Tectonics and human evolution

The Red Sea, Coastal Landscapes, and Hominin Dispersals

“…In the African Rift, which is one of the largest and longestlived tectonic structures on the planet, the particular style of tectonics results in the creation and continuous rejuvenation of complex landforms comprising near-vertical fault scarps, lake basins, numerous volcanic cones, extensive lava flows, and a swarm of minor faults and surface irregularities, all of which provide exactly these sorts of topographic opportunities for gaining tactical advantage and protection at the edges of the herbivore-rich savannah plains. As we have recently argued (Bailey et al, 2000;King and Bailey, 2006), the occurrence of some of the earliest and most concentrated fossil and archeological evidence of human evolution in the African Rift may not be merely a coincidence of geological visibility and survival of evidence, but may instead reflect the impact of a distinctive set of topographic conditions that exercised a powerful selective impact on the human evolutionary trajectory with its emphasis on meat-eating, an extended childhood, and wide-ranging bipedalism. Moreover, the sorts of topographic features resulting from active tectonics provide not only tactical advantage in scavenging and hunting, they also create localized basins that trap sediment and water, ranging from the largest lakes of the African Rift to small bodies of water in collapsed calderas, resulting in pockets of fertility of greater or lesser extent, which can sustain plant and animal life even in otherwise relatively arid and disadvantageous climatic conditions.…”

“…We describe this topographic complexity as topographic 'roughness', a 'rough' surface in this context being an irregular 'corrugated' surface at any geographical scale in contrast to a smooth and flat one. Described in this way, relative roughness can be measured and mapped over large areas using satellite imagery and digital elevation data (see King and Bailey 2006, figure 8a, for a simple example on a global scale using SRTM [Shuttle Radar Topography Mission] 30 data). The basis of the technique lies in the measurement of slope angles from relative height data and the mathematical transformation of this information using Fourier transforms to further smoothe the data for the purpose of creating a colored or shaded map.…”

“…It is one of several significant obstacles cutting across 'savannahstan' (Dennell and Roebroeks, 2005), a broad swathe of herbivore-rich savannah and grassy plains that began to extend over a vast area stretching from West Africa to China with climatic cooling from at least 2.5 Mya, and a key macro-environmental context for early hominin dispersal 1 . However, this concept of the Red Sea Basin as a barrier should not obscure the fact that its coastal regions also hold considerable potential attractions for early human settlement, especially under climatic conditions wetter than today, including a complex tectonic and volcanic topography not unlike that of the African Rift, capable of providing localized fertility for plant and animal life, tactical opportunities for pursuit of herbivores and protection from predators (King and Bailey 2006), along with inshore and intertidal marine resources.…”

Environments, Adaptation, and Evolutionary Medicine Should We Be Eating a Stone Age Diet?

“…The potential variability of hominin environments is supported by palaeoenvironmental data that indicate the availability of a wide range of habitats at many Plio-Pleistocene localities, including woodlands, grasslands and tropical forests [28,[36][37][38][39][40][41]. African environments altered considerably over time, partly in response to global climatic trends [16,42] but also due to regional processes, like tectonic activity [43,44]. A single species, such as Paranthropus boisei, with a relatively extensive geographic range and a long tenure in the fossil record would have been required to survive in different habitats and 'ride out' numerous environmental fluctuations [35,45].…”

Edaphic and Topographic Constraints on Exploitation of the Central Kenya Rift by Large Mammals and Early Hominins

“…This apparent association between Rift environments and finds of early hominins has given rise to the notion that there may be a causal relationship between the two phenomena, with the distinctive dynamics of rifting acting as a key agent in evolutionary change through one of three possible processes: (1) directly at a macro-geographical and temporal scale through the introduction of major barriers that have served to isolate populations along divergent evolutionary pathways (vicariance hypotheses, Coppens, 1994;Lewin & Foley, 2004); (2) indirectly by amplifying spatial and temporal variability in climate and vegetation (hypotheses of mosaic environments and variability selection, Potts, 1996Potts, , 1998Kingston, 2007;Maslin et al, 2014;Trauth & Maslin, 2009); or (3) directly but at a more localised spatio-temporal scale by the creation of a complex and dynamic regional topography that afforded opportunities for the evolution of the distinctive human niche with its emphasis on meat-eating, bipedalism and an extended period of juvenile dependency (the complex topography hypothesis or tectonic landscape model, King & Bailey, 2006;Winder et al, 2013). However, establishing robust correlations between environmental variables, especially features of the physical landscape, and distributions of fossil or archaeological sites has well-known difficulties: of accurately reconstructing ancient landscape features in regions subject to ongoing geological change; of biases introduced by differential deposition, preservation, exposure and discovery of bones and stones; of chronological correlation between disparate and stratigraphically unrelated features; and of integrating processes that operate over widely divergent spatio-temporal scales.…”