Evolutionary Perspective on Narmada Hominin Fossils

Understanding of human evolution in South Asia primarily rests on a solitary calvarium (partial skullcap) from Hathnora in the central Narmada valley, but its disputed taxonomic status has blurred the picture. Early explorations (1983-1992) led to the discovery of 2-clavicles and a 9 rib from Hathnora, but those were so tiny to fit with the calvarium, and fueled the debate whether the calvarium is of a dwarf or a pygmy. Further explorations conducted (2005-2010) brought out 6-femora, 3-humeri and 2-sacra. They were derived from different localities and bio-stratigraphic and archaeological contexts, and posed a challenge of association with the calvarium or with other unknown hominins. The present study is undertaken to address this problem, and the postcranial bones are sorted into possible morphotypes based on criteria of robustness, estimated sex and stature/body size under the control of their contexts. The study distinguished two major morphotypes which reflect the process of humanization in the central Narmada valley and a possible evolutionary scenario for South Asia. The earliest morphotype is a “robust tall hominin”, recognized as a unique hybrid cf. H. heidelbergensis, represented by the calvarium and two femora. It appeared around 300 150 ka in association with megaterrestrial fauna and late Acheulian tools-kit. The second morphotype is a “short and stocky” hominin, named Homo narmadensis Sp. Nov. This is hitherto unrecognized hominin represented by eight fossil bones in association with the “Upper Group fauna” and Middle to Upper Palaeolithic industry. It appeared about 150 100 ka and continued to ca. 40 ka, and was the likely precursor to the “short-bodied” ancient populations of India, including the Andaman pygmy.


Introduction
Current understanding of human evolution in South Asia greatly owes to the central Narmada valley, which stands unique for gifting us unambiguous Middle to Late Pleistocene hominin fossils in association with numerous mammalian fauna and Palaeolithic implements (Figure 1). After a long century's wait, a discovery of a half skullcap (calvarium) (Sonakia, 1984)  Hathnora, recognized by the author in 1995 and reported (Sankhyan, 1997a(Sankhyan, , 1997b(Sankhyan, , 2005. They shared the sex, age and locality of the calvarium, but were too tiny to go with a "large-headed" hominin, and created controversy whether the calvarium was of a "dwarf" or a "pygmy" (Sankhyan, 1999).

Bio-Stratigraphy and Dating
The central Narmada valley is a trough basin between the Satpura and the Vindhya hills, filled with the Lower and Upper Group Quaternary Alluvium.
Studies revealed that the Dhansi immediately overlays the palaeomagnetic reversal at ca 730 ka (Agrawal et al., 1988;Rao et al., 1997), such that the Dhansi was succeeded by the Middle Pleistocene Surajkund formation which had yielded human fossils. It was succeeded by the overlying Baneta and Hirdepur formations of the Late Pleistocene; the latter contained a layer of the Youngest Toba Ash (YTA) and thus provided a definite upper datum of ca.75ka (Chesner et al., 1991;Acharyya & Basu, 1993;Westgate et al., 1998). Other overlying formations were identified as Janbasa and Ramnagar mid-Holocene formations, capped by the black cotton soil.
The hominin calvarium site lies in the west of Hathnora village located 77˚53'N: 22˚52'E on the right bank of the Narmada, 22 km North-East of Hoshangabad town. The calvarium had come from the yellow sands of the Surajkund formation concealed by the older cemented sheet-gravel, called "Boulder Conglomerate". There are three visible successive consolidated cemented gravel sheets, named as U1, U2 and U3 (Khan & Sonakia, 1992) which concealed the Surajkund formation yellow sands ( Figure 3). We recognized such stratigraphic successions of sheet-gravel in entire Central Narmada valley, which broadly provide a temporal framework from Middle Pleistocene to Upper Pleistocene. However, there has been a widespread misinformation and confusion that the calvarium was re-deposited in the U1 sheet-gravel, which questioned its half million antiquity and was likely re-deposited and dated to ca. 236 ka (Patnaik et al., 2009   dug out. The next day a villager lifted out a cranium of Bubalus namadicus with one complete long horn. Later, a cranium of Bos namadicus was also discovered from the partly submerged U1 bed. Such complete fossils of typical Middle Pleistocene megaterrestrial mammals, and typical large flake Acheulian tools were not previously accessible to earlier workers who collected only small flakes from surfaces of U1 and U2 gravel sheets (de Badam et al., 1986). Thus, it was for the first time that the bio-stratigraphic status of the calvarium was ascertained. Interestingly, an Acheulian implement was stuck in the hard matrix deposited on the Equus namadicus mandible, suggesting contemporaneity of the archaeological findings.

