Periodic Mass Extinctions Research Articles

Revisiting the dark matter—Comet shower connection

We consider whether the observed periodicity of mass extinctions and of comet impacts on Earth is consistent with Solar oscillation about the Galactic midplane and spiral arm crossings. It is of further interest to determine whether a hypothetical thin dark disk is necessary to give the right periodicity, and whether such a dark disk is allowed given kinematic and other observational constraints on the Galaxy’s gravitational potential. We show that a dark disk consistent with recent bounds, combined with data for spiral arm crossing, can lead to the required periodicity. Moreover, we find that the best fit values correctly predict the date of the Chicxulub crater dated to 66 My ago.

Diversity and evolution of the animal virome.

The COVID-19 pandemic has given the study of virus evolution and ecology new relevance. Although viruses were first identified more than a century ago, we likely know less about their diversity than that of any other biological entity. Most documented animal viruses have been sampled from just two phyla - the Chordata and the Arthropoda - with a strong bias towards viruses that infect humans or animals of economic and social importance, often in association with strong disease phenotypes. Fortunately, the recent development of unbiased metagenomic next-generation sequencing is providing a richer view of the animal virome and shedding new light on virus evolution. In this Review, we explore our changing understanding of the diversity, composition and evolution of the animal virome. We outline the factors that determine the phylogenetic diversity and genomic structure of animal viruses on evolutionary timescales and show how this impacts assessment of the risk of disease emergence in the short term. We also describe the ongoing challenges in metagenomic analysis and outline key themes for future research. A central question is how major events in the evolutionary history of animals, such as the origin of the vertebrates and periodic mass extinction events, have shaped the diversity and evolution of the viruses they carry.

From the LIPS of a serial killer: Endogenic retardation of biological evolution on unstable stagnant-lid planets

Geological data imply plate tectonics was not active on the Archaean Earth pre-2.5 ​Ga. Key arguments include: the absence from the Archaean rock record of ophiolites and high-pressure metamorphic rocks; the rarity of Archaean andesites and lahars; the absence of arc-like, source-metasomatic, trace element signatures in Archaean calc-alkaline magmatic suites; and fundamental differences in overall structural style and constituent lithologies. Conversely, unstable stagnant-lid models better account for many features of Archaean geology. Thermo-mechanical models imply many unstable stagnant-lid planets would experience mobile-lid phases linked to periodic mantle overturns of 30–100 million years duration, separated by stable-lid phases lasting 100–300 My. Mantle overturn upwelling zones would be characterized by high magma fluxes that may have generated continental nuclei, and would have reworked and resurfaced tracts of pre-existing oceanic and continental lithosphere. Overturns would also have generated large-scale lateral mantle flow patterns that would have pushed against the sub-continental lithospheric mantle keels underlying continents, and so induced continental drift and orogenesis, allowing mobile-lid behaviour despite the absence of plate-boundary forces such as slab pull. Major resurfacing of Earth’s surface during overturns would have heated the hydrosphere and atmosphere, with many negative impacts on biota. The high magmatic fluxes associated with mantle overturn events are likely to have induced periodic mass extinctions that may have retarded biological evolution on Earth. Evolutionary progress towards more complex metazoan organisms may only have been possible after the more efficient plate tectonic cooling system helped create a stabler, more temperate planet; although causal relationships remain uncertain. Did the start of a plate tectonic, mobile-lid cooling system on Earth gradually end (or moderate) mantle overturn behaviour? Or was the world-girdling plate tectonic system only allowed to begin because ‘other factors’ gradually acted to suppress mantle overturns during the Proterozoic? These ‘other factors’ include: secular decay of radioactive isotopes, scavenging of radioactive elements into continents, and shrinkage of the fertile lower mantle reservoir that fed early overturns. When overturn behaviour ended on Earth is also uncertain. The 2.1–1.9 ​Ga magmatic and tectonic pulse on Earth is plausibly interpreted as an Archaean-style mantle overturn, but more research is needed to determine whether the Large Igneous Provinces (LIPs) of the Meso- and Neo-Proterozoic are as well. It is predicted that Earth-sized exoplanets with surface water and chondritic mantle compositions will spend at least the first 2 ​Ga of their evolution as unstable stagnant-lid planets, with periodic overturns preventing evolution of complex metazoan organisms. Many such planets could remain trapped in this cooling mode, with only rare cases transitioning into the more efficient plate tectonic cooling mode. If correct, this greatly decreases the probability that complex metazoans are present elsewhere in the universe.

