The Paleolithic in the Nihewan Basin, China: Evolutionary history of an Early to Late Pleistocene record in Eastern Asia

The Nihewan Basin of China preserves one of the most important successions of Paleolithic archeological sites in Eurasia. Stratified archeological sites and mammalian fossils, first reported in the 1920s, continue to be recovered in large‐scale excavation projects. Here, we review key findings from archeological excavations in the Nihewan Basin ranging from ~1.66 Ma to 11.7 ka. We place particular emphasis on changes in stone tool technology over the long term. Though Pleistocene lithic industries from East Asia are often described as simple in character, re‐evaluation of the stone tool evidence from the Nihewan Basin demonstrates significant, though periodic, innovations and variability in manufacturing techniques through time, indicating adaptive and technological flexibility on the part of hominins. Synthesis of paleoenvironmental and archeological data indicate changes in hominin occupation frequency in the Nihewan Basin, with chronological gaps suggesting that continuous presence in high, seasonal latitudes was not possible prior to the Late Pleistocene.

The last three decades have witnessed increasing archeological excavations in the Nihewan Basin, resulting in the identification of numerous sites over the long term (Table 1) Alongside continuous academic research on the recovered materials, 8,11,30 archeologists from the HPICR have been conducting large-scale excavations though these remain largely unpublished. As regularly noted by Chinese and international scholars, the Nihewan Basin provides one of the best opportunities for understanding the evolution of hominin cultural behavior in Eastern Asia over the long term. 4,31,32 Dating to~1. 66 Ma, the Majuangou-III site of the Nihewan Basin is so far the oldest well-dated site in northern China. 5 However, as recently reported in Nature, the earliest evidence for the presence of hominins in China is now dated to~2. 1 Ma at the Shangchen site, located in the southern Loess Plateau, 33 suggesting the possibility for earlier sites in the Nihewan Basin. Though other early archeological sites have been reported in southern and northern China, such as Longgupo, Renzidong, and Yuanmou, significant questions remain about their stratigraphy, chronology, and artifact authenticity. [34][35][36][37] In contrast, the Nihewan Basin contains a rich quantity of fossils and stone artifacts in good depositional contexts and with a sound relative chronology throughout the course of the Pleistocene. 5,7,[38][39][40][41] Moreover, dating of sedimentary sequences from the Pleistocene to the Holocene, using magnetostratigraphy, as well as electron spin resonance (ESR), luminescence, and radiocarbon methods, for example, has proven to be reliable for ascertaining relative site The size of the excavation is not clearly recorded in the report. b Jijiazhuang is a newly reported site and the dating is in process. The age of the site is probably Middle Pleistocene based on its stratigraphic position.
ages. 5,7,19,26,[39][40][41] Indeed, paleoenvironmental studies in and around the Nihewan Basin have been initiated, providing information on the ecology of the region. 6,[42][43][44][45] The well-dated environmental data, together with fossil and archeological information, provide unparalleled information about the interplay between environmental change and hominin behavioral evolution and adaptation.  Figure 1b). The northeastern portion of the Nihewan Basin contains dense concentrations of Pleistocene sites, though a few sites outside this area occur, which will also briefly be highlighted here ( Figure 1c).  30 Among these raw materials, chert predominates, representing more than 90% of the artifacts at Xiaochangliang, Donggutuo, and Huojiadi, and more than 60% at Maliang, Cenjiawan, and Feiliang.  (Table 1) and refitted pieces, allowing for detailed assessments of technological behaviors. 11,15,87 At Donggutuo, small flakes (n = 584) were recovered with some showing platform preparation. 11 One of the key innovations applied by the toolmakers at Donggutuo was the production of small, blade-like flakes by wedge-shaped preparatory core methods (originally called the "Donggutuo Core" by Hou 15 ) ( Figure 3 in Box 1). 11,15 Though these wedge-shaped cores are unlikely to be related to much younger microblade cores, as argued by Hou, 15 it does appear that small blade-like blanks were intended knapping products. 11 Some small flakes were retouched into various types of tools, and likely used in a range of tasks such as scraping, cutting, and boring ( Figure 3 in Box 1). 11 The relatively high percentage of refitted pieces in the Cenjiawan assemblage illustrate the development of controlled knapping methods, fixed planning in the knapping process, and increased tool production skills ( Figure 3 in Box 1). 15 Donggutuo contains a large number of fragmentary fossils, some identified as E. sanmeniensis and C. antiquitatis. Although most of the fossil fragments are not in good condition, 1.2% of these pieces reportedly display cutmarks. 4 Toward the end of the Early Pleistocene, at ca. 0.9-0. 78 Ma, fewer sites have so far been identified in the Nihewan Basin. 12 The Maliang site was first excavated in 1985, and 121 artifacts and some faunal remains were recovered from an area measuring ca. 20 m 2 in horizontal dimension. 17 Of the 121 lithic artifacts, most were flakes and flaking debris, with only four retouched items. 17 In recent years, additional sites have been reported near Maliang, and given their similar stratigraphic setting, they have been referred to as part of the Maliang site group. 88 Maliang Locality 10 yielded 1,500 animal fossils and 197 lithic artifacts, including cores, flakes, tools, pebbles, blocks, angular fragments, and shatter. 88 Flaking was by direct hard hammer percussion without any sign of core preparation. Most tools were described as scrapers with the application of casual retouch. 88 Raw

