Because Zhejiang belongs to a coastal province, its wide coastal lowland plain areas were significantly affected by Holocene sea-level fluctuations. In particular, the distribution of prehistoric cultural sites on both sides of Hangzhou Bay was strongly influenced by sea-level change. In areas to the north of Hangzhou Bay, research on Holocene sediment and transgression of the Hangjiahu Plain show that (Yan and Shao, 1989; Zhu et al., 2003), the largest transgression since the Holocene occurred prior to 7000 cal. a BP. After 7000 cal. a BP, the plain has experienced an obvious process of regression-epeirogenesis into the southeast. The area to the east and south of the Jiaxing-Majiabang-Chongfu-Changanzhen line was a neritic environment at that time, while the area to the west of the line and to the Luojiajiao site was also in a coastal marsh environment (Yan and Hong, 1987), being unsuitable for human settlement. Therefore, there were no prehistoric cultural sites found earlier than the Majiabang cultural period in the Hangjiahu Plain until now. By around 6000 cal. a BP, the coastline of eastern plain had advanced rapidly to the west of the Haiyan-Zhapu line, and the southern coastline had also advanced to the south of Yuhang (Yan and Huang, 1987). During this period, the Majiabang cultural sites were widely distributed in the Hangjiahu Plain, but the outboard area of paleocoastline, which was located to the east of the Haiyan-Zhapu line and to the south of Yuhang, did not have any distribution of Majiabang cultural sites at all. After 5000 cal. a BP, the Hangjiahu Plain had all become land locked, as it is today, and the area around Hangzhou City also ended the history of estuary depositional environments in the Liangzhu cultural period (Cai, 2001), as evidenced by the dense distribution of Liangzhu cultural sites in the coastal lowland of the eastern plain and the Hangzhou surrounding areas during this period. But in the Maqiao cultural period, cultural sites were greatly reduced in the coastal lowland of eastern Jiaxing and northeast Hangzhou. This might be related to a sea-level rise event between 4000-3000 cal. a BP (Chen et al., 2008).

In areas to the south of Hangzhou Bay, there was primarily a process of regression-epeirogenesis in the Ningshao Plain since the Holocene (Feng and Wang, 1986; Zhu et al., 2003). Correspondingly, the spatial distribution of prehistoric cultural sites gradually concentrated from the valley basin and hilly area of central Zhejiang during the Shangshan cultural period to the estuary and coastal plain area during the Kuahuqiao and Hemudu cultural periods. From the chronology, sedimentary stratigraphy and micropaleontology analysis of the Kuahuqiao site (30°08′42″N, 120°13′02″E, and 4.0 m a.s.l.) and the Xianghu section (30°08′36″N, 120°12′58″E, and 5.0 m a.s.l.) in the south bank of the Qiantang River of the west Ningshao Plain, as well as the Hemudu site (29°58′N, 121°22′E, 2.4 m a.s.l., and 75 km away from the Kuahuqiao site) in the east Ningshao Plain (Figure 5), we can see that neritic facies can be compared between the sediments below the Hemudu cultural layer and the accumulations above the Kuahuqiao cultural layer in the middle of the Xianghu section and the Kuahuqiao site. This means that the neritic sediments of the aforementioned three sites were formed as the products of contemporary transgressive processes, and also that the largest transgression of the Ningshao Plain since the Holocene should have happened between 7500-7000 cal. a BP. The first high sea-level since the Holocene might have occurred around 7500 cal. a BP in this area, and was close to or slightly higher than the modern sea-level at that time (Zhu et al., 2003; Gu et al., 2005; Zong et al., 2007; Shi et al., 2008). The geographic location of the Kuahuqiao-Xiasun site, and its marine bed above the cultural relics with the chronological evidence confirmed the occurrence of high sea-levels and a transgressive event in the middle-late stage of Kuahuqiao Culture (Shu et al., 2010), catching a glimpse of traces from the Qiantang tidal bore between 7500-7000 cal. a BP (Shi et al., 2008). This might be the important reason that cultural sites between the end of Kuahuqiao cultural period and the beginning of Hemudu cultural period about 500 years later have not been found in the Ningshao Plain. The Hemudu cultural sites appeared in the mid-east region of Ningshao Plain after 7000 cal. a BP, when the phase of low sea-level just occurred (Li et al., 2010), which was consistent with the sea-level changes in areas to the south of the Hangzhou Bay. From the comparison and formation analysis of “Event layers” (i.e. the cultural intermittent layer formed by fluviation) included in many typical archaeological strata in the Ningshao Plain (Shi et al., 2008), it can be seen that many archaeological strata of cultural sites have “Event layers” during 6000-5500 cal. a BP and 5000-4500 cal. a BP in this area. This may be associated with the rise of groundwater level or surface water expansion caused by some short scale sea-level fluctuations. The temporary migration phenomena of ancient humans may have occurred during the formative period of “Event layers” (Sun, 2002). This is another phenomenon that is worthy of attention. The cultural layer with the depth of 100-500 cm of HI core in the Hemudu site showed that the site area has formed land with lower sea-level between 6955±130 cal. a BP and 5330±130 cal. a BP. However, the Xianghu section of Xiaoshan displayed the depositional feature of tidal-flat facies during this period. This shows that even in the phase of regression, there still existed certain differences of sedimentary environment between the east and the west of the Ningshao Plain, reflecting the complexity of regional coastline changes.

