nú spoke an Iranian, Turkic, Mongolic or Yeniseian language, but the linguistic affiliation of the Xiōng-nú and the Huns is still debated. 

Here, we show that linguistic evidence from four independent domains does indeed suggest that the Xiōng-nú and the Huns spoke the same Paleo-Siberian language and that this was an early form of Arin, a member of the Yeniseian language family. This identification augments and confirms genetic and archaeological studies and inspires new interdisciplinary research on Eurasian population history.

Svenja Bonmann et al, "Linguistic Evidence Suggests that Xiōng‐nú and Huns Spoke the Same Paleo‐Siberian Language," Transactions of the Philological Society (June 16, 2025). DOI: 10.1111/1467-968X.12321

A news report about the paper spells it out this hypothesis at greater length:

New linguistic findings show that the European Huns had Paleo-Siberian ancestors and do not, as previously assumed, originate from Turkic-speaking groups. The joint study was conducted by Dr. Svenja Bonmann at the University of Cologne's Department of Linguistics and Dr. Simon Fries at the Faculty of Classics and the Faculty of Linguistics, Philology and Phonetics at the University of Oxford.

The results of the research, "Linguistic evidence suggests that Xiōng-nú and Huns spoke the same Paleo-Siberian language," have been published in the journal Transactions of the Philological Society.

On the basis of various linguistic sources, the researchers reconstructed that the ethnic core of the Huns—including Attila and his European ruling dynasty—and their Asian ancestors, the so-called Xiongnu, shared a common language. This language belongs to the Yeniseian language family, a subgroup of the so-called Paleo-Siberian languages. These languages were spoken in Siberia before the invasion of Uralic, Turkic and Tungusic ethnic groups. Even today, small groups who speak a Yeniseian language still reside along the banks of the Yenisei River in Russia.

From the 3rd century BCE to the 2nd century CE, the Xiongnu formed a loose tribal confederation in Inner Asia. A few years ago, during archaeological excavations in Mongolia, a city was discovered that is believed to be Long Cheng, the capital of the Xiongnu empire. The Huns, in turn, established a relatively short-lived but influential multi-ethnic empire in southeastern Europe from the 4th to 5th centuries CE.

Research has shown that they came from Inner Asia, but their ethnic and linguistic origins have been disputed until now, as no written documents in their own language have survived. A great deal of what we know about the Huns and the Xiongnu is therefore based on written documents about them in other languages; for example, the term "Xiōng-nú' derives from Chinese. 

 

[Based on the "World Topographic Map" by Esri. Sources: Esri, HERE, Garmin, Intermap, INCREMENT P, GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), OpenStreetMap contributors, GIS User Community, Simon Fries. Created with QGIS 3.36.]. Credit: Transactions of the Philological Society (2025). DOI: 10.1111/1467-968X.12321

From the 7th century CE, Turkic peoples expanded westwards. It was therefore assumed that the Xiongnu and the ethnic core of the Huns, whose own westward expansion dates back to the 4th century CE, also spoke a Turkic language. However, Bonmann and Fries have found various linguistic indications that these groups spoke an early form of Arin, a Yeniseian language, in Inner Asia around the turn of the millennium.

"This was long before the Turkic peoples migrated to Inner Asia and even before the splitting of Old Turkic into several daughter languages. This ancient Arin language even influenced the early Turkic languages and enjoyed a certain prestige in Inner Asia. This implies that Old Arin was probably the native language of the Xiongnu ruling dynasty," says Bonmann.

Bonmann and Fries analyzed linguistic data based on loan words, glosses in Chinese texts, proper names of the Hun dynasty as well as place and water names. Taken by itself, the data on each of these aspects would have comparatively little significance, but taken together it is hard to argue with the conclusion that both the ruling dynasty of the Xiongnu and the ethnic core of the Huns spoke Old Arin.

The findings of the study also made it possible for the first time to reconstruct how the Huns came to settle in Europe: For the two researchers, place and water names still prove today that an Arin-speaking population once left its mark on Inner Asia and migrated westwards from the Altai-Sayan region. Attila the Hun probably also bears an ancient Arin name: Until now, "Attila" was thought to be a Germanic nickname ("little father"), but according to the new study, "Attila" could also be interpreted as a Yeniseian epithet, which roughly translates as "swift-ish, quick-ish."

The new linguistic findings support earlier genetic and archaeological findings that the European Huns are descendants of the Xiongnu. "Our study shows that alongside archaeology and genetics, comparative philology plays an essential role in the exploration of human history. We hope that our findings will inspire further research into the history of lesser-known languages and thereby contribute further to our understanding of the linguistic evolution of mankind," concludes Fries.

In the body text, a section of the paper explores the previous conventional wisdom and its difficulties:

Although direct evidence is lacking, Iranian, Turkic and Mongolic languages have all been proposed as the language of the ruling dynasty of the Xiōng-nú (cf. e.g. Shiratori 1900; Benzing 1959; Pritsak 1982; Bailey 1985; Dybo 2007; Janhunen 2010; Beckwith 2018; Beckwith 2022) and of the Huns (cf. e.g. Doerfer 1973; Pritsak 1982; Savelyev 2020; Savelyev & Jeong 2020), because in the 1st millennium AD languages from these three families were spoken in Inner Asia. Inscriptions dating between the 4th and 9th century AD demonstrate that Iranian languages (Sogdian, early 4th to 6th century AD, Sims-Williams 2011; Vovin 2018) and Mongolic ones (Khüis Tolgoi and Bugut inscriptions of the 5th–6th centuries AD, Vovin 2018) as well as, much later, Turkic languages (isolated Turkish phrases in Bactrian manuscripts of the 7th century AD, Orkhon and Yenisei Kirgiz inscriptions between the early 8th and 9th century AD, Erdal 2004: 4–8) were spoken in the territory between the Yenisei River in the West, the Tian Shan range in the South and Mongolia in the East. Other Indo-European languages were spoken in oasis cities along the northern and southern ridges of the Takla Makan desert in the 1st millennium AD including Indo-Iranian (Iranian Khotanese and Tumshuqese Saka, Bactrian, Indo-Aryan Prakrit, Sanskrit) and ‘Tocharian’ languages (Agnean and Kuchean).

