The terminology used in our work as to plant fiber technologies refers to the use of different parts of the plants that have been worked into fibers for textiles, fabrics, basketry, and cordages (Dodge, 1897; Emery, 1966; Adovasio, 1977; Florian et al., 1991). In our analyses, we draw the distinction between bast fiber from cf. Asclepias and plant fibers from cf. Typha and cf. Scirpus.

We conducted microscopic observation of archaeological and modern reference materials, and we registered the presence and/or absence of particular stomata cells and nodes (dislocations) and cross-marking to attempt to identify plants at least at the family level (Sadrmanesh and Chen, 2019). Samples were mounted and viewed through both transmission light and reflected via a light microscope (LM) at magnifications ranging from 10 × to 50 × . Samples were also analyzed using Hitachi TM3000 TableTop SEM at the McDonald Institute for Archaeological Research, University of Cambridge. The following instrumental settings were used: analytical condition mode at 15.00 kV accelerating voltage, compositional imaging and working distance of 5–10 mm.

Observations revealed varying characteristics of the plant fibers of different species (see Figure 6). Cross-markings were distinctly visible on bast fibers of Asclepias sp. when observed through an LM. By contrast, nodes were prominently discernible on Scirpus spp. when examined via SEM, whereas both cross-markings and nodes on Typha spp. were relatively faint. Whether such variations in nodes and cross-marking visibilities arise from different processing techniques, usage-induced degradation of plant structures or aging will require further investigation.

The origin of nodes or dislocations which are found typically in close proximity to the bast fiber surface is uncertain and still debated (Bergfjord et al., 2010; Suomela et al., 2018). Sometimes referred to in the literature as kink bands, some argue that the quality of these nodes, influenced by fiber processing, offers an avenue to explore the correlation between different techniques of fiber processing and plant characteristics (Shah and Bourmad, personal communication 2023). Kink bands, for instance, observed in flax from Egyptian textiles (Melelli et al., 2021) are not inherent features of the fiber but rather a result of processing. These seem to arise from mechanical stresses during fiber extraction and processing, possibly related to retting. Such stresses may also arise from the rigorous decortication, scutching, and thread-making processes reported for flax bast fibers (Melelli et al., 2021). Some nodes in our samples have a resemblance to kink bands seen in flax (Shah and Bourmad, personal communication 2023), although their systematic analysis to identify specific plant processing stages is still pending. We hypothesize, however, that, like flax bast fibers, features of South American bast fiber node morphology, such as those noted in Asclepias, might be linked to plant-processing steps like extraction, decortication, and subtle retting.

These features are rarely sufficient to distinguish fiber plants at higher taxonomic levels on their own (Lukesova and Holst, 2021), so we combined these initial analyses with the identification of reproductive organs such as inflorescence, seeds, and other macro remains to enhance botanical identification of, for instance, Asclepias spp., Scirpus spp., and Typha sp. (Supplementary material 2, Figures 4, 5). Additionally, the analysis of almost-complete pieces of Typha spp. and Scirpus spp. woven into some artifacts with minimal processing (Figure 7) assisted the identification.

Nets, fishing lines, and fabrics were characterized using digital microscopy for structural textile analysis and SEM for fiber determination. We first observed how plant fiber and bast fiber bundles were worked into threads, for example, dislocations or nodes, which are exclusive to bast fibers remain adjacent to each other when plants have been processed manually. Then, the quality of the nodes as a result of fiber processing allowed us to interrogate the relationship between processing techniques (e.g., decortication or retting) and raw materials. Furthermore, here, we also focused on finding evidence relative to thread-making techniques, degrees of fiber processing, and any other new information that could help us reconstruct stages of the technological process.

The use of various taxa of estuarine and wetland plants reflects the sophisticated ecological understanding of the ancient inhabitants of La Yerba II and III and highlights the critical significance of such ecologies in fostering diverse economic and social dynamics observed in many regions worldwide (Ramsey and Rosen, 2016; Ramsey et al., 2017; Ramsey, 2023).

The Cyperaceae family provided a number of resources that were critical for the marine hunter-gatherers at La Yerba. Plants from this family have prolific underground vegetative growth that consists of a network of rhizomes, tubers, and basal bulbs offering various reliable wetland resources with year-round availability. The family's taxonomy suffers from numerous revisions and synonymy. Species within this family commonly known as sedges have fibrous stems making them suitable for stripping into cordage and ropes used in numerous artifacts (see Table 1) and have long, flexible leaves suitable for splicing.