Zhejiang is located in the coastal zone belonging to the eastern part of the East Asian monsoon region, and is one of the areas most sensitive to climate change in the world (Ma et al., 2009; Liu et al., 2010). Global climate change is often manifested in these sensitive areas first. The Qianmutian peat humification records of Mt. Tianmu in northwest Zhejiang and records from the muddy area on the inner shelf of the East China Sea outside the Oujiang River estuary reveal the process of Holocene climate change in Zhejiang region (Ma et al., 2009; Liu et al., 2010; Figure 6). The previous studies indicate that, between 8400-6300 cal. a BP, the East Asian winter monsoon was strong and volatile, but the temperature was higher on the whole in the region; while vegetation was mainly north subtropical forest represented by Quercus-evergreen, Castanopsis/Lithocarpus and Tsuga type (Xu et al., 2010), indicating that the environment was relatively humid as a whole in this period. During 6300-3500 cal. a BP, the summer monsoon precipitation was at a high value as a whole with a weakened winter monsoon. During the later stage of this period, the climate fluctuated greatly, among which, around 4200 cal. a BP, monsoon precipitation intensity declined rapidly, reaching the driest period around 3700 cal. a BP and then rising again rapidly (Ma et al., 2009). The environmental characteristics of this period (i.e. around the 4000 cal. a BP climate event) were of global significance (Cullen et al., 2000; Bond et al., 2001; Wu and Liu, 2004; Booth et al., 2005; Shao et al., 2006; Huang et al., 2011; Wu et al., 2012a). After 3500 cal. a BP, summer monsoon precipitation intensity was weak in the mass, but the winter monsoon was fluctuating and strengthened continuously from 1400 cal. a BP. There were also several small-scale dry-wet fluctuations in this period, and the climate environment generally presented a tendency of becoming colder and dryer.

In comparing the climate changes and prehistoric cultural changes in Zhejiang region (Table 1), we found that the time phase was consistent between prehistoric cultural changes and climate changes. During 8400-6300 cal. a BP, when the climate gradually developed from relatively cool and wet to warm and humid, it experienced the rise of Kuahuqiao Culture, Majiabang Culture and Hemudu Culture were successively. This might be related to the gradual coming of the climatic optimum warming period. The climate warm period between 6300-4200 cal. a BP was roughly corresponding to the active era from the Songze Culture to the Liangzhu Culture. Meanwhile, there were numerous cultural sites appearing in vast areas of Zhejiang region, showing the thriving development of prehistoric cultures. This might be related to the regression process during this period. The occurrence time of the climate transitional period between 4200-3700 cal. a BP was just in conformity with the disappearance of Liangzhu Culture and the rise of Maqiao Culture. During this period, the number of cultural sites was greatly reduced, with the phenomenon of living space contraction, cultural property change and cultural recession. These all might be related to the 4000 cal. a BP abrupt change of climate (Cullen et al., 2000; Bond et al., 2001; Wu and Liu, 2004; Booth et al., 2005; Shao et al., 2006; Huang et al., 2011; Wu et al., 2012a). These phenomena indicate that there were internal relationships between the prehistoric cultural vicissitude and climate changes.