However, this linguistic situation of a coexistence of Iranian, Turkic and Mongolic in Inner Asia can only be reliably established as such for the late 1st millennium AD. Hypotheses on an Iranian, Mongolic or Turkic identity of the Xiōng-nú primarily rest on written sources post-dating the Xiōng-nú era. 

While the theoretical possibility of a Mongolic or Turkic presence in Inner Asia already at the beginning of the common era cannot be ruled out a priori, it is important to note that there is, on the other hand, also no robust evidence – especially from textual sources – that could directly imply or prove a Turko-Mongolic presence in this area at such an early date. 

The earliest sources from the Tarim Basin and the territories alongside the Oxus River/Amu Darya (Chorasmia, Sogdia, Bactria) only document Indo-European languages from the Indo-Iranian and ‘Tocharian’ branches (to which might be added, as a cultural import, also Ancient Greek in Macedonian colonies). Judging by more indirect evidence – especially loanwords in other languages, toponyms, etc. – other Iranian languages, namely different Sakan varieties (Tremblay 2005) and ‘Old Steppe Iranian’ (Bernard 2023), must have been spoken in the steppe corridor from the Kazakh steppe to Dzungaria, and perhaps even to Gansu (see Beckwith 2022). It is only centuries later, namely in the Migration Period of the 5th–6th centuries AD, that a (Para-)Mongolic language might be attested in Inner Asia (Vovin 2018), and fragments of this (Para-)Mongolic language, in turn, are still much earlier documented than the earliest secure Turkic words dating from the 7th century AD.

There is thus neither direct nor indirect evidence supporting the claim of a Mongolic or Turkic presence in Inner Asia between the 3rd century BC and the 2nd century AD, and the hypothesis of a Mongolic or Turkic identity of the ethnic core of the Xiōng-nú (as proposed by Benzing 1959, Pritsak 1982; Tenišev 1997; Dybo 2007; Janhunen 2010; Savelyev 2020) is thus rather unlikely from the outset, as is the hypothesis of a completely unknown or unclassifiable language without any living descendants (as proposed by Doerfer 1973). The same applies to the Huns: there is a complete lack of evidence supporting claims of a Turkic presence among the Huns.1 On the other hand, an Iranian component in the Xiōng-nú Empire is possible, and indeed quite likely, although, as we intend to point out with the present study, such Indo-European ethnicity must not necessarily have been shared by the ruling dynasty or ethnic core of the Xiōng-nú (pace Bailey 1985; Beckwith 2022) or the Huns.

Concerning such an Iranian component, (Beckwith 2018, 2022) has argued recently that Xiōng-nú words preserved in Chinese texts are indicative of an Iranian language, which he calls ‘East Scythian’. However, his interpretation depends on a reconstruction of the Old and Middle Chinese pronunciation of Chinese signs which significantly differs from established reconstructions such as the classic one of Pulleyblank, and which has also been criticised by Vovin et al. (2016: 129–30). In addition to this, his Iranian etymologies must be met with serious doubts. For instance, the ethnonym ‘Aryan’, which is amply attested in many Indo-Iranian languages, is given by Beckwith with a word-initial laryngeal sound (discussion in Beckwith 2022: 183–86, cf. particularly p. 186): ‘East Scythian *ḥarya [ɣa.rya] “noble, royal; Scythian” → Old Chinese *ḥaryá 夏/*ḥâryá 華 “royal; Chinese, China”’. This would indeed be a remarkable Iranian word form, because no Indo-Iranian language points to an initial laryngeal (†Hā̆ri̯a- vel sim.): A word-initial laryngeal should have left direct traces in Persianide languages (see Kümmel 2018), but Old Persian <ariy-> /ariya-/ or inscriptional Middle Persian ēr ‘Iranian’ do not preserve such a sound. The hypothetical (East) Scythian would be the only Iranian language to preserve it, and independent evidence for this is entirely lacking. Other etymologies equally rest upon highly questionable ad hoc assumptions on Iranian historical phonology and must accordingly be dismissed (e. g. the etymology of Old Turkic täŋri ‘heaven’ that Beckwith 2022: 195, 203 wants to derive from an East Scythian *tagri through the application of an alleged Scythian syllable contact law of nasalization completely unheard of in the specialist literature and remaining without any reliable parallel; on this word rather cf. Georg 2001).

It must therefore be conceded that, while it is a priori likely that Iranian tribes were one factor among others in the ethnolinguistic melting pot of the eastern Eurasian steppe some 2000 years ago (the Sakan languages would be a good starting point for further research in this direction), the evidence adduced by scholars in favour of a dominant role of Iranian groups and their languages in the Xiōng-nú empire so far does not follow the rigorous methodological standards of Historical-Comparative Linguistics and is therefore insufficient to allow for any reliable inferences.

