Biological redundancy is defined as the presence of two very similar mechanisms in an organism such that if one is deleted the organism experiences little to no effect on fitness under standard laboratory conditions. Many scientists haven’t prioritized the study of redundant genes, but have instead focused on the more accessible fruit of essential genes or genes with cool knockout phenotypes.
Genes of Interest
In my graduate research studies, I observed that often one must justify the study of a gene without an obvious phenotype by demonstrating some fitness defect. Of course, it makes sense that one should have a reason for studying their gene of interest. However, justifying scientific investigation based on fitness under standard laboratory conditions always seemed problematic to me on a number of levels. Aside from the obvious issue that standard laboratory conditions do not accurately represent the different environments and stressors an organism encounters in nature, the following also troubled me:
- Why is justification based on fitness instead of function?
- Is it reasonable to deprioritize genes without clear fitness defects?
One reason “fitness justification” might currently be emphasized is because neo-Darwinism predicts duplicate and non-functional genetic material exists without a purpose. (Weir 1946; Zhang 2003; Magadum et al. 2013; Nei 1969) Indeed the amount of duplicate and nonessential DNA actually required by the neo-Darwinian stab-in-the-dark approach to create new functions is startlingly large. (Snoke, Cox, and Petcher 2015) Knowledge of this reality could leave scientists assuming that a significant portion of genetic material must be “junk” or in the “waiting to evolve” category. When the scientific community is still trying to understand the basics of an organism, studying a “waiting to evolve” gene isn’t top priority, hence preference goes to investigations of more obvious purposeful mechanisms in the cell.
Caveat: many scientists holding to neo-Darwinism, of one form or another, do not take the approach that genes without obvious phenotypes are unimportant, evolutionary remnants, or “genes in waiting.” Instead they disconnect from certain implications of the theory (namely that there must be loads of duplicate and junk DNA in the genome for a stab-in-the-dark approach to work) and embrace more strongly the idea that conserved genes, even duplicates, are important because they haven’t been eliminated by natural selection.
Confusion About Redundancy
The point I want to make is that confusion about redundancy begins with a conceptual conflict in what neo-Darwinism predicts regarding redundancy in genomes. In case you missed it, here’s the conflict restated. On the one hand, neo-Darwinism requires duplicate genetic material for developing evolutionary novelty. On the other hand, natural selection is in the business of purging genomes of fitness-null genetic material.
Martin Nowak explores and attempts to solve part of this conundrum in his paper “Evolution of genetic redundancy.” You’ll need to read more than just a quote to grasp his perspective. But he highlights the logic of redundancy from an engineering perspective and the problem this poses for Darwinism:
Such a redundant genetic organization is sensible from an engineer’s point of view: important functions require backup devices that can take over in case of failure. But can natural selection favour the emergence and stability of redundant genes?Nowak et al. 1997
Nowak points out that from an engineering perspective it is easy to make sense of genetic redundancy: engineers build back-up mechanisms to prevent system failure and from a design perspective there’s no requirement for loads of “junk” or “waiting to evolve” DNA. Therefore when design proponents encounter biological redundancy, they can assume function and use design triangulation instead of fitness defects to build testable hypotheses. In this way, intelligent design licenses scientists to be curious about non-conserved biological redundancy and to investigate the possibility that biological redundancy is purposeful.