Creation, Flood and Biogeography: Part 3

Effects of the Flood on Biogeographic Distributions

We have no information about the distributions of plants and animals at creation. The flood would have destroyed whatever distributional patterns might have been present. Most present species distributions probably do not date back further than the Biblical flood. We will examine how the flood might have influenced the distributions of various types of living organisms.

Starting Points for Dispersal

After the Flood, groups of organisms would begin to reproduce and disperse from the locations where they were preserved during the Flood. Terrestrial vertebrates that were preserved in the ark would disperse from Southwest Asia after the Flood. Marine and freshwater plants and animals would disperse from many different locations around the world, depending on where the survivors were found. Terrestrial invertebrates would disperse from their own refugia, perhaps logs or rafts of vegetation that had become beached as the waters receded.

There are far more species of invertebrates than of terrestrial vertebrates, and far more organisms would have survived the flood in aquatic refugia than in the ark. Predicting the distributional patterns of the surviving invertebrates would require knowledge of the locations of the various aquatic refugia. This information is not available, and creationary biogeographers have not attempted to propose where such refugia might have been. The situation is different for the terrestrial vertebrates, which are thought to have dispersed only from the ark. An important research goal of creation biogeography is to explain the distributions of terrestrial vertebrates as the result of dispersal from the ark, which is believed to have landed in Southwest Asia.

Dispersal Processes

 

Barriers. Members of a species tend to increase their distribution by dispersing until they encounter a barrier. A barrier is any environmental obstacle that prevents an organism from dispersing further. For marine organisms, oceans provide dispersal corridors while land masses act as barriers. For terrestrial organisms, oceans act as barriers while land masses act as dispersal corridors. Salinity, temperature differences and substrate type may produce impassible barriers for aquatic species, while moisture, temperature differences, availability of food, and topography may produce important barriers for terrestrial species.

 

Active and passive dispersal. Dispersal may be active or passive. Active dispersal means intentional locomotion by individuals seeking to enter new territory. Active dispersal may be accomplished by walking, flying, or swimming. Passive dispersal means transport by other organisms or by physical forces. Passive dispersal may be accomplished by wind, water currents, or transport by other organisms.

 

Ocean currents. If the surface of the earth was largely, or entirely, covered by water simultaneously during the Flood, powerful oceanic currents would be expected to develop. These would probably form a circum-global equatorial current along with one or more circular currents called gyres, rotating clockwise in northern hemisphere and counter-clockwise in the southern hemisphere. In the absence of exposed land, these powerful oceanic currents might flow at speeds of hundreds of miles per hour, and might transport organisms over long distances. During Miocene sedimentation, a circum-global equatorial current is believed to have passed between North America and South America and between Eurasia and Africa. This was probably near the end of the Flood, or possibly even after the Flood, and could have provided a means of dispersal that is no longer available.

 

Clues from islands. Islands provide information on the relative dispersal abilities of different groups. Not all islands are equal in their potential for information about dispersal. Continental islands are separated from the mainland by shallow water, and were connected to the rest of the continent at a time when sea level was lower than at present. Continental islands typically have abundant diversity, including freshwater fish. Examples of continental islands include Java, Trinidad, Britain, and Ceylon. Changes in sea level would also explain former land connections between North America and Asia. These considerations imply that past conditions were different from those of today. Species on continental islands probably arrived by the same dispersal methods used by these same species today.

 

Volcanic islands probably represent areas that formed during or after the flood, and have never been connected to any continent. Species found on volcanic islands must have dispersed across part of the ocean. Examples include certain types of plants and invertebrates, as well as birds, lizards and some bats. Volcanic islands rarely have land mammals, and almost never have native amphibians or primary freshwater fish. These observations indicate that the best dispersers to islands are those that can travel over the sea itself, such as certain plants, or through the air, such as flying animals and members of the “aerial plankton” such as tiny spiders. Lizards and other kinds of organisms that are able to grasp vegetation or hide inside rotten logs may occasionally be able to raft to islands, and are intermediate in dispersal ability. The least able dispersers to islands are those groups unable to survive in salt water, such as primary freshwater fish and amphibians. Mammals that cannot grasp vegetation are not good dispersers to islands beyond at most a few kilometers from a source area.

 

Some present insular distributions seem very difficult to explain. For example, iguanid lizards are found from South America to southern North America, and also on Madagascar, Samoa and Fiji. It appears that these lizards somehow dispersed from South America to Fiji. This seems impossible at the present time, but past conditions may have been different. Perhaps the flood resulted in large numbers of floating islands of plant material that might have been carried by ocean currents to various parts of the world, transporting various kinds of plants, invertebrates and lizards with them. This might have been enhanced by the circum-equatorial ocean current thought to have existed before closure of the Panamanian land bridge and the collision of Africa with Europe.

Patterns of Distribution

A global Flood would greatly alter the distributions of species and groups. Some species would be greatly reduced from their former distributions. Others might be transported to new areas where they would increase their distribution. These processes might produce any of the three basic distribution patterns: widespread, narrowly endemic, or disjunct.

 

Plants, invertebrates, and aquatic and marine organisms that survived through the Flood might be expected to have distributions that appear relictual. That is, their present range may be much more restricted than their fossil distribution. The flood might destroy most individuals of such a species, but leave isolated populations of survivors, perhaps in areas distant from the ark. This process could produce disjunct distributions if the species survived in more than one region. Some possible examples might include groups now restricted to the southern hemisphere, such as Nothofagus trees (present in South America and the Australian region), Araucaria trees (present in South America and the Australian region), characiform fish (present in South America and Africa), pleurodiran turtles (present in South America, Africa, Madagascar and Australia), and pipid frogs (present in South America and Africa). Alternatively, the species might be a restricted endemic if it survived in only one isolated location. Some examples might include the Australian lungfish (Neoceratodus), the New Zealand frogs, (Leiopelma) and the New World snapping turtles (Chelydridae).

 

The Flood might have produced cosmopolitan distributions also, most likely among pelagic groups such as foraminifera, algae, and some fish such as lantern fish. However, post-flood dispersal could also produce cosmopolitan distributions, and it might not be possible to distinguish between the two historical processes.

 

Conclusions

 

Biogeographic distributions have been influenced by both historical factors and current ecological conditions. Much of biogeography can be explained in the context of the biblical account of creation and the flood, keeping in mind that creationist theory includes formation of large numbers of groups of locally adapted species from a created ancestor, and that the animals that depended completely on the ark for protection through the flood are the terrestrial vertebrates – those that breathe through nostrils and walk on the ground.[1] Some biogeographic problems are without answers at present. For example, neither creationists nor evolutionists have provided a satisfactory explanation for this question of how certain South American mammals dispersed to that continent before it was connected with North America. Perhaps future fossil discoveries will help provide tentative answers. In the meantime, biogeography remains a fascinating topic for study.

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L. James Gibson

Geoscience Research Institute

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[1] Genesis 7:22

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