1) Research objectives and background 

[Research objectives] 

 The Indus civilization (2600BC−1900BC) is known for its cultural and technological achievements including its characteristic seals and scripts, fortified settlements and drain systems. Indus cities and cultures spread over 680,000 km² along the Indus and Ghaggar-Hakra River and into Gujarat in Western India, yet its urban phase lasted for only 700 years, much shorter than any of its contemporaries. This project aims to investigate the causes of this rapid decline of the civilization from the perspective of human-environment interaction. Drawing on various disciplines of both natural and human sciences, we compose social and environmental histories of key Indus civilization cities and their vicinities in order to determine whether and which environmental factors were the causes of their short life and rapid decline. 

 In order to fully grasp the causes of the decline, we find it important to look at the civilization in a wider context, both in space and time. For this reason we investigate diverse natural environment surrounding the civilization on one hand, and the history of the long-term climate change in South Asia on the other. The relationship of the societies and cultures of the Indus civilization with those of other ancient civilizations is also being investigated, side by side with their relationship with the post-Indus societies and cultures of South Asia. 

 

[Significance of our project with regard to global environmental problems] 

 The investigation of the relationship between global climate change and the rise and fall of ancient civilizations attracted many scholars around the world. As mentioned below some scholars hypothesize that the impact of abrupt climate change caused the decline of the Indus civilization, but actually there has been no reliable data to test this hypothesis. In this regard our research is a pioneering work; we provide detailed data on long-term climate change in the whole of South Asia for the first time. In addition, we investigate some regional environmental changes which might have made a significant impact on the civilization. By putting together the outcomes of these researches we will enhance our understandings on the relationship between both long- and short-term environmental changes and human civilizations, and thus make a contribution towards solving some key issues of current global environmental problems. 

 

[Background] 

 The supposed impact of environmental change on the decline of the Indus civilization has been studied from two different perspectives. The first group of researchers proposed that the main causes for the decline were local. There have been several different theories based on this local hypothesis — e.g. Wheeler’s Aryan invasion theory and Raikes’ flood theory. The second group of scholars, on the other hand, examined the issue from the global level. They focused their study on the global climate change observed during mid- and late Holocene. They claim that the Old World, especially Asia, witnessed a collapse of agriculture-based societies including the Indus societies during mid- and late Holocene which was coincidental with the abrupt climate change mentioned above. The past decades have seen a revival of ‘environmental determinism’ in palaeo-environmental research, with palaeo-climate shifts implicated in the collapse of many past civilizations. We do not accept the environmental determinism proposed by many scholars engaged in global-level analysis, but we also consider that it is important to integrate the outcomes of palaeo- environmental researches in South Asia into our project. Our standpoint is that we need to look at both local and global levels. 

 Furthermore, we consider that past theories, in general, are too simplistic and too narrow in scope. They failed to see the diversity of both natural and social environments of the Indus societies, and, as a result, failed to grasp the complexity of the process of the so-called decline in each region. This is why we emphasize the importance of looking at the process in a much more wider context on one hand, and much more in detail in the target regions on the other. 

 

2) Research methods and organization 

[Research methods] 

 As mentioned in 1), we combine the research methods of various disciplines of both natural and human sciences. For each key issue we collaborate the research outcomes of different research groups. 

 As for the reconstruction of the natural environment of the Indus civilization, various geoscience methods are employed to investigate both long-term climate change and regional environmental changes. The subsistence systems, which may have been subject to the influence of global climate change as well as regional environment changes, are being studied through ethno-botanical and archaeo-botanical analysis. 

 As for the reconstruction of socio-economic and cultural aspects of the civilization, we employ various methods of humanities: archaeological methods to recover cultural artefacts from the archaeological sites, and linguistic and anthropological methods to discover characteristics of the Indus societies at different levels. These methods are also useful to understand the relationship between Indus societies and other ancient civilizations. 

[Research organization] 

 We have five working groups; (1) palaeo-environment research group (PERG); (2) material culture research group (MCRG); (3) subsistence system research group (SSRG); (4) inherited culture research group (ICRG); and (5) DNA research group (DNAG). 

