The fossil record of hominids provides evidence for evolutionary processes that ultimately defined and shaped humanity. The record documents the emergence of bipedalism, the origin of the genus Homo, the initial utilization of tools made of stone, the gradual increase in brain size, the appearance of the present-day humans or Homo sapiens, and the development of advanced tools and cultural values. According to the National Research Council (2010), the evolutionary events described in geological records coincided with significant changes in Eurasian and African climate. Hence, they raise the possibility that past environmental features controlled or affected major junctures in the evolution of humans. Nevertheless, the specific impacts of the environment on the evolution of hominids remain speculative due to the current absence of a complete understanding of ancient climates and accurate hominid fossil records (National Research Council, 2010). Therefore, the topic on ‘climate’s effects on human evolution’ was selected because it presents an exciting opportunity for investigating the role of climate on biodiversity and human evolution. Most importantly, this research aims at shedding light on the forces of evolution that allowed people to become distinctively human. Consequently, the study examines the theory that many of the adaptations found in humans developed due to the effects of climate.
The duration of hominid evolution coincided with various climatic fluctuations. Evidence for the climatic changes that have occurred in the past can be found in oxygen isotope records derived from the measurement of oxygen in fossilized foraminifera’s skeletons. The measure allows researchers to identify changes in glacial deposits and global temperature over time. For instance, scientists have discovered two major trends: a significant degree of climatic fluctuations and decrease in global temperature over time (“Climate Effects,” 2016). In addition, the isotope records have shown that the variability level of environmental conditions increased considerably during the last phases of human evolution. Also, large-scale changes in precipitation and temperature occurred during hominid evolution causing “shifts from grasslands and shrub lands to woodlands and forests, and also from cold to warm climates” (“Climate Effects,” 2016). The effects of such climatic modifications occurred unexpectedly and, hence, raised the level of uncertainty and instability in the hominids’ survival conditions. Scientists have proposed various hypotheses aimed at explaining the early humans’ reaction to such uncertainties and instabilities. The savanna theory, for example, argues that adaptations like tool-making and upright walking occurred due to the spread of dry habitats and grasslands (“Climate Effects,” 2016). Thus, many human adaptations evolved in the East African savanna or occurred due to environmental pressures associated with expanding dry grasslands. The adjustments included genetic adaptations that allowed humans and other species to cope with rapid shifts in climatic conditions. Therefore, climatic modifications and the resulting organism adaptations helped to increase biodiversity in different habitats.
Researchers have also put forward the variability selection theory to explicate the response of organisms to climatic alterations. The hypothesis contends that organisms evolve unique behaviors and structures that allow them to colonize new environments (“Climate Effects,” 2016). Accordingly, the development of such characteristics improved the early humans’ capacity to cope with environmental diversity, habitat modification, and change in weather patterns. Overall, environmental records and hominids’ fossil records show that human ancestors evolved over a period of considerable environmental variations. Thus, changes in past climates shaped the adaptability of early humans and influenced human evolution significantly.
In conclusion, this study has supported the theory that many of the adaptations found in humans developed due to the effects of climate. For instance, the fossil record of ancient humans provides adequate evidence for the evolutionary processes that culminated in the emergence of Homo sapiens. Oxygen isotope records have also provided valuable evidence for the climatic modifications that have occurred in the past. The records have shown that significant climatic fluctuations and temperature declines during the last phase of human evolution helped to increase human adaptability. As such, the findings have supported evolution-related hypotheses such as the savanna theory and the variability selection theory. Accordingly, the view that key adaptations in human evolutionary history emerged in reaction to variability selection and environmental variations increases the understanding of the effect of climate on the evolution of humans.
References
Climate effects on human evolution. (2016). Retrieved from http://humanorigins.si.edu/research/climate-and-human-evolution/climate-effects-human-evolution
National Research Council. (2010). Understanding climate’s influence on human evolution. Washington, DC: National Academies Press.
