Putting Process and Product Conceptions of Natural Selection and Genetic Drift to the Test

This paper argues for two claims. First, despite a persistent appearance to the contrary in the philosophy of biology literature, the question of whether natural selection and genetic drift should be defined as processes or as the products (or outcomes) of those processes is independent of the question of whether natural selection and genetic drift are causally efficacious (the debate between the 'causalist' and 'statisticalist' interpretations of evolutionary theory). Second, there exist biological cases – cases which are quite prevalent in natural populations – that can be used to drive apart process and product notions of selection and drift, and hence which could provide evidence useful in determining which of these two classes of definitions is in line with biological practice. Two cases presented here weigh in favor of process definitions, though this does not suffice to resolve the question

Nietzsche’s Aesthetic Critique of Darwin

Despite his position as one of the first philosophers to write in the ‘post-Darwinian’ world, the critique of Darwin by Friedrich Nietzsche is often ignored, for a host of unsatisfactory reasons. I argue that Nietzsche’s critique of Darwin is important to the study of both Nietzsche’s and Darwin’s impact on philosophy. Further, I show that the central claims of Nietzsche’s critique have been broadly misunderstood. I then present a new reading of Nietzsche’s core criticism of Darwin. An important part of Nietzsche’s response can best be understood as an aesthetic critique of Darwin, reacting to what he saw as Darwin’s having drained life of an essential component of objective aesthetic value. For Nietzsche, Darwin’s theory is false because it is too intellectual, because it searches for rules, regulations, and uniformity in a realm where none of these are to be found – and, moreover, where they should not be found. Such a reading goes farthest toward making Nietzsche’s criticism substantive and relevant. Finally, I attempt to relate this novel explanation of Nietzsche’s critique to topics in contemporary philosophy of biology, particularly work on the evolutionary explanation of culture

It's Okay to Call Genetic Drift a “Force”

One hotly debated philosophical question in the analysis of evolutionary theory concerns whether or not evolution and the various factors which constitute it (selection, drift, mutation, and so on) may profitably be considered to be “forces” in the traditional, Newtonian sense. Several compelling arguments assert that the force picture is incoherent, due to the peculiar nature of genetic drift. I consider two of those arguments here – that drift lacks a predictable direction, and that drift is constitutive of evolutionary systems – and show that they both fail to demonstrate that a view of genetic drift as a force is untenable

Recent changes to a measure of U.S. household debt service

Changes in levels of aggregate household debt in the United States may contain information about the current state of the nation's economy and may affect its future direction. A commonly used measure of household indebtedness is the household debt service ratio (formerly known as the household debt service burden), published since 1980 by the Board of Governors of the Federal Reserve System. Recent changes in financial markets have prompted a comprehensive revision of this statistic. This article describes the revision and introduces a new measure, the financial obligations ratio, which adds recurring obligations -- rent, auto leases, homeowners' insurance, and property taxes -- to the traditional calculation of the debt service ratio. In total, these revisions change the level of the debt service ratio but do not substantively alter its trajectory over time. The article also presents separate estimates of the financial obligations ratio for homeowners and renters. The ratio for homeowners, which may summarize the effects of the recent refinancing boom on the financial obligations of homeowners, has risen gradually over the past decade; the ratio for renters has risen more steeply. The flat contour of the homeowner ratio in recent quarters suggests that homeowners may have rebalanced their portfolios toward lower-cost mortgage debt during the recent period of economic weakness.Households ; Debt

Lossless Astronomical Image Compression and the Effects of Noise

We compare a variety of lossless image compression methods on a large sample of astronomical images and show how the compression ratios and speeds of the algorithms are affected by the amount of noise in the images. In the ideal case where the image pixel values have a random Gaussian distribution, the equivalent number of uncompressible noise bits per pixel is given by Nbits =log2(sigma * sqrt(12)) and the lossless compression ratio is given by R = BITPIX / Nbits + K where BITPIX is the bit length of the pixel values and K is a measure of the efficiency of the compression algorithm. We perform image compression tests on a large sample of integer astronomical CCD images using the GZIP compression program and using a newer FITS tiled-image compression method that currently supports 4 compression algorithms: Rice, Hcompress, PLIO, and GZIP. Overall, the Rice compression algorithm strikes the best balance of compression and computational efficiency; it is 2--3 times faster and produces about 1.4 times greater compression than GZIP. The Rice algorithm produces 75%--90% (depending on the amount of noise in the image) as much compression as an ideal algorithm with K = 0. The image compression and uncompression utility programs used in this study (called fpack and funpack) are publicly available from the HEASARC web site. A simple command-line interface may be used to compress or uncompress any FITS image file.Comment: 20 pages, 9 figures, to be published in PAS

Optimal Compression of Floating-point Astronomical Images Without Significant Loss of Information

We describe a compression method for floating-point astronomical images that gives compression ratios of 6 -- 10 while still preserving the scientifically important information in the image. The pixel values are first preprocessed by quantizing them into scaled integer intensity levels, which removes some of the uncompressible noise in the image. The integers are then losslessly compressed using the fast and efficient Rice algorithm and stored in a portable FITS format file. Quantizing an image more coarsely gives greater image compression, but it also increases the noise and degrades the precision of the photometric and astrometric measurements in the quantized image. Dithering the pixel values during the quantization process can greatly improve the precision of measurements in the images. This is especially important if the analysis algorithm relies on the mode or the median which would be similarly quantized if the pixel values are not dithered. We perform a series of experiments on both synthetic and real astronomical CCD images to quantitatively demonstrate that the magnitudes and positions of stars in the quantized images can be measured with the predicted amount of precision. In order to encourage wider use of these image compression methods, we have made available a pair of general-purpose image compression programs, called fpack and funpack, which can be used to compress any FITS format image.Comment: Accepted PAS

Potential Controversies: Causation and the Hodgkin and Huxley Equations

The import of Hodgkin and Huxley’s classic model of the action potential has been hotly debated in recent years, with particular controversy surrounding claims by prominent proponents of mechanistic explanation (Bogen, 2008; Craver, 2008). For these authors, the Hodgkin-Huxley (HH) model is an excellent predictive tool but ultimately lacks causal/explanatory import. What is more, they claim that this is how Hodgkin and Huxley themselves saw the model. In the following, I argue that these claims rest on a problematic reading of the work. Hodgkin and Huxley’s model is both causal and, in an important sense, explanatory

A New Foundation for the Propensity Interpretation of Fitness

The propensity interpretation of fitness (PIF) is commonly taken to be subject to a set of simple counterexamples. We argue that three of the most important of these are not counterexamples to the PIF itself, but only to the traditional mathematical model of this propensity: fitness as expected number of offspring. They fail to demonstrate that a new mathematical model of the PIF could not succeed where this older model fails. We then propose a new formalization of the PIF that avoids these (and other) counterexamples. By producing a counterexample-free model of the PIF, we call into question one of the primary motivations for adopting the statisticalist interpretation of fitness. In addition, this new model has the benefit of being more closely allied with contemporary mathematical biology than the traditional model of the PIF