(1) PERG aims to investigate: (a) long-term climate change in South Asia, using core samplings from Rara Lake in the Lesser-Himalayan region and reconstructing the Asian monsoon by  chemical index of alteration and other proxies; (b) the palaeo-channel of the Ghaggar-Hakra River through the analysis of satellite imagery and field research including the dating of sand dunes; (c) sea-level change along the coastline of Gujarat during the Indus period through the analysis of satellite imagery, hydro-isostatic modeling and geological/topographical analysis; (d) local climate changes through the oxygen isotope analysis of otolith recovering from Indus sites in Gujarat; and (e) palaeo-seismological analysis for understanding the impact of earthquakes. 

(2) MCRG excavated two sites in India, i.e., Kanmer (Kachchh, Gujarat) and Farmana (Rohtak, Haryana). The members uncovered a number of structures including a citadel with stone walls, a large burial ground, plant and animal remains, and diverse artefacts such as pottery, ornaments, and Indus seals/sealings with and without Indus scripts. They analyze these data to reconstruct the society and culture of each region, as well as trade and other networks which united these regions with other regions within and outside the civilization. They also gather supplementary data on other Indus sites both in India and Pakistan. 

(3) SSRG reconstructs the subsistence systems of the Indus civilization by analyzing archaeo-botanical data obtained from Indus sites and ethno-botanical data found mainly in present-day Maharashtra and Karnataka. Their fieldwork focuses on the study of distribution and characteristics of emmer and Indian dwarf wheat, both of which were found in many Indus sites and must have been main winter crops during the Indus period. 

(4) ICRG reconstructs the history of the Indus societies using linguistic methods. The members of the Indologist subgroup analyze Vedic and Mesopotamian cuneiform texts, while those of the linguistic subgroup use comparative methods to reconstruct the substratum cultures and languages of South Asia. They have produced Language Atlas of South Asia which shows the distribution of modern South Asian languages, and on the basis of this atlas they have started to make maps showing the distribution of key cultural vocabulary of the Indus civilization. 

(5) DNAG was formed in 2009 when a huge amount of human bones were found in Farmana. The members have been working on cow and human bones in order to reconstruct the genetic histories.

For the first two years the central activities of our project were to excavate Kanmer and Farmana in India to collect archaeological data. Through this process we obtained a huge amount of data which helped us depict a detailed picture of the societies and cultures of the two contrasting regions — one along the coast of Gujarat and the other along the Ghaggar-Hakra River in Haryana — of the Indus civilization. 

What have been uncovered from these sites include: a number of structures including a citadel with stone walls, plant and animal remains, and diverse artefacts such as pottery, ornaments and others. At Kanmer we have found three sealing like pendants with Indus scripts (reported in Science Vol. 328 on May 28, 2010) and other Indus seals with and without Indus scripts — which provide important data for continued efforts to decipher the Indus writing system. At Farmana, we discovered a large-scale burial ground which has rarely been found in Indus sites except at Harappa. Each of these findings has made a significant contribution to our understandings of the societies, cultures and subsistence systems of the Indus civilization. They show that there existed strong regional differences within the civilization, as well as trade and other networks which united different regions within and outside the civilization. Detailed analysis of these data has been conducted by the members of MCRG. Part of the outcome of their analysis was published in the final report on Farmana excavation in March 2011. The rest will be published in the final report on Kanmer by February 2012. 

In the third and fourth years, our project members worked in collaboration to reconstruct: (1) long-term climate changes in South Asia; and (2) the history of regional environment surrounding Kanmer and Farmana where excavations were conducted. The objectives of these researches are to assess the impact of climate changes in South Asia, and of local environmental changes, on the societies and subsistence systems of these regions during the Indus period. 

