This is a really important article in that it shows how modern scientific tools and techniques can be used to cast surprising light on the assumptions and conclusions [myths?] that are often drawn from the limited set of evidence archaeologists have to work with. In this case, the numerous ancient Indus sites discovered along the Ghaggar-Hakra riverbed to the east of the Indus river led many to think it was the ancient Sarasvati River that must have flowed during the period (and has led to renaming by some of the ancient Indus civilization to the ancient Indus-Sarasvati civilization).

Instead, as the author's summarize in their conclusion, "our results firmly rule out the existence of a Himalayan-fed river that nourished Indus Civilisation settlements along the Ghaggar–Hakra palaeochannel. Instead, the relict Sutlej valley acted to focus monsoon-fed seasonal river flow as evidenced by very fine-grained sediments in the upper part of the valley-fill record. This and the potential to pond flood waters in the topographic depression formed by the valley likely offered favourable conditions that led Indus populations to preferentially settle along the incised palaeovalley. We find that river dynamics controlled the distribution of Indus sites in the region, but in the opposite sense to that usually assumed: it was the departure of the river, rather than its arrival, that triggered the growth of Indus urban settlements here. We posit that a stable abandoned valley, still able to serve as a water source but without the risk of devastating floods, is a viable alternative model for how rivers can nucleate the development of ancient urban settlements," (p. 12).

Elsewhere they make it clear that this paleo-channel, while it shows that "a major river system once flowed across the Kalibangan area" (p. 6), also "suggest that cessation of major fluvial flow along the entire length of the palaeovalley commenced at ~12–15 ka [roughly 10,000-13000 BCE] and was complete shortly after ~8 ka. [roughly 6000 BCE]" (p. 8). The authors taken on this "paleochannel" [a remnant of an inactive river or stream channel that has been filled or buried by younger sediment], and using all sorts of techniques that compare sediments drilled from different periods in the paleochannel including remote sensing, show that it was once where the Sutlej river flowed - thousands of years before ancient Indus times. The research provides evidence that the abandoned river channel created a stable environment, reducing the risk of flooding and enabling long-term settlement.

The second point in their conclusion needs to be re-emphasized, for although a large number of Indus settlements have been found along the Ghagar-Hakra paleochannel, they show how Indus people were able to use smaller water flows, monsoon-driven in an area that was less susceptible to the flooding and other shifting geographies in the Indus basin, to build villages, towns and even larger cities like Ganweriwala (where first excavations began in the summer of 2024).

Besides debunking myths, the article shows again how sophisticated ancient Indus people were when it came to water management and exploitation, and their adaptability to different kinds of circumstances. Climate change and shifts in monsoon patters after 2000 BCE may well have played a role in the civilization's decline, but it would not have been the only factor. This counter-intuitive influence of river morphodynamics underscores the complexity of human-environment interactions in ancient civilizations like the Indus and highlights the importance of interdisciplinary approaches in unraveling these relationships.

Images: 1. Fig. 1 Topographic map showing northwestern India and Pakistan, key Himalayan rivers and the distribution of urban-phase Indus Civilisation settlements. Note how Indus urban-phase settlements are not necessarily located along modern Himalayan river courses. The most prominent cluster of sites occurs located on the drainage divide between the Sutlej and Yamuna rivers, an area devoid of perennial Himalayan drainage. Base digital elevation map is derived from NASA Shuttle Radar Topography Mission (SRTM)53. Site locations are from the compilation of urban-phase Indus settlement locations collated in Possehl86. Inset locates figure in south Asia.
2. Trace of Ghaggar–Hakra palaeochannel on northwestern Indo–Gangetic plain. a Background shows Landsat 5 TM colour composite mosaic (bands 456). The Ghaggar–Hakra palaeochannel is visible as a sinuous, dark blue feature. Location of GS core sites adjacent to the Indus urban centre of Kalibangan, along with core sites at KNL1, MNK6, and SRH5, are also indicated. Location of key Indus urban settlements indicated by triangles. b Geomorphological map showing major alluvial landforms in the study region. Ch, Chandigarh; HFT Himalayan frontal thrust.