David Malcolm Raup (1933-2015) at the starting point of a new paradigm for Palaeontology

This is a tribute to the late David Malcolm Raup, one of the major palaeontologists of the second half of the 20th century. In addition, it is a critical review of his outstanding contributions, mainly in the field of theoretical palaeontology: quantitative modelling, the introduction of probabilistic methods in palaeontology, as well as his great imagination to use techniques from other fields, such as insurance actuary. After a general outline of his youth, I present a general depiction of the main topics of his research as a palaeobiologist: morphology, the structure of the fossil record, evolution, and extinction. He covered areas ranging from the theoretical morphology of coiled shells to the use of Montecarlo methods in evolution and extinction, or the periodicity of mass extinctions and its causes, as well as the episodic nature of background extinctions, which were some of his preferred subjects. With his textbook, co-authored by Steven Stanley, he introduced a new paradigm for palaeontology.

Fructose metabolism as a common evolutionary pathway of survival associated with climate change, food shortage and droughts.

Mass extinctions occur frequently in natural history. While studies of animals that became extinct can be informative, it is the survivors that provide clues for mechanisms of adaptation when conditions are adverse. Here, we describe a survival pathway used by many species as a means for providing adequate fuel and water, while also providing protection from a decrease in oxygen availability. Fructose, whether supplied in the diet (primarily fruits and honey), or endogenously (via activation of the polyol pathway), preferentially shifts the organism towards the storing of fuel (fat, glycogen) that can be used to provide energy and water at a later date. Fructose causes sodium retention and raises blood pressure and likely helped survival in the setting of dehydration or salt deprivation. By shifting energy production from the mitochondria to glycolysis, fructose reduced oxygen demands to aid survival in situations where oxygen availability is low. The actions of fructose are driven in part by vasopressin and the generation of uric acid. Twice in history, mutations occurred during periods of mass extinction that enhanced the activity of fructose to generate fat, with the first being a mutation in vitamin C metabolism during the Cretaceous-Paleogene extinction (65 million years ago) and the second being a mutation in uricase that occurred during the Middle Miocene disruption (12-14 million years ago). Today, the excessive intake of fructose due to the availability of refined sugar and high-fructose corn syrup is driving 'burden of life style' diseases, including obesity, diabetes and high blood pressure.

Exchange of material between solar systems by random stellar encounters

AbstractIt is shown that a mechanism involving only random motion of the sun with respect to the surrounding star field can account for the ~1 per 25 Myr characteristic frequency of large cometary impacts on Earth. In the proposed mechanism, the sun travels through the Oort Cloud of an encounter star, most typically a Type M dwarf, while the dwarf flies through the Oort cloud of our Sun. As a result, Oort Cloud objects from our Solar System are precipitated in large numbers to impact planets in the dwarf star system, while the dwarf's Oort Cloud objects are destabilized to impact planets in our Solar System. It is shown that it is this exchange of Oort cloud object between stellar systems, rather than the precipitation of Oort Cloud objects within a stellar system, that can account for the apparent periodicity of mass extinctions. Because the sun is more massive than ~90% of stars, its Oort cloud extends further, resulting in it delivering about a factor of three more bombardments on other solar systems than our Solar System receives. About 60% of the bombardments on our Solar System are found to be delivered by Type M dwarfs, about 20% by type K dwarfs, with the remaining 20% being delivered by stars of type G or larger. Foreign star Oort cloud objects can be captured by our Sun at typical ranges of 10 AU, resulting in a cometary approach to perihelion within a few years. It is found that assuming an effective Oort Cloud radius of 40 000 AU for a star of solar mass, increasing in size with the square root of the mass, accounts for the observed characteristic frequency of mass extinction events on Earth, given the local stellar number density of 0.003 stars per cubic light year. The frequency of mass extinction events in other solar systems would increase or decrease in linear proportion to the local stellar number density. It is shown that this exchange of materials between solar systems during close stellar encounters could be an important mechanism for spreading life throughout the galaxy. Implications for the evolution of life on Earth and in other solar systems are discussed.

Periodic mass extinctions and the Planet X model reconsidered

Abstract The 27 Myr period in the fossil extinction record has been confirmed in modern data bases dating back 500 Myr, which is twice the time interval of the original analysis from 30 years ago. The surprising regularity of this period has been used to reject the Nemesis model. A second model based on the Sun's vertical Galactic oscillations has been challenged on the basis of an inconsistency in period and phasing. The third astronomical model originally proposed to explain the periodicity is the Planet X model in which the period is associated with the perihelion precession of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated to mass extinctions, a trans-Neptunian super-Earth planet has been proposed to explain the observation that the inner Oort cloud objects Sedna and 2012VP113 have perihelia that lie near the ecliptic plane. In this Letter, we reconsider the Planet X model in light of the confluence of the modern palaeontological and outer Solar system dynamical evidence.

