If you go on a nature trek, you will notice several things:
- A multitude of species.
- Some areas have more species than others.
- Some species share morphological similarities with each other, but share few similarities with others.
- Interactions between species – insects feeding on plants, parasitic mites on those insects, mimicries, etc.
Conduct treks over an entire year or two, and you will start noticing some other phenomena:
- Sustained daily and hourly patterns of behaviour.
- Changes in behaviour and even appearance during different seasons.
- Migrations over short or large distances.
If you’re a biologist coming across these phenomena, your curiosity will be piqued and you will start asking questions, such as “where did all this diversity in species and interactions come from?”, “What is the relationship between all these species?”, or “What is the reason why these clockwork-like behavioural patterns exist?”.
You will find the answers in evolutionary biology. It’s the broadest discipline of biology, and its closest companion is phylogenetics, the study of generational successions over time. This relationship will be looked at throughout this series, but suffice it to say that without phylogenetics, evolution loses one of its most critical parameters, which is historical time.
This broadness in scope of evolution is why every biologist must be familiar with it. Evolution is the glue that holds all of biology together. It’s the theory that underlies the entire discipline, the theory in which all of the observations and experiments done by all biologists, from biochemists to ecologists, are framed.
Evolution is a historical, empirical science. When we talk about evolution in the wild or in the fossil record, we’re describing the results of observations done on a gigantic natural experiment that’s been going on for millions of years. We conduct these observations with a hypothesis in mind, a question that we want answered. Of course, there is also an experimental aspect to the study of evolution (the field of experimental evolution is a real thing), which is what we use to enlighten us on the processes behind evolution.
As with all sciences, human limitations must first and foremost be acknowledged when making observations. For example, we need special visual filters to see why many insects are attracted to plants, because we can’t see UV light. Without these filters, our conception of insect behaviour and evolution would vary – we wouldn’t know just how deep the coevolution between flowers and insects runs.
As with all scientific disciplines, evolution has always been very dynamic. Ideas and concepts get created, developed, and demolished constantly. Most of these take place at the cutting edges of the discipline, but occasionally the foundation of the science can get rebuilt. This happened most prominently with Charles Darwin‘s and Alfred Russel Wallace‘s definitive illustration of natural selection, and with the erection of the Modern Synthesis under which we still work today (with a new Synthesis coming soon!).
This makes for a very healthy science, but it also means one must be careful when reading older books and works on evolution, which are often very wrapped up in the scientific Zeitgeist of the time and place. You would gain very little knowledge from reading evolutionary biology from the Lysenkoist period of Soviet Russia. Reading the works from the late 19th century, even Darwin’s works, wouldn’t benefit you much – for example, you will often find heredity being referred to, but they had no idea about DNA or genetics (see the “Life as Chemical” slide here for made-up hereditary concepts).
In other words, always consider hypotheses, interpretations, and terminologies according to the time and place where they were written. And make no mistake: this rule applies to modern writings as well, whether they be this series or the course’s textbook. There’s a reason why textbooks go through multiple editions. For example, while it’s very highly unlikely that something as well-founded as natural selection will be shown to be wrong, the importance it’s given as an evolutionary process has been very variable in time and among different scientists. Thus, depending on what you read, you might get a very different view of the power of natural selection – your job is to critically synthesise all the information you dig up, and this is especially true for evolutionary biology, where the terminologies used have often gone through many phases of redefinitions.