The Hominin Findings
The project was extended to the entire central Narmada basin from Jabalpur to  (Sankhyan et al., 2012a(Sankhyan et al., , 2012b.
After a gap of three years, the AnSI called the author as a Visiting Fellow to study, catalogue the fossil and archaeological collections and write reports on them, including similar Siwalik research work at the North-West Regional Centre at Dehradun. The author had submitted a 4-year plan for these tasks as per the normal tenure of the fellowship, but the succeeding officials limited the fellowship to half and couldn't let research work complete. The author could manage the scrutiny of the fossil collection and was lucky to have discovered nine more hominin postcranial fossils, namely, 5-femora, 2-humeri and 2-sacra.
These were measured, scanned and photographed, but their detailed comparative study took one year after the fellowship leading to publication of three papers in the year 2017 (Sankhyan, 2017a(Sankhyan, , 2017b(Sankhyan, , 2017c. Thus, on date, there are 15 hominin fossils on record from the Narmada valley discovered from different localities and bio-stratigraphic and archaeological contexts, and pose a challenge to associate the bones with the calvarium. After a detailed morphometric study of the fossil bones, the present study is an attempt to sort out these into morphotypes using their robustness or gracility, estimated sex, stature or body size, and unique morphological traits under their stratigraphic control ( Figure 5). The

The Evidence for A "Robust" Tall Hominin
Three fossils represent one single robust Acheulian hominin in the central Narmada valley, whose salient features are discussed.

The Calvarium
The skullcap (calvarium) was initially sexed as male due to great robusticity (10 mm cranial vault thickness: Figure 2: 1d), but later due to stubby mastoid process it was assigned to a female. It is heavily mineralized and indicates considerable antiquity. It preserves most of the right half from orbit, supraorbital ridge and frontal to the zygomatic unto the occipital, its base, the auditory meatus and the mastoid process. The left side includes only a bit along the mid-sagittal plane. The cranial base preserves the margin of the foramen magnum; the occipital bone is preserved and pitted by gravels; the sagittal and lambdoid sutures are traceable; the mid sagittal plane is slightly furrowed.
It invoked considerable interest in public and debate among scholars. The great robustness or thickness of the cranial vault, first indicated it a Homo erectus, which was further attested by a landmark morphometric study by M-A de Lumley in France. The study concluded that the calvarium belonged to an "evolved" Homo erectus , also maintained by another study (Mallasse, 2009). The second study conducted by Kenneth A.R. Kennedy in USA assigned the calvarium to "archaic" Homo sapiens (Kennedy 1989(Kennedy , 1999(Kennedy , 2000(Kennedy , 2007Kennedy et al., 1991), Unique traits: (a) the furrowed sagittal ridge, (b) large external auditory meatus (ear hole), (c) unusually long temporal bone. These are absent in erectus and modern sapiens and distinguish Narmada hominin at the trinomial level only (Kennedy, 2007).
The overall score of maximum affinity (within ±5 mm) is in the order of: Petralona (11), La Ferrassie (10), La Chapelle Aux Saints (8) classic Neanderthals, followed by Rhodesian man from Kabwe (7). The other African and Asian hominins show minimal affinities. In other words, Narmada hominin calvarium belonged to a "big-brained" species, Homo heidelbergensis or a similar "archaic" Homo sapiens than to Homo erectus sensu stricto. But, its considerable affinities with the classical Neanderthals are more a surprise and difficult to explain, except through hybridization. There is a great possibility of hybridization due to Narmada Valley's mid-intercontinental place in the Old World as a possible crossroad or corridor of early hominin migrations. This is very likely why the calvarium possesses a mosaic of characters. Its unique features may be explained as a result of considerable local evolution after hybridization as happened among the Neanderthal group of hominins in Europe.

