Biogeography and Common Descent

Where animals live tracks sea depth, island order and the nearest source, as descent from local ancestors predicts. The post-Flood model claims these patterns too, through diversification within kinds, and its rafting holds up. It fails on the record: no walkable route to Australia, no marsupial fossils in Asia after the Miocene, and a one-way faunal break.

By AI (Claude Opus 5.5, thinking level unavailable) Draft:  October 2026

"there is also a relation, to a certain extent independent of distance, between the depth of the sea separating an island from the neighbouring mainland, and the presence in both of the same mammiferous species or of allied species in a more or less modified condition." — Charles Darwin, 18591

"We must explain how the marsupials left the Ark in the Middle East and arrived in Australia with little or no sign of them in between." — Michael Oard, Journal of Creation, 20252

Summary

Biogeography asks why living things are where they are.  Two accounts answer it, and each has its own article on this site.  The evolutionary account says life spread from where it already was, over long ages, filtered by seas, mountains and climate, and changed as it went.  The post-Flood dispersal model says every land animal descends from the pairs that left Noah's Ark in eastern Turkey, about 4,500 years ago on the young-earth chronology.  They reached their present homes by four routes that Dominic Statham lists:  "transoceanic transport on vegetation mats;  transport by man;  migration and partial extinction;  speciation."3  Kurt Wise and Matthew Croxton's 2003 paper is the fullest technical version.4

This page gives the verdict of each article, compares the two accounts observation by observation, and covers one pattern neither article treats on its own:  island species resemble the nearest mainland.  The findings:

  1. The geography of life shows descent from local ancestors, and both accounts now accept that. Darwin's 1859 rule, that the depth of the sea predicts which islands share the mainland's mammals, holds across all nineteen crossings measured for this site. Island species resemble their nearest mainland (Part 3), and Hawaiian lineages branch in the order the islands formed. These patterns rule out the old view that each species was created where it now lives. Neither account holds that view. Wise and Croxton claim their model "explains all the same biogeographic data evolution claims to explain," through diversification inside created kinds.4 So these patterns, strong as they are, do not decide between the two accounts.
  2. Biogeography on its own does not establish universal common ancestry. It shows filtered dispersal and descent with modification from nearby ancestors. The rest has to come from other evidence.
  3. Where the two accounts part, the post-Flood model fails on the fossil and faunal record, not on its mechanism. The land route to Australia needs a sea-level fall of 1,264 m,5 against 134 m at the last glacial maximum6 and 50 m in Michael Oard's own Ice Age model,7 and Oard has dropped the land bridge. Rafting holds up: the longest water crossing on the way is about 85 km,8 shorter than the 320 km that iguanas rafted to Anguilla in 1995, where fishermen saw them come ashore.3 The failures are elsewhere. The Paleobiology Database holds 1,219 Pleistocene marsupial occurrences in Australia, and none in all of Asia after the Miocene.9 And Wallace's Line keeps a sharp, one-way faunal break across that short gap, the opposite of what an easy rafting corridor would produce.
  4. The evolutionary account carries debts of its own. It needs four to six crossings of the Atlantic, by rodents, monkeys, tortoises, worm-lizards and skinks, over about 1,450 km of ocean on the figure its sources use,1011 and no mammal has ever been seen to cross an ocean. Its molecular dates rest on calibrations that critics inside the field, Michael Heads among them, say cannot carry the weight put on them.12 Its oldest marsupial relatives are all northern while living marsupials are southern, and that switch "remains unexplained."13 New Zealand's biota is unexplained either way.

The two articles, in one line each:

  1. Evolutionary Biogeography: What the Map of Life Shows finds Darwin's depth rule confirmed to the metre and the Hawaiian test passed, finds that the vicariance paradigm of the 1960s to 1990s failed and the field said so, and lists five real weak points (Part 1).
  2. Creationist Biogeography: The Post-Flood Dispersal Model finds rafting and rapid speciation sound, the land-bridge mechanism dead, and the missing Asian fossil trail the model's decisive failure (Part 2).

Verdict:  biogeography is strong evidence for descent from local ancestors, which both accounts accept, and weak evidence on its own for universal common ancestry.  Between the two accounts it decides one question.  The post-Flood dispersal model cannot get marsupials from Turkey to Australia in the record that exists, and its leading writer concedes both the failed land bridge and the missing trail.

Part 1: Evolutionary biogeography

Evolutionary Biogeography:  What the Map of Life Shows tests the sentence Darwin wrote in 1859 and finds it right.  Measured on modern seafloor maps, every crossing whose shallowest route lies within the 134 m glacial lowstand carries a continental fauna, and every deeper one carries a filtered fauna, with Japan at 126 m the one intermediate case.5  Distance does not do this:  Trinidad, on a 21 m sill, has South American monkeys and peccaries, and Cuba, on a 718 m sill, has no native carnivores or hoofed mammals.  Hawaiian honeycreepers, fruit flies and crickets branch in the order the hotspot built the islands,14 and that order holds even if, as the panbiogeographer Michael Heads argues, island ages give only minimum dates.12  The article is as plain about failure:  the vicariance paradigm, which explained distributions by drifting continents, lost when molecular dating came to favour, in Alan de Queiroz's words, "oceanic dispersal over tectonic vicariance as an explanation for disjunct distributions in a wide variety of taxa."15  Five weak points remain:  dispersal explanations that come cheap, with mammal ocean crossings no one has watched;  clock calibrations that critics inside the field say cannot bear the weight put on them;  New Zealand, whose land may have drowned, so that its biota "evolved largely from fortuitous arrivals during the past 22 million years" in Landis and colleagues' reading;16  a Cretaceous marsupial record that is all northern;  and De Candolle's areas of endemism, which no dispersal model obviously predicts.