Etymological analyses of Xiōng-nú glosses in Chinese sources (collected by Pulleyblank 1962, criticised and reanalysed by Dybo 2007), complemented by the interpretation of the so-called Jié couplet, the only short text preserved in the Xiōng-nú language,2 have led to a more promising alternative hypothesis. This hypothesis acknowledges both the multi-ethnic composition of the Xiōng-nú empire as such and the presence of Indo-European and specifically Iranian languages in Inner Asia at the beginning of the common era, yet adds to the complexity the idea that the native language of the ruling dynasty of the Xiōng-nú empire might have been a Yeniseian one (Ligeti 1950; Pulleyblank 1962; Dul'zon 1966; Dul'zon 1968; Vovin 2000; Vovin 2003; Vovin 2007; Werner 2014; Vovin 2020). Yeniseian languages are usually considered remnants or survivors of the original linguistic diversity of Siberia, historically spoken in retreat areas as the result of several waves of superimposition or displacement by expanding Uralic/Samoyedic, Turkic and Tungusic languages. Therefore, Yeniseian languages are also known as Paleo-Siberian languages.3 Several different Yeniseian languages were spoken in the 18th century AD alongside the middle reaches of the Yenisei River and some of its tributaries, yet this probably reflects a northward migration from a point of departure further south, around the headwaters of the Yenisey, the Ob and the Irtyš rivers (see Dul'zon 1959a; Dul'zon 1959b; Dul'zon 1964; Maloletko 1992; Maloletko 2000; Vajda 2019: 194–95; cf. also Janhunen 2020: 167). From the six historically attested Yeniseian languages Ket, Yugh, Kott, Assan, Arin and Pumpokol, it has so far been suggested that Ket/Yugh (Ligeti 1950; Pulleyblank 1962) or Pumpokol (Vovin 2000, 2003, 2007, 2020; Vovin et al. 2016) may have been the native language of the Xiōng-nú ruling dynasty.

Adding value to this hypothesis is the fact that the northward migration of Yeniseian-speaking groups, as reflected in toponyms, from the Altai-Sayan area would well agree with detailed historical studies considering Indic, Iranian and Chinese written sources (de la Vaissière 2005; de la Vaissière 2014). These studies indicate that, following the eventual demise of their steppe empire, remnants of the Xiōng-nú migrated to the north of the Altai-Sayan Mountain ranges in the mid-2nd century AD and that this retreat area was the starting point of a secondary expansion of Xiōng-nú descendants roughly two hundred years later, between ca. 350–370 AD. This expansion occurred in three directions: One migratory trajectory led northward and left traces in the form of toponyms. This population movement downstream of the major rivers Yenisey, Ob and Irtyš perfectly explains the linguistic situation as documented for the first time in the 18th century and provides a direct link between Yeniseian languages and the Xiōng-nú. Another migratory route led to southern Asia and involved groups known from Iranian and Indic sources as Chionites, Kidarites, Hephthalites, Alchons as well as the so-called Huṇa (cf. Pfisterer 2013). A third migratory trajectory led westward, into Europe and involved the Huns who appeared in Eastern Europe in 370 and posed a threat to Roman hegemony until Attila's death in 453, the Battle of Nedao shortly afterwards and the ensuing disintegration of their confederation (cf. e.g. Heather 1996; Bóna 2002; Halsall 2007; Schmauder 2009; Maas 2014; Pohl 2022).

Several nomadic groups of late Antiquity that originated in Inner Asia and migrated to the southern and western peripheries of the Eurasian landmass apparently used the same ethnonymic constituent (Chion-ites – Al-chon – Huṇa – Huns; cf. de la Vaissière 2005; de la Vaissière 2014, but see Atwood 2012), and the traditional hypothesis of a link between the ethnic core of the European Huns of the 4th–5th centuries AD and the Inner Asian Xiōng-nú of the 3rd century BC–2nd century AD, first proposed by the French scholar Joseph de Guignes in the 18th century, has, strictly speaking, never been falsified (de la Vaissière 2005: 15). 

A genetic connection between the Xiōng-nú and the Huns is usually considered unlikely in modern archaeological and historical scholarship (e.g. Beckwith 2009: 72; Savelyev & Jeong 2020; Pohl 2022; Maenchen-Helfen 1944–1945; Maenchen-Helfen 1955; Maenchen-Helfen 1973; Schmauder 2009), partly because of the large chronological gap between the dissolution of the Xiōng-nú empire in the 2nd century AD and the appearance of the Huns in the 4th century AD, and partly because only two archaeological features render a connection likely: large bronze cauldrons of a certain type and artificially deformed or elongated skulls (Pohl 2022: 147).

Despite the prevailing scepticism of historians and archaeologists, the hypothesis of a connection between the Xiōng-nú and the Huns has been corroborated recently by previously unknown and unavailable genetic data analysed by Gnecchi-Ruscone et al. (2025): ‘(…) long-shared genomic tracts provide compelling evidence of genetic lineages directly connecting some individuals of the highest Xiongnu-period elite with 5th to 6th century AD Carpathian Basin individuals, showing that some European Huns descended from them’. 

On the provision that there was indeed some continuation between the ethnic core of the European Huns and the former Xiōng-nú, the ruling classes of both multi-ethnic confederations may have spoken the same language in two different diachronic stages (an older form and a younger one), implying that the identification of the linguistic affiliation of one of these groups probably also means identifying the native language of the other group. 

In the following, we will discuss previously unknown linguistic evidence from four domains independently supporting such a connection and thus corroborating the recent archaeological and genetic findings: (1) loanwords, (2) glosses, (3) anthroponyms and (4) toponyms/hydronyms.

This analysis, which moves the Turkic and Tungistic migrations several centuries later in history than previously believed, is also relevant to the Altaic linguistic hypothesis and our understanding of these ethnic mass migrations more generally.