Depositional facies and platform architecture of microbialite-dominated carbonate reservoirs, Ediacaran–Cambrian Ara Group, Sultante of Om

Intrasalt carbonates of the Ediacaran–Cambrian Ara Group constitute a significant reservoir element of the intrasalt “stringer” play in Oman, in which dolomitic carbonates are encased in salt at depths of 3 to 7 km (1.9 to 4.3 mi). These reservoir carbonates have significant microbial influences. Although Ara Group reservoirs are mostly latest Precambrian, the models developed here may be applicable to younger microbially dominated carbonate reservoirs in basins of higher salinity when higher organisms are excluded, in lacustrine settings where calcified invertebrates are not a significant source of carbonate, or after periods of mass extinction before faunal recovery. A broad range of carbonate facies provides the context in which to understand the origin of the microbialite-dominated reservoirs developed across both ramp and rimmed shelf profiles. Major facies associations include carbonate-evaporite transition zone, deep ramp and slope, subtidal microbialites, clastic-textured carbonates, and restricted peritidal carbonates. Microbialites are subdivisible into a number of facies that all have significance in terms of understanding environmental history as well as reservoir properties, and that help in predicting the location of reservoir fairways. Microbially influenced facies include shallow subtidal thrombolites with massive clotted textures and very high initial porosities (>50%), shallow subtidal pustular laminites with cm-scale variability of lamina morphology, deeper subtidal crinkly laminites that show mm-scale variability of lamina morphology, and intertidal tufted laminates that show mm- to cm-scale tufted textures. Other reservoir facies are more conventional grainy carbonates including ripple cross-stratified grainstone–packstone, hummocky cross-stratified grainstone–packstone, flat pebble conglomerate, ooid and intraclast grainstone–packstone, and Cloudina grainstone–packstone. These facies are almost invariably dolomitized and all have moderate to excellent reservoir quality. These facies comprise carbonate platforms, broken up during salt tectonics, that range up to 160 m (525 ft) in thickness and extended laterally, prior to halokinesis, for tens to over 50 km (31 mi). The distribution of reservoir facies follows sequence stratigraphic predictions, with microbialites occurring in every accommodation profile. Late highstand and early transgressive systems tracts favor greater lateral extent of thrombolite build-ups, whereas later transgressive to early highstand system tracts favor greater lateral discontinuity and compartmentalization of buildup reservoir facies. Pustular laminites occur in close association with thrombolite buildups but form laterally extensive sheets in late transgressive to late highstand periods. Crinkly laminites form during late transgressive to early highstand systems tracts and may represent maximum flooding intervals when the flux of carbonate sediment was greatly reduced allowing pelagically derived organics to accumulate.

The intersection of specialization and speciation

The intersection of specialization and speciation

Network growth approach to macroevolution

We propose a novel network growth model coupled with the competition interaction to simulate macroevolution. Our work shows that competition plays an important role in macroevolution and it is more rational to describe the interaction between species by network structures. Our model presents a complete picture of the development of phyla and the splitting process. It is found that periodic mass extinction occurred in our networks without any extraterrestrial factors and the lifetime distribution of species is very close to the fossil record. We also perturb networks with two scenarios of mass extinctions on different hierarchic levels in order to study their recovery.

Long-term evolution of an ecosystem with spontaneous periodicity of mass extinctions

Twenty years ago, after analysing palaeontological data, Raup and Sepkoski suggested that mass extinctions on Earth appear cyclically in time with a period of approximately 26 million years (My). To explain the 26 My period, a number of proposals were made involving, e.g., astronomical effects, increased volcanic activity, or the Earth's magnetic field reversal, none of which, however, has been confirmed. Here we study a spatially extended discrete model of an ecosystem and show that the periodicity of mass extinctions might be a natural feature of the ecosystem's dynamics and not the result of a periodic external perturbation. In our model, periodic changes of the diversity of an ecosystem and some of its other characteristics are induced by the coevolution of species. In agreement with some palaeontological data, our results show that the longevity of a species depends on the evolutionary stage at which the species is created. Possible further tests of our model are also discussed.

The Astronomical Pulse of Global Extinction Events

The linkage between astronomical cycles and the periodicity of mass extinctions is reviewed and discussed. In particular, the apparent 26 million year cycle of global extinctions may be related to the motion of the solar system around the galaxy, especially perpendicular to the galactic plane. The potential relevance of Milankovitch cycles is also explored in the light of current evidence for the possible causes of extinction events over a geological timescale.

