scholarly journals History is written by the victors: the effect of the push of the past on the fossil record

2017 ◽  
Author(s):  
Graham E. Budd ◽  
Richard P. Mann
Keyword(s):  
Fossil Record ◽  
Molecular Clocks ◽  
Phenotypic Evolution ◽  
Mass Extinctions ◽  
The Past ◽  
Extinction Rates ◽  
The Mean ◽  
Birth Death

AbstractPhylogenies may be modelled using “birth-death” models for speciation and extinction, but even when a homogeneous rate of diversification is used, survivorship biases can generate remarkable rate heterogeneities through time. One such bias has been termed the “push of the past”, by which the length of time a clade has survived is conditioned on the rate of diversification that happened to pertain at its origin. This creates the illusion of a secular rate slow-down through time that is, rather, a reversion to the mean. Here we model the controls on the push of the past, and the effect it has on clade origination times, and show that it largely depends on underlying extinction rates. An extra effect increasing early rates of lineage generation is also seen in large clades. These biases are important but relatively neglected influences on many aspects of diversification patterns, such as diversification spikes after mass extinctions and at the origins of clades; they also influence rates of fossilisation, changes in rates of phenotypic evolution and even molecular clocks. These inevitable features of surviving and/or large clades should thus not be generalised to the diversification process as a whole without additional study of small and extinct clades.

2. Extinction today and efforts to stop it

2019 ◽  
pp. 18-32
Author(s):  
Paul B. Wignall
Keyword(s):  
Big Five ◽  
Food Chain ◽  
Fossil Record ◽  
Abundant Species ◽  
Marine Conservation ◽  
Mass Extinctions ◽  
Species Extinction ◽  
The Past ◽  
Extinction Rates

The fossil record shows that life has experienced five major mass extinctions. A sixth catastrophe may be underway. Past mass extinctions were geologically short-lived intense crises that affected animals and plants in all environments. They removed the dominant and abundant species, leaving ecological voids to be filled by groups that were often rare or insignificant beforehand. Uniquely, the big five also saw the collapse of the base of the food chain in the oceans. The current extinction crisis does not yet have any of these attributes, but there are concerns over rising species extinction rates. ‘Extinction today and efforts to stop it’ compares current extinction rates with those of the past, and considers different terrestrial and marine conservation approaches.

3. Extinction in the past

2019 ◽  
pp. 33-50
Author(s):  
Paul B. Wignall
Keyword(s):  
Fossil Record ◽  
The Past ◽  
Extinction Rates ◽  
History Of ◽  
Extinction Events

Despite the less-than-perfect nature of the fossil record, it still provides a unique window on the history of life, and reveals that there have been dramatic fluctuations in extinction intensities since complex life evolved around 600 million years ago. ‘Extinction in the past’ considers Jack Sepkoski’s database compiled in the 1980s, and his series of highly informative charts showing both diversity and extinction rates since the start of the Cambrian Period 541 million years ago. The calculation of extinction rates and the improved dating of extinction events are discussed, along with the extinction trends that can be observed. Fossils also provide valuable evidence on the nature of selection during extinction.

On the statistical detection of cycles in extinctions in the marine fossil record

Paleobiology ◽  
1987 ◽  
Vol 13 (4) ◽  
pp. 465-478 ◽  
Author(s):  
James F. Quinn
Keyword(s):  
Fossil Record ◽  
Null Hypothesis ◽  
Time Lags ◽  
Mass Extinctions ◽  
A Posteriori ◽  
Alternative Analysis ◽  
Extinction Rates ◽  
Statistical Detection ◽  
Definition Of ◽  
Parameter Estimation Techniques

Periodicity has recently been reported in the extinction rates of fossil marine families since the Permian. The analysis used appears particularly sensitive to parameter estimation techniques, particularly in the definition of mass extinctions. It also fails to incorporate autocorrelation in the fossil record into its null hypothesis and rests on an inappropriate a posteriori comparison to the null hypothesis. An alternative analysis, examining the time-lags between periods of high extinction rates, produces no evidence of a cycle.