Close in time and space: Slavic ethnogenesis

The Slavic people emerged around the same time as the fall of the Roman Empire and the demise of the short lived Hunnic Kingdom in the Balkans, but before the Magyar conquest of what is now called Hungary and before the appearance of Gypsies in Europe. This period was traditionally called the "Dark Ages" in Europe. There are some historical roots, however, which suggest Slavic origins several centuries earlier (from the Wikipedia link at the start of this paragraph):

Ancient Roman sources refer to the Early Slavic peoples as "Veneti", who dwelt in a region of central Europe east of the Germanic tribe of Suebi and west of the Iranian Sarmatians in the 1st and 2nd centuries AD, between the upper Vistula and Dnieper rivers. Slavs – called Antes and Sclaveni – first appear in Byzantine records in the early 6th century AD. Byzantine historiographers of the era of the emperor Justinian I (r. 527–565), such as Procopius of Caesarea, Jordanes and Theophylact Simocatta, describe tribes of these names emerging from the area of the Carpathian Mountains, the lower Danube and the Black Sea to invade the Danubian provinces of the Eastern Empire.

Jordanes, in his work Getica (written in 551 AD), describes the Veneti as a "populous nation" whose dwellings begin at the sources of the Vistula and occupy "a great expanse of land". He also describes the Veneti as the ancestors of Antes and Slaveni, two early Slavic tribes, who appeared on the Byzantine frontier in the early-6th century.

Procopius wrote in 545 that "the Sclaveni and the Antae actually had a single name in the remote past; for they were both called Sporoi in olden times". The name Sporoi derives from Greek σπείρω ("to sow"). He described them as barbarians, who lived under democracy and believed in one god, "the maker of lightning" (Perun), to whom they made sacrifice. They lived in scattered housing and constantly changed settlement. In war, they were mainly foot soldiers with shields, spears, bows, and little armour, which was reserved mainly for chiefs and their inner circle of warriors. Their language is "barbarous" (that is, not Greek), and the two tribes are alike in appearance, being tall and robust, "while their bodies and hair are neither very fair or blond, nor indeed do they incline entirely to the dark type, but they are all slightly ruddy in color. And they live a hard life, giving no heed to bodily comforts..."

Jordanes describes the Sclaveni as having swamps and forests for their cities. Another 6th-century source refers to them living among nearly-impenetrable forests, rivers, lakes, and marshes.

Menander Protector mentions Daurentius (r. c. 577 – 579) who slew an Avar envoy of Khagan Bayan I for asking the Slavs to accept the suzerainty of the Avars; Daurentius declined and is reported as saying: "Others do not conquer our land, we conquer theirs – so it shall always be for us as long as there are wars and weapons".

The Slavic languages are a relatively recent offshoot of the Indo-European Baltic languages, which in turn may be the most direct descendants of the language(s) of the Corded Ware culture (ca. 3000 BCE to 2350 BCE).

Eurogenes reports on new ancient DNA driven discoveries drawn from the earliest ancient Slavic DNA at his blog.

A paper dealing with the origin of Slavic speakers, titled Ancient DNA connects large-scale migration with the spread of Slavs, was just published at Nature by Gretzinger et al. (see here).

The dataset from the paper includes ten fascinating ancient samples from Gródek upon the Bug River in Southeastern Poland. These individuals are dated to the so called Tribal Period (8th – 9th centuries), and, as far as I know, they represent the earliest Slavic speakers in the ancient DNA record.

The really interesting thing about these early Slavs is that they already show some Germanic and other Western European-related ancestries. Nine of the samples made it into my G25 analysis (see here). In the Principal Component Analysis (PCA) plots . . . five of them cluster near present-day Ukrainians, while the rest are shifted towards present-day Northwestern and Western Europeans. . . .  GRK015, a female belonging to Western European-specific mtDNA haplogroup H1c, shows Scandinavian ancestry. On the other hand, GRK014, a female belonging to the West Asian-specific mtDNA haplogroup U3b, probably has Southern European ancestry.

These results aren't exactly shocking, because the people who preceded the early Slavs in the Gródek region were Scandinavian-like and associated with the Wielbark archeological culture. In other words, they were probably Goths who also had significant contacts with the Roman Empire.

However, it's not a given that the ancestors of the Tribal Period Slavs mixed with local Goths. It's also possible that they brought the western admixture, or at least some of it, from the Slavic homeland, wherever that may have been.

That's because the early Slavs who migrated deep into what is now Russia also showed Western European-related admixture. This is what Gretzinger et al. say on page 74 of their supplementary info (emphasis is mine):

The only deviation from this pattern is observed for ancient samples from the Russian Volga-Oka region, where we measure higher genetic affinity between present-day Southern/Western Europeans and the SP population compared to the pre-SP population (Fig. S17). This agrees with the pattern observed in PCA and ADMIXTURE that, in contrast to the Northwestern Balkan, Eastern Germany, and Poland-Northwestern Ukraine, the arrival of Slavic-associated culture in Northwestern Russia was associated with a shift in PCA space to the West, a decrease of BAL [Baltic] ancestry, and the introduction of Western European ancestries such as CNE [Continental North European] and CWE [Continental Western European].

Thus, it's highly plausible that the Tribal Period Slavs from Gródek were very similar, perhaps even practically identical, to the proto-Slavs who lived in the original Slavic homeland. Hopefully we won't have to wait too long to discover whether that's true or not. More Migration period and Slavic period samples from the border regions of Belarus, Poland and Ukraine are needed to sort that out.

Eurogenes goes on to criticize a suggestion in the supplemental materials to the Slavic ancient DNA paper that suggests that 

Sycthian groups from Ukraine show varying fractions of South Asian ancestry (between 5% and 12%), a component present in many ancient individuals from Moldova, Ukraine, Western Russia, and the Caucasus, but (nearly) absent in the SP genomes from Central and East-Central Europe (<5%). [Ed. references to specific samples showing this omitted.]

Eurogenes, rightly, explains that the data are really showing European introgression into South Asia arising from the Indo-Aryan invasion of the region in the Bronze Age, and before that from Iran. 

