What is a species? Philosophy, Science and Scicomm

What is a species? This apparently simple question is one of the best ways to get scientists arguing.

A recent article by Henry Taylor, a philosopher at University of Birmingham, asks this question from a philosophical perspective. The article itself is okay. But there is zero chance of biologists adopting its recommendation, ‘to scrap the idea of a species’, any time soon (see also this older article at the same platform, on the same subject, from a biologist’s perspective).

What I found interesting is how different audiences interpreted the article in the comments and on social media. I saw a mix of reactions (based on my network and a few searches; obviously not indicative of everyone) – some scientists were condemning the article vocally and aggressively, while others who didn’t appear to be scientists (based on their Twitter bio), shared the article in agreement and support.

‘What is a species?’ is a classic philosophical question, not a scientific one. Philosophical questions are a valuable tool for life. They are conceptual, not factual; they are rarely ‘solved’ (in the scientific sense); and they need to be addressed with complex thinking, not just facts or empirical research. You don’t have to agree with this approach, it’s just how Philosophy differs from Science. Disciplines are defined by different methodologies, standards, systems, and norms.

Taylor’s argument isn’t new – philosophers and biologists have been arguing about how to define a species since long before Darwin. Yet, like most humanities vs. science disciplines, these two groups of scholars are predominantly publishing in different journals, rarely citing each other, and rarely collaborating.

This isn’t a problem, unless you are seeking a definitive answer to the question. Disciplinary silos are a key driver of interdisciplinary research problems, i.e. most modern environmental problems. A good example is the false dichotomy between agriculture and ecology, influenced by decades of siloed agricultural research that mistakenly segregated nature into discrete components that were either ‘pest’ or ‘beneficial’. The reality is far more complex, but this popular myth of nature as an antagonist to agriculture has prevailed. Ecosystem services vs. Conservation is another example.

But back to ‘What is a species?’. I’m not going into the nitty-gritty of the species concept; it’s not my area of expertise. But the responses to this article got me thinking about how we educate and communicate about biology and ecology.

Species is one of the most fundamental units in biology. Like everything in life, it has its caveats and messiness…e.g. microbes, cryptic species, asexual plants, and fertile hybrids. Life scientists across disciplines and fields use many different methods to identify and measure ‘life’, including taxonomy, morphology, phylogeny, function, communities, genes, interactions etc. This may be frustrating for those looking for global generalisation, but it is 100% scientifically valid. (hey, there are still three countries in the world that don’t use the metric system.)

Taylor’s article suggests that scrapping the biological species concept would be a “natural progression” in biological thought, and that this radical new approach would produce enormous changes “both for our scientific and philosophical view of life”, i.e. we should fundamentally shift our thinking to consider life as “one immense interconnected web”.

This has already happened. Many decades ago, scientists fundamentally shifted our thinking to show that life was in fact “one immense interconnected web”. It’s called ecology, the science of studying interactions between organisms and their environments.

In fact, advances in ecological knowledge are fuel for philosophical discussion. For example, the existence of many insect species depends on the existence of another…think of specialist herbivores and parasitoids that rely on one host species to exist. Galls, where insect and plant DNA meet in a heady mix of uncertainty, are another mind-blowing example of how plant-insect interactions push the conceptual boundaries of ‘species’ as a discrete unit.

So yes, scientists already know that life is an interconnected, complicated web. Sometimes, it’s a headache. But we still need a way to measure the components of the web, understand them, and connect with audiences on how to protect them.

This is where scientific answers to ‘What is a species?’ are important. It’s also a valuable reminder that sometimes scientific knowledge doesn’t easily translate into non-scientific knowledge. This is a huge problem for conservation and management actions.

For example, many legal instruments for environmental protection do not explicitly define ‘a species’ (e.g. USA Endangered Species Act), or explicitly define a species to a degree that eliminates some organisms (e.g. Australia’s Environment Protection and Biodiversity Conservation Act defines species as a group of biological entities that: (a) interbreed to produce fertile offspring; or (b) possess common characteristics derived from a common gene pool).

At a broader scale, journalists/editors in popular media outlets may contribute to the confusion, by referring to functional groups (e.g. bees, deer), or entire ecological communities*, as ‘species’.

And what about school education? I don’t remember learning about the issues with the biological species concept until well into my PhD – this was in my mid-20s, after two undergraduate degrees, in humanities and science.

So ‘What is a species?’ may be out of date. A more contemporary question is ‘How do we explain what a species is?”.


*Story may be paywalled. Initial excerpt: “Listing of endangered trees angers farmers and threatens dam plan. The Mercury-4 Jul 2019. The decision to list two Tasmanian tree species as critically endangered was “appalling and ill-informed”, the state’s peak farmers group says….” Story is about recent listing of Tasmanian woodland community.

Chamaemyiidae fly ovipositing into a gall on a eucalypt, Shelley (VIC) Australia

© Manu Saunders 2019

6 thoughts on “What is a species? Philosophy, Science and Scicomm

  1. Bartosz Bartkowski July 23, 2019 / 10:53 PM

    This is where scientific answers to ‘What is a species?’ are important.

    I generally agree with the gist of your argument, but I think this claim is wrong. I’d argue that there is no such thing as a “scientific answer” to this question. There are many different definitions of species and they sometimes have different analytical consequences – but neither is “right” or “wrong”, and neither can be tested as a hypothesis. Thus, the question does not really have a “scientific answer”. Which also holds for most concepts that we use in science – you can analyse a phenomenon only if you can somehow define it and say where it “starts” and where it “ends”. Nonetheless, these definitions, so crucial for practicing science, are always in a way “arbitrary” and not really “scientific” (unless you define as “scientific” anything “relevant to science” or “based on some basic criteria of logic”). Using the adjective “scientific” may imply that there is a correct definition – something that you, as I understand it, actually want to avoid.


    • Manu Saunders July 23, 2019 / 11:00 PM

      I completely agree. I used the plural “scientific answers” to indicate that there are multiple scientific answers to the problem, and I think I have made it clear that “important” does not mean “the right answer”.


      • Bartosz Bartkowski July 23, 2019 / 11:20 PM

        My main issue is with the term “scientific”. While defining terms/concepts is part of scientific inquiry, there is no scientific method available to answer the question “What is a species?” because a species is not something really “out there”, but rather simply a category that helps us in analysing phenomena. I may be nitpicking though;-)


  2. cinnabarreflections July 24, 2019 / 7:59 AM

    To me, a species is only useful as a concept to allow us to communicate about organisms, whether in science or any other context. So the question as such is somewhat meaningless in terms of biology, yet critical for scientific inquiry of biology. If we were to ‘scrap’ the species concept, it would make it extremely difficult to meaningfully describe organisms as study subjects. So as imperfect as attempts at definition may be, particularly for unicellular organisms and fungi etc., it is still the best we have. Always a great discussion topic though!

    Liked by 1 person

  3. Jeremy Bruhl October 4, 2019 / 10:26 AM

    “I don’t remember learning about the issues with the biological species concept until”–good point, Manu! I remember thinking I was the “odd one out” challenging the narrow treatment of concept (yes, singular) of “species” in biology text books when teaching starting to teach biology to first year uni students in the early 1990s. Part of the ‘problem’ is that everyone wants a single, simple, unified concept and biological evolution does not ‘follow the same recipe’.

    Liked by 1 person

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