Patrimony and the Evolution of Risk-taking

2011-03-22T11:12:00.001-07:00

This paper by Michael D. Stern provides an interesting insight into the evolutionary dynamics of risk-taking: it is evolutionarily favored when and only when parental resources can be passed to offspring. The paper deserves to be widely read and followed up by testing its robustness to changing assumptions, probing its applicability in biological and social contexts, and teasing out its implications for the generation of diversity by evolutionary processes. One question that immediately springs to mind is how this fits in with Peter Richerson's and Robert Boyd's theory of cultural evolution—see Not By Genes Alone: How Culture Transformed Human Evolution (affiliate link). Another is to what extent this relates to Dean K. Simonton's historically-based viewpoint laid out in Origins of Genius: Darwinian Perspectives on Creativity (ditto). A third is the interplay between this dynamic and “relaxed selection.” I personally would be most interested in seeing to how this dynamic extends to cooperating groups, whether of kin or of nonrelated individuals—see Genetic and Cultural Evolution of Cooperation (ditto).

Patrimony and the Evolution of Risk-Taking

Abstract: The propensity to make risky choices has a genetic component, and recent studies have identified several specific genes that contribute to this trait. Since risk-taking often appears irrational or maladaptive, the question arises how (or if) natural selection favors risk-taking. Here we show, using a stochastic simulation of selection between two hypothetical species, “R” (risk-seeking) and “A” (risk-averse) that, when expected reproductive fitness of the individual is unaffected by the making of the risky choice (winnings balanced by losses) natural selection (taken to the point of extinction) favors the risk-averse species. However, the situation is entirely reversed if offspring are permitted to inherit a small fraction of the parent's increased or decreased fitness acquired through risk-taking. This seemingly Lamarckian form of inheritance actually corresponds to the human situation when property or culture are transmitted in families. In the presence of this “cultural inheritance”, the long-shot risk-taking species was overwhelmingly favored, even when 90% of individuals were rendered sterile by a losing choice. Given this strong effect in a minimal model, it is important to consider the co-evolution of genes and culture when interpreting the genetics of risk-taking. This conclusion applies, in principle, to any species where parental resources can directly affect the fecundity of offspring. It might also be relevant to the effects of epigenetic inheritance, if the epigenetic state of zygotes can be affected by parental experiences.

Protein Space Still Ripe For Exploration

2010-03-13T13:19:00.000-08:00

Proteins are Nature's Robots: they carry out most of the activities of life, as well as constituting some of its major structural building blocks. Many of them fold into structurally stable conformations, which can then form crystals. Crystallographers “solve” the 3-dimensional structure of a protein by computing the coordinates of each of its constituent atoms from the X-ray diffraction pattern of these crystals. Thousands of such structures have been deposited in the Protein Data Bank (PDB). These beautiful macromolecules constitute The Machinery Of Life; author and illustrator David S. Goodsell highlights some of the fascinating stories of how they work in his Molecule of the Month column.

Clearly, only a finite number of proteins exist among all the living organisms on the Earth today. How far have we gotten in exploring the space of proteins? From a historical point of view, we can judge the extent to which a culture had explored the surface of the Earth over time by looking at the maps drawn by people of that culture. Had they encountered all the continents? How fine is the level of detail for each continent?

Current maps of protein space can be found at SCOP: Structural Classification of Proteins and CATH: Protein Structure Classification Database. For simplicity I'll discuss SCOP, although CATH is similar. From the Introduction to SCOP, “the different major levels in the hierarchy are: Family: Clear evolutionary relationship; Superfamily: Probable common evolutionary origin; and Fold: Major structural similarity.” Let's look at the growth of each of these categories in SCOP over time:

In each case I've set the height of the Y-axis at three times the value in July 2001 when SCOP version 1.55 was released. The rate of finding new folds (the “continents” of protein space) is neither taking off (as we might expect if there had been the same kinds of fundamental advances in protein structure determination as in sequencing) nor levelling off (as we might expect if we had explored most of the existing space). The conclusion is clear: there's plenty of unknown territory left for the pioneers of tomorrow.

Datta Analysis

Patrimony and the Evolution of Risk-taking

Protein Space Still Ripe For Exploration