Fluting is a technological and morphological hallmark of some of the most iconic North American Paleoindian stone points. Through decades of detailed artifact analyses and replication experiments, archaeologists have spent considerable effort reconstructing how flute removals were achieved, and they have explored possible explanations of why fluting was such an important aspect of early point technologies. However, the end of fluting has been less thoroughly researched. In southern North America, fluting is recognized as a diagnostic characteristic of Clovis points dating to approximately 13,000 cal yr BP, the earliest widespread use of fluting. One thousand years later, fluting occurs more variably in Dalton and is no longer useful as a diagnostic indicator. How did fluting change, and why did point makers eventually abandon fluting? In this article, we use traditional 2D measurements, geometric morphometric (GM) analysis of 3D models, and 2D GM of flute cross sections to compare Clovis and Dalton point flute and basal morphologies. The significant differences observed show that fluting in Clovis was highly standardized, suggesting that fluting may have functioned to improve projectile durability. Because Dalton points were used increasingly as knives and other types of tools, maximizing projectile functionality became less important. We propose that fluting in Dalton is a vestigial technological trait retained beyond its original functional usefulness.

Forty years ago, Knut Fladmark (1979) argued that the Pacific Coast offered a viable alternative to the ice-free corridor model for the initial peopling of the Americas—one of the first to support a “coastal migration theory” that remained marginal for decades. Today, the pre-Clovis occupation at the Monte Verde site is widely accepted, several other pre-Clovis sites are well documented, investigations of terminal Pleistocene subaerial and submerged Pacific Coast landscapes have increased, and multiple lines of evidence are helping decode the nature of early human dispersals into the Americas. Misconceptions remain, however, about the state of knowledge, productivity, and deglaciation chronology of Pleistocene coastlines and possible technological connections around the Pacific Rim. We review current evidence for several significant clusters of early Pacific Coast archaeological sites in North and South America that include sites as old or older than Clovis. We argue that stemmed points, foliate points, and crescents (lunates) found around the Pacific Rim may corroborate genomic studies that support an early Pacific Coast dispersal route into the Americas. Still, much remains to be learned about the Pleistocene colonization of the Americas, and multiple working hypotheses are warranted.

Eolian sediments are common within the middle Gila River Valley, southern Arizona, and reflect variability in eolian and fluvial processes during the late Holocene. This study focuses on deciphering the stratigraphic record of eolian deposition and associated luminescence dating of quartz extracts by single aliquot regeneration (SAR) protocols. Stratigraphic assessment coupled with luminescence ages indicates that there are four broad eolian depositional events at ca. 3145 ± 220 yr, 1950–1360 yr, 800 ± 100 yr, and 690–315 yr. This nascent chronology, correlated with regional archeological evidence and paleoclimate proxy datasets, leads to two general conclusions: (1) loess deposits, transverse-dune formation and sand-sheet deposition in the late Holocene are probably linked to flow variability of the Gila River, though the last two events are concordant with regional megadroughts; and (2) the stability of eolian landforms since the 19th century reflects the lack of eolian sediment supply during a period of fluvial incision, resulting in Entisol formation on dunes. The prime catalyst of eolian activity during the late Holocene is inferred to be sediment supply, driven by climate periodicity and variable flow within the Gila River catchment.

Radiocarbon dates from archaeological sites in Whitewater Draw, Arizona, place the Sulphur Spring stage of the Cochise Culture between 8000 and 10,000 yr B.P., and possibly back to 10,400 yr B.P. Geoarchaeological investigations of Whitewater Draw do not substantiate an earlier claim that Sulphur Spring stage ground stone artifacts are associated with extinct megafauna, nor the hypothesis that Sulphur Spring stage artifacts are specialized plant processing tools of the Clovis Culture.

Freshwater lakes existed intermittently in the Salton Trough of southern California during the late Holocene. The lakes formed north of the subaerial Colorado River Delta whenever the Colorado River flowed west into the trough instead of south to the Gulf of California. Water filled the trough to a maximum altitude of 12 m. Stratigraphy, radiocarbon dates, and supplementary evidence document four lacustral intervals of Lake Cahuilla between A.D. 700 and 1580. Archaeological sites are associated with the 12-m shoreline and their occupation correlates with these lacustral intervals.

The floodplain along a 75-km segment of the Brazos River, traversing the Gulf Coastal Plain of Texas, has a complex late Quaternary history. From 18,000 to 8500 yr B.P., the Brazos River was a competent meandering stream that migrated from one side of the floodplain to the other, creating a thick layer of coarse-grained lateral accretion deposits. After 8500 yr B.P., the hydrologic regime of the Brazos River changed. The river became an underfit meandering stream that repeatedly became confined within narrow and unstable meander belts that would occasionally avulse. Avulsion occurred four times; first at 8100 yr B.P., then at 2500 yr B.P., again around 500 yr B.P., and finally around 300 yr B.P. The depositional regime on the floodplain also changed after 8500 yr B.P., with floodplain construction dominated by vertical accretion. Most vertical accretion occurred from 8100 to 4200 yr B.P. and from 2500 to 1250 yr B.P. Two major and three minor periods of soil formation are documented in the floodplain sequence. The two most developed soils formed from 4200 to 2500 yr B.P. and from around 1250 to 500 yr B.P. These changes on the floodplain appear to be the result not of a single factor, but of the complex interplay among changes in climate, sediment yield, and intrinsic floodplain variables over time.