5.3.1 Impact of climate on production activities of prehistoric culture in Zhejiang

From archaeological data, the prehistoric cultural vicissitude of Zhejiang region was accompanied by a certain change of production activities (Jiao, 2010). Represented by some early Neolithic cultures, in particular the Shangshan Culture and the Xiaohuangshan Culture, rice cultivation had become a part of economic activity, and there were long-term settled villages with more mature technology, such as ceramics (Wang, 2006; Jiang and Sheng, 2007). The Kuahuqiao Culture also took rice cultivation, terrestrial plant collection and animal hunting as the main forms of livelihood (Yang and Jiang, 2010), but residents had come to know and use the sea at that time. The Kuahuqiao site unearthed the earliest canoes, indicating that Kuahuqiao people had begun to use boats (Zong et al., 2007). However, this period was just the initial stage of the marine economy. Marine animal remains unearthed from the site include dolphin, and sea turtle, etc. in small amount (ZPICRA, 2004), which indicate that the acquisition of marine animals was only the supplement of agricultural economic activities. The Hemudu cultural period entered a new marine economic development stage. Although rice cultivation, terrestrial plant collection and animal hunting were still the main economic forms during this period, the marine economy and prehistoric navigation of the coastal Zhejiang had developed to a higher level (ZPICRA, 2003). The existing archaeological materials indicate that, at least six kinds of marine animals had become regular fishing catches of Hemudu Cultural ancients, including sea turtle, whale, shark, naked top snapper, tuna and sea crab. Seashells could also be the important food source of Hemudu ancestors. More than 20% of the unearthed potteries are decorated with the shell plating at the Hemudu site. The Tianluoshan site of Hemudu Culture also found some potteries with shells. There were a number of wood pulps found in the Hemudu and Tianluoshan sites, showing that the Hemudu ancestors had been very good with boat technology (Li et al., 2010). Therefore, in the late stage of Hemudu Culture, the cultural and economic forms of Zhejiang region were changing; compared with rice agriculture, marine resources became a more important source of food. After the Hemudu Culture, the regional differentiation of Neolithic cultures emerged in the coastal area of Zhejiang, mainly reflected in the differentiation of economic forms. During the Liangzhu cultural period, inland residents still gave priority to a rice based agrarian economy, while coastal residents attached equal importance to the marine economy and the agricultural economy. Meanwhile, island residents (such as residents in the Zhoushan Islands and Nanji Islands) basically gave priority to the marine economy, and did not engage in any agricultural activity. The navigation technology of these island residents developed to a higher level, and they could often come-and-go across the islands or between island and land (Tsang, 2001; Jiao, 2007). During this period, ancestors’ further adaptation and development of the ocean pushed the marine economy and marine culture into a peak stage of Zhejiang’s prehistoric era. However, great changes took place in the economic forms during the Maqiao cultural period. In the north of Zhejiang, the proportion of rice cultivated agriculture in Maqiao Culture’s economic life was noticeably less than the Liangzhu Culture (SMCPAM, 2002). According to the minimum individual statistics of unearthed animal remains of Maqiao Culture, the number of pigs was more than cervid animals during the Liangzhu cultural period, but the number of pigs was less than cervid animals during the Maqiao cultural period, especially in the early Maqiao Culture. This indicates that, from the Liangzhu Culture to the Maqiao Culture (Table 2), ancient people’s meat resources changed from the animal husbandry as the main form with hunting as complement to the hunting as the main form with animal husbandry as complement. In the south of Zhejiang, for example, the Huangguashan Culture was distributed mainly in the coastal area of the Oujiang River estuary, although agricultural production and marine fishing still coexisted, the agricultural economy became more important, and marine economy was no longer in a leading position. The remains of rice phytolith and grain were widespread in the site formations of Huangguashan Culture, and new crops such as barley and wheat were also found in later formations (Jiao, 2010). In the animal bones unearthed from the Huangguashan cultural sites, pigs’ remains number over 25%, suggesting that livestock farming also became an important source of food (Jiao, 2007).

It can be seen from the above discussion that obvious changes took place in economic forms of prehistoric cultures in Zhejiang region around 4000 cal. a BP. The economic form mainly changed twice: the first occurred in the late stage of the Hemudu Culture, the second

