Biology: Evolution and Life

In The Selfish Gene (1976) and The Extended Phenotype (1982), Richard Dawkins reframed evolution around genes as the units of selection and replication. In this view, organisms are vehicles for genes, and natural selection operates at the genetic level. Genes replicate with occasional errors, and those errors that improve a gene's chances of copying itself become more common.

This perspective helped explain many evolutionary puzzles: why genes would build large bodies and complex brains, why organisms often act against the interests of their species, and how traits that seem to damage an organism can persist if they benefit the genes that code for them. The gene-centric view unified Darwinian evolution with Mendelian genetics and became central to the modern evolutionary synthesis.

Critics argue that this view, though powerful, can overlook the hierarchical nature of biological organization: genes do not act in isolation, but within cells, tissues, organs and organisms. The gene-centric model explains inheritance but struggles with how complex systems arise from genetic instructions, and with the role of regulatory mechanisms, epigenetics, and the organism's environment in shaping what genes do.

Denis Noble and other systems biologists propose that genes are necessary but not sufficient to explain life. In this view, causation flows in multiple directions: genes influence cells, but cells also regulate which genes are active; tissues shape cell behaviour; organisms interact with their environments. Life is a multi-level system in which no single level holds all the answers.

Noble's principle of biological relativity states that the level at which causation appears to operate depends on the question asked and the scale at which we look. A mutation in a gene affects the protein it codes for, the cell containing it, the organ it helps build, the organism's behaviour, and the ecosystem it inhabits. Each level has real causal power.

This view explains epigenetics, in which the same DNA sequence is read differently depending on chemical modifications that are reversible and can be inherited; developmental plasticity, in which the same genes build different forms in different environments; and the canalization of development, in which multiple genetic and environmental perturbations can be buffered by the system's robustness.

Genes carry information copied from parent to offspring, but so does the environment. An organism inherits DNA from its parents, but also the cell's epigenetic state, maternal effects such as hormones and antibodies, its ecological niche, and the behaviour of other organisms around it.

Recent work in developmental biology, epigenetics and environmental science shows that the boundary between 'nature' and 'nurture' is porous. Gene expression is controlled by regulatory sequences that respond to the environment. Histone modifications and DNA methylation, which affect which genes are read, can be inherited for generations without changing the DNA sequence. Microbes in and around an organism influence its development and health.

Both perspectives agree that genes are crucial to life. The disagreement is about what 'genes' do and at what level we need to look to understand inheritance, development and evolution. Genes interact with regulatory networks, other genes, the cell, the organism, the ecosystem, and history. Understanding life means understanding all these interactions.