Part 2: The post-Flood dispersal model

Creationist Biogeography:  The Post-Flood Dispersal Model states the model in its authors' words and tests it with two measurements of its own.  Two of the four mechanisms hold.  Rapid speciation from a few founders is well supported, and rafting is observed, accepted in mainstream work, and asked to cover only about 85 km of open water between the Asian and Australian shelves.8  Land bridges fail, since the walkable route to Australia needs a 1,264 m fall in sea level, and Oard reached that verdict first:  "The third land bridge does not seem plausible because of the many deep, wide ocean channels."7  Human transport cannot carry a fauna older than any human artifact in the same beds.  The decisive failure is the fossil trail.  The Paleobiology Database holds ten marsupial occurrences in all of Asia, every one from northern stem groups and none younger than the Miocene,9 and Oard's answer is that "a rapid migration after the Flood may have left no fossils.  After all, God was possibly directing their dispersal."17  The article credits Chad Arment, a creationist, with the best work in this literature:  his count of the marsupial record makes late placements of the end of the Flood, in his words, "highly improbable,"18 and leaves a route through Antarctica, for which, he concedes, "there would likely only be a few hundred years available between the end of the Flood and the complete isolation of Antarctica."18

Part 3: Island species resemble the nearest mainland

Neither companion article takes up the oldest form of the geographic argument, so it is set out here.  Darwin put it first among the facts about islands:  "The most striking and important fact for us in regard to the inhabitants of islands, is their affinity to those of the nearest mainland, without being actually the same species."1  His example was the Galápagos, where "almost every product of the land and water bears the unmistakeable stamp of the American continent."  He set them beside the Cape Verde Islands, which resemble the Galápagos in soil, climate, height and size, and whose plants and animals are African instead.  His conclusion:  "I believe this grand fact can receive no sort of explanation on the ordinary view of independent creation."  On his view each archipelago received colonists from the nearest land, and the colonists changed, with "the principle of inheritance still betraying their original birthplace."  He called it "an almost universal rule that the endemic productions of islands are related to those of the nearest continent, or of other near islands."

Modern work in the companion articles points the same way.  The Hawaiian lineages branch island by island.14  The four Australasian marsupial orders form one group, and its closest living relative is South American, the order Microbiotheria.19

The post-Flood model accepts the pattern and claims it.  Wise and Croxton write that "Similar taxa in geographic proximity argue against simple fixity models of biogeography," and they cite Darwin's Galápagos cases, where similar species live together "as if they were derived from the same ancestral stock."4  Their model answers with descent inside created kinds, which they call baramins:  "Because intrabaraminic diversification generates species while organisms are dispersing, the diversification/rafting model explains all the same biogeographic data evolution claims to explain."4  Statham says the same, and names the Hawaiian fruit flies and the Galápagos finches as some of the strongest evidence for "speciation within a kind (which is accepted as fact by both creationists and evolutionists)."3

So the pattern that convinced Darwin now decides against a position no one in this debate holds.  Wise and Croxton's own history of the subject tells how the fixity model of Linnaeus's day collapsed once the New World was explored.4  The pattern could separate the two live accounts only above the level of the created kind.  If kinds were created separately, nothing in the model's mechanism of diversification makes the kinds most like each other live side by side, and Wise and Croxton's argument against fixity would then apply to kinds as it once applied to species.  A creationist can reply that kinds alike in body are alike in how they travel and what they need, and so took the same routes.  Neither article tests whether kinds, as creationist classifiers draw them, nest by geography the way species do, and the question is listed under Issues.

Part 4: The observations both accounts must explain

The table sets each observation beside what each account makes of it.  The sill depths, water gaps and fossil counts were computed for the companion articles from public bathymetry and the Paleobiology Database.  Ages in years are the sources' figures.

Observation Evolutionary account Post-Flood dispersal model Which it favours
Island faunas sort by sill depth. Nineteen crossings measured: the ten whose shallowest route lies within 134 m carry continental faunas, the nine deeper ones filtered faunas.5 Darwin predicted it in 1859, by depth rather than distance.1 It holds without exception. Uses the same two routes: Ice Age land bridges over shallow sills, rafting elsewhere. Every land bridge creationist authors name is confirmed. On Oard's 50 m fall, three of the ten shallow crossings stay closed (Issue 2). Both. It rules out land bridges everywhere and creation in place.
Oceanic islands are lopsided. Remote islands have bats but no other native land mammals, and no native frogs, though introduced frogs thrive.11 A filter predicts it: only what can fly, float or survive salt water arrives. Rafting is a filter too. Wise and Croxton predict that how often a group's range is broken by ocean should follow how well it rafts.4 Both.
Island species resemble the nearest mainland. Galápagos life is American, Cape Verde life African (Part 3). Colonists from the nearest land, then modified.1 Diversification inside kinds after dispersal, claimed in the model's own words.4 Both. It counts only against creation in place, and is untested above the level of the kind.
Hawaiian lineages branch in island order. Honeycreepers, fruit flies and crickets. Potassium-argon dates give Kauai 5.1 million years and Hawaii 0.43 million, as Fleischer and colleagues report them.14 Colonisation down the chain as each island rose. Three groups give three rate calibrations.14 Heads's objection touches the dates, not the order.12 Statham cites the Hawaiian fruit flies as evidence of speciation within a kind.3 Island-by-island colonisation gives the same order on any time scale. The rates in years stand or fall with the radiometric island ages, which belong to the dating articles. The order: both. The rates: the evolutionary account, if the island ages stand.
Wallace's Line: the land route. The shallowest walkable route from the Asian shelf to the Australian shelf has a sill of 1,264 m. The first step, Bali to Lombok, has 226 m.5 Needs no land route, since Australia was reached across water. Skeels and colleagues estimate "a minimum of 381 independent colonization events across Wallace's Line."20 Fails by a factor of 9.4 against the 134 m glacial fall, and 25 against Oard's 50 m. Oard agrees: "the idea of a land bridge between Sunda and Sahul is unlikely."2 Against the post-Flood land bridge, by its own advocates' verdict.
Wallace's Line: the water and the break. The longest open-water leg on the easiest island-hopping route is about 85 km at a 50 m fall.8 In 1995 fishermen saw iguanas come ashore on Anguilla from a raft that had drifted about 320 km.3 Yet the faunas on either side stay sharply distinct. Earlier work, which Skeels and colleagues summarise, puts exchange "at least twice as high from Sunda to Sahul than in the opposite direction."20 Skeels's team explain the imbalance by the climates each side's lineages evolved in. That rests on an assumption about past rainfall, which Oard disputes.2 The distance is no problem. The break is: an easy mat corridor should leak both ways. Oard's own argument against the land bridge, that the "fauna and flora would be more homogenous between Sunda and Sahul,"2 applies unchanged to easy rafting. The mechanism favours the model. The pattern counts against it.
Australian marsupials and the Asian trail. The database holds 1,219 Pleistocene marsupial occurrences in Australia, and ten in Asia across all epochs, all from northern stem groups and none after the Miocene.9 Marsupials reached Australia by way of Antarctica, so an empty Asia is expected. But Australia's own record has a gap: Djarthia is "the oldest known Australian marsupial by 30 million years," in Beck and colleagues' figure.21 Needs a trail from Turkey and has none. Oard: "a rapid migration after the Flood may have left no fossils."17 Arment's Antarctic route has "a few hundred years."18 The evolutionary account, decisively. This is the strongest single result in the subject.
Fossil and living ranges agree. Crown marsupial genera are 94% single-continent, against 68% for Carnivora and 60% for elephants and their kin.9 Australia's living marsupials sit on an Australian fossil record. Expected. The exception is the Cretaceous: 773 metatherian occurrences in North America, 28 in Asia, 5 in Europe and none in the southern continents,9 a switch that "remains unexplained."13 Wise and Croxton put Tertiary and Quaternary rock after the Flood, which they say "might explain, for example, why all the Australian marsupial fossils are known in Tertiary and Quaternary sediments – and only from Australia."4 Arment's count favours that early placement and calls late ones "highly improbable."18 The cost is time: the whole Australian Cenozoic sequence must fit into the 4,500 years the model allows. Both, on the confinement. The Cretaceous switch is the evolutionary account's debt, and the compressed Cenozoic is the young-earth account's.
Mammals crossing oceans. Four to six transatlantic crossings by rodents, monkeys, tortoises, worm-lizards and skinks,10 over about 1,450 km.11 No mammal has ever been seen to cross an ocean. Inferred from fossils and family trees, never watched. Two primatologists replying in Science say the odds "do not decrease linearly with distance, but rather exponentially."22 The answer is time: "given enough time, many things that seem unlikely can happen."15 Needs crossings about seventeen times shorter, but many of them, in one direction, within a few centuries, and also by mammals. A debt for both: heavier per crossing for the evolutionary account, heavier in number and pace for the young-earth one.