Diring Yuriakh, an archaeological site on the highest terrace of the Lena River in subarctic eastern Siberia, provides evidence for the oldest and northern-most Early Paleolithic occupation in Asia. Stratigraphic and sedimentological studies at the site show that artifacts occur on a single eolian deflation surface that is underlain by fluvial sediments with inset cryogenic sand wedges and overlain by eolian deposits. Thermoluminescence ages on the fine-grained extracts from the eolian sediments and sand wedges that bound the artifact level indicate that the occupation occurred >260,000 yr B.P. and may possibly date between 270,000 and 370,000 yr B.P. This study documents that the artifacts from Diring Yuriakh are an order of magnitude older than artifacts from any previously reported site from Siberia. The antiquity and subarctic location of Diring Yuriakh indicates that people developed a subsistence strategy capable of surviving rigorous conditions in Siberia by ≥260,000 yr B.P.

Stratigraphy and dating provide an 18,000 yr record of erosion and deposition by the middle Gila River. Prior to 18,000 cal yr B.P., the Gila River cut into its floodplain and created a deep, wide channel. Sand and gravel accumulated within this channel until 4250–4400 cal yr B.P. By this time, the channel of the Gila River was narrow and deep. Around 5000 cal yr B.P., fine-grained sediments began to accumulate on the floodplain. At 800–950 cal yr B.P., there was a major period of channel widening. After this erosional episode, the channel again narrowed as it filled with sand and gravel until around 200 cal yr B.P. On the floodplain, deposition continued from about 5000 cal yr B.P. to 500 cal yr B.P. A period of stability and soil formation occurred on the floodplain between 500 and 200 cal yr B.P., after which overbank deposition resumed and buried the soil. Channel widening again occurred in the late 19th century. The changes observed in the sedimentologic history of the Gila River show that during the late Pleistocene, the Gila River was a competent stream capable of carrying and depositing coarse sediment loads. Later deposition of sand and gravel during the first half of the Holocene implies an increase in sediment yield from upstream watersheds. Changes during the last 4000 years reflect the response of the river to climatic perturbations, the timing of large floods, internal landscape thresholds, and human impacts.

Stable carbon isotope analysis of organic carbon in alluvial deposits and soils of three streams in central Texas reveals significant shifts in the ratio of C3 to C4 plant biomass production during the past 15,000 yr. These temporal changes in vegetation appear to be in response to changes in climate. During the late Pleistocene, C4 plants comprised only about 45 to 50% of the vegetative biomass in this area, suggesting that conditions were cooler and wetter than at any time during the past 15,000 yr. The time between 11,000 and 8000 yr B.P. is interpreted as transitional between late Pleistocene conditions and warmer and drier Holocene conditions based on a slight increase in the abundance of C4 plant biomass. During the middle Holocene, between approximately 6000 and 5000 yr B.P., mixed C3/C4 plant communities were replaced almost completely by C4-dominated communities, indicating prairie expansion and warmer and drier climatic conditions. By 4000 yr B.P., the abundance of C4 plant biomass decreased to levels similar to the early Holocene transitional period, suggesting a return to cooler and wetter climatic conditions. No significant shift in the ratio of C3 to C4 productivity has occurred during the last 4000 yr, except for a slight increase in the abundance of C4 plant biomass around 2000 yr B.P. The results of this investigation correlate well with other regional late Quaternary climatic interpretations for central and north Texas, the Southern Plains region, and with other portions of the Great Plains.

During the latest Quaternary, freshwater pluvial lakes intermittently formed in the topographically closed Willcox basin, Arizona. A lacustrine sequence of six separate high stands of Lake Cochise is documented by stratigraphic studies, 19 radiocarbon ages, and supplementary evidence. Two stands of pluvial Lake Cochise, older than 14,000 yr B.P., reached elevations above 1290 m. The prominent 1274-m shoreline of Lake Cochise, which circumscribes the basin, was largely created during a high stand between 13,750 and 13,400 yr B.P. During the Holocene, water filled the Willcox basin three times to an elevation slightly below the crest of the 1274-m shoreline. This occurred once during the early Holocene around or before 8900 yr B.P. and twice during the later part of the middle Holocene. Since the middle Holocene, only shallow ephemeral lakes have occupied the deflated central portion of ancient Lake Cochise, a depression known as the Willcox Playa. The lacustrine sequence of Lake Cochise provides an independent evaluation of late Quaternary paleoclimatic reconstructions for southern Arizona and the American Southwest.

