What Exactly is a "Species," and is the Answer Even Worth Our Time?
Charles Darwin wrote in On the Origin of Species in 1859, "No one definition has satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of a species."
So, what is a species? To most people, a species is almost synonymous with a type of animal. We all know that a giraffe is different than a lion because they're different species. But do we really know what it means when we talk about the different species of giraffe? And why are they not comparable to different breeds of dog?
This conversation has been going on and on in the scientific community for decades, if not centuries. And each time a new species is declared, the debate is shoved back into the limelight.
Nater and colleagues recently published a paper titled, “Morphometric, Behavioral, and Genomic Evidence for a New Orangutan Species" where they claim they have "discovered" a new species of orangutan, which just so happens to be extremely endangered. But the term "discovery" here does not mean that these scientists suddenly stumbled upon an entirely new species of orangutan while trekking in a Sumatran forest. It means they studied the genetic and morphological differences between populations of orangutans that have been known to scientists since the 1930s.
So why is this "discovery" relevant? I agree that separating populations into separate species is great for our collective scientific knowledge when a population differs from other populations of a species at the genetic level substantially. However, this knowledge does not remain only in the scientific community; these findings are picked up by the media, spreading excitement to the lay person at home, making them think there are more creatures on the planet than previously thought. This "discovery" has grave implications that effects those outside of the taxonomy realm.
Professor Volker Sommer from University of College London was quoted in Nicola Davis' Guardian article on the new orangutan species saying, "Any bunch of expertised biologists can invent a new species, if they get their arguments together."
And to me, this is exactly what is happening. Susan Milius writes in her article in Science News, "Species, Schmescies." She points out how difficult it is to define all species using just one concept, such as the biological species concept which separates a species by those that can successfully breed. But we all know this does not apply to all animals (ie. mules). This becomes especially difficult when we try to apply just one species concept to define plants. Because of this difficulty, there are countless species concepts being used by scientists to define their species. Each time I read a paper, I discover a new species concept. So where does it end? Will we ever have a standard species concept to define the creatures that we share our planet with?
Stephen Garnett and Les Christidis approached this question in their Nature article titled "Taxonomy Anarchy Hampers Conservation." They argue that this inability to establish a consistent species concept is hampering our ability to effectively conserve endangered species. They bring up the very valid point that taxonomic inflation, the act of splitting species into more and more separate species, incentivizes groups and countries with the promise of funding. Think about it: if a country lists more endangered species than another country, who will get more funding? BirdLife International lists hundreds more bird species than the International Ornithological Congress. The other problem occurs when we introduce policy to protect these "new" species. The Convention on International Trade in Endangered Species (CITES) protects endangered species from being traded across boarders. To protect an endangered species, a country must propose that it falls under protected status at a convention, and member countries must vote whether or not to protect it. This is a long, political process, leaving plenty of time for actors to jump on the chance to trade a "new" species that has yet to be protected under CITES. The article ends with a fantastic point, "vagueness is not compatible with conservation.” They therefore propose that defining species falls under the International Union of Biological Sciences to create a standard and stop this endless "discovery" of species.
Colin Groves writes in his 2014 paper titled "Primate Taxonomy: Inflation or Real" that splitting species does increase our understanding of the natural world because we can gain a better understanding of what causes species to differ. But Ian Tattersall writes in his 2007 "Madagascar’s Lemurs: Cryptic Diversity or Taxonomic Inflation" paper that “The number of primate species recognized world-wide in some quarters has more than doubled over the past few decades, while actual diversity has, if anything, declined as a result of human activity." We must therefore remember that evolution is an ongoing process and with increased fragmentation from increased human development, we will continue to see more and more isolated populations. At some point in the future, we will end up with a countless number of species, almost all of which will be endangered. At that point, how will conservation funds be distributed? The dangers are that this constant "discovery" of species will make it seem like extinction rates are slowing because more species will be created than go extinct, when really, populations are just becoming more and more isolated.
So is this constant desire to separate species even worth the funding? I was curious to see how many species are newly discovered, so I took to Google Scholar and typed in "new species discovered" and got 354 results since 2013. I realize that not all of these papers are describing a new species, but 354 papers published on the topic is still a pretty significant chunk of scarce scientific funding. If the reason for separating species is to save them, then why not focus funding on saving populations? The species definition is arbitrary, and in general, the lay person doesn't care about the genetic differences between the three species of orangutan; they just care that orangutan conservation happens.
Instead of focusing resources on separating species, I argue that we should focus our funding on rejoining populations to preserve gene pools, and in the long run, the species as a whole.
Check out the Oxford BCM Podcast where Cathy Clegg and I discuss this very topic!
Special thanks to Cody James for pointing me in the direction of primate-specific taxonomy articles.