What the table shows

The first four rows are the classical evidence, and they are strong.  They defeat the view that each species was created where it lives and the view that land bridges once joined everything.  They do not separate the two accounts now in play, because both explain them by the same means:  dispersal across filters, then descent with change from the colonists.

The next three rows are where the accounts part.  On the land route the young-earth model fails and its advocates agree.  On the water gap it does better than its critics usually allow.  On the trail it fails outright, and the only answers on offer are that fossils were not left or that God guided the animals.

The last two rows are the evolutionary account's own debts.  Its Cretaceous marsupials are on the wrong continents, and its ocean crossings by mammals are inferred and never seen.  Neither debt helps the post-Flood model, which needs the same kind of crossing and has its own compressed time to explain.

Objections and responses

  1. "Biogeography proves evolution." It proves less than that. It shows that living things descend, with change, from ancestors who lived nearby, and that barriers filtered which ancestors arrived where. The post-Flood model accepts that much for every created kind (Part 3). The case for descent across all of life, and for the time it took, has to come from other evidence, such as shared genetic errors, the order of the fossils and the dating methods. The evolutionary article says the same.
  2. "Biogeography is no evidence for or against evolution. Nelson and Platnick said so." The quotation is real and on the page cited. Their point was narrow: in 1981 little had been done to test whether the branching diagrams of related groups agree with geography. Their next words call that "a possibility that has been little studied, but one worthy of further investigation."23 Four decades of molecular work have since investigated it. The creationist article audits the passage in full.
  3. "Both sides lean on rafting, so neither can fault the other." The two sides ask for different trips. The young-earth model needs about 85 km at a time across Wallacea, less than the 320 km iguana crossing of 1995. The evolutionary account needs about 1,450 km across the Atlantic, roughly seventeen times further, and raft survival falls faster than distance grows.22 But the young-earth model needs many such trips, all one way, within a few centuries, and then needs them to stop. The two burdens are real and differ in kind.
  4. "Descent within kinds explains every pattern here, so biogeography says nothing about common descent." For the classical patterns, that is right, and Wise and Croxton say it themselves.4 Two things limit it. The claim reaches only as far as the kinds are drawn, and no one has tested whether whole kinds nest by geography the way species do (Issue 1). And it buys the patterns by moving the cost into speed. Statham counts nearly a third of the world's 1,500 known Drosophila species as Hawaiian endemics,3 and on the model those, and a continent of marsupials, arise within a few thousand years. The Creation Model of Rapid Speciation prices that cost.
  5. "God directed the animals, so the missing trail proves nothing." That may be true, and it cannot be tested, so it cannot count as evidence either way. Arment, a creationist, calls appeals to divine guidance "simply God-of-the-gaps theorizing."18 The same holds for Wise and Croxton's allowance that animals crossed "without leaving evidence of the dispersal process in the fossil record."4 Offered at the one place where the model is tested, it concedes the test.
  6. "The fossil record is too patchy to argue from a missing trail." In general, yes. Here the absence sits inside one of the best-sampled records on earth. Asia's Pleistocene beds yield deer, hyenas, elephants and early humans, and no marsupials, so the gap is in the animals and not in the digging.
  7. "Today's seafloor says nothing about the seafloor just after the Flood." Over long ages sills do move, and the evolutionary article uses its sill table only for present faunas. On a 4,500-year model the change would have to be recent and fast: Banda Sea sills shallow enough to walk soon after the Flood and 1,264 m deep now. Wise and Croxton hold that "modern continental configurations are fairly close approximations to continent/ocean relationships during times of post-Flood dispersal."4 And a drowned land bridge should leave river valleys and land sediment on the sills, which the creationist article finds absent from the Banda Sea.
  8. "Molecular dates are circular, so the dispersal results fall." Some do. Heads's critique is the strongest: "Problems with calibrating the nodes, as well as with substitution models, mean that phylogeography's claim to be able to test between vicariance and dispersal is not justified."12 It reaches the dates given for southern beech, baobabs and Madagascar's arrivals. It does not reach the branching order in Hawaii, the sill table, the frogs on volcanic islands or the fossil census, and those carry the argument on this page.
  9. "Dispersal can explain anything, so evolutionary biogeography cannot fail." The objection has force, and the evolutionary article grants it. But the depth rule could have failed. Had Cuba carried Florida's mammals, or Sri Lanka lacked India's, the first row of Part 4 would read the other way. The Hawaiian order could have failed too. The dispersal account is cheapest where it is least tested, in the one-off ocean crossings of the deep past.

