Impact of the Great American Interchange on Evolution Research Paper

Pages: 5 (1472 words)  |  Bibliography Sources: 6


[. . .] If these theories are true, then the evolutionary impact of the Panamanian bridge is far more complex and layered than the traditional theory states.

A third challenge to the traditional equilibrium theory is the belief in other sources of migration, which would lessen the impact of the Panamanian bridge on the evolution of animals by placing it in the context of several types of migration. For example, some experts believe some of the diversification may have actually been caused through migration over water through "rafts" or floating rather than or in addition to the natural Panamanian bridge (MacFadden 164). This is because rodent and primate fossils that originated outside of South America prior to the Great American Interchange have been found in South America (MacFadden 164). If this theory is true, then some of the evolutionary impact on species in South America would come from the sea and some of that impact would come prior to 3 -- 4 million years ago, rather than exclusively from the Panamanian bridge 3 -- 4 million years ago. The questions and controversies challenging the traditional theory of the Great American Interchange are not necessarily fatal to the traditional theory; rather, they expand, deepen and place that traditional theory in context as we amass more knowledge about pre-History.

3. Conclusion

The Great American Interchange was a migration of Northern or Nearctic species to South America and migration of Southern or Neotropic species to North America. According to traditional theory, it was accomplished due to the rise of a natural Panamanian bridge between North and South America 3 -- 4 million years ago. The migrations are traditionally believed to be essentially equal, according to the equilibrium theory. In addition, the traditional theory finds that Northern species evolved and survived in greater numbers after migrating to South America because of prior migrations from larger land masses and easier acclimation to South America's climate.

As experts deepen their knowledge through new discoveries, they challenge the traditional theory. The belief that the migration was basically equal has been challenged by discoveries showing several migrations over different periods from the North to the South. The traditional theory has also been challenged by discoveries showing several migrations over different periods from the South to the North. A third challenge to the traditional theory has come from the discovery of rodents and primates in South America who must have arrived by water before the Panamanian bridge arose, which points to migrations by water. As the number of discoveries increases and contradicts the traditional theory, the theory is actually deepened, expanded and placed into greater context of pre-History. Given later discoveries, it appears that there were multiple migrations at different times from North to South, South to North and over water, all combining to create a bionic soup of species, some of whom evolved and survived successfully and some of whom did not.

A researcher in this field should seek data on long-term studies of known animal species. The research currently seems legitimate but piecemeal and limited by time. A long-term study seems necessary to answer evolution questions. In addition, a researcher should add more experimental factors in the field to narrow down the possible evolutionary explanations and perhaps even arrive at a single explanation supported by all the data. Conducting experiments in a long-term study is the ideal, of course. There would be serious questions about the available resources for such extensive research.


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Perini, FA, CA Russo and CG Schrago. "The Evolution of South American Endemic Canids: A History of Rapid Diversification… [END OF PREVIEW]

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