(1) As regard the reconstruction of long-term climate changes, PERG conducted coring from Rara Lake in the Lesser-Himalayan region in 2009. They have been analyzing the monsoon pattern of the last five thousand years by using chemical index of alteration and other proxies. The preliminary analysis has shown that: (a) 6 intervals of weak summer monsoon events during the Mid-Late Holocene centered at 0.7, 1.1, 1.5, 2.7, 3.3, and 4.3 cal ka BP ; and (b) the summer monsoon became stronger when the Indus civilization was on decline. 

(2) Our research on regional environmental changes centers around two issues: (a) the avulsion of the Ghaggar-Hakra or the old Sarasvati River, and (b) the palaeo-coastline of Gujarat. The research on these issues have mainly been led by the members of PERG, but linguistic analysis of Vedic texts and Mesopotamian cuneiform texts conducted by ICRG have greatly assisted to put the outcomes of their researches in proper contexts. 

(a) The first issue concerns the long-standing debate about the Ghaggar-Hakra River, identified as the mighty Sarasvati River in the Rig-Veda text. Many Indian scholars have thought that it was a big river as described in the Vedic text, and together with the Indus River it supported the agricultural systems of the civilization. Our PERG team, however, established through the dating of sand dunes that during the Indus period no part of the Ghaggar was much bigger than today’s Ghaggar which is rather a small river highly affected by monsoon. Professor Maemoku presented a paper on this issue in the AGU Chapman conference in March 2011. His view was subsequently reported in Science Vol. 332 on April 1, 2011. 

(b) The second issue concerns the history of trade networks within and outside the Indus societies. Sea trade between Indus regions and the west has been reconstructed to some extent by the study of Mesopotamian cuneiform texts. Furthermore, from the artefacts discovered at sites in Gujarat such as Lothal, we can clearly see that they functioned as centers of trade with Mesopotamia and Africa during the Indus period. PERG examined the sea level change of Lothal by means of hydro-isostatic modeling and geological/topographical analysis. They have found that due to the gradual fall of sea level, this important seaport became out of use in the first millennium BC. This suggests that regional environmental change was responsible, at least to some extent, for the decline of trade along the coast of Gujarat. 

As regards networks between different Indus regions, our MCRG team has discovered ample examples for giving us a detailed picture of how such networks functioned at different levels. To supplement their findings, recent study by Dr. Randall Law of University of Wisconsin-Madison depicts complex trade routes of different types of mineral resources such as limestone, steatite, carnelian, lapis lazuli, etc. from the places of origin to big cities like Mohenjodaro, Harappa, Dholavira and others. This clearly shows that inter-regional trade networks were highly active during the Indus period. Law’s voluminous work has been published as part of our RIHN-Manohar series in August 2011. 

The regional variation of the Indus societies and cultures is in part the reflection of the enormous diversity of natural environment across different regions of the civilization. The Indus civilization regions comprise the so-called Yellow Belt in the west where agriculture is largely dependent on irrigation systems, and the Green Belt on the northeast where agriculture depends on monsoon, dissected by the dry Thar Desert where the current annual rainfall is less than 100 mm. It seems that the climate during the Indus period was much the same as it stands now. Based on the analysis of archaeo-botanical data obtained from Indus sites SSRG has found that the Indus civilization could be divided into three regions in terms of crops — the winter crop region in the west, the summer crop region along the coast of Gujarat and the mixed crop region in the northeast. Furthermore, Dr. Mallah, a core member of our project in Pakistan, discovered new Indus sites in the western rim of the Thar Desert where the climate is very dry. This suggests that some pastoralists lived even in the desert area during the Indus period. In general, the decline of the Indus civilization seems to coincide with the shift of human habitation from the winter crop region to the mixed crop region. 

The agricultural systems are highly dependent on main crops. Wheat and rice coexist in South Asia. The domestication of rice in India is still a matter for debate. We have found some rice remains both at Farmana and Kanmer but whether they belong to the Indus period or not has not yet been confirmed. Wheat, on the other hand, was clearly predominant at Harappa and other sites along the Indus River, i.e. in the winter crop region. Among different sub-species of wheat, (Indian dwarf wheat), the remains of which were found in several Indus sites, appears to be indigenous to the region and have been the main winter crop alongside of emmer wheat (which was probably brought from Africa) during the Indus period. The former sub-species was considered to have disappeared from India due to the green revolution in the late 1960’s. The members of SSRG, however, discovered that it is still being cultivated in Maharashtra and Karnataka. It is fascinating to see that India has still retained this sub-species which provides us a key to understand the Indus subsistence systems. In this regard India could be called a (residual area), as it tends to retain her tradition for a long time even in the face of globalization. Residual areas are naturally areas of diversity, as opposed to spread areas which tend to be homogeneous (Nichols 1992:193). 

