, 1996 and Graf, 1999), but they have had a dramatic effect on river form and function. Dam effects on river Selleck LBH589 morphology and fluvial processes have become increasingly important to watershed management during recent decades. Flow regimes, channel morphology, sediment transport, and ecological processes such as the quality of riparian and aquatic habitats have been influenced by dams (Heinz Center, 2002). The downstream impact of dams is well documented (Williams and Wolman, 1984, Brandt, 2000, Fassnacht et al., 2003, Grant et al., 2003, Graf, 2006, Petts and Gurnell, 2005, Schmidt and Wilcock,

2008 and Hupp et al., 2009). Several authors have developed generalized conceptual models of the downstream effects of dams on rivers (Brandt, 2000, Grant et al., 2003 and Schmidt and Wilcock, 2008). The fundamental cause of channel change is the imbalance between sediment supply and stream flow, leading to post-dam sediment deficit or surplus and channel change that can persist for hundreds of kilometers downstream (Schmidt and Wilcock, 2008). Because of the differing degree of these imbalances (due to varying watershed, climate, and dam characteristics), channel adjustments downstream of dams are often complex. Previous

work emphasizes the variability of downstream channel response which include bed degradation and narrowing, changes in channel bed texture Everolimus or armoring, bed aggradation, bar construction, channel widening (Williams and Wolman, 1984 and Brandt, 2000), or no measurable change Reverse transcriptase (Fassnacht et al., 2003 and Skalak et al., 2009). Bed degradation, in some instances, can persist for decades and extend spatially from a few kilometers to as far as 50 km or more (Williams and Wolman, 1984). Bed degradation downstream of the Hoover Dam extended more than 120 km thirty years after dam closure (Williams and Wolman, 1984). Hupp et al. (2009) also suggest that impacts on channel morphology on the Roanoke River are measurable 150 km downstream of the dam. A

wide variety of controls have been identified that create a diverse range of geomorphic responses for channels downstream of dams (Grant et al., 2003). Previous research suggests that sediment loads downstream of dams require long distances to recover. Williams and Wolman (1984) state that the North Canadian River required more than 182 km and possibly as much as 500 km of channel distance to provide enough sediment to have pre-dam concentrations. On the Missouri River (8 km downstream from Gavins Point dam), post-dam sediment load is 1% of pre-dam conditions; 1147 km downstream of Gavins Point dam the post-dam load is only 17% of pre-dam loads (Jacobson et al., 2009 and Heimann et al., 2011). Data for the Nile River in Egypt show that 965 km downstream from the dam, post-dam loads are only 20% of pre-dam conditions (Hammad, 1972).

Mousterian assemblages in Eurasia show greater variation through space and time, but are still relatively static compared to the rapid technological changes that characterize the technologies developed by AMH. After the beginning of the Middle Stone Age in Africa about 250,000 years ago, there is evidence for a rapid and accelerating tempo of technological change among AMH populations, beginning with blade-based technologies, more sophisticated bifacial tools, the first appearance of microlithic tools, as well as formal bone,

ground stone, weaving, ceramic, and other technologies. Progressing through the Upper Paleolithic, Mesolithic, Neolithic, Bronze, and Iron ages, technological change among AMH often occurred very rapidly, marked by nearly constant find more innovation and ingenuity. Regorafenib cell line Such innovations include the first widespread evidence for art and personal ornamentation, tailored clothing, boats, harpoons, the domestication of the dog, and much more. By 10,000 years ago, humans were domesticating a variety of plants and animals independently in various parts of the world (see Goudie, 2000 and Smith and Zeder, 2014), a process of experimentation and genetic manipulation that led to a fundamental

realignment in the relationship of humans to their local environments. With better technologies and increasingly productive methods of food production (combined with foraging), human populations expanded and developed increasingly complex social, economic, and political institutions, again almost simultaneously

in multiple parts of the world. These processes fueled additional innovation and ever-greater human impacts on local and regional ecosystems. As early states evolved into kingdoms, empires, and nations, the stage was set for broader social and economic networks, leading to exchange of goods and ideas, exploration, competition, cooperation, and conflict, the results of which still play out today in a globalized but highly competitive world. Fossariinae Since the 1960s, archeologists have debated the nearly simultaneous appearance of domestication, agriculture, and complex cultures in widely dispersed areas around the world, areas with very different ecologies as well as human colonization and demographic histories. Traditional explanations for this Holocene ‘revolution’ have relied on environmental change, population pressure, and growing resource stress as the primary causes for such widespread yet similar developmental trajectories among human societies around the world (e.g., Binford, 1968, Cohen, 1977, Cohen, 2009 and Hayden, 1981; see also Richerson et al., 2001). All these stimuli may have contributed to cultural developments in various regions, but today, armed with much more information about the very different colonization, environmental, and developmental histories of human societies in various areas, such explanations no longer seem adequate.