On the origin of pattern and form in early Metazoans

The 'Cambrian explosion', about 540 million years ago, may have occurred within 10 to 50 million years. Almost all of the modern phyla, a very restricted group and many groups that may represent extinct phyla, suddenly appear near that time in the fossil record. Numerous extensive periods of mass extinction since that time led to no new phyla. This is taken as an impetus to examine a possible source, beyond Darwinian adaptation, of the apparently restricted number of phyla. Such a postulated constraint or restriction beyond adaptation is proposed to be based on a mutation or mutations allowing single celled or colonial precursors to begin forming into epithelial sheets and gene activation patterns of a particular kind, those giving rise to the very earliest metazoans. The interaction of signaling pathways in pairs, with different pairs acting sequentially are proposed as key to this earliest patterning, such patterning being extensively elaborated over the last approximately 550 million years. Restrictions on the very large set of possible forms and patterns on which adaptation acts are discussed.

Willis, K.J., McElwain, J.C. The evolution of plants

Willis, K.J., McElwain, J.C. The evolution of plants

Consequences of a Change in the Galactic Environment of the Sun

The interaction of the heliosphere with interstellar clouds has attracted interest since the late 1920's, both with a view to explaining apparent quasi-periodic climate catastrophes as well as periodic mass extinctions. Until recently, however, models describing the solar wind - local interstellar medium (LISM) interaction self-consistently had not been developed. Here, we describe the results of a two-dimensional (2D) simulation of the interaction between the heliosphere and an interstellar cloud with the same properties as currently, except that the neutral H density is increased from the present value of n(H) ~ 0.2 cm^-3 to 10 cm^-3. The mutual interaction of interstellar neutral hydrogen and plasma is included. The heliospheric cavity is reduced considerably in size (approximately 10 - 14 AU to the termination shock in the upstream direction) and is highly dynamical. The interplanetary environment at the orbit of the Earth changes markedly, with the density of interstellar H increasing to ~2 cm^-3. The termination shock itself experiences periods where it disappears, reforms and disappears again. Considerable mixing of the shocked solar wind and LISM occurs due to Rayleigh-Taylor-like instabilities at the nose, driven by ion-neutral friction. Implications for two anomalously high concentrations of 10Be found in Antarctic ice cores 33 kya and 60 kya, and the absence of prior similar events, are discussed in terms of density enhancements in the surrounding interstellar cloud. The calculation presented here supports past speculation that the galactic environment of the Sun moderates the interplanetary environment at the orbit of the Earth, and possibly also the terrestrial climate.

Giant comets, evolution and civilization

Giant comets thrown into short-period, Earth-crossing orbits are a major source of mass flux into the inner planetary system. Their disintegration products may give rise to climatic cycles, ice epochs, periodic mass extinctions and other global disturbances. Comets ≳100 kilometres in diameter, in chaotic orbits beyond Jupiter, probably constitute a more substantial current hazard than stray asteroids.

Diversification and extinction in the history of life.

Analysis of the fossil record of microbes, algae, fungi, protists, plants, and animals shows that the diversity of both marine and continental life increased exponentially since the end of the Precambrian. This diversification was interrupted by mass extinctions, the largest of which occurred in the Early Cambrian, Late Ordovician, Late Devonian, Late Permian, Early Triassic, Late Triassic, and end-Cretaceous. Most of these extinctions were experienced by both marine and continental organisms. As for the periodicity of mass extinctions, no support was found: Seven mass extinction peaks in the last 250 million years are spaced 20 to 60 million years apart.