To sum up, the achievements of our research teams have so far shown that there was an enormous diversity both in the natural environment and the societies/cultures of the Indus civilization, and as such, the causes of its decline are multi-dimensional. It is wrong to assume that all the Indus societies were dependent on the irrigation-based agriculture. It is natural to consider that the societies consist not only of agriculturalists but also traders, pastoralists, and even hunter-gatherers. The Indus societies must also have been multi-lingual, multi-ethnic and multi-cultural, as they had such complex and diverse trade and other networks within and outside themselves. The previous understandings of the Indus civilization were largely based on the assumption that it was analogous to the other ancient civilizations; they were also mainly based on the reports of excavations at Mohenjodaro and Harappa. Our project has presented an alternative picture of the civilization which is much more rich and diverse. 

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ACHIEVEMENTS IN FULL RESEARCH

 

Our research project examines the social character and environmental context of the Indus civilization and attempts to determine how they are related to the civilization’s short life and rapid decline. In particular, we aim to evaluate the impact of environmental change on the subsistence economy and trade network that sustained the Indus civilization’s urban system. Our research has also provided data on the long-term processes of climate change in South Asia. Such data help us develop historical perspective on, and practical understanding of, contemporary environmental problems in the region. 

The distribution of Indus cites spans a vast area beyond the Indus valley. It covers both arid and humid areas, and mountainous and coastal areas. Annual rainfall is less than 100mm in the Indus River basin and Cholistan area whereas it is more than 800 mm in the Gujarat area (see Figure 11). As far as the water management is concerned Indus societies in the coastal area were not dependent on a large river. Thus the civilization’s natural environment was not homogeneous but heterogeneous, and it is one of the key factors to understand the Indus civilization. 

As Dr. Weber (2011) pointed out the agricultural system of the civilization, in terms of crop, was not homogeneous, either. It is a well-known fact for South Asianists that the Indian subcontinent has two types of crops; Kharif (summer) crops and Rabi (winter) crops. Kharif includes rice, millets, mung bean, sesame, grams etc. while Rabi is represented by wheat, barley, lentil, peas etc. According to Dr. Weber, the Indus region could be divided into three areas; the winter crop area (mainly the present Sindh and Punjab states of Pakistan), the summer crop area (the present Gujarat state of India), and the mixed crop area (the present Haryana state of India). Crops are dependent on climate. Different crop systems of the civilization must reflect different natural environments at that time. 

As regards the study of the natural environment surrounding the Indus civilization, PERG produced a preliminary analysis of the sediment core samples obtained from the Rara Lake in Nepal in 2009. PERG has also established through the dating of sand dunes that, contrary to its description in the Rig-Veda text (which was transliterated by ICRG), the Ghaggar was not a large river, but a small one capable of providing water for agriculture only during the monsoon. Professor Maemoku of Hiroshima University presented a paper discussing the latter issue at the Chapman Conference on “Climates, Past Landscapes and Civilization” organized by the American Geophysical Union in March, 2011. His presentation was subsequently reported in Science Vol. 332 on April 1, 2011 (Figure 6). 

Another PERG team investigating the palaeo-coast of Gujarat has collected geological and topographical field data and analyzed satellite imagery. Their findings coincide with the result of hydro-isostatic modelling, suggesting that the sea level during the Indus period was two meters higher than it is in present-day Gujarat. Thus the ancient seaport of Lothal, Gujarat, an important base for trade with Mesopotamia, would have become inaccessible by the end of the Indus period. The study of cuneiform texts conducted by ICRG members and archaeological data obtained at the Kanmer site help us establish the local evidence for this historical change. 

