Behaviour evolves, but evolution is a lot more than 'survival of the fittest'
by Agustín Fuentes on
Recent headlines promise to tell us about the evolution of human sociality, the evolution of war and peace, and even the evolutionary and genetic correlates of cellphone use. Pretty cool, but there is no way that these can be simple, straightforward stories, no matter how well told. Evolution involves complicated genetics, messy development, and niche construction.
Not everything we do is directly the product of evolutionary forces, or even evolutionarily relevant, but evolution is important to understanding behaviour. Our bodies and the neurological and psychological processes that influence the way we think, feel and act are, in part, shaped by our evolutionary histories and ongoing evolution. But evolution is not simply 'survival of the fittest.' It is more complicated than that.
Our basic understanding of how evolution works in the early twenty-first-century can be summarized as follows: Mutation introduces genetic variation which in interaction with epigenetic and developmental processes produces variation in organisms, which may be passed from generation to generation.
Natural selection shapes variation in response to specific constraints and pressures in the environment, but dynamic organism-environment interaction can result in niche construction, changing the shape of natural selection and creating ecological inheritance.
In humans, cultural patterns and behavioural actions and perceptions can impact genetic patterns and the process of natural selection, which in turn can affect developmental outcomes.
We have to be aware that multiple systems of inheritance (genetic, epigenetic, behavioural, and even symbolic) can all provide information that influence our interactions with the world around us, with one another, and can cause biological change over time (evolution). Looking at two of the many evolutionary relevant processes, epigenetics and niche construction, can give a bit of insight into how complex evolution is.
Genes play an important role in our development and functioning, not as directors, but rather as parts of a complex system. Simple models and labels like 'blueprints,' 'building blocks,' or 'code of life' are really poor ways to describe our DNA. It is misleading to talk about genes as doing things by themselves, they exist as part of a larger, integrated system.
Epigenetics is the study of all the systems of interactions in development above the level of the gene. It reflects the reality that multiple factors influence the development of an organism and that there are very, very few instances of direct gene-to-trait scenarios. Traits like body size and shape, face form, and so on, emerge from the interaction of many genes and a range of developmental and environmental influences.
Epigenetic processes such as DNA methylation, chromatin remodeling, and micro-RNAs are all supra-DNA processes that can affect gene function and regulation, but are not coded for in the DNA. Their actions can have cross generational, evolutionary, impacts. For example, non-genetic responses by the foetus to uterine and external environments can also have multi-generational physical and morphological effects.
Many early physiological stresses can affect gene expression and patterns of inheritance later in life. And, all of these epigenetic variations can produce different outcomes for organisms with the same DNA sequences!
Obviously epigenetics can influence behavioural patterns, but not in a linear or easily described manner. The concept that there are two core variables in human development, the outside (environment) and the inside (genes), is incorrect. Our systems of development and inheritance are too complicated, and the boundaries between our genes, epigenetic systems, bodies, and ecologies much too fluid.
Niche construction is the concept that organisms and their environments interact with and shape one another across evolutionary time. Under the traditional assumptions about natural selection, the environment acts as a filter and constraint on organisms, causing functional changes over time.
With niche construction, organisms have an active role in shaping the environment in response to the pressures it exerts. This leads to an organism-environment relationship that is dynamic, and bi-directional.
Take earthworms, for example. When you introduce earthworms to a new plot of soil they are challenged by the soil and its chemical and structural consistency. Over time, as the worms move through the soil they ingest it and excrete it and that process alters the chemical make up of the soil and its consistency, changing the pressures that the soil environment exerts on subsequent generations of earthworms in the same location.
Now think about human action with agriculture and domestication…radical niche construction.
Niche construction results in an ecological inheritance that goes alongside the genetic, and epigenetic, inheritance, and has to be considered when thinking about evolutionary explanations. Niche construction theory is particularly relevant to the dynamics of human behaviour as the process includes the effects of the cultural context and human behaviour as an active part of our evolutionary dynamic.
Evolution of human behaviour is always a synergy of multiple processes, not just the product of selection on genes. Natural selection, the process by which variants have differential representation in subsequent generations, is just one of the many processes in evolution.
When we think about human behaviour it is a mistake to think that our biology exists separate from our social and structural ecologies or that our cultural selves are not constantly entangled with our biological landscapes.
Thinking about evolutionary processes in a modern context gives us an improved chance at getting better answers to questions about the evolution of human behaviour.
Evolution involves complicated genetics, messy development, and niche construction.