This work by Feng and papers which published its conclusions do not cite nor do they deal with objections by the author published in 2013-2014. There are many fundamental problems. We will summarize here the principal problems, as published by Melott
and Bambach which render irrelevant most of the work presented by Feng.
Major discrepancies have been noted for some time between fossil ages and molecular divergence dates for a variety of taxa. Recently, systematic trends within avian clades have been uncovered. The trends show that the disparity is much larger for mit
ochondrial DNA than for nuclear DNA, also that it is larger for crown fossil dates than stem fossil dates. It has been argued that this pattern is largely inconsistent with incompleteness of the fossil record as the principal driver of the disparity. A case is presented that given the expected mutations from a fluctuating background of astrophysical radiation from such sources as supernovae, the rate of molecular clocks is variable and should increase back to a few Ma, before returning to the long-term average rate. This is a possible explanation for the disparity. One test of this hypothesis is to look for an acceleration of molecular clocks 2 to 2.5 Ma due to one or more moderately nearby supernovae known to have happened at that time. Another is to look for reduced disparity in benthic organisms of the deep ocean. In addition, due to the importance of highly penetrating muon irradiation, the disparity should be magnified for megafauna.
Unfortunately, Liu et al. contains a number of errors and omissions which compromise its conclusions. These have to do with the amount of 14C which is necessary to deposit in the atmosphere in order to see a perturbation like that in 774 AD, and the ability of a comet to do so.
We examine possible sources of a substantial increase in tree ring 14C measurements for the years AD 774-775. Contrary to claims regarding a coronal mass ejection (CME), the required CME energy is not several orders of magnitude greater than known so
lar events. We consider solar proton events (SPEs) with three different fluences and two different spectra. The data may be explained by an event with fluence about one order of magnitude beyond the October 1989 SPE. Two hard spectrum cases considered here result in moderate ozone depletion, so no mass extinction is implied, though we do predict increases in erythema and damage to plants from enhanced solar UV. We are able to rule out an event with a very soft spectrum that causes severe ozone depletion and subsequent biological impacts. Nitrate enhancements are consistent with their apparent absence in ice core data. The modern technological implications of such an event may be extreme, and considering recent confirmation of superflares on solar-type stars, this issue merits attention.
The investigation into the possible effects of cosmic rays on living organisms will also offer great interest. - Victor F. Hess, Nobel Lecture, December 12, 1936 High-energy radiation bursts are commonplace in our Universe. From nearby solar flares
to distant gamma ray bursts, a variety of physical processes accelerate charged particles to a wide range of energies, which subsequently reach the Earth. Such particles contribute to a number of physical processes occurring in the Earth system. A large fraction of the energy of charged particles gets deposited in the atmosphere, ionizing the atmosphere, causing changes in its chemistry and affecting the global electric circuit. Remaining secondary particles contribute to the background dose of cosmic rays on the surface and parts of the subsurface region. Life has evolved over the past ~ 3 billion years in presence of this background radiation, which itself has varied considerably during the period. As demonstrated by the Miller-Urey experiment, lightning plays a very important role in the formation of complex organic molecules, which are the building blocks of more complex structures forming life. There is growing evidence of increase in the lightning rate with increasing flux of charged particles. Is there a connection between enhanced rate of cosmic rays and the origin of life? Cosmic ray secondaries are also known to damage DNA and cause mutations, leading to cancer and other diseases. It is now possible to compute radiation doses from secondary particles, in particular muons and neutrons. Have the variations in cosmic ray flux affected the evolution of life on earth? We describe the mechanisms of cosmic rays affecting terrestrial life and review the potential implications of the variation of high-energy astrophysical radiation on the history of life on earth.
There may be structural principles pertaining to the general behavior of systems that lead to similarities in a variety of different contexts. Classic examples include the descriptive power of fractals, the importance of surface area to volume constr
aints, the universality of entropy in systems, and mathematical rules of growth and form. Documenting such overarching principles may represent a rejoinder to the Neodarwinian synthesis that emphasizes adaptation and competition. Instead, these principles could indicate the importance of constraint and structure on form and evolution. Here we document a potential example of a phenomenon suggesting congruent behavior of very different systems. We focus on the notion that universally there has been a tendency for more volatile entities to disappear from systems such that the net volatility in these systems tends to decline. We specifically focus on origination and extinction rates in the marine animal fossil record, the performance of stocks in the stock market, and the characters of stars and stellar systems. We consider the evidence that each is experiencing declining volatility, and also consider the broader significance of this.
It is shown that the historical summary of the growth in size of N-body simulations as measured by particle number in this review is missing some key milestones. Size matters, because particle number with appropriate force smoothing is a key method t
o suppress unwanted discreteness, so that the initial conditions and equations of motion are appropriate to growth by gravitational instability in a Poisson-Vlasov system appropriate to a Universe with dark matter. Published strong constraints on what can be done are not included in the review.
The hypothesis of a companion object (Nemesis) orbiting the Sun was motivated by the claim of a terrestrial extinction periodicity, thought to be mediated by comet showers. The orbit of a distant companion to the Sun is expected to be perturbed by th
e Galactic tidal field and encounters with passing stars, which will induce variation in the period. We examine the evidence for the previously proposed periodicity, using two modern, greatly improved paleontological datasets of fossil biodiversity. We find that there is a narrow peak at 27 My in the cross-spectrum of extinction intensity time series between these independent datasets. This periodicity extends over a time period nearly twice that for which it was originally noted. An excess of extinction events are associated with this periodicity at 99% confidence. In this sense we confirm the originally noted feature in the time series for extinction. However, we find that it displays extremely regular timing for about 0.5 Gy. The regularity of the timing compared with earlier calculations of orbital perturbation would seem to exclude the Nemesis hypothesis as a causal factor.
We use Fourier analysis and related techniques to investigate the question of periodicities in fossil biodiversity. These techniques are able to identify cycles superimposed on the long-term trends of the Phanerozoic. We review prior results and anal
yze data previously reduced and published. Joint time-series analysis of various reductions of the Sepkoski Data, Paleobiology Database, and Fossil Record 2 indicate the same periodicity in biodiversity of marine animals at 62 Myr. We have not found this periodicity in the terrestrial fossil record. We have found that the signal strength decreases with time because of the accumulation of apparently resistant long-lived genera. The existence of a 62-Myr periodicity despite very different treatment of systematic error, particularly sampling-strength biases, in all three major databases strongly argues for its reality in the fossil record.
A variety of events such as gamma-ray bursts and supernovae may expose the Earth to an increased flux of high-energy cosmic rays, with potentially important effects on the biosphere. Existing atmospheric chemistry software does not have the capabilit
y of incorporating the effects of substantial cosmic ray flux above 10 GeV . An atmospheric code, the NASA-Goddard Space Flight Center two-dimensional (latitude, altitude) time-dependent atmospheric model (NGSFC), is used to study atmospheric chemistry changes. Using CORSIKA, we have created tables that can be used to compute high energy cosmic ray (10 GeV - 1 PeV) induced atmospheric ionization and also, with the use of the NGSFC code, can be used to simulate the resulting atmospheric chemistry changes. We discuss the tables, their uses, weaknesses, and strengths.