Climate change is recently one of the most widely discussed issues - not only among environmental scientists but also among all kinds of people who are concerned about environmental problems. Staubwasser and Weiss (2006) suggest that there were abrupt climate change events such as the widespread droughts around 8200, 5200 and 4200 cal yr BP, and these events, especially the 4.2 ka event, led to the collapse of civilizations such as the Akkadian empire and the Indus cities, although “chronological imprecision for the transition from urban Harappan to post-urban remains a problem” (Staubwasser and Weiss 2006: 10). According to their scenario, the cereal agriculture was damaged by the precipitation diminution due to the 4.2 ka event, followed by the collapse of the politico-economic superstructure.

Our scenario is not as simple as this. As pointed out by Weber, there were three crop systems 

(winter, summer, and mixed) and different climate zones (arid areas as well as humid areas affected by summer monsoon) in the Indus civilization (Figure 10). The situation was quite complex, and we think it is too simplistic to conclude that an abrupt climate change event, such as 4.2 ka event, directly caused the decline of the Indus civilization. We need to make clear precisely what kind of impact climate change had on the different regions and societies of the civilization. 

As for the decline of the trade with Mesopotamia, our result on sea level change supports this hypothesis. According to PERG, the sea level during the Indus period in the coastal area of Gujarat was two meters higher than present. So during the Indus period, it must have been easy to secure ship transportation not only within Indus region but also to Mesopotamia, but this network must have been gradually out of use by the end of the Indus civilization. 

It is clear now that the Indus civilization never collapsed due to the simple event such as abrupt climate change, natural disaster including earthquake and flood, Aryan invasion, etc. 

The conclusion after our five years’ research on the causes of decline of Indus civilization is that the case of the Indus Civilization should be seen as a transformation due to population migration from Indus river basin to monsoon affected areas, rather than a sudden collapse due to some drastic natural or social events. This conclusion sounds similar to a suggestion made by Possehl (2003), but some of the proposed causes for transformation in his theory are too abstract. For example, he claims nihilism is one of the causes for the decline of civilization, but I do not think that anybody can prove this. It seems that his theory is a set of speculation based on his long personal experiences associated with the Indus civilization. Rather than making any further comments along this line, I just summarize the outcome of our project in several points, and suggest a set of criteria which would help understanding the Indus civilization. 

(1) The natural environment of the Indus civilization is diverse. The Indus civilization is not simply dependent on a large river. 

(2) The crop system of the civilization could be divided into three types: winter, summer, and mixed. 

(3) Complex trade networks existed between diverse societies within the Indus regions, and also with outside regions such as Mesopotamia. 

(4) The decline of the civilization was not caused by a single event but by multi-dimensional factors. 

From these points I propose the following criteria for understanding the Indus civilization. 

(A) Continuity vs. Discontinuity. We tend to look at the Indus society by drawing an analogy with its contemporary civilizations such as Egypt and Mesopotamia. Instead of doing this, we should rather investigate the later Indian society. I think that an analogy can be drawn not with its contemporary societies at remote places but with the later societies at the same place. 

(B) Multiplicity vs. homogeneity. The Indus society was a multi-ethnic, multi-linguistic, multi-cultural society just like the modern Indian society is. There coexisted people of diverse professions such as agriculturalists, pastoralists, merchants, artisans and so on. 

(C) Regionalization vs. Centralization. When we talk about an ancient civilization we generally focus on its centralized system rather than on its regional hegemony. The Indus society, however, had no centralized power to govern the whole region. Thus we should rather look at the society as a network of highly diverse regional hegemony. 

(D) Abrupt change vs. gradual change. General readers familiar with the literature on the ancient civilizations expect the causes of decline of civilizations to be abrupt change. Environment determinists tend to emphasize a natural collapse or disaster as a main factor while social determinists tend to think a conquest or an invasion as a prime factor. We should reconstruct the Indus society on the basis of facts. Thus we avoid putting forward a hypothesis based on environmental and social determinism.