Extinction, the Causes of Extinction and the Conservation of Biodiversity

2008 ◽  
Vol 3 (3) ◽  
pp. 166-173 ◽  
Author(s):  
Hisashi Nagata ◽  
Keyword(s):  
Global Warming ◽  
Theoretical Background ◽  
Natural Process ◽  
Habitat Destruction ◽  
Mass Extinctions ◽  
Species Extinction ◽  
Biodiversity Crisis ◽  
The Past ◽  
Extinction Rates ◽  
Conservation Of Biodiversity

Over 25% of species are currently categorized as threatened. Extinction is a natural process in organism evolution, and 99% of all organisms that have thus far existed are already extinct. Current extinction rates, however, is progressing at least 2,500 times faster than in the past. Ongoing extinction is so fast, in fact, that organisms may not be able to adapt environment and to evolve. Current biodiversity crisis is called “sixth extinction” because it is severer than five geological mass extinctions. Habitat destruction, overexploitation, and invasion of species through human activities are currently the major causes of species extinction. Global warming is also expected to pose a considerable threat to Earth’s organisms. I briefly review the nature of species extinction, its processes, causes, theoretical background, and ongoing threats.

scholarly journals The dynamics of stem and crown groups

2019 ◽  
Author(s):  
Graham E. Budd ◽  
Richard P. Mann
Keyword(s):  
Molecular Clock ◽  
Fossil Record ◽  
Null Hypothesis ◽  
Mass Extinctions ◽  
Crown Group ◽  
Stem Group ◽  
Group Members ◽  
Evolutionary Explanations ◽  
Birth Death

ABSTRACTThe fossil record of the origins of major groups is of great interests to many biologists, especially when the fossil record apparently conflicts with timings based on molecular clock estimates. Here we model the diversity of “stem” (basal) and “crown” (modern) members of groups as seen in the fossil record, using a “birth-death model”. Under background conditions, the stem group members must diversify rapidly until the modern crown group emerges, at which point their diversity rapidly collapses, followed shortly by their extinction. Mass extinctions can disturb this pattern to create very diverse stem groups such as the dinosaurs and trilobites. Understanding these null-hypothesis patterns is essential for framing ecological and evolutionary explanations for how major groups originate and subsequently evolve.

scholarly journals Crustacean biodiversity through the marine fossil record

2000 ◽  
Vol 69 (4) ◽  
pp. 213-222 ◽  
Author(s):  
J. John Sepkoski
Keyword(s):  
Fossil Record ◽  
Major Group ◽  
Mass Extinctions ◽  
Data Bases ◽  
Extinction Rates ◽  
Marine Crustaceans ◽  
History Of ◽  
Fossil Preservation ◽  
Fossil Records ◽  
High Diversity

Approximately 2,600 genera of marine crustaceans have been recognized in the fossil record, and crustaceans constitute the major component of marine arthropod diversity from the mid- Paleozoic to the Recent. Despite problems of sporadic fossil preservation and/or taxonomic ambiguity, some general statements can be made about the history of crustacean biodiversity, based on global taxonomic data bases. Ostracodes were the first major group to radiate, attaining high diversity during the Ordovician Period with other members of the Paleozoic evolutionary fauna; rates of extinction and responses to mass extinctions were also similar to those of groups within the Paleozoic fauna. Malacostracans and barnacles (cirripedes), the two other crustacean groups with important fossil records, had minor diversity throughout the Paleozoic Era. Both groups experienced diversification from the mid-Mesozoic to Recent with lower extinction rates, as characteristic members of the Modern evolutionary fauna.

scholarly journals The dynamics of stem and crown groups

2020 ◽  
Vol 6 (8) ◽  
pp. eaaz1626 ◽  
Author(s):  
Graham E. Budd ◽  
Richard P. Mann
Keyword(s):  
Molecular Clock ◽  
Fossil Record ◽  
Large Scale ◽  
Mass Extinctions ◽  
Crown Group ◽  
Stem Group ◽  
Considerable Controversy ◽  
Long Stem ◽  
Evolutionary Explanations ◽  
Birth Death

The fossil record of the origins of major groups such as animals and birds has generated considerable controversy, especially when it conflicts with timings based on molecular clock estimates. Here, we model the diversity of “stem” (basal) and “crown” (modern) members of groups using a “birth-death model,” the results of which qualitatively match many large-scale patterns seen in the fossil record. Typically, the stem group diversifies rapidly until the crown group emerges, at which point its diversity collapses, followed shortly by its extinction. Mass extinctions can disturb this pattern and create long stem groups such as the dinosaurs. Crown groups are unlikely to emerge either cryptically or just before mass extinctions, in contradiction to popular hypotheses such as the “phylogenetic fuse”. The patterns revealed provide an essential context for framing ecological and evolutionary explanations for how major groups originate, and strengthen our confidence in the reliability of the fossil record.