Some species of the Cyperaceae family, such as C. esculentus, also produce rhizomes that offer a starchy food source. Charred and desiccated C. esculentus rhizomes were recovered in some quantities from some La Yerba II contexts alongside their inflorescences (Table 1, Figure 7, Supplementary material 2). Similarly, Eleocharis flavescens and cf. Schoenoplectus have been reported at other Preceramic archaeological sites along this Pacific coast (Weir and Dering, 1986; Dillehay and Rossen, 2002; Benfer, 2008; Pearsall, 2009). C. esculentus is a perennial sedge that is 30–80 cm tall with triangular stems with fibrous roots. The plant can regenerate completely if even a single tuber is left in place. Tubers typically survive up to ~3–4 years. A single plant can produce thousands of tubers annually, while the carrying capacity is estimated at 1,030 million tubers/ha without crop interference. In tropical regions, where there is less seasonal variation, C. esculentus may have continuous growth throughout the year, whereas in temperate regions with distinct seasons, it may have a more pronounced growth period during the warmer months (Thullen and Keeley, 1979; Johnson and Mullinix, 1999; De Castro et al., 2015). Surface flow in dryland rivers like the Río Ica is highly seasonal and erratic, although its estuary has subsurface supplies all year round. Cyperaceae family plants can, therefore, be expected to persist all year round but thrive particularly during the austral summer when the river flows and soil moisture levels are high. Cf . Scirpus (Schoneoplectus) is typically a perennial or rhizomatous geophyte, which in temperate regions is often deciduous, undergoing dormancy during winter months, although roots and rhizomes remain alive underground. In a cool tropical maritime desert environment like the Río Ica estuary, its active growth season will follow the arrival of summer river flow when lush, grass-like foliage and inflorescences or flower spikes emerge. Small, clustered flowers can sometimes be used to identify Cyperaceae plants at the species level, but they are often clustered together. Flowers are followed by the production of seeds, which can contribute to the plant's spread and propagation.

Cf . Typha (T. domingensis) is a helophyte and grows primarily in the subtropical biome, where it provides medicine, fuel, and food (Arenas and Scarpa, 2003). Where water and nutrient supplies are sufficient, they can rapidly spread and colonize wetland areas. With warmer summer temperatures and enhanced river flow, Typha's growth will be promoted in the Río Ica estuary, and it will flower. As the dry season approaches, Typha plants may start to decline or enter a dormant phase but will rely on groundwater and nutrients and reserves stored in underground rhizomes to survive. Plants of the Typhaceae family are also distributed along the coast of Peru and Chile (Towle, 1961; Leon and Young, 1996; Beresford-Jones, 2011; Whaley et al., 2019) and some members also provide edible rhizomes and roots (Towle, 1961). The ethnobotany of Gran Chaco's Indigenous people (Arenas and Scarpa, 2003, p. 184–185, Figure 2) describes how “women go to the wetlands to cut the flowering stalks of cf. Typha and prepare the pollen at the edges of the wetlands, which is later consumed as a kind of yellow powder like sulfur” (Arenas and Scarpa, 2003, p. 184; Figure 7A). Typhaceae, likely T. dominguensis remains, have been reported in other Preceramic contexts along the coast of Peru (Weir and Dering, 1986; Dillehay and Rossen, 2002; Benfer, 2008; Pearsall, 2009). Typha spp. fibers are typically soft and have good tensile strength (Liu et al., 2017), making them ideal for weaving and twining structures into fabric artifacts.

Notably, different parts of Scirpus and Typha spp. plants were abundant in seasonally available starchy carbohydrates and fibers. Their harvesting may have entailed, beyond their seasonal exploitation, incipient wetland management to promote a continuous supply of food from edible components of tubers, seeds, and young shoots. Most importantly, however, they offered a consistent supply of fibers for crafting twined mats, looped bags cordage, and other essential artifacts. This all unfolded within the broader economic and ecological contexts of the Middle Preceramic, a time of significant shifts in consumption patterns and resource intensification dynamics (Beresford-Jones et al., 2021). These included an increased reliance on pelagic or pelagic-consuming marine resources, accompanied by the growing importance of cultivated food crops, not least high-protein beans. Throughout wetland resources, Scirpus and Typha complemented and enabled the harvesting technologies of Preceramic marine-based diets. Their exploitation doubtless shaped and influenced socio-economic structure. The multi-functional significance of both Scirpus and Typha plants may have promoted more efficient harvesting practices, assisted by their overlapping seasons for both food and fibers. This might have encompassed strategies such as seasonal, rotational harvesting practices alongside other mechanisms for regulating resource access and utilization, thereby enabling the hunter-gatherers of La Yerba II and III to manage these critical wetland resources adeptly and sustainably.

