Coherent catastrophism

Impact-related microspherules in Late Pleistocene Alaskan and Yukon "muck" deposits signify recurrent episodes of catastrophic emplacement

Large quantities of impact-related microspherules have been found in fine-grained sediments retained within seven out of nine, radiocarbon-dated, Late Pleistocene mammoth (Mammuthus primigenius) and bison (Bison priscus) skull fragments. The well-preserved fossils were recovered from frozen “muck” deposits (organic-rich silt) exposed within the Fairbanks and Klondike mining districts of Alaska, USA, and the Yukon Territory, Canada. In addition, elevated platinum abundances were found in sediment analysed from three out of four fossil skulls. In view of this new evidence, the mucks and their well-preserved but highly disrupted and damaged vertebrate and botanical remains are reinterpreted in part as blast deposits that resulted from several episodes of airbursts and ground/ice impacts within the northern hemisphere during Late Pleistocene time (~46–11 ka B.P.). Such a scenario might be explained by encounters with cometary debris in Earth-crossing orbits (Taurid Complex) that was generated by fragmentation of a large short-period comet within the inner Solar System.

Impossible to Disprove Yet Impossible to Believe: the Unforgiving Epistemology of Deep-Time Oral Tradition

Writing about American Indian reactions to their discovery of large fossil remains, Adrienne Mayor observes in passing that “[f]olklore scholars now generally accept that oral traditions about historical events endure for about a thousand years, although some oral myths about geological and astronomical events can be reliably dated to about seven thousand years.” Mayor's chosen task is to demonstrate that American Indian legends suggest that they rightly regarded fossils as the remains of long extinct megafauna populations. In aid of this, Mayor accepts these arguments in her own work. While this claim might seem extravagantprima facie, and while most folklorists would disown Mayor's claim, she is not without support from the work of a relatively small, but not uninfluential (and possibly growing), cadre of anthropologists, mythographers, geologists, and historians, whose efforts on behalf of deep-time oral tradition I address here.

Some interesting—even intriguing—things have been happening recently in discussions of the carrying capacity of oral tradition—its long-term historicity, in particular.À laMayor, the thrust of this is to credit tradition with being able to preserve “intact” various pieces of information for as long as tens of thousands of years. To the historian interested in the reality of the past in oral societies, this state of affairs is challenging, perplexing, and no doubt to some, highly promising. If, for instance, it can be demonstrated that certain information in oral data is thousands of years old and at the same time an accurate recollection, then reservations about much later (say, several centuries old) orally transmitted information might need to be reassessed, and with such rethinking would come new ways to approach great swaths of the past.

Small theories and large risks--is risk analysis relevant for epistemology?

Ought we to take seriously large risks predicted by "exotic" or improbable theories? We routinely assess risks on the basis or either common sense, or some developed theoretical framework based on the best available scientific explanations. Recently, there has been a substantial increase of interest in the low-probability "failure modes" of well-established theories, which can involve global catastrophic risks. However, here I wish to discuss a partially antithetical situation: alternative, low-probability ("small") scientific theories predicting catastrophic outcomes with large probability. I argue that there is an important methodological issue (determining what counts as the best available explanation in cases where the theories involved describe possibilities of extremely destructive global catastrophes), which has been neglected thus far. There is no simple answer to the correct method for dealing with high-probability high-stakes risks following from low-probability theories that still cannot be rejected outright, and much further work is required in this area. I further argue that cases like these are more numerous than usually assumed, for reasons including cognitive biases, sociological issues in science and the media image of science. If that is indeed so, it might lead to a greater weight of these cases in areas such as moral deliberation and policy making.

Astrobiological complexity with probabilistic cellular automata

The search for extraterrestrial life and intelligence constitutes one of the major endeavors in science, but has yet been quantitatively modeled only rarely and in a cursory and superficial fashion. We argue that probabilistic cellular automata (PCA) represent the best quantitative framework for modeling the astrobiological history of the Milky Way and its Galactic Habitable Zone. The relevant astrobiological parameters are to be modeled as the elements of the input probability matrix for the PCA kernel. With the underlying simplicity of the cellular automata constructs, this approach enables a quick analysis of large and ambiguous space of the input parameters. We perform a simple clustering analysis of typical astrobiological histories with "Copernican" choice of input parameters and discuss the relevant boundary conditions of practical importance for planning and guiding empirical astrobiological and SETI projects. In addition to showing how the present framework is adaptable to more complex situations and updated observational databases from current and near-future space missions, we demonstrate how numerical results could offer a cautious rationale for continuation of practical SETI searches.

Galactic punctuated equilibrium: how to undermine Carter's anthropic argument in astrobiology

A new strategy by which to defeat Carter's "anthropic" argument against extraterrestrial life and intelligence is presented. Our approach is based on relaxing hidden uniformitarian assumptions and considering instead a dynamical succession of evolutionary regimes governed by both global (Galaxy-wide) and local (planet- or planetary system-limited) regulation mechanisms. Notably, our increased understanding of the nature of supernovae, gamma-ray bursts, and strong coupling between the Solar System and the Galaxy, and the theories of "punctuated equilibria" and "macroevolutionary regimes" are in full accordance with the regulation-mechanism picture. The application of this particular strategy highlights the limits of application of Carter's argument and indicates that, in the real universe, its applicability conditions are not satisfied. We conclude that drawing far-reaching conclusions about the scarcity of extraterrestrial intelligence and the prospects of our efforts to detect it on the basis of this argument is unwarranted.