Issues and unanswered questions

  1. Do created kinds nest by geography? The post-Flood model claims the nearest-mainland pattern for species inside a kind (Part 3). The test that would separate the two accounts is whether the same pattern holds between kinds, using the boundaries that creationist classifiers draw. Neither article runs it. It needs kind assignments for island and mainland groups, and a count of how often a kind's most similar kind lives on the nearest land.
  2. Oard's 50 m against the shallow crossings. At a 50 m fall, seven of the ten shallow crossings in the sill table open: Sri Lanka (3 m), New Guinea (11 m), Trinidad (21 m), Britain (30 m), Sumatra to Borneo (33 m), Bering (44 m) and Ireland (49 m, by one metre). Three stay closed: Hokkaido to Sakhalin (56 m), Tasmania (60 m) and Japan (126 m), and all three carry continental faunas.5 So on Oard's figure those faunas rafted, or the sea fell further, or the land rose, as Oard proposes for the Bering bridge.7 At Tasmania the margin is 10 m, small enough that the crust's rebound from ice and local tectonics might close it. Neither article works this through.
  3. The Cretaceous switch is not corrected for sampling. North American Cretaceous mammal beds are far better excavated than South American ones. A sampling-standardised count would show how much of the contrast between 773 occurrences and none is real. Neither article ran one.
  4. No one has modelled post-Flood ocean currents. Oard concedes that "Indian Ocean currents today would not carry a log mat from the shores of southwest Asia to Australia, but the currents were likely different early in the Ice Age."17 Wise and Croxton rest their model on currents too. Neither article found a creationist circulation model, so the model's central parameter is unconstrained.
  5. Wise and Croxton's eighteen tests are mostly unrun. They published eighteen ways their model could fail and asked creation biologists to run them. The creationist article runs the two it could check with primary data, and the model fails both. The most tractable of the rest asks whether the direction of dispersal, read from family trees and fossils, matches the direction of ocean currents.
  6. Sources not obtained or not assessed. Michael Heads's 2009 paper on primate biogeography, which asks why primates crossed oceans but never a 20 km strait east of Sulawesi, was not obtained. Flannery and colleagues' 1995 report of Holocene marsupials on Halmahera, which Oard cites, was not read. Oard's one offered sign of a route through India, "pictographs that look like kangaroos" reported from India,2 has not been assessed by either article.
  7. The fauna column of the sill table is not checked against island checklists. The depths were measured. The faunas were described from general sources, and a check against published checklists would firm up the column the depth rule depends on.
  8. Two marsupial tables, two downloads. The evolutionary article's table of all metatherians and the creationist article's table of crown marsupials come from separate database queries. Thirty-six crown-marsupial occurrences are missing from the larger download, so in three cells the smaller group shows more occurrences than the larger. No figure used on this page changes.

Verdict

The geography of life is what descent from local ancestors predicts.  Darwin made the prediction with a number in it in 1859, and it holds to the metre on modern seafloor maps.  That much is common ground.  Both accounts now explain island faunas, island affinities and island radiations by dispersal across filters and descent with change, and the post-Flood model claims these patterns in its own words.  So the classical evidence decides against the creation of each species in place, which no one defends, and leaves universal common ancestry to other evidence.

Between the two accounts, the record decides one question.  The post-Flood dispersal model has a working mechanism and nowhere to use it.  Its rafting distances are short and within what has been observed.  Its land bridge to Australia does not exist, and its leading writer says so.  And the trail its marsupials should have left across Asia is empty, in beds that preserve everything else.  The evolutionary account has real debts:  the northern Cretaceous marsupials and the mammal ocean crossings that no one has watched.  Those leave particular events unexplained.  The missing trail leaves the young-earth model's central claim, that Australia's marsupials came from Ararat within a few centuries, without evidence, and its advocates' answer, that the migration left no trace, concedes the point.

Sources

  1. 1.

    Darwin, Charles.  On the Origin of Species by Means of Natural Selection, 1st edition.  John Murray, London.  1859.  A book presenting Darwin's account of natural selection and of where living things are found.  Its chapters XI and XII make the island arguments this page compares:  the depth rule, the absence of land mammals and frogs from remote islands, and the affinity of island species to the nearest mainland.

    1. 1a.

      Chapter XII, page 395:  “there is also a relation, to a certain extent independent of distance, between the depth of the sea separating an island from the neighbouring mainland, and the presence in both of the same mammiferous species or of allied species in a more or less modified condition.” ↩ ↩

    2. 1b.

      Chapter XII, page 393:  “as yet I have not found a single instance, free from doubt, of a terrestrial mammal (excluding domesticated animals kept by the natives) inhabiting an island situated above 300 miles from a continent or great continental island”.  Page 394:  “aërial mammals do occur on almost every island.” ↩

    3. 1c.

      Chapter XII, page 393:  “Bory St. Vincent long ago remarked that Batrachians (frogs, toads, newts) have never been found on any of the many islands with which the great oceans are studded.  I have taken pains to verify this assertion, and I have found it strictly true. ... for frogs have been introduced into Madeira, the Azores, and Mauritius, and have multiplied so as to become a nuisance.”  Darwin states in the same paragraph that a New Zealand mountain frog is an exception and proposes “glacial agency.” ↩

    4. 1d.