Postcranial Evidence for Robust Tall Hominin
So far the Hathnora Narmada calvarium represents a robust hominin. We may look for robust postcranial fossils from Hathnora and nearby/adjoining localities of the same/equivalent horizon, along with associated archaeological and mammalian fossils. In this connection two femur fossils could be considered for the possible association, viz., (1) NTK-F-07-05-a left distal femur shaft from Netankheri and (2) GRL-F-16-06-a left femur distal shaft from Gurla (Sankhyan et al., 2012a(Sankhyan et al., , 2012b.

The Left Distal Femur from Netankheri (NTK-F-07-05)
The Netankheri, located 3 km upstream from Hathnora along the northern bank of the River Narmada, has a 19.2 m thick litho section, whose lower 3.7 m part is Netankheri left femur is 81 mm mineralized distal-most shaft portion of the femoral body or corpus femoris, detached from the condyles. It is typically cylindrical in shape, which broadens and flattens distally near the condylar region and forms a distinct well preserved triangular popliteal surface on its posterior aspect. The articular surface of the patellar deep notch and the intercondylar fossa are eroded. The lateral surface is rounded compared to the slightly pinched medial surface above the condyles, which flare medially when the femur is held perpendicularly. The femur, though limited by the degree of preservation, yet shows a notable feature of low development of the medial and lateral lips that results in a sub-circular/ovoid shape of the diaphysis in cross-section. In this respect it is unlike the modern human femur where the two lips emerge into linea aspera prominent ridges resulting in a posterior pilaster or flatness. In this respect the robust Netankheri femur is comparable to the robust and rounded femur of the Neanderthal which generally lacks the pilaster. Therefore, it may draw closer to the "late archaic" hominins (Carretero et al., 2009;Franciscus & Churchill, 2002;Weaver, 2009), e.g. Tabun 3, Qafze 9 and Skhul 5. In the metric comparison the Netankheri femur draws closer to Homo heidelbergensis. The estimated stature for the Netankheri femur comes to 164.83 ± 5 cm (male) 159.82 ± 5 cm (female), which conforms to a medium tall robust male hominin.
The Faunal and Cultural Context: The Netankheri U1 level yielded only a few mammalian fossils; notably the molar fragments of Stegodon insignis ganesa, suggesting Middle Pleistocene age (Badam & Sankhyan, 2009) for the Netankheri femur as for the Hathnora hominin calvarium. Only a few heavy-duty Acheulian implements were recovered from the Netankheri U1 level, which include a large pick. But, due to submergence, it remained largely unexplored. It is apparent that the Hathnora calvarium and the Netankheri femur are derived from a larger robust archaic H. sapiens sharing H. erectus and Homo neanderthalensis mosaic morphology or like a Homo heidelbergensis (Sankhyan et al., 2012a(Sankhyan et al., , 2012b.

A Left Femur from Gurla (GRL-F-16-06)
The femur comes from Gurla (22˚51'26"N: 77˚52'08"E) located just opposite to Hathnora across the river Narmada along its left bank in District Hoshangabad. The preserved 10.5 cm bone fragment yields a stature of 159.03 cm (for female), but considering its great robustness it belonged to a tall male of 164.08 cm height. In this respect it is similar to the Netankheri robust femur, and could be associated with the robust Hathnora calvarium.
The datum: An electron spin resonance (ESR) date (Cameron et al., 2004) of >236 kya fits within the biostratigraphic and cultural time of the findings, though linear uranium uptake show a confusingly wider range of 40 -280 ka (Patnaik et al., 2009). Considering the overall evidence we may tentatively keep the U1 hominin fossils, the Hathnora calvarium and the Netankheri femur at ca.

Postcranial Evidence for "Short-Stocky" Hominin
There are several fossil bones for this hominin discussed below.

