Understanding Evolution

Lines of evidence: The science of evolution :

Geography

The distribution of living things on the globe provides information about the past histories of both living things and the surface of the Earth. This evidence is consistent not just with the evolution of life, but also with the movement of continental plates around the world-otherwise known as plate tectonics.

marsupial distribution worldwide
 

Marsupial mammals are found in the Americas as well as Australia and New Guinea, shown in brown on the map at right. They are not found swimming across the Pacific Ocean, nor have they been discovered wandering the Asian mainland. There appear to be no routes of migration between the two populations. How could marsupials have gotten from their place of origin to locations half a world away?

Fossils of marsupials have been found in the Antarctic as well as in South America and Australia. During the past few decades scientists have demonstrated that what is now called South America was part of a large land mass called Gondwana, which included Australia and Antarctica. Click on the map below for a short animation that shows how Gondwana split apart 160 to 90 million years ago. Marsupials didn't need a migration route from one part of the world to another; they rode the continents to their present positions.

Gondwana split-up animation

 

View this article online at:
http://evolution.berkeley.edu/evolibrary/article/lines_11

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