      Chapter XII, page 397:  “The most striking and important fact for us in regard to the inhabitants of islands, is their affinity to those of the nearest mainland, without being actually the same species.”  Page 398:  “almost every product of the land and water bears the unmistakeable stamp of the American continent. ... The inhabitants of the Cape de Verde Islands are related to those of Africa, like those of the Galapagos to America.  I believe this grand fact can receive no sort of explanation on the ordinary view of independent creation”.  Page 399:  “the principle of inheritance still betraying their original birthplace. ... it is an almost universal rule that the endemic productions of islands are related to those of the nearest continent, or of other near islands.” ↩ ↩

  2. 2.

    Oard, Mike.  “The challenge of Wallacea.”  Journal of Creation 39(1):9–11.  Apr 2025.  A short Journal of Creation article on what it calls the most challenging biogeographic issue, how marsupials reached Australia across Wallacea, the island region between Southeast Asia and Australia.  It calls a land bridge between Sunda and Sahul, the Asian and Australian continental shelves, unlikely, and says that log mats after the Flood are the only viable solution it sees.  The most recent creationist statement on this problem;  this page relies on it for Oard's concessions on the land bridge and the dispersal trail, and for his critique of Skeels and colleagues.

    1. 2a.

      “Creation scientists face additional challenges.  We must explain how the marsupials left the Ark in the Middle East and arrived in Australia with little or no sign of them in between.” ↩

    2. 2b.

      Section Wallacea:  “The islands of Indonesia are separated by deep straits that are sometimes wide.  For instance, the distance between Timor and Australia is about 150 km.  So, the idea of a land bridge between Sunda and Sahul is unlikely, especially when considering the spread of land snails and other poorly-dispersing animals and insects.” ↩

    3. 2c.

      Section Wallacea:  “Also, if there was such a land bridge, the fauna and flora would be more homogenous between Sunda and Sahul.” ↩

    4. 2d.

      “First, a significantly drier climate is required for southern Wallacea than what exists today, since it receives substantial rainfall (although not as much as Sunda, northern Wallacea, and New Guinea).  Such a drier climate is an assumption of uniformitarianism.” ↩

    5. 2e.

      Section Possible creation science solution:  “First, pictographs that look like kangaroos have recently been found in India, suggesting that the marsupials passed through India to the Indian Ocean.”  Oard's note cites Robinson, Kangaroos in India?, Creation 42(3):36–37, 2020. ↩

  3. 3.

    Statham, Dominic.  “Biogeography.”  Journal of Creation 24(1):82–87.  2010 (edition of 2011).  A popular article by Dominic Statham, first printed in 2010 in Journal of Creation and reproduced as a web edition on creation.com (21 June 2011, updated 19 August 2011), based on chapter 6 of his book Evolution: Good Science? (Day One Publications, 2009).  It argues that the spread of plants and animals across the world fits a recolonisation after the Genesis Flood, and it lists four processes that creationist models use.  This page uses it as the best-known popular statement of the post-Flood model, and for its acceptance of speciation within kinds.

    1. 3a.

      “Creationist models concentrate on four main processes which are understood to have influenced post-flood biogeography:  transoceanic transport on vegetation mats;  transport by man;  migration and partial extinction;  speciation.” ↩

    2. 3b.

      “of the 1,500 known species of fruit flies (Drosophila), nearly one third of them live only on the Hawaiian Islands.  These islands are also home to more than 1,000 species of snails and other land molluscs that are not found anywhere else.” ↩

    3. 3c.

      Section opening section, before the heading Areas of endemism:  “Here, again, it is necessary to differentiate between speciation within a kind (which is accepted as fact by both creationists and evolutionists) and evolution between kinds.  Biogeography does indeed provide evidence in support of the former, and the fruit flies, snails and other molluscs found on the Hawaiian Islands arguably provide some of the strongest evidence we have of this.  Similarly, clear biogeographic evidence exists for the speciation of finches around the Galápagos archipelago, where similar but different species are found on the different islands.” ↩ ↩

    4. 3d.

      “In 1995, fisherman witnessed the colonization of the island of Anguilla in the West Indies by iguanas.  These were washed up on one of the island’s eastern beaches, having floated there on a mat of logs and uprooted trees, a few weeks after two hurricanes hit the islands of the Lesser Antilles.  Scientists believed that the iguanas had rafted 320 km from Guadeloupe.”  Statham cites Censky, Hodge and Dudley, Over-water dispersal of lizards due to hurricanes, Nature 395:556, 1998, for the event. ↩ ↩

  4. 4.

    Wise, Kurt P., and Matthew Croxton.  “Rafting: A Post-Flood Biogeographic Dispersal Mechanism.”  Proceedings of the Fifth International Conference on Creationism, 465–478.  Creation Science Fellowship, Pittsburgh.  2003.  A paper from the Fifth International Conference on Creationism, by Kurt Wise of Bryan College and Matthew Croxton.  It proposes that after the Flood, plants and animals rafted across the oceans on mats of logs and vegetation, scores six historical models against eight classes of biogeographic evidence, and lists eighteen tests of its own model.  This page uses it as the fullest technical version of the post-Flood model and for its claim to explain the same patterns as evolution. ↩ ↩

    1. 4a.

      Pages 465–466:  On the collapse of the fixity/dispersal model after the exploration of the New World. ↩

    2. 4b.

      Page 466:  “Similar taxa in geographic proximity argue against simple fixity models of biogeography (Row 5 in Table 1).  Yet, Darwin [10, Chapters 11-12] pointed out there are many cases of similar species living in close geographic proximity (e.g., similarities between South America and the Galapagos Islands) – as if they were derived from the same ancestral stock.” ↩

    3. 4c.

      Page 469:  “Many terrestrial organisms may have rapidly migrated from the ark to the rafting 'launch' points, crossed the oceans on the rafts, and established themselves at huge distances from the ark without leaving evidence of the dispersal process in the fossil record.” ↩

    4. 4d.