The Evidence from Two Clavicles
The two tiny clavicle fossils were discovered from the U2 bed of the Surajkund Formation of Hathnora and sexed as adult female of 25 -30 years age at death (Sankhyan, 1997a(Sankhyan, , 1997b(Sankhyan, , 2005 but show bilateral asymmetry due to left-sided ante mortem trauma. The locality name, similar age, and female sex of the clavicles and the calvarium evoked considerable interest and debate for about a decade (Sankhyan, 1999). A doctoral work (Sankhyan, 2010) presents detailed comparative morphometric analysis on the clavicles including estimation of the body dimensions of the hominin, the stature and the shoulder width by employing the databases of many studies (Flower, 1880;Parsons, 1916;Chatterjee, 1955;Gupta et al., 1960;Jit & Singh, 1956;Vrba, 1979;Churchill, 2007;Pearson, 2000). The results indicate that the clavicles belong to a very "short and stocky" hominin with short shoulder width (= biacromial diameter) comparable to the Onge or Great Andaman Negrito pygmy (Sankhyan & Rao, 2007). Their stature estimates ranged from 130 -142 cm averaging at 138 cm worked out from a sample of 16 adult Onge females (Sankhyan & Sahani, 2015). A similar estimate of 135 cm was worked out from a very large sample of modern clavicles (Jit & Singh, 1956) that yielded regression value as: Y = 5.76x + 83.01 cm, where x (9 cm) is the length of the Narmada right clavicle.

The Evidence from the 9 th Fossil Rib
It shows typical human/hominin character of the 8 th to 10 th rib in being thinner and less twisted shaft with shallow and single costal groove, depressed tubercle, similar angle-tubercle distance, marked angle and M. scalenus posterior muscle scar behind the angle. It bears the peculiarities of the 9 th rib, namely, a large tubercle projecting below the inferior border, thicker and broader angle-tubercle region; shallower and broader costal groove, obliterated below the tubercle, rectangular non-articular part of the tubercle, etc. In its expanse, the fossil rib is similar to a pygmy 9 th rib or modern human 4 th /5 th rib, again pointing towards a thorax scaled to a pygmy-size and reflected on similar ecological adaptations in consonance with the clavicles.
Thus, the tiny robust clavicles and the 9 th rib are a mismatch to the calvarium and revealed the additional presence of a hitherto unknown pygmy-sized archaic hominin species in the Narmada Valley, further confirmed by the additional postcranial fossils, excavated Palaeolithic tools and fauna.

The Evidence from a Right Femur Mid-Shaft (HTN-F-18-05)
While the Hathnora U1 stratigraphic bed yielded the calvarium, its U2 yielded two femoral portions (HTN-F-18-05 and HTN-F-45-08) at different times along the right bank of river Narmada in district Sehore. While the hominin calvarium was derived from its basal cemented conglomerate (U1) bed of the Surajkund Formation, the two femora were discovered from the overlying U2 cemented gravel bed, which has previously yielded two clavicles and a rib. Both femoral parts bear similar light brown coloration and mineralization, and are likely the

The Evidence from a Right Femur Distal Shaft (HTN-F-45-08)
It preserves only 1/4 th of the distal shaft, just 2.5 cm of the estimated 10 cm long Segment 4. It is mineralized and shares the coloration of the HTN-F-18-05 right femur, and likely represents its distal part from which the condyles have been detached off. The total femur length from 10 cm long segment 4 comes to 31.7 cm and statures 132.4 cm (female) and 139.07 cm (male). Similarity in the estimated statures reveals that both proximal and distal parts are derived from the same male individual, who was very "short and stocky". Interestingly, similar stature estimates for the Hathnora clavicles indicates that they could have been derived from the same "short and stocky" ("pygmoid") hominin population.