The Pattern of Phyletic Speciation

Paleobiology ◽  
1982 ◽  
Vol 8 (1) ◽  
pp. 56-66 ◽  
Author(s):  
Doug Petry
Keyword(s):  
Allele Frequency ◽  
Quantitative Trait ◽  
Fossil Record ◽  
Punctuated Equilibrium ◽  
Time Span ◽  
Quantitative Character ◽  
Phenotypic Evolution ◽  
Adaptive Peak ◽  
The Mean ◽  
Equilibrium Pattern

Phyletic speciation arising from a shift between adaptive peaks in the selective surface is modeled. At a locus initially monomorphic, a new allele is introduced that triggers phenotypic evolution by making a new adaptive peak available. A phenotypic model is used to describe the evolution of a quantitative character that is important for fitness but not directly affected by the new allele. Recursion equations are derived for both the allele frequency and the mean of the quantitative character. It is shown that the dynamics of the quantitative trait fit a “punctuated equilibrium” pattern of evolution. Phyletic speciation is seen to occur over a time span so short as to make observation of the transition in the fossil record unlikely.

Numerical experiments with model monophyletic and paraphyletic taxa

Paleobiology ◽  
1993 ◽  
Vol 19 (2) ◽  
pp. 168-184 ◽  
Author(s):  
J. John Sepkoski ◽  
David C. Kendrick
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Mass Extinction ◽  
Fossil Record ◽  
Numerical Experiments ◽  
Mass Extinctions ◽  
Diversity Patterns ◽  
Extinction Rates ◽  
Low Levels

The problem of how accurately paraphyletic taxa versus monophyletic (i.e., holophyletic) groups (clades) capture underlying species patterns of diversity and extinction is explored with Monte Carlo simulations. Phylogenies are modeled as stochastic trees. Paraphyletic taxa are defined in an arbitrary manner by randomly choosing progenitors and clustering all descendants not belonging to other taxa. These taxa are then examined to determine which are clades, and the remaining paraphyletic groups are dissected to discover monophyletic subgroups. Comparisons of diversity patterns and extinction rates between modeled taxa and lineages indicate that paraphyletic groups can adequately capture lineage information under a variety of conditions of diversification and mass extinction. This suggests that these groups constitute more than mere “taxonomic noise” in this context. But, strictly monophyletic groups perform somewhat better, especially with regard to mass extinctions. However, when low levels of paleontologic sampling are simulated, the veracity of clades deteriorates, especially with respect to diversity, and modeled paraphyletic taxa often capture more information about underlying lineages. Thus, for studies of diversity and taxic evolution in the fossil record, traditional paleontologic genera and families need not be rejected in favor of cladistically-defined taxa.

scholarly journals The past and future human impact on mammalian diversity

2020 ◽  
Vol 6 (36) ◽  
pp. eabb2313 ◽  
Author(s):  
Tobias Andermann ◽  
Søren Faurby ◽  
Samuel T. Turvey ◽  
Alexandre Antonelli ◽  
Daniele Silvestro
Keyword(s):  
Human Impact ◽  
Fossil Record ◽  
Human Population ◽  
Biodiversity Crisis ◽  
The Past ◽  
Extinction Rates ◽  
Current Trends ◽  
Predictive Methods ◽  
Near Future ◽  
Better Than

To understand the current biodiversity crisis, it is crucial to determine how humans have affected biodiversity in the past. However, the extent of human involvement in species extinctions from the Late Pleistocene onward remains contentious. Here, we apply Bayesian models to the fossil record to estimate how mammalian extinction rates have changed over the past 126,000 years, inferring specific times of rate increases. We specifically test the hypothesis of human-caused extinctions by using posterior predictive methods. We find that human population size is able to predict past extinctions with 96% accuracy. Predictors based on past climate, in contrast, perform no better than expected by chance, suggesting that climate had a negligible impact on global mammal extinctions. Based on current trends, we predict for the near future a rate escalation of unprecedented magnitude. Our results provide a comprehensive assessment of the human impact on past and predicted future extinctions of mammals.

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