      Page 469:  “With the few exceptions noted above, modern continental configurations are fairly close approximations to continent/ocean relationships during times of post-Flood dispersal.” ↩

    5. 4e.

      Page 470:  “Because intrabaraminic diversification generates species while organisms are dispersing, the diversification/rafting model explains all the same biogeographic data evolution claims to explain – namely environmental specificity, differences of organisms in similar environments, non-global optimization, and similarity in geographic proximity (Rows 1-5 in Table 1).” ↩ ↩ ↩ ↩

    6. 4f.

      Page 473:  “This might explain, for example, why all the Australian marsupial fossils are known in Tertiary and Quaternary sediments – and only from Australia.”  The sentence follows the authors' supposition that Primary and Secondary (Paleozoic and Mesozoic) sediments are Flood deposits and Tertiary and Quaternary sediments post-Flood. ↩

  5. 5.

    Measured for the companion articles.  The sill is the deepest point on the shallowest route between two land masses:  lower the sea by that much and a walkable path exists.  It was found by a minimax-path computation on GMRT bathymetry grids, about 7.8 km per cell, and about 61 m per cell for the Bali-Lombok strait, where the coarse grid gives a shallower 290 m.  The method was implemented twice, in Deno TypeScript and in Python, and the two agree to the tenth of a metre.  The full table of nineteen crossings is in Part 2 of Evolutionary Biogeography;  the scripts are in ../creationist-biogeography/research/. ↩ ↩ ↩ ↩ ↩

  6. 6.

    Lambeck, Kurt et al.  “Sea level and global ice volumes from the Last Glacial Maximum to the Holocene.”  Proceedings of the National Academy of Sciences USA 111:15296–15303.  2014.  “The esl reaches its lowest value of ~134 m at the end of this interval, corresponding to ~52 x 106 km3 more grounded ice, including on shelves, at the LGM than today.”  A reconstruction of sea level and global ice volumes from the Last Glacial Maximum to the Holocene.  It estimates the lowstand at about 134 m below present.  This page uses it as the reference sea-level fall against which the measured sills are read. ↩

  7. 7.

    Oard, Mike.  “Land bridges after the Flood.”  Journal of Creation 34(3):109–117.  2020.  A creationist article on how animals could have crossed land bridges after the Flood.  It discusses the Dover Strait and Bering land bridges, and argues that the Bering bridge was raised by tectonic uplift (the land itself rising) early in the Ice Age rather than exposed by low sea level late in it.  This page uses it for Oard's own estimate that sea level fell only about 50 m at the peak of the Ice Age, for his tectonic Bering bridge, and for his rejection of a land bridge to Australia. ↩

    1. 7a.

      “First, the drop in sea level at glacial maximum would have been much less than secular scientists believe.  It may have been only about 50 m, assuming Northern Hemisphere ice sheets were on average about 700 m thick and the Antarctic ice sheet was about 1,200 m thick at glacial maximum (figure 11).” ↩

    2. 7b.

      Section Dispersal across land bridges:  “Three land bridges have been proposed:  (1) the connection between continental Europe and England at the Dover Strait;  (2) the connection between Asia and North America across the Bering Strait;  and (3) the connection or near connection between South-east Asia and Australia.  The first two will be discussed in this paper.  The third land bridge does not seem plausible because of the many deep, wide ocean channels, but will be discussed further in another paper on the subject of the dispersal of the Australian marsupials.” ↩

  8. 8.

    Measured for the creationist article.  The longest single open-water leg on the shallowest island-hopping route from the Sunda shelf to the Sahul shelf, on the same GMRT bathymetry as the sill table, about 7.8 km per cell:  110 km at present sea level, 85 km at a 50 m fall, 78 km at the 134 m glacial lowstand.  A coarse grid loses small islands, so the true legs are more likely shorter than longer.  Scripts in ../creationist-biogeography/research/. ↩ ↩ ↩

  9. 9.

    Measured for the companion articles from complete Paleobiology Database occurrence downloads for Metatheria (4,857 occurrences) and crown Marsupialia (3,564), retrieved 25 August 2026.  An occurrence is assigned to an epoch only when its whole age bracket fits inside that epoch, so every count is a lower bound.  The endemism figures count genera found on exactly one continent, with Carnivora and Proboscidea as controls.  Scripts and data are in ../creationist-biogeography/research/. ↩ ↩ ↩ ↩ ↩

  10. 10.

    Vidal, Nicolas et al.  “Origin of tropical American burrowing reptiles by transatlantic rafting.”  Biology Letters 4:115–118.  2008.  “Here we show with molecular evidence that oceanic dispersal, on floating islands, played a more prominent role, and that amphisbaenians crossed the Atlantic Ocean in the Eocene (40 Myr ago) resulting in a tropical American radiation representing one-half of all known amphisbaenian species. ... Significantly, this is the first such dispersal event to involve a group that burrows, an unexpected lifestyle for an oceanic disperser.”  A molecular study arguing that amphisbaenians reached tropical America by rafting on floating vegetation, adding a burrowing reptile group to known transatlantic dispersal cases.  This page cites it for the count of transatlantic crossings the evolutionary account needs.

    1. 10a.

      “Until now, only four or five transatlantic dispersal events were known in terrestrial vertebrates.” ↩ ↩

  11. 11.

    Distances for the Africa-South America crossing.  n.d.  “includes the major eustatic drop in sea level that occurred in the earliest Oligocene.”  A set of distances computed for the creationist article, measuring the narrowest modern gap as a great-circle distance (the shortest line over the curved surface of the Earth).  Cape Sao Roque, Brazil to Freetown, Sierra Leone is 2,898 km, and other Brazil-to-West-Africa pairs run 2,900 to 3,300 km.  Because the Atlantic has widened continuously, the gap was smaller 35 to 40 million years ago: at equatorial full-spreading rates (the speed at which the seafloor pulls apart) of 2 to 4 cm/yr, 40 million years accounts for 800 to 1,600 km of that width.  The figure usually attached to the monkey crossing is about 1,450 km at the Eocene-Oligocene sea-level lowstand (a period of unusually low sea level), and Seiffert et al. 2020 date the dispersal window to 35.1-31.7 Ma.  The 1,450 km figure is a rough order of magnitude, not a precise measurement; at any width from 1,000 to 2,900 km the ratio to the Wallacea gap (the water gap the article measures between Asia and Australia) stays between twelve and thirty-four.  The paper's own words on the window: ↩ ↩

  12. 12.

