Author: Justin Kong
Artist: Amber Stratton
Editor: Sacha Goldenberg
Before Darwin’s monumental monograph On the Origin of Species, the question of what exactly drove an organism to change had confused biologists for a long time. Only after Mendel’s work on peas did evolutionary biology have a cohesive, plausible, and testable hypothesis on how organisms may change progressively over time–through the action of genes. Following the influential work of Fisher and Weissmann, genes had come into a position that had never been envisioned by pioneers of evolutionary biology before: genes are not simply molecules coding for traits, they are the only things which give rise to any biological structure. Organisms disappeared from modern evolutionary thought, leaving genes in focus. Genes replicate, inherit and evolve; while organisms are merely a “transition.”
Is it the full picture though? Should genes be bestowed a theoretical privilege in evolutionary causation? It is indisputable that genes are central in generating diverse forms and functions, but are they the only factor affecting an organism? Following the discovery that environmental changes can produce distinct phenotypes among organisms of identical genomes (called phenocopies), the immovable position of genes in trait productions started to bulge. Maybe there isn’t such a “blueprint” in each of us after all, and just as Darwin had envisioned, maybe we are the child of both the “environment” and the “gene.”
Another blow to the unquestionable centrality of genes in controlling an organism comes from how little genetic changes correspond to most evolutionary changes. Higher organisms such as mammals and flowering plants can adapt to environmental changes so quickly that random mutations will never have the time to spread through populations. Even primal organisms like bacteria and Protoctista, which were thought to be a mere container of genes, have colony structures and dynamics minimally controlled by genes. In predatory bacteria such as Myxococcus–which hunt in packs–the leader cell is not chosen based on who has a better genotype, but rather how colonies are arranged before they encounter their prey.
This gene-minimalist (as opposed to gene-centralist) nature in inheritance and evolution is even more obvious when it comes to how a bacterial colony evolves over time. Rather than pure genetic control, a colony can change its structure (e.g., how many cells in each community, the genetic composition of each cell, how different cells utilise resources) based on different ways a colony “reproduces”. Just like a true multicellular system, bacterial colonies spread by producing progenies consisting only of portions of the parental colony. Logically, the genetic composition of cells of their offspring colonies are not dependent solely on which gene is the fittest, but rather the organisation of parental colonies. Thus, genes can be said to play a highly diminished role in such selection processes.So what are the implications? Stating genes are not the only player for evolutionary change does not mean genes should be discarded, but rather suggests that their role in directing an evolutionary change has been severely overestimated and needs to be reconsidered in the light of other possible inheritance mechanisms. A more holistic approach in inheritance, in which environmental factors in evolution are explicitly considered and modelled, means selection and evolution do not need to wait for genetic change; and may shed light on the evolution of multicellularity, social structures of animals, or even cancer.
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