Defenders of evolution commonly make the assertion that biogeography provides unequivocal support for neo-Darwinian theory. For example, the pro-Darwin National Center for Science Education (NCSE) claims that "consistency between biogeographic and evolutionary patterns provides important evidence about the continuity of the processes driving the evolution and diversification of all life, " and "[t]his continuity is what would be expected of a pattern of common descent."
The reality, however, is that the NCSE has dramatically overstated its case.
In making its case for common descent, the NCSE essentially ignores the numerous and significant examples where the biogeographical evidence does not fit well with purported "evolutionary patterns." In other words, they cherry pick the data and ignore examples where there are great discontinuities between biogeography and neo-Darwinism. One of the most significant discontinuities, the origin of South American monkeys ("called platyrrhines"). The NCSE made a specific argument for common descent based upon the "continuity" and "consistency" between biogeography and evolution. The evidence presented below refutes their assertion.
In its response regarding marsupials, the NCSE admits, "If the [North American] opossum truly had roots in Australia, it would indeed be a biogeographic conundrum." Since North American opossums are not descended from Australian "possums, " their high morphological similarity dictates to neo-Darwinian evolutionists that this must be another case of extreme convergent evolution that challenges the methodology by which neo-Darwinism infers homology and common descent.
But what if North American opossums were descended from Australian possums? Why does the NCSE observe that this hypothetical situation would pose a "biogeographic conundrum?" The NCSE says this because there would be no route by which Australian possums could have migrated to North America. The NCSE's reasoning here is sound: they presume that if organisms in Locale B are descended from organisms in Locale A, then there must have been some migration route by which organisms could migrate from A to B. If there is no such route, then we're presented with, in the NCSE's own words, a "biogeographic conundrum." Using such reasoning, the NCSE then argues that marsupials and other groups have biogeographic histories that are congruent with the tectonic history of islands and continents, thus allegedly supporting common descent:The same pattern of diversification and migration seen in marsupials can also be seen in other groups of plants and animals. That consistency between biogeographic and evolutionary patterns provides important evidence about the continuity of the processes driving the evolution and diversification of all life. This continuity is what would be expected of a pattern of common descent, and is not what would be expected with the creationist orchard scheme. With marsupials, the NCSE claims that the "continuity" of geography and evolution predicts that there will always be some land bridge or migratory pathway which terrestrial organisms can follow. This was claimed to allegedly show "consistency between biogeographic and evolutionary patterns" that demonstrates "what would be expected of a pattern of common descent." Ignoring the NCSE's continued inappropriate usage of the "creationist" label, their claim is simply not true, for there are many examples of terrestrial organisms existing and appearing in locations where no land-based migratory route is apparent. The NCSE's approach is to cherrypick examples to support their arguments for universal common descent, but a large number of "biogeographic conundrums" that challenge neo-Darwinism could be discussed.