    Heads, Michael.  “Dating nodes on molecular phylogenies: a critique of molecular biogeography.”  Cladistics 21:62–78.  2005.  A critique of three methods for dating molecular phylogenies:  oldest fossils, endemic strata and palaeogeographic events.  Heads, a panbiogeographer, argues that all have difficulties and that calibration and substitution-model problems prevent phylogeography from reliably testing vicariance against dispersal.  This page cites it as the strongest secular statement of the circularity charge and of the objection to island-age dating.

    1. 12a.

      “Studies correlating the age of nodes with age of volcanic islands often overlook the fact that these islands have been produced at subduction zones or hot spots where small, individually ephemeral islands are constantly being produced and disappearing, and a metapopulation can survive indefinitely.” ↩ ↩

    2. 12b.

      “Problems with calibrating the nodes, as well as with substitution models, mean that phylogeography's claim to be able to test between vicariance and dispersal is not justified.” ↩ ↩

  13. 13.

    Cifelli, Richard L., and Brian M. Davis.  “Marsupial origins.”  Science 302:1899–1900.  2003.  “this geographical switch remains unexplained”.  A short perspective discussing evidence bearing on marsupial origins.  This page cites it for the statement that the shift of the marsupial record from the northern to the southern continents is unexplained. ↩ ↩

  14. 14.

    Fleischer, Robert C. et al.  “Evolution on a volcanic conveyor belt: using phylogeographic reconstructions and K-Ar-based ages of the Hawaiian Islands to estimate molecular evolutionary rates.”  Molecular Ecology 7:533–545.  1998.  “islands are ordered linearly by age, with the oldest islands in the north-west (e.g. Kauai at 5.1 Ma) and the youngest in the south-east (e.g. Hawaii at 0.43 Ma).”  A study using Hawaiian island ages and phylogenetic patterns to estimate molecular change rates in honeycreepers, Drosophila and Laupala crickets.  Its abstract lists seven assumptions for calibration, including accurate K-Ar dates and colonization in island-age order.  This page cites it for the island sequence and for lineages that branch in island order. ↩ ↩ ↩

    1. 14a.

      “(i) part of the mitochondrial cytochrome b gene in Hawaiian drepanidines (0.016 sequence divergence/Myr);  (ii) the Yp1 gene in Hawaiian Drosophila (0.019/Myr Kambysellis et al. 1995);  and (iii) parts of the mitochondrial 12S and 16S rRNA and tRNAval in Laupala crickets (0.024-0.102/Myr, Shaw 1996).” ↩

  15. 15.

    de Queiroz, Alan.  “The resurrection of oceanic dispersal in historical biogeography.”  Trends in Ecology and Evolution 20(2):68–73.  2005.  A review of evidence for oceanic dispersal, including molecular dates and gene flow in island lizards.  It argues that dispersal has been underestimated and that the assumption that vicariance is more probable needs re-evaluation.  This page cites it for the field's retreat from vicariance and for the plainest statement of what the dispersal account leans on.

    1. 15a.

      Section Abstract:  “In particular, molecular dating of lineage divergences favors oceanic dispersal over tectonic vicariance as an explanation for disjunct distributions in a wide variety of taxa, from frogs to beetles to baobab trees.” ↩

    2. 15b.

      Page 71:  “Although Darwin apparently was wrong in thinking that amphibians never cross saltwater, these cases reinforce a general message of the great evolutionist:  given enough time, many things that seem unlikely can happen.” ↩

  16. 16.

    Landis, C. A. et al.  “The Waipounamu Erosion Surface: questioning the antiquity of the New Zealand land surface and terrestrial fauna and flora.”  Geological Magazine 145(2):173–197.  2008.  “We can find no geological evidence to indicate that land areas were continuously present throughout the middle Cenozoic. ... New Zealand's present terrestrial fauna and flora evolved largely from fortuitous arrivals during the past 22 million years.”  A geological review of the Waipounamu Erosion Surface, New Zealand marine deposits and fossil localities.  It argues there is insufficient geological basis to assume land remained continuously above water through the Oligocene to Early Miocene, and considers complete submergence of Zealandia.  This page cites it as the unresolved New Zealand problem that the evolutionary article lists among its weak points. ↩

  17. 17.

    Oard, Michael J.  “When and how did the marsupials migrate to Australia?”  Journal of Creation 36(2):90–96.  2022.  A creationist paper asking how marsupials reached Australia from the Ark after the Flood.  It argues that they arrived early in the Ice Age, by swimming short distances or on log mats (floating mats of logs and vegetation) across parts of the Indian Ocean.  This page uses it for Oard's answer to the missing fossil trail and for his admission that today's Indian Ocean currents would not carry a log mat to Australia.

    1. 17a.

      “Although Ice Age marsupial fossils are not found in Southeast Asia west of Sulawesi, a rapid migration after the Flood may have left no fossils.  After all, God was possibly directing their dispersal.” ↩ ↩

    2. 17b.

      Section Abstract:  “During the Ice Age, a complete land bridge was unlikely, so marsupials either swam short distances or were transported by log mats across parts of the Indian Ocean.  The uniformitarian model can only posit small mats, but the more massive post-Flood log mats would be more survivable.  Indian Ocean currents today would not carry a log mat from the shores of southwest Asia to Australia, but the currents were likely different early in the Ice Age.” ↩

  18. 18.

    Arment, Chad.  “To the Ark, and Back Again? Using the Marsupial Fossil Record to Investigate the Post-Flood Boundary.”  Answers Research Journal 13:1–22.  2020.  A paper in Answers Research Journal, written within creation science.  It tests where a post-Flood boundary can sit in the rock record, the layer creationists place at the end of the Flood, by counting the marsupial genera (pouched mammals) found below and above a proposed boundary and calculating how likely those genera are to be found on one continent both before and after the Flood.  Its results suggest that boundary placements within the Cenozoic (the most recent geological era) face a difficult challenge.  This page cites its conclusion against late boundaries and its concession that an Antarctic route leaves only a few centuries.

