Endless forms most stupid, icky, and small: The preponderance of noncharismatic invertebrates as integral to a biologically sound view of life (2020) Jesse Czekanski‐Moir & Rebecca J. Rundell, Ecology & Evolution, https://doi.org/10.1002/ece3.6892

The Crux

When we think about evolution, too often our perception is that it drives species towards larger, more complex, more beautiful forms. It’s driven by popular media in part, but also by the way we teach it and the organisms we choose to focus on. This goes right back to early conceptions of evolution, with Darwin’s seminal text The Origin of Species referencing “endless forms most beautiful and most wonderful”, instead of “most basic and abhorrent”.

But the authors of today’s paper want to challenge that preconception of evolution as favouring larger or more complex or beautiful organisms, and they have some truly magnificent examples to do so with.

Simplification

We mostly think of evolution as creating more complex organisms, but it’s often not the case. The authors here use the head as an example of the perceived pinnacle of complexity. From an anthropogenic point of view it makes sense – our heads and the contents of our heads have allowed us to become such a dominant species. But evolution hasn’t resulted in heads on every type of animal, and the lack of a head doesn’t seem to detract from the diversity or success of those types of species. Jellyfish, corals and sponges don’t seem particularly perplexed at their lack of a head*.

Evolution has also resulted in many organisms losing heads, or at least simplifying their nervous systems. Bivalves (including clams and oysters) and octopuses both belong to the mollusc family. And while octopuses are famous for their intelligence, the bivalves lost their heads through the process of evolution, yet have still managed to diversify into over 9,000 different species.

Miniaturisation

So often biologists, conservationists and even TV personalities (YES EVEN DAVID ATTENBOROUGH) draw our attention to larger, more charismatic species. It makes sense. We empathise with them more, and they’re often more appealing to kids. But they’re generally the exception to the rule, with the vast majority of diversity taking place on tiny scales. There are currently 400,000 described species of beetle alone, with most entomologists estiamting the total number of living beetle species at over a million. If we go smaller than the insects, groups like copepods and nematodes are diverse to the point that any marine sample could produce an unidentified species (read the article linked below for more).

Read More: Consider the Copepod: Researching the Base of the Food Web

Disgust

This is my favourite part of the paper. While we think of evolution as producing more elegant, dare I even say refined species, many species have evolved very particular traits that are flat-out gross to a reasonable human. The authors’ first and finest example goes such: snails crap on their own heads. They’ve been crapping on their heads for 500 million years, and they’ll probably do so for 500 million more years. Parasites also tend to freak people right out, but the incredibly specific evolution that many parasites have been through beggars belief (more in the link below).

Read More: Where is the Love for Parasites?

Here I kind of get why these things aren’t so much in the public consciousness. No-one wants to teach high school kids about the cruelty of duck sex lives, or what a newly-hatched bird looks like with a face full of nest flies (seriously check that out in the article above too it’s GROSS. But they do lend credence to the argument that evolution is by no means a driver of what we would consider elegance.

Problems?

It’s the ‘Jurassic Park’ conundrum (does ‘Jurassic Park’ inherently sound cooler than ‘Cretaceous Park’ or is that just because the movie did so well?). Do people inherently find this version of evolution less interesting? Or is that just a product of biologists having portrayed evolution as producing big beautiful bois for so long? I doubt that we’ll be able to switch lectures or documentaries to focus on the less appealing products of evolution in the immediate future, but it’s definitely worth starting a transition to a more holistic view of the process.

So What?

This paper is a fantastic reminder that evolution isn’t driving species to climb some invisible ladder of progress. Evolution results in species having simply whatever works at the time, and that might not be a more complex or larger form. It’s something we’d do better to remember when we talk about it.

Sam Perrin is a freshwater ecologist currently completing his PhD at the Norwegian University of Science and Technology who believes that 2020 makes evolving headlessness seem like a really solid option. You can read more about his research and the rest of the Ecology for the Masses writers here, see more of his work at Ecology for the Masses here, or follow him on Twitter here.

*Though this might be ‘cos they’re headless idiots I dunno.

Title Image Credit: W. carter, CC0 1.0, Image Cropped