Release of scientific papers
A new release on bioRxiv analyses the abundance trajectories for more than 1200 populations of birds and mammals to examine whether they are explained by selection-regulated dynamics or by density-regulated growth.
It is estimated that selection-regulation is 25,000 times more probable than density-regulated growth at the median, and that less than 3% of the best population dynamic models have density-regulated growth as assumed in most population dynamic studies.
A release on bioRxiv estimates complete equilibrium life history models for 90% of all bird and mammal species. These models are used in a new publication series to document the importance of population dynamic feedback selection for the evolution of life histories and population dynamics in birds and mammals.
Population dynamic feedback selection is an entangled process that links the frequency-independent selection of the physiology to the density-frequency-dependent selection of interactive competition. This ecological interdependence of several processes makes it difficult to understand many of the details in the selection. With the new publication series I aim for an easier visualisation by using data-plots instead of mathematical equations to describe the underlying natural selection mechanisms.
A release in Evolutionary Biology shows how the selection of metabolism bends body mass evolution over millions of years by dilation and contraction of natural selection time.
Unconstrained natural selection predicts an exponential (i.e., log-linear) increase in body mass on the per-generation timescale of natural selection. But the log-linear trajectory is bent in physical time because the timescale of natural selection evolves with the evolutionary changes in mass.
Natural selection time evolves by the inverse of mass specific metabolism, and the selection of metabolism generates part of the net energy for the natural selection of mass. The bend of body mass evolution thus reflects the importance of metabolism for the natural selection of mass. The potential continuum of metabolic selection ranges across four scale dependent modes of selection, with each mode being confirmed by a unique bend of fossil trajectories over millions of years.
A released in Oikos shows how the natural selection of metabolism is bending inter-specific allometries over time; explaining curvature and outlier species in metabolic scaling.
Metabolic outliers have remained an unsolved mystery in evolutionary biology. Why have shrews and the honey possum evolved a higher metabolism than expected from their small size, and why have the bowhead whale and the hairy-nosed wombat a smaller metabolism than expected from their large size?
The lifeform paper is now published in Ecology and Evolution.
A major hole in our understanding of evolution relates to the natural selection of life history differences among negligible-sized organisms, as observed between virus, bacteria and larger unicells. The original version of Malthusian Relativity was well-suited for the prediction of life histories in multicellular animals, but all low energy organisms were selected to a lower size limit with no mass.
While this was clearly not fully correct, it might be that accurate predictions in the lower size range might not be possible. But the paper in Ecology and Evolution shows that the inclusion of primary selection on metabolism makes the selection equations for organisms below multicellularity unfold into the three life history classes of virus, bacteria and larger unicells.
The allometry paper is out in Theoretical Population Biology.
The inter-specific allometries are a fingerprint of evolution, a print that can reveal the natural selection laws that have created the diversity of living organisms on Earth. And with the publication in Theoretical Population Biology, biology has its first theory that shows how the natural selection of metabolism and mass is explaining allometric transitions from prokaryotes over unicellular eukaryotes to multicellular animals.
In a new paper on bioRxiv I show how the natural selection of metabolism bends inter-specific allometries over time; explaining the curvature in the metabolic allometry of mammals.
The natural selection of metabolism and mass predicts linear inter-specific allometries from invariant selection responses in clades of animals that diversity with speciation into different ecological niches. But this evolution stops when species adapt to their niches, with a body mass distribution that evolves over time to be more and more affected by the background selection of mass specific metabolism.
While this background selection is expected to be invariant of mass on the per generation time-scale of natural selection, the relative increase in physical time is largest in the smaller species that evolve over a larger number of generations. And as the net energy that is generated by the metabolic increase is selected into mass, it follows that the left-hand side of the allometry is bending upward over evolutionary time.
A new paper on bioRxiv shows how the natural selection of metabolism is bending body mass evolution in the fossil record by dilation and contraction of natural selection time.
Unconstrained population dynamic feed-back selection predicts an exponential (log-linear) increase in body mass on the per-generation time-scale of natural selection. But the log-linearity is bend in physical time whenever the time-scale of natural selection is evolving with the evolutionary changes in mass.
And with a natural selection time that evolves as the inverse of mass specific metabolism, the degree of bending is given by the dependence of the metabolic allometry on the relative importance of metabolism for the evolution of mass. The result is body mass evolution that varies over four modes of selection; with each mode being confirmed by a unique bend of the relevant trajectories in the fossil record.
A new study on bioRxiv presents the first natural selection theory that is sufficient to explain the joint evolution of lifeforms from virus over prokaryotes and larger unicells to multicellular animals with sexual reproduction.
Evolution on Earth have created distinct lifeforms with discrete size classes and unique life histories. These include i) virus with no metabolism, no cell, and almost no mass; ii) prokaryotes with a small cell, asexual reproduction, and a mass specific metabolism that increases with mass; iii) asexual unicellular eukaryotes with a larger mass than prokaryotes, and a mass specific metabolism that is first increasing and then declining with an increase in mass; and iv) large multicellular animals with sexual reproduction and a mass specific metabolism that declines with mass.
This macro evolutionary pattern is explained from the primary selection of mass specific metabolism and mass.
In a new paper on bioRxiv I show how the primary selection of metabolism and mass is explaining allometric transitions from prokaryotes over unicellular eukaryotes to multicellular animals.
It is difficult to overestimate the importance of inter-specific allometries for our understanding of evolution, as the allometric exponents reveal the correlated evolution between the life history and mass. This correlation is not restricted to well-known Kleiber scaling, where the exponent is -1/4 for the allometry between mass specific metabolism and mass. The metabolic exponent is instead increasing on a macro evolutionary scale with a decline in mass, over an apparent body mass invariance in unicellular eukaryotes, to a strongly positive value of about 0.84 in prokaryotes (Makarieva et al., 2008; Delong et al., 2010).
This change indicates a change in the mechanisms of natural selection across the tree of life. And by integrating the primary selection of metabolism into the natural selection of mass and allometries (Witting, 1995, 2008), I find that a change in the importance of mass specific metabolism for the selection of mass is explaining the allometric transitions from prokaryotes over larger unicells to multicellular animals.
In a 2013 paper in Population Ecology I study the commercial over-exploitation of large whales in past centuries, an exploitation that introduced the biggest population dynamic experiment on Earth. It had been running for more than fifty years when Newton introduced his Law’s of motion in physics in 1687, showing that it is the acceleration, and not the speed, of a planet that is determined by the gravitational force acting upon it. Today, population biology faces a similar transition. Data are accumulating from the experiment that started before Newton, showing that populations resemble planets with growth acceleration, and not growth, being determined by the density dependent environment.
A universal theory of natural selection would predict evolution from first principles of self-replication; but evolutionary theory was originally constructed backwards with natural selection being contingent upon evolutionary history. Instead of providing a mathematical theory that explained observed patterns from self-replication, Darwin proposed that existing species are understood from their evolutionary history of common origin. This contingency became the paradigm of theoretical biology in 20th Century; with the theory of Malthusian Relativity being constructed as an alternative to show that biotic evolution is an inevitable unfolding from the origin of self-replicating entities. In a 2008 paper in Biological Reviews I describe differences and similarities between contingent and inevitable evolution, showing that natural selection unfolds to higher-level selection for major evolutionary trends and transitions.