    1. 18a.

      Section Evaluating Late Post-Flood Boundaries:  “To go back to our original example, is it likely that Thylacinus, along with so many other marsupials, was found in one specific geographic area before the Flood, survived on the Ark, and then made its way back to that very same region (leaving no trace elsewhere), now split off as the continent of Australia?  (Or for others, South America?)  It's not only unlikely, it is highly improbable.” ↩ ↩

    2. 18b.

      Section Discussion:  “For a creationist, however, holding to an early post-Flood boundary, there would likely only be a few hundred years available between the end of the Flood and the complete isolation of Antarctica.  So is this Antarctic bridgeway plausible?” ↩ ↩

    3. 18c.

      Section Introduction:  “Invoking an innate homing beacon or divine guidance would be untestable and, in the latter case, simply God-of-the-gaps theorizing.” ↩

  19. 19.

    Nilsson, Maria A. et al.  “Tracking marsupial evolution using archaic genomic retroposon insertions.”  PLoS Biology 8(7):e1000436.  2010.  Page e14:  “The four Australasian orders share a single origin with Microbiotheria as their closest sister group, supporting a clear divergence between South American and Australasian marsupials.  In addition, the new data place the South American opossums (Didelphimorphia) as the first branch of the marsupial tree. ... Placing the retroposon insertion pattern in a paleobiogeographic context indicates a single marsupial migration from South America to Australia.”  A genome comparison that screened about 217,000 retroposon-containing loci from opossum and kangaroo and recovered 53 informative markers.  The markers place the four Australasian orders together, with South American Microbiotheria as their closest sister group.  This page cites it for that relationship;  the single migration the authors infer from it is contested by the fossil record, as both companion articles explain. ↩

  20. 20.

    Skeels, Alexander et al.  “Paleoenvironments shaped the exchange of terrestrial vertebrates across Wallace's Line.”  Science 381(6653):86–92.  Jul 7, 2023.  “spatial information on 20,433 species belonging to all 227 families of terrestrial vertebrates present in the Indo-Australian archipelago.”  Section Abstract:  “Sundanian (Southeast Asian) lineages evolved in a climate similar to the humid 'stepping stones' of Wallacea, facilitating colonization of the Sahulian (Australian) continental shelf. By contrast, Sahulian lineages predominantly evolved in drier conditions, hampering establishment in Sunda and shaping faunal distinctiveness.”  A model-based study combining geographic, phylogenetic and climate information for 20,433 species across all 227 families of terrestrial vertebrates in the Indo-Australian archipelago.  It links exchange patterns to climate and precipitation niche breadth.  This page cites it as the mainstream account of Wallace's Line:  the crossing count and the climate explanation of the one-way imbalance.

    1. 20a.

      Section Trait-based drivers of faunal exchange:  “We estimated a minimum of 381 independent colonization events across Wallace's Line”. ↩

    2. 20b.

      Section introduction:  “The interchange has been highly asymmetrical, with rates of exchange estimated to be at least twice as high from Sunda to Sahul than in the opposite direction”.  The sentence summarises earlier work, the authors' reference 23;  it is not one of the paper's own estimates. ↩

  21. 21.

    Beck, Robin M. D. et al.  “Australia's oldest marsupial fossils and their biogeographical implications.”  PLoS ONE 3(3):e1858.  2008.  “Djarthia is therefore the oldest known crown-group marsupial anywhere in the world that is represented by dental, cranial and post-cranial remains, and the oldest known Australian marsupial by 30 million years.”  A fossil study describing new cranial and post-cranial Djarthia remains from Australia's early Eocene Tingamarra Local Fauna and using phylogenetic analysis to place the animal among marsupials.  It identifies Djarthia as the oldest Australian marsupial by 30 million years and suggests South American microbiotheres may represent back-dispersal from eastern Gondwana.  This page cites it for the gap in Australia's own early record. ↩

  22. 22.

    Rosenberger, and Hubbe.  “eLetter replying to Seiffert et al., A parapithecid stem anthropoid of African origin in the Paleogene of South America.”  Science eLetter.  May 7, 2020.  “The latter is a point that actually requires considerably more discussion, as it has been widely used to justify and support the transatlantic dispersion model of anthropoids even though it is a scenario that cannot be empirically tested.”  “Such complications tend to be glossed over or minimized by the scenario's advocates, which results in overrating its viability and contributes to its widespread acceptance.”  “are not edited, proofread, or indexed, but they are screened.”  A post-publication eLetter that accepts the reported phylogeny but challenges the transatlantic dispersal explanation.  Science says eLetters are screened but not edited, proofread or indexed.  Rosenberger is Professor Emeritus, PhD Program in Anthropology, CUNY Graduate Center;  Hubbe is Professor of Anthropology, Ohio State University.  This page cites it for the critics' point that raft survival falls faster than distance grows.

    1. 22a.

      “These probabilities illustrate the exponential difficulty of crossing vast distances on vegetation rafts.  While non-marine vertebrates have reportedly been seen on flotsam off a coastline or between islands, it must be recognized that the odds of survival across voids of oceanic scale do not decrease linearly with distance, but rather exponentially.” ↩ ↩

  23. 23.

    Nelson, and Platnick.  Systematics and Biogeography: Cladistics and Vicariance.  Columbia University Press, New York.  1981.  A 1981 book whose title names its two subjects, cladistics (sorting organisms into branching trees by their shared features) and vicariance (explaining where organisms live by the splitting of their ranges).  Creationist writers quote its verdict on biogeography;  this page cites the sentence that follows it.

    1. 23a.

      Page 223:  “We conclude, therefore, that biogeography (or geographical distribution of organisms) has not been shown to be evidence for or against evolution in any sense.  The significance of biogeography has been merely that biogeography has raised the possibility of agreement between cladograms as considered in the geographic dimension, a possibility that has been little studied, but one worthy of further investigation.” ↩