(Sunrise on top of Mt. Fuji)
This is the first time I attended a conference of this size, and I expected myself to explore the various topics currently studied in the molecular biology of evolution.
One variation among different symposia is the definition of evolution at which the researchers are interested. The most limited definition might be any change in the frequency of alleles within a population from one generation to the next, which is a useful definition for population geneticists to estimate if a population is evolving. Therefore, symposia like ecological genomics showed lots of data and analysis on alleles frequency. But a more expansive definition driven by the more accessible genomic sequencing data is widely considered in different talks: any change in the properties of a population from one generation to the next is evolution, which includes the origin and the spread of alleles, variants, trait values, character states… etc. Questions focusing on human migration, human-pathogen interaction, somatic mutation… etc. heavily rely on this definition to approach the answers. Interestingly, this definition is not expansive enough to include molecular evolution, which focuses on the molecular changes within macromolecules such as DNA and RNA. Symposia of the evolution of transposable element, epigenetics, and post-transcriptional modification, show me various exciting topics on the level of molecular evolution. How the evolution on the molecular level and populational level are linked together is also an intensively studied question. Symposia like weak forces in genome evolution, non-functional DNA, and selection on complex traits provided many interesting theories to unite the two levels.
A very different definition that can also be found in this conference is that evolution is the control of development by ecology. Symposia relevant to evo-devo (e.g., the evolution of human brain) have many topics think about questions based on this definition. Researchers working with this definition also have their interest in the question about how much information of the change in environment is recorded in genome? Of what unit ?(individuals, effective population, or species?). For example, a talk about the evolution of domestic animals try to answer a question: Is the change of behaviors across generations a proxy of genomic change, or is it so easy to be acquired that genomic change is not involved?
There were also some biologists sought to extend evolutionary ideas to the cultural realm. E.g., the evolution of music. It is not hard to image that cultures store informations that increase fitness of social animals. Researchers are interested in applying methods of quantification and try to construct phylo tree.
Researchers in this conference also showed various degree of different modes of evolution. Current mathematical evolutionary models in population genetics are typically statistical models. Whether natural selection and genetic drift should be understood as causes of evolution or as mere statistical summaries of lower-level causes: births, deaths, etc.? Researchers working in macro level directly assumed the causality as true and made many hypothesis with adaptive storytelling. On the other hand, researchers working in micro level showed a higher interest in experimental design that can directly address the causal relationship because manipulation on the environment is easier.
Whether natural selection is the most prevalent or most important mode of evolution is also assumed variously in different topics. Should we test natural selection hypotheses or toward a variety of possible evolutionary modes? If natural selection is not the most prevalent as neutral theory suggests, then how do we explain adaptation? The exploration of fitness landscape may give us some data to approach these questions, while most the time natural selection hypotheses are the default in many talks.
But even within those talk that focus only on natural selection showed variety in the definition of fitness. Typically, natural selection invoke fitness: why X was more successful than Y might invoke X’s higher fitness. So what does fitness mean? What entities does it apply to (genes, organisms, groups, individuals, types… etc). Is it a priori knowledge or empirical knowledge? How should we calculate it?
If there is anything in common amount the evolution biologists, that would be that they all disagree with creationism. However, how a researcher treats teleological terms frequently used in biology (e.g., a function of a trait) varies widely as well. In principle, a hypothesis that involves teleological terms should naturalize (i.e., reduce into mechanistic explanation) these concepts, otherwise this hypothesis would not be empirically testable because of some “life-force” or backward causation implied by teleological terms. Natural selection can theoretically be applied to naturalize the concept of function: a trait’s function causally explain how this trait is maintained in a given population through the mechanism of natural selection. Therefore, when a function of a trait is proposed, some data of fitness assay with quantifiable modifications on traits can confirm this function. The current difficulty is the mechanistic connection between genotype and phenotype through population fitness. Researchers of micro level are motivated by questions like “How SNP affect fitness?”, “What is the fitness landscape of every point mutation of a given gene?” and test different theories. Researchers of macro level, on the other hand, usually compromise and directly assume functions that they care are results of natural selection. Can a macro level/more complicated fields (e.g., evolutionary psychology) that appeal to lots of adaptive storytelling be secured as long as the micro level/more reduced fields are empirically testable? If natural selection on a macro trait is neither necessary nor sufficient to natural selection on micro traits that emerge this macro trait, then the answer is no. Questions involving this difficulty also include “How biological functions originally evolved from non-biological mechanism?”, “How much portion of genome can be under natural selection so the genotype can maintain in a population?”… etc.
Maybe what makes all of us move on in this field is the curiosity that motivates us to understand how this world becomes what we observe today but not just an equilibrium state of second thermodynamic law.