A Notable Modified Gravity Theory

Mach's principle is basically that inertia is a product of the combined gravitational pulls of everything in the Universe (although it can be expressed in about a dozen different ways, not all of which are perfectly consistent with each other or observation).  This, in turn, implies that (from the link and also from paper cited below): "Inertial mass is affected by the global distribution of matter."

A new paper tries to derive a relativistic version of a modified gravity theory similar to MOND by incorporating Mach's principle into the theory. This is something that Einstein tried to do until it became clear that this was inconsistent with plain vanilla General Relativity.

The general theory of relativity (GR) was proposed with an aim of incorporating Mach's principle mathematically. Despite early hopes, it became evident that GR did not follow Mach's principle. Over time, multiple researchers attempted to develop gravity theories aligned with Machian idea. Although these theories successfully explained various aspects of Mach's principle, each of these theories possessed its own strengths and weaknesses. 

In this paper, we discuss some of these theories and then try to combine these theories into a single framework that can fully embrace Mach's principle. This new theory, termed Machian Gravity (MG) is a metric-based theory, and can be derived from the action principle, ensuring compliance with all conservation laws. The theory converges to GR at solar system scales, but at larger scales, it diverges from GR and aligns with various modified gravity models proposed to explain dark sectors of the Universe. 

We have tested our theory against multiple observational data. It explains the galactic rotation curve without requiring additional dark matter (DM). The theory also resolves the discrepancy between dynamic mass and photometric mass in galaxy clusters without resorting to DM, but it introduces two additional parameters. It can also explain the expansion history of the Universe without requiring dark components.

Santanu Das (from the Raman Research Institute, Bangalore, India), "Machian Gravity: A mathematical formulation for Mach's Principle" arXiv:2308.04503 (last revised September 7, 2025) (53 pages). 

The theory's success with rotation curves is explored in this preprint (August 31, 2023). The idea was originally proposed in a set of three preprints from the same author in 2012: "Machian gravity and a cosmology without dark matter and dark energy" (May 17, 2012); "Mach's principle and the origin of the quantum phenomenon" (June 4, 2012); Mach Principle and a new theory of gravitation (June 26, 2012).

The introduction to the paper explains that:

Newtonian gravity can provide a very accurate description of gravity, provided the gravitational field is weak, not time-varying and the concerned velocities are much less than the speed of light. It can accurately describe the motions of planets and satellites in the solar system. Einstein formulated GR to provide a complete geometric approach to gravity. GR is designed to follow Newtonian gravity at a large scale. It can explain the perihelion precession of Mercury’s orbit and the bending of light by the Sun, which were never realized before, using Newtonian mechanics. Over the years, numerous predictions of GR, such as the existence of black holes, gravitational waves, etc. have been observed. This makes GR one of the most well-accepted theories of gravity. 

However, the drawbacks of GR come to light when GR is applied on the galactic and cosmological scale. It fails to produce the galactic velocity profiles, provided that calculations are made just considering the visible matter in the galaxy. This led researchers to postulate a new form of weakly interacting matter named dark matter. Earlier it was commonly believed that dark matter (DM) is made up of particles predicted from supersymmetry theory. However, the lack of evidence of these particles from Large Hadron Collider (LHC) strengthens the proposition of other candidates, such as Axions, ultra-light scalar field dark matter, etc.

A further mysterious puzzle is the dark energy (DE) because that requires to produce a repulsive gravitation force. Cosmological constant or Λ-term provides an excellent solution for this. However, as the observations become more precise, multiple inconsistencies come to light. 

There can be two ways to solve the dark sector of the Universe. 

Firstly, we can assume that there is in need some type of matter that does not interact with standard-model particles and acts as dark matter, and we have some form of energy with a negative pressure and provide a dark-energy-like behavior. 

While this can, in need, be the case, the possibility that the GR fails to explain the true nature of gravity in kilo-parsec scale can also not be overlooked. In such a case, we need an alternate theory of gravity that can replicate GR on a relatively smaller scale while deviating from it on a galactic scale. 

Several theories have been proposed in the last decade to explain DM and DE. Empirical theories like Modified Newtonian Dynamics (MOND) can explain the galactic velocity profiles extremely well but violates momentum conservation principles. Therefore, if a mathematically sound theory is developed that can mimic the MOND empirically, then that can explain the dark matter. Bekenstein proposed AQUAdraticLagrangian (AQUAL) to provide a physical ground to MOND. Other theories, such as Modified gravity, Scalar-Tensor-VectorGravity (STVG),Tensor–Vector–Scalar gravity (TeVeS), Massive gravity etc. are also proposed to match the galactic velocity profiles without dark matter. Other higher dimensional theories such as induced matter theory etc. are also proposed by researchers. However, all these theories came from the natural desire to explain the observational data and not build on a solid logical footing. 

Now, let us shift our focus to another aspect of GR. In the early 20th century, Earnest Mach hypothesized that the inertial properties of matter must depend on the distant matters of the Universe. Einstein was intrigued by Mach’s Principle and tried to provide a mathematical construct of it through the GR. He later realized that his field equations imply that a test particle in an otherwise empty Universe has inertial properties, which contradicts Mach’s argument. However, intrigued by the overwhelming success of GR in explaining different observational data, he did not make any further attempt to explain Mach’s principle. 

In view of this, it is worthwhile searching for a theory that implies that matter has inertia only in the presence of other matter. Several theories that abide by Mach’s principle have been postulated in the last century. Among these, the most prominent are Sciama’s vector potential theory, Brans Dicke (BD) theory or the scalar-tensor theory of gravity and Hoyle Narlikar theory etc. Although each of these theories addresses certain aspects of Mach’s principle as discussed in the respective articles, none offers a complete explanation. Thus, only a unified theory that combines these approaches could provide a comprehensive understanding of Mach’s principle in its entirety. 

In this article, we address all the issues described above and propose a theory of gravity based on Mach’s principle. It is based on the following premises. 