Fell's Cave lies near the Magellan Straits of South America's Southern Cone. This was the first site to provide evidence of a late Pleistocene occupation of South America, and it is the site where the Fishtail projectile point type was defined. Previous radiocarbon ages from Fell's Cave on charcoal samples from three hearths in the late Pleistocene artifact-bearing levels yielded dates ranging from ca. 11,000 to 10,100 radiocarbon years before present. New radiocarbon dates on curated charcoal samples from these same hearths yield revised ages of ca. 10,800 to 10,400 radiocarbon years before present. These new dates from Fell's Cave agree well with ages from other South American sites in the Southern Cone with Fishtail points and show that the Fishtail projectile point was made from ca. 10,850 to 10,300 radiocarbon years before present or ca. 12,800 to 12,100 calibrated years before present.

The Paleoindian Goshen complex occurs in the northern Plains and eastern Rocky Mountains. Since its identification, there has been much discussion about the chronological placement of the Goshen complex. This is especially true because diagnostic Goshen projectile points occur stratigraphically below Folsom artifacts at two sites, and early dates from the Mill Iron site, Montana, and the Hell Gap site, Wyoming, have suggested that this point type might be coeval with Clovis or the very earliest Folsom sites. This report presents new radiocarbon dates from the Mill Iron site, reviews Goshen chronology, and revises the age of the Goshen complex as 10,450 ± 15 to 10,175 ± 40 radiocarbon years B.P.

Humans first left Siberia and colonized the Americas perhaps around 16,000 years ago, and the Clovis archaeological complex in North America has traditionally been linked to this migratory pulse. Archaeologists searching for evidence of Clovis technological antecedents have focused their attention on the Beringian and Siberian archaeological records. Growing evidence for the pre-Clovis occupation of North America provides a possible alternative source for the origins of Clovis. In this paper, we present new data on the pre-Clovis lithic assemblage from the Debra L. Friedkin site, Texas, and compare Clovis and pre-Clovis lithic technological signatures. We show that while Clovis and pre-Clovis share some important technological traits, they also differ in important ways. We conclude that the pre-Clovis assemblage from Debra L. Friedkin cannot be called “Clovis,” but it could represent a technological antecedent of Clovis.

Contemporaneity of people and the American mastodon (Mammut americanum) at Big Bone Lick, Kentucky, has been extensively debated for more than two hundred years. Newly interpreted stratigraphic excavations and direct AMS ¹⁴C measurements on mastodon bones from Big Bone Lick, Kentucky, indicate that the megafauna are a palimpsest of fossils spanning at least 1,200 calendar years (11,020 ± 30 to 12,210 ± 35 RC yr B.P.). The radiocarbon evidence indicates that mastodons and Clovis people overlapped in time; however, other than one fossil with a possible cut mark and Clovis artifacts that are physically associated with but dispersed within the bone-bearing deposits, there is no incontrovertible evidence that humans hunted Mammut americanum at the site.

Direct dating of a Paleoindian bone point from Sheriden Cave, Ohio, yielded a radiocarbon age of 10,915 ± 30 ¹⁴C yr B.P. (UCIAMS-38249). This date was derived on highly purified bone collagen. This bone point was found in association with another bone projectile point and a reworked, fluted Clovis projectile point. The artifacts from Sheriden Cave fall within the age range of other Clovis sites in North America, dating to the late Allerød, before the start of the Younger Dryas.

A regional episode of erosion between A.D. 1020 and 1160 coincides with social, political, economic, and demographic changes in the Hohokam culture. This regional erosional event was of such magnitude that it accelerated cultural changes that were already underway. The Ensor et al. (2003) commentary and attempt to layer a number of hypotheses on our original interpretations are fraught with problems.

Changes in river floodplain morphology can have devastating consequences for irrigation agriculturalists. Channel erosion occurred in the late nineteenth century, on the flood plain of the middle Gila River, Arizona and severely impacted the native Akimel O' odham (Pima) farmers. Prior to the Akimel O' odham, the prehistoric Hohokam also pursued irrigation agriculture along this river. Geoarchaeological investigations of the Gila River flood plain document a major period of channel cutting and widening sometime between A.D. 1020 to 1160. This channel erosion is coincident with the partial abandonment of large Hohokam villages and significant population rearrangements. It also marks the beginning of a major social reorganization when ball-courts were replaced by platform mounds as the social integrative structure and the Hohokam sphere of influence contracted. Other rivers utilized by the Hohokam—the Santa Cruz River, San Pedro River, and Tonto Creek-also experienced channel cutting between A.D. 1050 and 1150. Thus, a regional episode of channel erosion appears to have been a major factor that contributed to the reorganization seen in the Hohokam archaeological record. These synchronous landscape changes would have severely impacted Hohokam irrigation systems and food production capabilities. This undoubtedly created stresses within Hohokam society which in turn may have accelerated social, political, economic, ideological, and demographic changes that were already underway.

Analysis and dating of new Upper Palaeolithic sites suggest that microblades emerged in the Transbaikal after 18,000 years ago. These findings encourage review of earlier assertions that such technologies developed in northeast Asia prior to the last glacial maximum.