was in the transition period from the Liangzhu Culture to the Maqiao Culture around 4000 cal. a BP. The root cause for this kind of economic change in production should be climate change. In the Holocene climatic optimum, the economy of original inhabitants was mainly focused around agricultural planting. This is also the important reason that these cultural forms spread along the river valleys to the eastern part with flat terrain and better hydrothermal conditions. Favourable climate and flat-fertile land are suitable for developing agriculture. In the meantime, since the study area has experienced a low sea-level phase between 7000-4000 cal. a BP (Zhu et al., 2003; Wu et al., 2012a), the sea-level dropped and the land area increased. The coastal lowland of Zhejiang was exposed, and the marine environment was open and stable, which provided good conditions for the development of marine economy and culture in this area. This kind of production pattern led to the geographical distribution pattern of island residents. However, the climate became dryer and colder around 4200 cal. a BP, and the change has reached its apex around 4000 cal. a BP. Meanwhile, the adjustment of East Asian climate system appeared, and the summer monsoon intensity declined rapidly, with the increased climate changing rate and frequent disasters. This is the widely proved “Holocene Event 3” (Wu and Liu, 2004). This climatic event led to the difference of production activity changes in different parts of Zhejiang region. In the north of Zhejiang, the main economic activities of the Liangzhu Culture were based on rice cultivated agriculture, which required higher conditions of sunlight and rainfall. The cold and drought caused by this climatic event had extremely adverse effects on rice growing. With the deterioration of the living environment, the vulnerability of Liangzhu Culture response to environmental disaster events and social crisis was greatly increased. Instead of the Liangzhu Culture, in order to adapt to climate change, especially the cool weather and possible frequent flooding events (SMCPAM, 2002; Wu and Liu, 2004), the production mode of Maqiao Culture experienced a significant change; hunting became an important production activity again. In the coastal area and southern Zhejiang, due to the impact factors of lower latitude, coastal location and terrain block, the cooling and drought of this area were less severe than the northern part of Zhejiang. Thus, the agricultural economy continued to develop. However, more and more sedimentary records of marine environment pointed out that great changes have taken place in ENSO (El Niño-Southern Oscillation) around 4000 cal. a BP during the Holocene (Clement et al., 2000; Cole, 2001; Barron and Anderson, 2011; MacDonald, 2011). The coral records of Galapagos Islands and New Guinea indicate that the El Niño event was very weak before 4000 cal. a BP, and ENSO only had regular but very weak seasonal cycles; but after 4000 cal. a BP, the El Niño event was significantly stronger, and the obvious interannual variability of ENSO masked the weak seasonal changes (Tudhope et al., 2001; Riedinger et al., 2002). The interannual oscillation of El Niño and La Niña made the emergence of frequent alternation between typhoon-storm surges, monsoon weakening-droughts and other disasters in the west Pacific region (Sandweiss et al., 1996; Xia, 1997; Rodbell et al., 1999). It was not until 3000 cal. a BP that this oscillation enhanced to the current level and tended to be stable (Riedinger et al., 2002). This was undoubtedly a huge blow to marine economic development of southeast coastal residents in the Maqiao cultural period. It was quite clear that, in the prehistoric coastal economic activities during this period, the significant increase in the proportion of agriculture and livestock, and the decline of marine economy, were the result of the ancient peoples’ adaptation to the deterioration of the coastal marine environment. The agricultural economy revived again and became the important production activity. The adjustment of the above production mode means there were major changes in the activity areas of prehistoric cultures.

5.3.2 Impact of climate on the activity areas of prehistoric culture in Zhejiang

The previous discussion shows that the climate optimum of Zhejiang region was between 8400-4200 cal. a BP. During this period, the Majiabang Culture, which originated from the Taihu Lake Basin, settled in northern Zhejiang, and expanded rapidly, forming the Majiabang-Songze-Liangzhu cultural system. The climate was generally warm and wet with little fluctuation during this period. Therefore, the agricultural based Majiabang Culture and Songze Culture gradually expanded to the eastern coastal areas, and then occupied the vast Hangjiahu Plain. Meanwhile, the Hemudu Culture of indigenous origin in southern Zhejiang developed in the Ningshao Plain, and gradually diffused to the southeast coastal area. In addition to rice farming, terrestrial plant gathering and animal hunting, marine economic modes and prehistoric navigation developed to a higher level. During the Liangzhu cultural period, prehistoric cultures in Zhejiang reached their apex. The settlement sites not only extended all over the mountains, valleys and plains, but also were widely distributed in the lower coastal areas and offshore islands. This phenomenon that the sites generally diffused to the east coast were associated with the development demands of the northern rice agricultural economy and the southern marine economy, which responded to the relatively stable climatic environment during this period. However, after the 4000 cal. a BP abrupt climatic event, the number of settlement sites declined sharply in Zhejiang region, and the activity areas of prehistoric cultures shrunk dramatically. Especially, the number of sites reduced substantially along the broad coastal zone, and all the sites in offshore islands disappeared at the same time. This showed that prehistoric residents changed their production mode in the Maqiao cultural period. In northern Zhejiang, the main economic form of Maqiao Culture turned to hunting and gathering activities again, with atrophy of rice agriculture. But in the southern Zhejiang, due to the marine economic decline of each prehistoric culture, the agricultural economy became the more important production activity again. The common result brought by two different modes of production and economic transitions of the north and south Zhejiang region, was the termination of the eastward expansion of prehistoric cultures to the coastal zone sustaining more than 7000 years in Zhejiang region.

Thus it can be seen that these two significant expansions (i.e. the Majiabang-Hemudu cultural period and the Liangzhu cultural period) and a significant contraction (i.e. the Maqiao cultural period) of prehistoric cultures were positively correlated with the climate environment in Zhejiang region. This has much in common with many modern theories about the influence of climate environment on the early human civilization (Cullen et al., 2000; Polyak and Asmerom, 2001; Núñez et al., 2002; Haug et al., 2003; Yasuda et al., 2004; Booth et al., 2005; Turney and Brown, 2007; Chen et al., 2008; Liu et al., 2010; Wu et al., 2010, 2012b; MacDonald, 2011).

According to the above discussion, it can be found that the climate change triggered changes of production-life styles and economic forms, and these induced prehistoric inhabitants to change their area of activity, even brought on the rise of a new cultural form. Therefore, climate change was the important inducement of the prehistoric cultural change in Zhejiang region, which showed great influence on the distribution, diffusion, expansion and evolution of the prehistoric cultures.