The Demons of Eden

Demons 'r Us

“Demons in Eden” by Jonathan Silvertown is an incredibly fascinating book that brings to your view a vision of the world that most of us tend to miss.

For most of us, the concept of “evolution by natural selection” is obvious, but we rarely pause to think of the paradox involved. If evolution favors the fitter over the less fit, why doesn’t a single species takes everything and becomes the only one of the ecosystem? Such a species could be rightly called a “demon.” (*)

Darwin himself was puzzled by this problem, until he had a flash in his mind that led him to the answer: ecological niches. Every species is adapted to a specific ecological niche, you could say it “dominates” it, but that leaves space to a complex ecosystem where the normal condition is that of a great variety of species. Darwin’s finches are the perfect example of this condition. With their beaks adapted to different kinds of seeds, they don’t compete with each other as species.

But there is a problem. If demons cannot exist, why did Silvertown write a book about them? They do exist and it is, indeed, a paradox. Silvertown provides a large number of fascinating examples of how invasive plant species create havoc to entire ecosystem by wildly reproducing and replace the native species.

I have to say that on this point Silvertown doesn’t provide a good definition of what a demon is, exactly. The reader has to work it out by himself on the basis of the many examples provided. After some head scratching, I think I can provide this definition as:

A demon species is one in its early stages of occupation of a new ecological niche

A good example among those provided in the book is the colonization of the island of Tenerife by olive trees. Today, the ancient olive forest has been largely destroyed by human activity but once they formed a thick olive forest. They couldn’t possibly have evolved there, so they had to be taken there as seeds by birds from Africa. Then, once they gained a foothold on the island, they grew to replace most of the earlier vegetation. A “demon,” according to the definition.

There are many other examples, both for plants and for animals. A classic example is rabbits in Australia. Someone brought a few rabbits there to have fun hunting them, and today, there may be more than 200 million of them (!!). This is mainly because they don’t have competitors or predators in the new environment.

There are several other possibilities, but, of course, you have already understood that the main demon of this planet is one species: the one called “homo sapiens.”

Humans perfectly fit the definition. They have been expanding into an ecological niche that was unoccupied before they moved into it. Their combination of sophisticated social skills, tool-making abilities, and turbo-charged endurance makes them predators of almost every other species on Earth. And we keep expanding, destroying all other species. Demonic, indeed.

So, humans are not evil; they are just exploring a new set of parameters in the ecosystem. As Silvertown says (p. 14), “Every species must have its day as a demon.”

Eventually, the perturbation of a demon species must create the conditions for its demise. It doesn’t mean the species will go extinct (although it may), just that it won’t be a demon any longer. The whole system will explore the parameter space until it finds a reasonably stable condition — aka “homeostasis.”

It is well-known in the field of population dynamics. Silvertown's contribution is to name the first oscillation, the most intense one: the demon. In the jargon of system dynamics, we call it “overshoot,” but mabye demon is a better term. In any case, eventually, the ugly creature will be tamed by the ecosystem in which it lives.

That will also happen to humans, who are now nearing the top of their first demonic rampage of the planet. What will bring them down fast is an open question. Right now, it seems that they are un-demonizing themselves by spreading pollution into the ecosystem that damages their capability to reproduce. So, they may go down with a whisper rather than a bang.

But, of course, there are many possibilities, including the rise of a predator of humans, which will take care of keeping their numbers in check. It may be a humble pathogen in the form of a micro-organism or something much more sophisticated, such as an AI that decides to cull the human species for its own unfathomable reasons. And the universe will continue oscillating and seeking its homeostasis.

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(*) Among many other things, Silvertown’s book made me understand something that I had completely missed before: how the “Gause principle” (aka the “competitive exclusion principle”) applies to plants. The principle says that no two species can occupy the same ecological niche, and it sounds right if you apply it to animals. Every animal species tends to specialize in a specific food; having no direct competition with other species. Again, Darwin’s finches provide a good example: they do not compete with each other: a species’ food is not food for another species.

Conversely, plants do compete for the same resource: if you think of “solar light” as forming an ecological niche, then all plants compete for it. And also for carbon dioxide (CO2) it is the same. So, plants species do directly compete with each other, typically tending to shade out their adversaries. Remarkably, this is competition among different species, not among individuals of the same species. Individual trees gain little or nothing by shadowing their neighbors: on the contrary, they risk being uprooted by winds if they do so. Also, plants have no “sexual selection” — adult male trees do not have harems of female trees!

It is a long story that illustrates the unbelievable complexity of the ecosystem and the genius of Charles Darwin who unraveled its main principles.