|The Hidden Kingdom of Marsupials|
n the late Mesozoic Era, the continents which were to become South America, Antarctica, and Australia were connected. The isolation of this continent grouping from the grouping which was to become Eurasia and North America permitted the separate, but parallel, development of the two great mammalian orders-- the marsupials in the former grouping, and the placentals in the latter.
The extraordinary diversity of marsupials in Australia is well known, thanks to the survival of most species into historical times. There were marsupial "deer" (kangaroos), "cats" (Tasmanian devils), and "dogs" (thylacenes). Predation by humans and dingoes extinguished only a few of the larger forms, at least until the arrival of European colonists.
There was also a great flowering of marsupial evolution in South America. Most of these species, however, are known only through fossil evidence. The joining of North and South America in the Pliocene allowed the southward migration of equivalents, who competed effectively against their marsupial parallels in nearly every ecological niche. Extinction of the marsupial forms ensued. There were, however, a few conspicuous survivors, notably the opossums.
It is a safe assumption that there was a third great flowering of the marsupial forms, on the Antarctic continent. In the late Mesozoic this continent was situated in temperate southern latitudes, between South America and Australia. South America and Antarctica remained joined through about two-thirds of the Cenozoic Era, only "pulling apart" about 28 million years before the present (BP). Thus, the mammalian species diversity of Antarctica of that time is likely to have been much like that of South America.
My hypothesis is that the marsupial lifeforms of Antarctica eventually attained a higher stage of evolution than those of the other two great marsupial continents. Consider this: in the late Oligocene (35 to 28 million years BP) the Antarctic continent had drifted near enough to the Pole to have led to considerable glaciation. This glaciation accelerated after the "pulling apart" from South America, leading in few million years to the near-total domination of the continent by the ice cap, and the consequent annihilation of all large land plants and animals. But in those last few million years while land life survived, the plants and animals may have been put under the same kind of evolutionary pressure that was seen in North America and Eurasia during the Pleistocene-- ice-age pressure that forced a variety of adaptations that were both swift and marvelous. Is it not possible that very advanced forms of marsupials developed-- not only "cats", "dogs", and "deer", but also "primates"?
Of course, the great icecaps have erased or covered virtually all of the fossil record. A search for fossils will be logistically difficult, possibly requiring much drilling through ice. But it behooves us to select carefully a few likely spots, with emphasis on riverine formations of the middle Miocene period (22 to 16 million years BP). Here we would have the best chance of finding evidence of marsupial species at the advanced levels of evolutionary development I hypothesize. From the way that Antarctica seems to have drifted during the Miocene, it appears that the area around the Princess Martha Coast (0° E) was the last to have passed south of 60° S, and hence may have been the site of the "last stand" of land-mammal life on the continent. Just one lucky strike, such as that of the Fossil Butte area of Wyoming, is all we need.
I propose that a syndicate of "enlightened amateurs" be created, whose chief purpose would be to fund a research project of this sort. Enlightened amateurs-- I refer to the hundreds of keenly curious and intelligent persons among the continent's recent tourists-- have two great qualities not often found among Antarctic scientists. First, most of them are persons of considerable private means. And second, their imaginations are unconstrained by the narrow focus of professional specialization. Amateurs have a rich tradition of contributing to the advance of knowledge-- most of all because they are capable of "generalist" thinking which combines insights from two or more disciplines. For just this reason, I expect that several other promising proposals for Antarctic research could arise from the group with whom I visited the continent in February 1989-- for example, along the lines of "submarine hot springs lifeforms" research. Any one of these proposals could be as worthy of a search for funding as my own.(printer friendly version)