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Modern humans evolved in Africa approximately 200,000 years ago (Campbell and Tishkoff 2010). As groups migrated out of Africa they underwent bottlenecks leading to sharp reductions in population size and genetic diversity (Amos and Hoffman 2010; Harpending and Rogers 2000; Ramachandran et al. 2005). To this day, African populations retain the most genetic diversity globally (Auton et al. 2015). In order to survive both within and out of Africa, early human populations had to adapt to their novel environments, including new food resources, colder climates, higher altitudes, and, especially, infectious diseases (Balaresque et al. 2007; Fumagalli et al. 2011). These adaptive requirements, facilitated by natural selection, led to an increased frequency of alleles that were beneficial in that environment. Due to the fact that these adaptive requirements were driven by local environmental pressures, some of these evolutionarily advantageous alleles display geographic and ancestral specificity, as observed in the genomes of present-day humans (Fumagalli et al. 2011).
The geomagnetic field extending outward beyond Earth’s solid surface encounters a strong, highly variable flow of hot ionized gas from the Sun called the solar wind. This compresses and shapes the dayside of Earth’s magnetic field. On the night (anti-sunward) side of the Earth, the magnetic field gets drawn out into a long, comet-like tail. Present evidence is that this magnetotail region extends to hundreds or thousands of Earth radii. Research over the past six decades has revealed much about the various current systems that shape the Earth’s "magnetosphere". This chapter is devoted to providing a broad overview of the individual current systems that, acting together, generate the complex and fascinating geomagnetic field.
In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean–atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010–2011, construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a nearly continuous, lacustrine/wetland sedimentary sequence that preserved evidence of past plant communities between ~140 and 55 ka, including all of MIS 5. At an elevation of 2705 m, the Ziegler Reservoir fossil site also contained thousands of well-preserved bones of late Pleistocene megafauna, including mastodons, mammoths, ground sloths, horses, camels, deer, bison, black bear, coyotes, and bighorn sheep. In addition, the site contained more than 26,000 bones from at least 30 species of small animals including salamanders, otters, muskrats, minks, rabbits, beavers, frogs, lizards, snakes, fish, and birds. The combination of macro- and micro-vertebrates, invertebrates, terrestrial and aquatic plant macrofossils, a detailed pollen record, and a robust, directly dated stratigraphic framework shows that high-elevation ecosystems in the Rocky Mountains of Colorado are climatically sensitive and varied dramatically throughout MIS 5.
Magnetospheric substorms represent the episodic dissipation of energy stored in the geomagnetic tail that was previously extracted from the solar wind. This energy release produces activity throughout the entire magnetosphere-ionosphere system, and it results in a wide variety of phenomena such as auroral intensifications and the generation of new current systems. All of these phenomena involve the acceleration of particles, sometimes up to several MeV. In this paper we present a brief overview of substorm phenomenology. We then review some of the evidence for particle acceleration in Earth’s magnetosphere during substorms. Such in situ observations in this most accessible of all cosmic plasma domains may hold important clues to understanding acceleration processes in more distant astrophysical systems.
Subject headings: acceleration of particles — Earth — solar wind
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