The Evidence from a Left Humerus Shaft (NTK-F-02-07)
It was recovered from U2/U3 stratigraphic level at Netankheri. The humerus was associated with several bone artefacts. The U2/U3 units of the cemented gravel where the brachialis narrows superiorly and widens distally. Distally, the posterior surface is flattish and covered by the lateral and medial heads of the tricep brachii that give origin to part of the brachialis (Sankhyan et al., 2012a(Sankhyan et al., , 2012b. There is a broad, shallow, oblique depression in the center. It is pertinent to know whether the NTK humerus is of the archaic hominins or of modern humans. Studies (Todd & Churchill, 2006) show that the archaic/modern human dichotomy could be established by the proximal ulna, but this is not supported by the distal humeral morphology.
The humerus yielded an estimated maximum length of 240 mm, which is even shorter than the mean length of five Chaurite humeri (291.4 ± 13.43 mm) as well as from a larger sample of 33 mixed mainland Eastern Indians plus the Chaurite (284.74 ± 27.19 mm). Interestingly, the NTK and Chaurite Nicobari population is shorter and stockier in the available comparative sample (Todd & Churchill, 2006;Bermudez de Castro et al., 2012;Trinkaus, 2007;Trinkaus & Ruff, 1999), which includes Omo Kibish and Cro-Magnon 1. As such the present specimen may only be suggested as "late archaic" human from its mineralization also shared with the associated bone tools, which are typo-technologically late Middle or early Upper Palaeolithic.
Faunal & Cultural Contexts: The U2/U3 interface at Hathnora has yielded fossil fragments; we dug out an antler of the Axix axix at Hathnora. But, at Netankheri the U2/U3 has yielded the human humerus along with an isolated dentition of Equus hemionus khur. But, the important associations are with the bone implements discovered for the first time in Narmada Valley at Netankheri and Amkheri just on the opposite bank and at a few other localities with collapsed upper Surajkund gravel. They were found along with other lithic tools of quartzite, chert, chalcedony, jasper and agate. They are mostly of splintered bone fragments, which show marks of secondary chipping and intentional modifications resulting in shapes found among the Middle and Upper Palaeolithic industries. Some of the better recognized typo-technological categories found include, spatulas-cum-end scrapers, dagger, knifes, borers, awls, burins, blades, etc. and the bone implements recovered within the collapsed U2/U3 interface of the Surajkund Formation located below the Baneta Formation stratigraphic boundary.

The Left Femur from Umaria (UMR-F-08-07)
The section at Umaria is located at 23˚00'50"N, 79˚01'18"E) on the right bank of river The preserved bone 10.3 cm is a 66.67% part of the Segment-4, such that the complete segment 4 would be 15.45 cm which would yield total length of the femur as 30.43 cm, and therefore, the stature 129.26 cm (female) and 136.13 cm (male). As the femur belongs to an archaic robust individual, so we may prefer a male stature of 136.13 ± 5 cm, which falls among the "short and stocky" early modern humans and at par with the Andaman pygmy.

The Left Femur from Devakachar (DKC-F-05-09)
It comes from Devakachhar Section (on river Sher), a tributary of river Narmada (23˚00'25"N: 79˚07'32"E) between Umaria and Devakachhar in district Narsingpur (M.P.). The exposed section is 15.5 m thick of Surajkund Formation, disconformably overlain by the Baneta Formation comprised of quartz, chert, agate, jasper and few numbers of quartzite, etc., sealed by a 0.2 m thick black soil at the top. It is a 12.17 cm long distal body shaft detached from the condyles and preserves a bit of the Segment 3, the full Segment 4 (9.7 cm) and a bit of the condylar Segment 5 intact. Proximally, a chip of the cortical bone is deeply chipped off from the medial aspect; the bone is mineralized and patinated. The specimen is typical human femur with a cylindrical body, slightly arched and more convex in front anteriorly (dorsally) and slightly concave or flattish behind (ventrally). Due The anterior (dorsal) surface is smooth, convex, and slopes medially thereby broadening the lateral surface, whereas the posterior (ventral) surface is nearly rounded but slightly flattened distally in the popliteal area. The gracility of the bone and non-muscular character indicates a young adult female. The total femoral length was estimated from the length of the Segment 4 (9.7 cm) × 3.17 = 30.75 cm, and accordingly the mean stature of the DKC individual comes to be: if female = 130.05 cm; and if male = 136.87 cm. Since, the gracility of the bone suggests a female, we may consider hominin as 130.05 cm, which is quite "short and stocky" as that of Hathnora and Netankheri.

The Left Humerus Midshaft from Dhanaghat (DHG-F-42-06)
The Its upper extent is up to the mid of the pectoralis major and teres major muscular region, just below the beginning of the lateral head of the triceps. It is typically the cylindrical upper humeral body part with the lateral and medial heads of the triceps enclosing a distinct radial sulcus or the spiral groove for the radial nerve. Only a little part of the lower body is preserved which reveals the distal widening, which turns prismatic below. We can notice a medial bend or distinct twist on the posterior surface of the mid-shaft body where the brachialis narrows upward medialward and widens downward lateralward. Nearly the whole of the body surface is covered by the lateral and medial heads of the Triceps brachii, the former arising above, and the latter below the radial sulcus, a broad but shallow oblique musculospiral groove or depression. The specimen bears mineral signatures of the Surajkund Fm U2/U3 cemented gravel showing dark colour and whitish grey patches of quartz depositions, suggesting considerable antiquity.