• Action principle: The theory should be derived from an action principle to guarantee that the theory does not violate conservation laws. 

• Equivalence principle : Various research groups have tested the Weak Equivalence Principle (WEP) at an exquisite procession. Therefore, any theory must follow the weak equivalence principle. However, the strong equivalence principle has not been tested on a large scale. If the ratio of the inertial mass and the gravitational mass changes over space-time (on a galactic scale or cosmological scale), then that does not violate results from our local measurements. In accordance with Mach’s principle, the inertial properties of matter come from all the distant matter of the Universe. As the matter distribution at different parts of the Universe is different, the theory may not follow the strong equivalence principle. 

• Departure from GR: As GR provides an excellent result in the solar system scale, the proposed theory should follow GR on that scale, and it only deviates from GR at the galactic scale to mimic some of the modified gravity theories proposed by researchers to explain the dark sectors of the Universe. Along with this, the proposed theory should also be able to replicate the behavior of theories like Sciama’s theory or BD theory under the specific circumstances for which they were proposed. 

The paper is organized as follows. 

In the second section I briefly discuss previous developments in gravity theory to explain Mach’s principle. Most of the points covered in this section are generally known positions form various previous research. However, since Mach’s principle is not a mainstream area of study, this discussion is necessary and important for understanding the new insights presented in this article. In some cases I interpret these established ideas from the perspective of this paper, that will help me to built the gravity theory in the later section. 

In the next section, we explain Mach’s principle and discuss the mathematical tools used to formulate the theory. We present the source-free field equations for the theory in the same section. 

The static spherically symmetric solution for the theory in weak field approximation is presented in the fourth section. We show that the solution follows Newtonian gravity and GR at a smaller scale but deviates from it at a large scale. 

Section five presents examples of galactic rotation curves and galaxy cluster mass distributions, demonstrating that the theory yields results in close agreement with observations. 

The source term of the theory has been described in the 6th section. 

In the next section, we provide the cosmological solutions to the MG model. 

The final section is the conclusion and discussion section. We have also added five appendices where we describe the nitty-gritty of the calculations and add multiple illustrations.

This theory is formulated in a 4+1 dimensional space-time. It states that "The momentum in the fifth dimension represents the inertial mass of the particle, which remains constant in any local region." The paper could be more clear regarding which two additional parameters are added to the theory, but appear to be related to a vector field and a scalar field, respectively:

The proposed framework is built upon a five-dimensional metric involving three essential elements: a scalar field ϕ, a vector field Aµ, and an extra dimension x4. (note that these two fields behave as scalar and vector field only if the metric is independent of x4.)

Side commentary on dark matter particle theories 

There are a wealth of papers constraining various versions of dark matter particle theories out there, and I bookmark almost all of them as I encounter them. But synthesizing them into a comprehensive set of constraints on dark matter, in the way that the Particle Data Group does for high energy physics data, is a daunting task.

The bottom line for those papers is that the parameter space of possible dark matter particle candidates is ever more tightly constrained within the context of many dark matter particle proposals, and that there are no positive confirmations of any of them.

More Neutrino Oscillation Physical Constant Measurements

Almost all of the experimental data favors a normal mass ordering for neutrinos over an inverted mass ordering, but given the limitations of current experiments, the preference is almost always a weak one.

The Particle Data Group value for delta m(32) squared in normal ordering is as follows:

Taking the square root, the PDG value is a gap of 49.5 meV.

A new paper's results are consistent with the world average. The paper, its abstract, and the chart below from its supplementary materials are as follows:

This Letter reports measurements of muon-neutrino disappearance and electron-neutrino appearance and the corresponding antineutrino processes between the two NOvA detectors in the NuMI neutrino beam. These measurements use a dataset with double the neutrino mode beam exposure that was previously analyzed, along with improved simulation and analysis techniques. 

A joint fit to these samples in the three-flavor paradigm results in the most precise single-experiment constraint on the atmospheric neutrino mass-splitting, Δm^2(32) = 2.431 +0.036 −0.034 (−2.479 +0.036 −0.036) × 10^−3 ~eV^2 if the mass ordering is Normal (Inverted). In both orderings, a region close to maximal mixing with sin^2(θ23) = 0.55 +0.06 −0.02 is preferred. 

The NOvA data show a mild preference for the Normal mass ordering with a Bayes factor of 2.4 (corresponding to 70% of the posterior probability), indicating that the Normal ordering is 2.4 times more probable than the Inverted ordering. When incorporating a 2D Δm^2(32) --sin^2(2*θ13) constraint based on Daya Bay data, this preference strengthens to a Bayes factor of 6.6 (87%).

NOvA Collaboration, "Precision measurement of neutrino oscillation parameters with 10 years of data from the NOvA experiment" arXiv:2509.04361 (September 4, 2025).

The Pair Instability Gap

There is a mass range, called the "pair instability gap" in which intermediate mass black holes in binary black hole systems are predicted to be scarce.

Stellar theory predicts a forbidden range of black-hole masses between ∼ 50 - 130 M⊙ due to pair-instability supernovae, but evidence for such a gap in the mass distribution from gravitational-wave astronomy has proved elusive. Early hints of a cutoff in black-hole masses at ∼ 45 M⊙ disappeared with the subsequent discovery of more massive binary black holes. 

Here, we report evidence of the pair-instability gap in LIGO-Virgo-KAGRA's fourth gravitational wave transient catalog (GWTC-4), with a lower boundary of 45 +5 −4 M⊙ (90% credibility). While the gap is not present in the distribution of primary masses m(1) (the bigger of the two black holes in a binary system), it appears unambiguously in the distribution of secondary masses m(2), where m(2) ≤ m(1). The location of the gap lines up well with a previously identified transition in the binary black-hole spin distribution; binaries with primary components in the gap tend to spin more rapidly than those below the gap. 