Ancient reef ecosystem expansion and collapse

Platform carbonate and, particularly, reef ecosystem development (with reefs representing the acme of carbonate platform growth) were highly cyclical in early to mid Paleozoic time, especially in relation to known or postulated times of global warming or cooling. These cycles do not appear to correspond to postulated 26 Ma rhythms seen in diversity patterns, nor were they regular. There were major periods of worldwide reef expansion (e.g. mid-Silurian-Late Devonian), corresponding to global warming well above present day norms, and periods of complete global reef collapse (e.g., mid-Cambrian to mid-Ordovician, Late Devonian) corresponding to global perturbations. At times of major reef expansion in the Paleozoic, areas covered by equatorial reef and inter-reef carbonate platforms are conservatively estimated to have periodically exceeded 5 million sq. km, nearly ten times that in the modern ocean. At times of global reef collapse, e.g. the Famennian (Late Devonian), reef complexes were completely absent or, at best, covered <1000 sq. km. The chief factors relating to periodic collapse and mass extinction of reef biotas appear to be related to climatic change and possibly ocean anoxic events, in turn as a response to large scale, geologically disruptive factors such as plate collisions, plate movement across equatorial belts and volcanism. Stress “signals” in Cambrian through Cretaceous reef ecosystems appear to be comparable to those of today: whether these relate to physical versus biological stress is uncertain. Reef stress is evident in globally reduced areas and thicknesses of reef carbonate production, the absence of large scale barrier reef systems and reduction to smaller patch reef complexes (or, periodically, following mass extinctions, no reefs at all), reduced species and genus diversity, small skeletons or colonies, limited or no biotic zonation along reef transects, and arrested succession and ecologic replacement of complex, more highly evolved taxa by “simpler”, stress-resistant disaster taxa at the genus to ordinal (or even phylum) level.

THE STELLAR ANGULAR CORRELATION: CLUES TO WIDE BINARY STAR PROPERTIES

ABSTRACT The angular distribution of stars brighter than visual magnitude 14 is analyzed for evidence of gravitationally bound systems with widely separated components. Binary stars with separations on the order of 0.1 parsec are interesting as probes of Galactic dynamics, disk dark matter, the Oort comet cloud, and the postulated solar companion star, Nemesis. Catalogs of stars, complete to a resolution limit of four arcseconds, were constructed from digitized Schmidt telescope plates covering over 600 square degrees of the sky in four directions. I analyze the clustering properties of stars and star pairs using two-point and three-point angular correlation functions. Significant correlation (assumed to be due to binary stars) is detected only for angular separations less than 40 arcseconds. No significant numbers of ternary systems are detected. Employing a modified Wasserman-Weinberg technique, I directly compare the angular correlation functions with a simple model of wide binary star properties. The wide binary semimajor axis distribution at low Galactic latitudes is best described as a single power law of index -1.3. Near the North Galactic Pole (NGP), the power law is less steep and the distribution is consistent with a cutoff near 0.1~parsec. The derived wide binary density is unrealistically large, suggesting that the basic model inadequately characterizes wide binary properties. I also study a sample of stars from the Space Telescope Guide Star Catalog (GSC). The region analyzed lies within thirty degrees of the NGP and covers 2500 square degrees of sky. This large, low-resolution sample complements the smaller, more uniform plate catalogs. I identify many systematic errors in the GSC and attempt to account for image misclassifications and poorly defined resolution limits. The corrected stellar correlation function from the GSC is found to be consistent with a wide binary separation cutoff near 0.1parsec. The dissolution of a poor Galactic cluster at the NGP may explain the observed wide binary distribution in that direction. Evidence for weak clustering on scales of one degree is seen in the pair-pair correlation function. The unphysically large wide binary density derived from magnitude-limited samples is explained well by a luminosity correlation between the binary components. An alternative solution requires all F to K dwarfs to be members of wide binaries. Based on the observed properties of wide binary stars, the probability that the Sun has a stellar companion capable of inducing periodic mass extinctions on Earth is only 0.05 percent. In an analogy with Oort cloud dynamics, I suggest a mechanism that can substantially reduce the number of wide binaries with separations greater than 0.1 parsec.

Cretaceous/Tertiary and Permian/Triassic boundary events compared

The Cretaceous/Tertiary ( K T ) and Permian/Triassic ( P Tr ) events differ in many more aspects than they are similar. This alone makes it unlikely that they are parts of a common web of periodic mass extinction events (MEE). Unlike the K T , most MEE have no Ir anomalies and where (in the comparatively complete section of the P Tr at Gartnerkofel, Austria) weak Ir concentrations are found, their ratios to siderophile elements (Co, Ni, Cr) are far less than chondritic. In contrast, ratios to chalcophile elements (As, Sb, Zn) never approach chondritic, even in K T peaks and locality differences suggest local depositional processes that may also affect the siderophiles. Profiles of isotopes ( δ 13 C carb , 87Sr 86Sr , and possibly δ 18 O carb ) across these boundaries also differ radically. Whereas the K T profile of surface ocean δ 18 O carb has been shown to be mainly a drop in primary productivity, the P Tr profile is interpreted at least in part to be a consequence of a large and accelerating oxidation of previously stored C org, with greatly differing consequences for climate. These and other differences of proximate forcings for these two MEE lead us to a hypothesis that such external exigencies were ever (intermittently and severally) with us, but were effective only when the biotic web had already internally unravelled in some crucially strained patch. Gaia became Antigaia!