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Marauding Marsupials?

by  Brad Harrub, Ph.D.

Get out the drawing board—again. Evolutionists are having an extremely hard time trying to construct the phylogenetic trees of marsupial and placental mammals. For a while, it appeared they would be able to blame the differences between the two groups on variations within geographical regions. Thus, kangaroo-like animals allegedly “needed” to care for their young in a pouch because of the environment in which they found themselves. Or so the story went. The latest find—which has evolutionists reaching for a bottle of aspirin—upsets that “just-so” story of origins. The newly discovered fossil mammal, Sinodelphys szalayi (found in the Liaoning Province in northeast China) allegedly lived during the early Cretaceous period (144-65 million years ago). Reporting on their find, Zhe-Xi Luo and colleagues noted: “This fossil dates to 125 million years ago and extends the record of marsupial relatives with skeletal remains by 50 million years” (2003, 302:1934). But pushing the supposed timeline back 50 million years, and having evidence of a marsupial in China, is not helping evolutionists determine exactly how their beloved evolutionary tree should appear. Writing on this issue in the December 12, 2003 issue of Science, Richard Cifelli and Brian Davis remarked: “To date, the geological record has yielded few fossils that bear directly on the origin of marsupials” (2003, 302:1899, emp. added).

While Luo and his colleagues no doubt are thrilled to be able to announce the oldest fossilized marsupial, other evolutionists recognize the problems it poses. Commenting on the new discovery, Cifelli and Davis observed: “The balance of paleontological and morphological data suggests that the last common ancestor of metatherians and eutherians was Laurasian” [i.e., European/North American—BH] (302:1899, emp. added). Evolutionary theory has an extremely difficult time explaining why fossil marsupials are found predominately in North America, while living ones are found primarily in Australia and South America. And now, the oldest fossilized remains are reported in—China! As Cifelli and Davis went on to note: “This geographical switch remains unexplained. The timing of the split between eutherians [placental mammals—BH] and metatherians [marsupials—BH] is also controversial” (302:1899).

But this ancient marsupial creates even larger puzzles for evolutionists. How do they explain both mammals and marsupials in similar environments? As Cifelli and Davis admitted, “Clearly, the relative successes of the two groups differed widely on the two continents. Yet, the early representatives of both groups seem to have been highly similar ecologically—most were small, insectivorous, and probably nocturnal. This puzzle remains to be resolved” (302:1900, emp. added). It also is commonly known that many marsupials, such as the marsupial wolf, have placental look-alikes, yet very different reproductive systems. Evolutionary theory also is unable to account for this dramatic difference.

In order for evolutionists to be able to complete their mammalian tree, they must pick a point at which placental mammals and marsupials “branched apart.” This latest find pushes that point back 50 million years. But fossil data alone do not provide the only unanswered questions in regard to when these two groups parted ways. As Cifelli and Davis lamented: “Molecular data have yielded conflicting results for the timing of the metatherian-eutherian split.” [NOTE: Molecular estimates generally are older than fossil estimates.]

In an effort to try and rectify their beloved “out-of-whack” evolutionary tree, scientists often rely on comparative studies. But even standard means of comparative identification are causing problems with this new marsupial fossil. Cifelli and Davis admitted, for example:

Except in rare instances, soft-tissue differences between marsupials and placentals are not reflected in the fossil record. In their absence, paleontologists have used dental criteria to distinguish Late Cretaceous and some earlier metatherians from eutherians. But such criteria are not applicable to dentally more primitive fossils. Furthermore, they are of limited utility when it comes to assessing which biological niches they might have occupied, beyond the suggestion that most early metatherians fed on animal tissues ranging from insects to meat, depending on body size (302:1900, emp. added).

As it turns out, researchers are unable to use the teeth of Sinodelphy szalayi to help them sort out this puzzle, and, in fact, the teeth do not even tell them much about the environment in which this creature lived.

In the conclusion of their review of this latest find, Cifelli and Davis wrote:

These divergence estimates have implications for the relative timing of most other divergences on the mammalian family tree. However, they are difficult to reconcile with the (admittedly imperfect) mammalian fossil record. When the entire tree is considered, it becomes clear that large gaps in the fossil record (most with durations of more than 30 million years) must be inferred to explain the distribution of each group represented” (302:1900, parenthetical items in orig., emp. added).

They summarized this conundrum by stating:

The paleontological evidence is important because it provides an independent test for dates based on molecular data. It also provides some basis for calculating the rates of change of skeletal (and dental) morphology and molecular structure. Given the far-reaching implications for evolutionary studies, it is crucial that the widely differing estimates of divergence time are reconciled and that the place of origin of both metatherians and eutherians is further elucidated with fossil discoveries (302:1900, parenthetical item in orig., emp. added).

The distribution of marsupials is not well answered by evolutionary theories. As evinced by this discovery of Sinodelphy szalayi, geographic separation cannot be as significant to the marsupials’ development as evolutionists posit. A better explanation—one that fits this latest scientific discovery—is that God created the various kinds of marsupials along with the placental mammals. In doing so, He distributed them (and all creatures) all over the world. The lack of dissimilarities, and the occurrence of unique animal or plant assemblages in various parts of the world (not just Australia), could easily be construed as compelling scientific evidence for a rapid resettlement of these types of creatures in relatively recent times—a concept that would be much more consistent with the Genesis account of Creation than the amoeba-to-man theory of organic evolution.

REFERENCES

Cifelli, Richard L. and Brian M. Davis (2003), “Marsupial Origins,” Science, 302:1899-1900, December 12.

Luo, Zhe-Xi, Qiang Ji, John R. Wible, and Chong-Xi Yuan (2003), “An Early Cretaceous Tribosphenic Mammal and Metatherian Evolution,” Science, 302:1934-1940, December 12.




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