We interpret these findings as evidence for a subpopulation of hierarchical mergers: binaries where the primary component is the product of a previous black-hole merger and thus populates the gap. Our measurement of the location of the pair-instability gap constrains the S-factor for 12C(α,γ)16O at 300 keV to 256 +197 −104 keV barns.

Hui Tong, et al., "Evidence of the pair instability gap in the distribution of black hole masses" arXiv:2509.04151 (September 4, 2025).

Medieval Supernova

Astronomy is one of the oldest sciences. Advanced scientific astronomy calculation instruments were in existence in the Greek classical period and megalithic solar observatories came into existence independently shortly after agriculture was invented in multiple places. There is even evidence of astronomy being done in a stone temple in Anatolia built before agriculture was invented. By around Y1K, astronomy was taught in universities, and was done in a quite scientific manner in multiple civilizations around the globe. Prior to the Renaissance, however, it was all done with the naked eye. 

The remnant of the historical supernova SN 1181 is under discussion: While the previously suggested G130.7+3.1 (3C58) appears too old (3000-5000 yr), the unusual star IRAS 00500+6713 with a surrounding nebula (Pa-30) has an expansion age not inconsistent with a SN Iax explosion in AD 1181 under the assumption that neither acceleration nor deceleration occurred. 

Previously, only reports from China and Japan were known, pointing to an event near the northern circumpolar region. Any further reports from other cultures can therefore be highly relevant. 

We present here an Arabic poem in praise of Saladin by the contemporaneous author Ibn Sanā' al-Mulk (Cairo, Egypt). We re-date its composition to between Dec 1181 and May 1182. It contains a new bright star, which can be identified as SN 1181. The poem also provides new and independent information on the object type (called `najm' for `star'), location on sky (in or near the Arabic constellation al-Kaff al-Khabīb, lit. the henna-dyed hand (five bright stars in Cassiopeia), and brightness (brighter than alpha Cas, 2.25 mag). 

In addition, we present another Arabic text on SN 1006, also from Cairo, by the historian al-Maqrīzī, probably based on the contemporaneous al-Musabbihī

J.G. Fischer, H. Halm, R. Neuhäuser, D.L. Neuhäuser, "New Arabic records from Cairo on supernovae 1181 and 1006" arXiv:2509.04127 (published August 19, 2025 at 346 Astronomical Notes e70024).

The Climate Driven Narrative Of The Prehistory of India

 

These maps are useful in shedding light on the prehistory of India. 

The Harappans

The Gangetic plain is predominantly in the temperate zone which has the highest population density in India and the most agriculturally oriented economy. 

This region had agriculture very early on, probably no later than 4000 BCE and possibly sooner, initially using Fertile Crescent Neolithic crops, via the Caucuses and Iran in its formative era, whose migrating farmers account for a significant share of the genetic roots of of the Indus Valley Civilization (a.k.a. the Harappan civilization a.k.a. the Meluhha). The Harappan civilization later adopted rice as a crop as well, via Austroasiatic migrants from Southeast Asia who gave rise to the Munda languages of India, ca. 2000 BCE.

We know from well dated residues on Harappan pots, by the way, that curry was a Harappan invention that predated the Indo-Aryans and the Munda people.

The prevailing view is that Harappan society was united politically, perhaps in a federation of city-states, and was largely free of war or fortifications, apart from some trade outposts on its frontiers, until it collapsed. It has relatively modern plumbing for the Bronze Age and its cities lack obviously palatial complexes, that one might associate with a more hierarchal society dominated by local kings who simply enriched themselves. 

Harappan society had its own script. The majority view is that this was a proto-script used for accounting and trade purposes, similar to the Vinca script in the Neolithic Balkans and the earliest Sumerian cuneiform inscriptions, but not a full fledged written language.

Harappans had trade connections to Sumeria, where they had a historically attested trade colony, and based on those records, know that the Harappans called themselves the Meluhha. 

Meluḫḫa or Melukhkha (Sumerian: 𒈨𒈛𒄩𒆠 Me-luḫ-ḫaKI) is the Sumerian name of a prominent trading partner of Sumer during the Middle Bronze Age. . . . most scholars associate it with the Indus Valley Civilisation. . . . Sumerian texts repeatedly refer to three important centers with which they traded: Magan, Dilmun, and Meluhha. The Sumerian location of Magan is now accepted to be the area currently encompassing the United Arab Emirates and Oman. Dilmun was a Persian Gulf civilization which traded with Mesopotamian civilizations. The current scholarly consensus is that Dilmun encompassed Bahrain, Failaka Island and the adjacent coast of Eastern Arabia in the Persian Gulf.

The Harappans also had trade (and possibly a sphere of influence) in the adjacent region of Central Asia known as the BMAC (for Bactria–Margiana Archaeological Complex a.k.a. Oxus culture).

The BMAC culture (ca. 2400 BCE to 1700 BCE with some dispute over the dates on each end of this range) was wedged between the Indo-European Andronovo culture (ca. 2000 BCE to 1150 BCE) and the terminal Harappan/Indo-Aryan transition Cemetery H (ca. 1900 BCE to 1300 BCE), and Painted Gray Ware (ca. 1300 BCE to 300 BCE) cultures. 

The BMAC would have fallen to Indo-European advances before the Indo-Aryans arrived in what remained of the Harappan region, and before the proto-Indo-Iranians arrived in Iran.

The Yaz culture, which had previously been part of the BMAC cultural region, was abruptly replace by an Indo-Iranian early Iron Age culture around 1500 BCE, and is a likely source of the Avestan language and what became the Zoroastrian religion associated with it. The Yaz culture persisted until it was absorbed by the Achaemenid Empire in the 300s BCE.