Bast fiber yarns at La Yerba are likely to be of Asclepias spp. (milkweed), or a closely related plant of the dogbane (Apocynaceae) family (Endress et al., 2014). This family includes a number of climbing vines of the tribe Asclepiadeae native to Peru, such as Asclepias curassavica and Funastrum clausum, recorded today in the Ica Valley (Whaley et al., 2019).

As hinted at by vernacular names such as “white twine vine,” “silkweed,” and, in Peru, “algodóncillo” (little cotton) and “flor de seda” (silk flower), plants of the Apocynaceae family have long been an important resource for fiber production throughout the Americas (Whiting, 1943). This plant yields copious seed floss – also known as vegetable silk or milkweed floss that can be harvested in late autumn, although at La Yerba people used the plant to produce fibers from the stems and not from the seeds.

Although Asclepias spp. seed pods have been reported at a number of Preceramic sites on the central (Patterson and Moseley, 1968; Cohen, 1978) and northern coasts of Peru, including at Huaca Prieta (Bird et al., 1985; Splitstoser et al., 2016), information on the use of its bast fibers is limited. Bird et al. (1985, p. 14) notes that “(Asclepias fabrics have) not made entirely of these fibers suggest(s) that either the supply was limited or that it was not very satisfactory.” We suggest, however, that the under-representation of Asclepias bast fibers in the archaeological record may be a problem of identification. Since these fibers are processed differently compared to those of cf. Scirpus and cf. Typha, their quality and color are also very different. Spliced fine Asclepias bast fibers look white and fluffy to the naked eye, so their initial classification is rather problematic. Even under low-definition microscopy, noting any residues of plant tissues and assigning them to a plant family without reference material is challenging. It is only when fibers are examined under a high-definition microscopy camera that we can make accurate observations of nodes (dislocation) and cross-marking in the fibers, these being key features for the classification of Apocynaceae bast fibers (Figure 5). These features of Asclepias bast fiber make spliced yarns from them all too easily mistaken for cotton (G. barbadense), so we suspect that some yarns and fibers previously identified as cotton without careful observation under a high-definition microscopy camera and proper contrasting with distinctive G. barbadense fibers (the seed fibers of which have, for instance, no nodes and dislocation features) may well be made of Asclepias.

Here, we emphasize riparian and estuarine habitats not only for the critical fiber plants they provided for fabric technologies but also for starchy foods for the Middle Preceramic coastal hunter-gatherers at La Yerba II and III. Before they were utterly changed by agriculture and the removal of much of their riparian woodlands, these offered very different floral and faunal landscapes from those that prevail today (Beresford-Jones, 2011). We suggest then that the spatial and ecological relationships that Preceramic people established with these habitats through the changing seasons helped define their patterns of occupation here.

Estuaries and coastal wetlands provided significant biomass of the low-ranked resources, such as the edible rhizomes of Cyperaceae esculentus and other plants of cf. Scirpus and cf. Typha (cf. Santoro et al., 2017). These were harvested, processed, and consumed probably by grinding them into flour or pounding them to extract the starch. Many mortars (batanes) have been recovered from La Yerba contexts (Figure 7). Such starch-rich food likely played an important role in coastal hunter-gatherers' diet and subsistence economy, not least likely to dilute the nitrogen load of very high-protein marine diets (cf. Speth and Spielmann, 1983; Dillehay, 2017; Beresford-Jones et al., 2018, 2021). For plant fiber technologies, evidently, coastal wetlands were ecological points that provided critical raw materials for the development of fiber production, specifically the bast fibers of cf. Scirpus and cf. Typha. These plants were harvested and processed to extract the strong fibers which were then spliced to create threads of varying thickness, as explained in the next section. Additionally, estuaries are composed of fine sediments that offer habitats for fish spawning, such as lisa (Mugil cephalus), which can be easily trapped as river levels fall, alongside habitats vital for nesting, breeding, and spawning of various coastal fauna and stopping points for migratory shorebirds. These ecological phenomena generally occur in summer when estuarine levels are high. Estuarine rhizomes provided an important dietary supplement alongside other food sources, including fish, shellfish, game, and foraged plants, together enabling sustainable human subsistence alongside marine, lomas fog oasis, riverine oasis, and estuary environments.