Left Humerus from Budhni (BDG-F-04-07)
The specimen was collected from the Baneta Formation and bears its brownish grey colour of the sediments with mineralization attesting younger antiquity. It Thus, the "short and stocky" mode-3 archaic Homo sapiens, tentatively denoted by a new species Homo "narmadensis" (Sankhyan, 2013) may have been a product of local evolution or an early "African import" to South Asia via the Arabian Peninsula (Petraglia & Alsharekh, 2003;James & Petraglia, 2005;Petraglia, 2007) between 150 -100 ka via Darri-I-Kur of northeastern Afghanistan (Angel, 1972). They survived the "volcanic winter" (Chesner et al., 1991;Ambrose, 1998;Oppenheimer, 2002Oppenheimer, , 2003Rose & Chesner, 1990) due to unique cultural adaptations, such as bone tool technology, which could have facilitated rapid attainment of anatomical modernity (Sankhyan, 2013). The recent mtDNA M-haplotype signatures > 60 kya found in the Munda, Pauri Bhuiya (Barik et al., 2008;Chandrasekar et al., 2009;Mondal et al., 2016) inhabiting the eastern or Northeastern fringes of Narmada Valley, who interestingly, also share these signatures with the Andaman pygmies, likely attest continuity of the "short-bodied" populations. Similar later Upper Palaeolithic and Mesolithic hominin occupants extended to extreme South Asia ~30 ka in the Fa Hien cave in Sri Lanka (Kennedy & Deraniyagala, 1989) as well as, which would continue to fuel the debate on "continuity" versus "replacement". On the other hand, the Narmada-like Late Acheulian "robust tall morphotype" (cf. H. heidelbergensis) expanded to northward Sankhyan, 2020) and southeastward (Sankhyan et al., 2011). The palaeoenvironmental scenario with prevalence of warm climatic conditions (Kotlia & Joshi, 2008) in the Narmada valley favoured continuity and diversity of "short-bodied" populations since the later Middle to Late Pleistocene. Very likely the "Volcanic Winter" made a little impact on the Narmada hominins who continued thereafter too (Haslam et al., 2011). They had extended to its Vindhya-Satpura confinements and had a safe haven in the numerous rock-shelters where they had "creative explosion" or developed "technological ingenuity" leading to development of rock-art, and even portable art as early as  (Sankhyan, 2017d). The biological change responded to these cultural activities by shedding out the archaic adaptive morphologies, especially through hybridization. A recently excavated Acheulian site Tikoda in the Vindhya Range (Ota & Deo, 2014) may reveal more secrets of human evolution.
Beyond the central Narmada valley, the well-dated older Acheulian sites of Peninsular India, such as Attirampakkam (Pappu et al., 2011), Isampur, Hunsgi and Baichbal (Paddayya, 2003(Paddayya, , 2008, Morgaon and Bori (Westaway et al., 2011;Kailath et al., 2000;Misra et al., 1995) are attributed to Homo erectus on African analogy. Although fossils are yet awaited from these sites, it is apparent that Homo erectus was endemic in South India, which evolved further in the central Narmada valley, where it was also hybridized with western late Acheulian hominins, H. heidelbergensis. It was overtaken by the "short and stocky" H. "narmadensis" on the onset of the Middle Palaeolithic Mode 3, which may have origins within India as evident at Attirampakkam (Akhilesh et al., 2018). It showed adaptive continuity and survived the "Volcanic Winter", both in central India and southern India, and probably evolved and splitted to several short-bodied ancient Indian tribes, including the Andaman pygmy.

General Evolutionary Scenario
A summary of the nine long bone fossils, their dates, stratigraphic and archaeological contexts, and physical morphotypes based on sex, robustness, and estimated statures, and equivalent species, is presented in note Petralona date is ~200 ± 50 ka and by fauna, agree with a date of ~250 ka.