Understanding Climate's Influence on Human Evolution (2010) / Chapter Skim
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3 The Research Vision–Priority Research Themes
3 The Research Vision–Priority Research Themes
Pages 44-57
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From page 44... ...
The dominant environmental signals over the past several million years have been the global cooling trend, the growth of polar ice sheets, the climate variability at orbital-variation timescales (20, 40, 100, and 400 ky) as reflected in glacial/interglacial and monsoon cycles, and the existence of millennial-scale variability and abrupt changes.
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From page 45... ...
. Despite this broad understanding of the history of global environmental change, there is limited understanding of the regional environments in which hominins evolved, and an incomplete understanding of the processes that have forced these global and regional climatic and environmental changes over the past 8 Ma.
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From page 46... ...
, which have potential to offer critical tests of the climate-evolution relationship; • stratigraphic and geochronologic limitations; • the rarity of quantitative paleoenvironmental records situated close to fossil localities; and • the need for broad application of newly-emerging techniques for quantitatively and accurately reconstructing past climates. The central goal of the research activities encompassed by this research theme is to make substantial progress in overcoming these limitations and to introduce novel analytical approaches that build upon the existing scientific foundation, thereby enabling rigorous tests of how human evolution and the adaptability of our own species have been shaped by climate change.
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From page 47... ...
Hypotheses of how climate change affected evolution generally start by correlating patterns of evolution recorded in continental basins with marine or lake climate records that are located hundreds or thousands of kilometers away. Identification of such broad correlations has stimulated productive research, but these largely independent efforts have yielded fossil samples and climate records that are distant from one another, unable to be analyzed quantitatively, or are otherwise inadequate to address critical questions about evolutionary processes (see, e.g., Barnosky, 2001)
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From page 48... ...
• Close the geographic gap in the study of evolution and climate by obtaining high-precision climate records in close proximity to locations where the evolutionary events in question are recorded. Although progress has been made concerning certain hypothesized linkages between climate and evolution, many of the specific relationships and processes are largely unknown and/or untested, e.g., the relationship between global climate change and local environmental effects; the causal processes that relate climate and evolutionary change observed at specific sites; and the precise temporal expression of novel behaviors and ecological interactions in early humans as these may relate to climate.
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From page 49... ...
The second -- and related -- priority is to develop high precision records of climate change from long stratigraphic sequences proximal to hominin sites and, simultaneously, to expand lake and ocean drilling efforts that will be essential to integrating the local climate records from hominin sedimentary basins with regional and global records. By bringing together environmental records at diverse geographic scales the climatic forcing factors that relate global, regional, and local climate can be investigated and better understood.
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From page 50... ...
This overall approach, in which projects are unified by shared strategic goals, requires unprecedented collaboration across disciplines and encourages the development of innovative scientific tools and data exchange. THEME II: INTEGRATING CLIMATE MODELING, ENVIRONMENTAL RECORDS, AND BIOTIC RESPONSES The integration of physical and biotic records of past environmental change with regional climate modeling studies offers considerable potential for an improved understanding of the causes of the changes, as a basis for exploring specific questions concerning potential connections between environmental changes and hominin evolution and dispersal.
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From page 51... ...
Both kinds of modeling have been applied in the past, and can form a starting point for future experimentation. Major initiatives linking climate models and environmental records have contributed significantly to our understanding of the causes and patterns of climate at particular times, for example, during the mid-Holocene (6 ka)
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From page 52... ...
(2006) examined the probable climatic impact of the uplift of mountain ranges associated with the East African Rift System (EARS)
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From page 53... ...
Last Glacial Maximum time, compared with (A) modern-day vegetation distribution reconstructed from remotely sensed data.
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From page 54... ...
Although these largely marine-based environmental records of global and regional trends, along with sparse terrestrial records from Africa and Eurasia, indicate large changes in climate during this time window, the details are obscure. Climate models for the pre-Northern Hemisphere ice sheet expansion period (the 8- to 4-Ma interval)
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From page 55... ...
For example, climate models have proven to be quite accurate in their ability to predict middlelatitude and tropical monsoonal responses to orbital forcing, the critical factors that might have triggered the onset of high-latitude glaciation, and the cause of the dramatic shift in equatorial ocean temperatures that may have had major consequences for tropical and subtropical climates. The great challenge will be to study the combination of these processes, including multiple experiments with different greenhouse gas levels to take into account uncertainties in CO2 concentrations at this time, and uncertainties about the degree of ocean transport through
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From page 56... ...
With improved density, accuracy, and dating of environmental records during this period, there is a major opportunity to use climate models to ask more detailed questions and to obtain more detailed information about both the climate and vegetation comprising hominin habitats. In particular, the availability of accurate estimates of atmospheric CO2 will permit simulation of both the direct effects of greenhouse gases on climate (and vegetation)
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From page 57... ...
There is evidence of megadroughts in tropical Africa between 135 ka and 90 ka, a period that preceded the dispersal of humans out of Africa around 60 ka and their widespread movements thereafter. It will be possible to use climate models, focusing primarily on the known orbital forcing and known glacial boundary condition forcing (ice sheets, sea level, CO2 level)
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