We all learn the concept of a “species” in primary school. Science teachers say that a “species” is a category used to classify living things, specifically to separate populations into groups of organisms that can breed with one another.
But as is the case with many scientific concepts taught to children, that is a lie — or at least a massive oversimplification. The reality is that “species” is a mushy, complicated concept that is more theory than actual hard truth.
Oftentimes taxonomy (the study of how we classify organisms) boils down to semantics, and while research in the field is important for the sake of knowledge, it rarely has much practical application and in extreme cases might hinder conservation efforts.
Taxonomists classify organisms into species based on a variety of markers. Some are based on breeding patterns; others are based on where the animals live and what they look like; and others differentiate populations based on DNA — which has become more common thanks to genome sequencing technology. Charles Darwin himself was a bit fuzzy on the concept in “On the Origin of Species,” saying: “No one definition [of species] has as yet satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of a species.”
What this means in practice is that the way we define species is often flawed or arbitrary. One of the most common examples is the distinction between eastern and western meadowlarks. These birds are almost indistinguishable except for the different chirps they sing to attract mates. Scientists have come to the conclusion that because of these songs, meadowlarks have a Capulet-and-Montague thing going on, making them two different species. But this isn’t a hard-and-fast rule. Dedicated birdwatchers have, in fact, seen the two species interbreed in the wild — a shocking scandal requiring entire bird families to be plucked from their nests and studied intensively (poor things).
In the field of taxonomy, we run into flaws like this all the time. A recent paper by French biologists at the University of Montpellier shows just how nebulous the concept can be, detailing the “gray areas” in which organisms exist in an awkward genetic limbo between two species. How different does the DNA of two animals have to be before they’re considered different species? And as a separate issue, how do we differentiate between extinct animals we know of only through the fossil record? The field is confusing, unstandardized and surprisingly case-specific.
To muddy things up even further, species are constantly changing. Populations diverge from one another after becoming isolated — often thanks to the destruction of their habitats by humans. Smaller populations increase the risk of inbreeding, mutations and “genetic drift,” or the general change in the DNA of a species due to a lack of diversity.
Of course, taxonomy is still important. Classifying organisms is essential to understanding how they evolved and to provide a common language for scientific discussion. Carl Linnaeus, who came up with the classification system we use today, originally did so to make exploration and trade more efficient.
Biologists also argue that taxonomy is essential to conservation. After all, how can you protect something if you don’t know what it is? But today that argument can be a bit oversold. Skeptics of modern taxonomy criticize over-classification as a hurdle to conservation techniques, preventing interventions to save endangered species by introducing similar animals from elsewhere to help breed.
The panther population in Florida — which was on the verge of extinction and at high risk of genetic drift — saw this debate play out: Conservationists who wanted to preserve the genetic makeup of the panther resisted releasing Texas cougars (a separate sub-species) into the Florida cat’s territory, but two decades after eight cougars were introduced, the population is now recovering.
In general, it’s healthy to have some skepticism when discussing taxonomy — especially regarding news articles on “newly discovered” animals that are really just animals we’ve rebranded after sequencing their genomes. Science is rarely the rigid discipline we often think it is. It’s worth reminding ourselves that we’re defining the way we talk about these things as we go.