Abstract
The traditional concept of long and gradual, glacial-interglacial climate changes during the Quaternary has been challenged since the 1980s. High temporal resolution analysis of marine, terrestrial and ice geological archives has identified rapid, millennial- to centennial-scale, and large-amplitude climatic cycles throughout the last few million years. These changes were global but have had contrasting regional impacts on the terrestrial and marine ecosystems, with in some cases strong changes in the high latitudes of both hemispheres but muted changes elsewhere. Such a regionalization has produced environmental barriers and corridors that have probably triggered niche contractions/expansions of hominin populations living in Eurasia and Africa. This article reviews the long- and short-timescale ecosystem changes that have punctuated the last few million years, paying particular attention to the environments of the last 650,000 years, which have witnessed key events in the evolution of our lineage in Africa and Eurasia. This review highlights, for the first time, a contemporaneity between the split between Denisovan and Neanderthals, at ~650-400 ka, and the strong Eurasian ice-sheet expansion down to the Black Sea. This ice expansion could form an ice barrier between Europe and Asia that may have triggered the genetic drift between these two populations.
Highlights
Long-term climate changes have been proposed as one of the main driving mechanisms of speciation, extinction, adaptation and changes in the distribution of animals and plants (Darwin, 1859; Gulick, 1872; Vrba, 1995; Cowling et al, 2008)
This review aims to provide, based on relevant palaeoclimatic records, a comprehensive overview of the nature, timing and frequency of the African and Eurasian environmental changes that have characterized the past 1 million years (Myr)
West and eastern African regions climate changes led to an opposite vegetation response: glacial and interglacial, and probably stadial and interstadial, periods were respectively contemporaneous with the expansion of grasslands and woodland development
Summary
Long-term climate changes have been proposed as one of the main driving mechanisms of speciation, extinction, adaptation and changes in the distribution of animals and plants (Darwin, 1859; Gulick, 1872; Vrba, 1995; Cowling et al, 2008). Climate change would create new ecosystems where the best adapted species would survive (natural selection through competition; Darwin, 1859). It has been proposed (deMenocal, 2011) that during the Quaternary, starting at 2.58 million years ago (Ma), periods of dryness in Africa coinciding with the largest northern hemisphere glaciations led to the appearance of new morphological traits in grassland bovid species, and hominin speciation and extinction and, the emergence in Africa of the small-brained Homo (H. erectus) at 2 Ma. the pervasive orbitally driven growth and decay of continental ice-sheets during the Quaternary resulted in sea-level changes and consequent shifts in the configuration of the continents. The recurrent emergence of land bridges and continental shelves during glacial periods provided
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