The Ghaggar-Hakra river f.k.a. the Saraswati River, which features prominently in the Rig Vedas, once coursed through what is now arid Indian steppe along the dashed orange route shown in the map above. Its now mostly dry bed is the home of many Harappan ruins.

But, the Saraswati River dried up around 2000 BCE, as part of a major climate event which made the region more arid that stretched, at a minimum from Egypt to India, and caused the Middle Bronze Age Late Harappan society to collapse.

As explained, for example, in Sujay Rao Mandavilli, "The Demise of the Dravidian, Vedic and Paramunda Indus Hypotheses: A brief explanation as to why these three Hypotheses are no longer tenable" SSRN (August 25, 2020) and the sources cited therein:

Dravidian languages, Sanskrit or Paramunda languages could not have been candidates for the [language of the] Indus Valley Civilization which flourished from 2600 BC to 1900 BC in the North-West of India and Pakistan.

If anything, the evidence that none of these three historical linguistic hypotheses can be supported by the evidence is stronger now than it was twenty-five years ago. 

Like the Paleo-European languages (of which the only survivor is Basque), the Harappan language can probably never be fully reconstructed, even if we can glean some knowledge of it from inscriptions in Harappan script, and from substrate influences in Sanskrit and related languages, and areal influences on the Munda languages.

The Indo-Aryans

The Indo-Aryans, who had wheeled chariots and domesticated horses, and were used to a more arid climate, rushed in to fill the political vacuum. They may have had some farming, or may have ruled subject societies of farmers, but were ancestrally herders.

The Indo-Aryans arrived from Central Asia, ca. 2000 BCE - 1500 BCE, bringing with them Sanskrit, that later diversified into the various Indo-European languages of South Asia. The language of the Indo-Aryans extinguished the Harappan language as anything but a substrate influence on Sanskrit.

Another branch of the same people at about the same time gave rise to the oldest Indo-Iranians and the Mittani Kingdom in Northeast Mesopotamia in mostly what is now Iran. 

We know that Indo-Aryans were the conquerors and not the conquered, because Indo-Aryan genes are more common in higher castes in India, and because these genes have origins (confirmed with ancient DNA) from outside the Indian sub-continent.

The religion of the Indo-Aryan migrants and the Harappan religion mutually influenced each other to produce the early Vedic religion, that would eventually give rise to modern Hinduism. But, given the differences between the Vedic religion and the religions that emerged in other places that the Indo-Europeans conquered, and the Rig Vedic references to things like the Saraswati river societies that were gone or almost gone by the time that the Indo-Aryans arrived, we know that the Indo-Aryan religious tradition and the Harappan religious tradition both influenced the fused religion that emerged from their fused culture.

Genetic evidence tells us that more than one wave of Indo-Aryan migration affected the area of India where Indo-Aryan languages are now spoken.

The Dravidians

The monsoon driven tropical region (in a medium blue on the first map), that makes up most of Southern India, didn't adopt agriculture until the South Indian Neolithic revolution, around 2500 BCE, had significant reliance upon crops domesticated in the African Sahel, and even then, wasn't as optimal for agriculture. The Fertile Crescent package of crops wasn't naturally suited to this climate region and it took many centuries for these crops, under the close guidance of early farmers, to adapt to this tropical monsoon driven climate.

The Dravidian language family probably has its roots in the South Indian Neolithic revolution, probably from one of the South Asian hunter-gatherer population that was one of the first to adopt agriculture, possibly with some linguistic influence from the Africans who brought the Sahel African crops that made this Neolithic Revolution possible.

While the Harappan society had trading posts at the fringe of what was Dravidian India at the time, mostly along the northwest coast of the Deccan peninsula, the Harappans almost surely did not speak a Dravidian language and had only thin trade ties with Dravidian society.

The first wave of Indo-Aryan migration reached the Dravidian society, leaving traces in genetic admixture found in lower amounts in almost everyone in India, even Dravidians. In this initial wave, the fused Vedic religion took hold (although the preference for vegetarianism found among the formerly Harappan regions did not), and all but a small core of this region probably experienced language shift, with their local Dravidian dialects going extinct. The Dravidian society on the eve of the Indo-Aryan arrival was not as technologically advanced as the Harappan one, but also may not have been in as advanced a state of collapse as the Harappan civilization. The climate event that impacted the Harappans so decisively, may not have affected their part of the Deccan peninsula so strongly. 

But in Southern India, the Indo-Aryans were spread thin, were in an eco-region less familiar to them, and less completely dominated the Dravidian society. The core region )probably within the region where Telugu is now spoken) that held out expanded and reconquered almost all of the former Dravidian territory, bringing its sole surviving Dravidian dialect with it (which is why the Dravidian language family seems much younger than one that stretches back to the South Indian Neolithic). But this reconquest never ended up replacing the Vedic religion that had replaced or absorbed its own religion (which may not have been as well-developed as the Harappan religion, and arose in an illiterate society). Unlike Northern India, which had multiple waves of Indo-Aryan migration, no later big wave of Indo-Aryan migration followed the Dravidian reconquest of Southern India.

The geographic range of the Dravidian languages prior to the arrival of the Indo-Aryans was probably wider than it is today, possibly extending to the fringes of the Indus River Valley civilization, as indicated by toponyms in these regions.

But, the North Dravidian languages (Brahui in what is now Pakistan, and the Kurukh-Malto languages of Northeast India), were probably not part of the original Dravidian language range and were the product of much later colonizations (probably around 1000 CE in the case of Brahui, where it was spoken as a result of an elite driven language shift, similar to the one that occurred at about the same time in what is now Hungary, rather than a mass migration of Dravidians to the region). Oral traditions among the Krukh-Malto peoples, at least, assign their origins to Dravidian homelands further south.