The utilization of riverine and riparian resources, however, must have required careful management and adaptation to the arid environment to ensure the sustainability of water and ecosystem resources in this challenging desert landscape. Along the river floodplains or other areas with groundwater sources, riparian vegetation is densely concentrated, providing habitats for hunted game, leguminous Prosopis woodlands with edible fruit, and a host of valuable resources, such as bottle gourd (Lagenaria sp.) for fishing floats or diverse containers; flexible willow (Salix humboltiana) wood for house construction and wood for fuel, and Apocynaceae vines for bast fibers. More widely, riparian vegetation performs important ecological functions, including serving as terrestrial and aquatic habitats, ensuring stream-bank stability, and providing natural corridors for larger migratory wildlife (Beresford-Jones, 2011).

Somewhat further afield from estuarine and riverine oases, Middle Preceramic patterns of marine hunter-gatherer occupation at La Yerba were also shaped by their interdependence with ephemeral winter-blooming lomas (Eichler and Londoño, 2013; Beresford-Jones et al., 2018). Lomas habitats provided seasonally critical terrestrial resources, including starchy rhizomes and land snails (Bostryx sp., 25% of total mollusc assemblage by MNI at La Yerba II), alongside hunted guanaco (Lama guanicoe), deer (Odocoileus virginianus), and vizcachas (Lagidium viscacia), all noted in the midden remains of both La Yerba II and III. Engel (1957, p. 275) suggests that Tillandsia sp. plants from fog oases were sources of fibers, although without providing much detail or evidence for the idea. Presumably, he meant fibers stripped from their leaf rosettes, but we have no evidence of distinctive Tillandsia trichome cells in plant fibers from La Yerba II or III. However, lomas habitats, nonetheless, required another set of ecological knowledge, where the temporality of subsistence strategies merged with seasonal exploitation of coastal resources through alternating cycles of austral winter and summer.

We invoke the concept of “craft specialization” to reflect how bast fiber technologies–encompassing an array of techniques, tools, and gestures–comprise a comprehensive technological system that fosters a sense of community by bringing together skilled bodies, specialized knowledge, and plant materials into an intricate chaîne opératoire. In both instances of La Yerba II and La Yerba III, this technological framework yielded social and technological advantages. It is likely that individuals within these groups organized various activities: tending aquatic environments, propagating resources, and collecting edible and fibrous raw materials in conjunction with other coastal activities in seasonal rounds like fishing, diverse seafood collection, hunting, and other terrestrial foraging. While we infer that social groupings within these societies might have organized themselves according to age, skills, and social identities, there might be other, even less visible, social categories that also defined roles in these ancient societies.

It has long been assumed that women played a significant–albeit not exclusive–role in these social dynamics in activities such as monitoring, picking, weeding, watering, watching, trimming, tending, and replanting plants (e.g., Reiter, 1975; Binford, 1982; Jochim, 1988; Hastorf, 1998). As Hastorf (1998, p. 77) notes, women were likely consistently and intimately engaged in the task of plant tending, nurturing, and the earliest forms of plant management, emerging from their primary engagement with the foraging of wild plant resources. While Hastorf primarily discusses plant domestication and cultivation for food purposes, she also highlights the broader importance of plants in early human societies, including their roles in technology, medicine, and so on. Indeed, gender almost certainly emerges as a crucial social category in the context of early bast fiber production. This significance is not necessarily restricted to the physical fabrication of artifacts but, rather, to the wider potential roles women may have played in nurturing wetlands, estuaries, and riverbanks as productive zones for both food and raw materials, within the context of Middle Preceramic lifestyles along the southern coast of Peru.

While roles often stereotypically ascribed to women, such as plant gathering, weaving, and plant tending, were once perceived as secondary contributions to the past economy and, therefore, less defining of social life, such notions have long been challenged (see, e.g., Mason and Hather, 2002). We suggest that on the Pacific coast of South America, bast fiber production, if anything, occupied a central position within the social, economic, and ecological relationships of the long Preceramic Period. Conceivably, most craft production toward the creation of bast fiber artifacts was carried out by women, with children and older adults perhaps also contributing in various capacities. We refrain, however, from proposing a strict binary division of labor between men and women (e.g., Jochim, 1988). Nonetheless, our perspective serves to underscore the need to shed further light on women's often less visible roles in the Preceramic Period without embracing axioms calling for new theoretical perspectives beyond the binary women/men division of society.