| The Late Pleistocene
By the beginning of the Late Pleistocene, the cultural history of the Nihewan Basin entered into a new stage, 4,91 with significant increases in site numbers and higher numbers of artifacts within sites (Table 1).  102 The stone tools were made on quartzite (49%) and quartz (34%), with chert and agate accounting for 3% of the artifacts; in addition, sandstone, dolomites, and limestone were used in small quantities. 102 The Xujiayao lithic assemblage is composed of a variety of small tools, including scrapers, points, notches, burins, borers, and denticulates ( Figure 5 in Box 1). Discoid cores and blade-like cores were described in the original report 91  Xujiayao is the best studied site for taphonomic analysis in the basin, providing high-quality data and the reconstruction of hominin subsistence activities. 93,103 The fauna at Xujiayao has been identified as E. przewalskii and E. hemionus, supporting an interpretation that the environment was relatively cold and dry. 102 Banjingzi is dated to 86 ± 4 ka by OSL. 19 In the 1988 excavation, more than 3,000 lithic artifacts were recovered. 4 The lithic assemblages are relatively advanced, showing the production of finely made scrapers and points ( Figure 5 in Box 1). Some of the cores have been described as "prepared" and related to "Levalloisian methods," although it was noted that the shapes and structure of the cores differed from classic Levallois techniques. 4 The lithic assemblages at Banjingzi are dominated by high quality chert nodules, which were advantageous for making more refined tools. A large number of fossils was also recovered, though no detailed zooarcheological study has been carried out. 4  Another key site in the Late Pleistocene is Shiyu, occurring in the southwest end of the basin (Figure 1c) and radiocarbon dated to ca. 39-31 ka. 24,25 A very large number of stone artifacts (n = 15,000) was recovered, together with bone tools and a single ornament fragment. 78 The lithic industries were similar to Xibaimaying, as the tools are primarily well-made small tools, including points, scrapers, and burins, as well as a single projectile point ( Figure 5 in Box 1). The projectile point was made on an elongated chert flake, with careful retouch on the base to form a stem. 78 Microblade core methods were not reported, although some small cores are said to have "micro-core" traits. 78,106 The "micro-cores" are mainly made on igneous rocks, typically with one plain platform and flaked in the same direction repeatedly. The recovery over 200 individuals of horses and onagers was interpreted to be the result of specialized hunting activities. 78 (Table 1). 4,16,19 With the exception of Hougou, artifact densities are generally low at the sites, with exceedingly few artifacts found in some site excavations (e.g., Motianling, Jijiazhuang, and Que'ergou), thus also signaling some significant changes in landscape behaviors. In contrast with the focused use of chert in the Early Pleistocene, hominins used a wider range of raw materials available across the basin. 16,19 The lithic assemblages have been described as relatively simple, with a small number of flakes obtained from unprepared cores, though occasional finely retouched tools were also manufactured, indicating that knappers had the ability to manufacture fine implements. Little further information is available about Middle Pleistocene sites in the Nihewan, making this the least understood period of time concerning hominin activities in the basin.

| Trends in the ecology and occupation history of the Nihewan Basin
In the Late Pleistocene, site counts, artifact numbers, and artifact densities increased dramatically in comparison to the earlier records.
Several site excavations have yielded more than 10,000 artifacts each, thus providing detailed information on behavioral activities (Figure 7a,  Figure 7d). 122,123 The Late Pleistocene record is generally characterized by a high abundance and mixture of cold-adapted mammals, and regional vegetation studies also showed relatively dry climate (Figure 7b,c). 4

| Gaps in the record and their meaning
Although there is no doubt that the Nihewan Basin contains an impressive set of sites over the long term, this synthesis identifies two substantial and long-term lacunae in the record, one prior to 1. China is of importance, 33 as it is 400 ka older than Majuangou III at~1 . 66 Ma, if we assume that the paleomagnetic age estimates are correct. Based on the presence of the long lacustrine sequences in the Nihewan Basin, it is entirely possible that older archeological sites will be located, as sediments and mammal fossils extend to more than 3 Ma in the basin, and include finds of horse (Hipparion) and rhinoceros (Chilotherium). 52 Early deposits extending to between 1.7 and The lack of archeological evidence in the Nihewan Basin has been interpreted to be the consequence of either the lack of archeological investigations or to a dry environment at the time. 45 After the MPT and into the Middle Pleistocene, the length and intensity of the glacial-interglacial cycles significantly increased, with the dominant periodicity of high-latitude climate oscillations changing from 41 ka to 100 ka (Figure 7d), 118,119 indicating that cold and dry glacial periods became longer. As the Nihewan Basin is located in a high northern latitude, the regional and local environments were harsh and highly seasonal, which presumably influenced hominin settlement patterns. In sum, and as frequently stated in the literature, the Nihewan Basin is an ideal setting to examine the behavioral evolution of hominin populations in Eastern Asia based on the abundance of archeological sites over the long term and the good to excellent preservation conditions of many sites. Yet, increased scrutiny needs to be paid to understanding the ecological settings of sites in the basin, to site formation and taphonomy, and changes in hominin behavior over time.
And, indeed, there is a need to conduct high-precision interdisciplinary field work to understand hominin adaptations to northern latitudes and to determine how climatic fluctuations and changes in environments influenced hominin expansions, contractions, and extinctions over the long term. As hopefully demonstrated here, the research potential of the Nihewan Basin and surrounding regions is unparalleled in Eastern Asia, allowing for an exploration of many key topics in human evolutionary studies.

We thank Michelle O'Reilly for assistance with the figures and
Dr. Jian-Ping Yue for help on the references.