Work in Progress: Problems of Human Ecology

Friday 07 October 2022

Nick Nielsen
13 min readOct 10, 2022

How can we describe the ecological role of human beings in the biosphere? There are many ways to approach this question. One could come at it as William H. McNeill did in Plagues and Peoples, where he distinguished between micro-parasites and macro-parasites, with the latter being human beings that live off other human beings. This isn’t a very flattering way to view human ecology, but there is an element of truth in it. However, McNeill’s conception isn’t sufficiently substantive or detailed to give a comprehensive answer to the problem of the ecological role of human beings in the biosphere.

One could use the conventional conceptual framework of ecology to comment upon some of the practices of human beings that seem to be unprecedented in the history of the planet (and which therefore make it difficult to understand the ecological role of human beings). Thus I said to myself a few days ago that human beings are the keystone species of a weedy biosphere. Again, this isn’t very flattering, but it has an element of truth in it. By distributing ourselves on a planetary scale, and then producing technologies that make planetary scale transportation routine, we have facilitated the spread of weedy species at the expense of indigenous species that often cannot compete against the hardy invasive species. I think it was nature writer David Quammen who coined the evocative phrase “planet of weeds,” and this has stuck with me.

However, it is arguable that purposive human agriculture has had a much greater impact on the biosphere than our unintentional facilitation of invasive species. Enormous tracts of land have been cleared for export agriculture, resulting in industrial-scale habitat loss and the installation of a monoculture of a small number of plants that human beings find to be economically valuable. The whole of human agriculture is, in a sense, an ecology that is singularly dependent upon human activity, and if a human-specific disease came along that killed off all of us, while parts of the weedy biosphere we unknowingly facilitated would remain and thrive in our absence, the entirety of the agricultural biosphere would fall apart, and the long process of nature reclaiming that which was once hers would begin.

The agricultural biosphere isn’t “weedy” in the sense that weedy invasive species are “weedy,” but it is “weedy” in the sense that is brought about and exclusively sustained by a weedy invasive species — i.e., ourselves — and would fail without us, to be replaced by a biosphere, perhaps temporarily impoverished by our activities, that can thrive without us.

Thinking about human beings as a keystone species of a weedy biosphere, or an agricultural biosphere, I read a little about keystone species and found a classic paper in conservation biology on keystone species, “The Keystone-Species Concept in Ecology and Conservation,” by L. Scott Mills, Michael E. Soulé, and Daniel F. Doak. The authors note that “keystone species” has been used loosely to mean different things in different ecological contexts, and they distinguish five different keystone species concepts based on the position of the keystone species in the trophic pyramid and the knock-on effects of the loss of a keystone species that holds a crucial place in its given position in the trophic pyramid. This kind of clarification was welcome, and I see I have a lot to learn about keystone species.

We can give another twist to the question by rephrasing it like this: what is, or what ought to be, the ecological role of human beings in the biosphere? By distinguishing a descriptive and a prescriptive sense of our ecological role, we open up a can of worms. Is there a way in which we can determine what the role of a species (any species) ought to be? One could argue that species evolve to fill a role in the trophic pyramid, and they ought to fulfill that role. Is this “ought” a moral “ought”? Are we violating the moral order of nature when we fail to uphold our part of the ecological bargain? Insofar as science rigorously observes the is/ought distinction (and there is a broadly-based consensus that this ought to be the case, i.e., that science has a moral obligation not to read moral obligations into nature), there should be no role for “ought” in a purely descriptive science. Nevertheless, we can certainly see when a discussion is tending in the direction, as when the implication is that human beings, or some weedy species we have enabled, has overshot the capacity of the planet to sustain it.

Lineages can evolve so that species within that lineage can ascend or descend the trophic pyramid. When Earth was covered in stromatolites and there effectively was no trophic pyramid, there were no apex predators, no prey, and no primary producers as we know them today. Indeed, one could define the initial stage of the maturity of a biosphere in terms of establishing a differentiated trophic pyramid with relatively clear distinctions in ecological function between levels of the pyramid. In this sense, we could say that Earth’s biosphere attained an initial stage of maturity around the time of the Cambrian Explosion, or maybe a little before that (and by “a little before that” I mean maybe a few hundred million years before that).

As animal clades appeared during the Cambrian Explosion, some of them specialized as apex predators, some of them as predators, and some of them specialized as prey. It took time for the trophic pyramid to take shape, because it takes shape over biological scales of time. The natural rate of speciation, the average longevity of a given species, and the natural rate of extinction define the biological time scale over which the trophic pyramid forms, and then slowly and gradually changes. The trophic pyramid experiences “sudden” shocks as well, with mass extinction events, which can collapse large portions of the pyramid and leave so-called “disaster taxa” in its place, until the ecosystem rebuilds itself (a process of millions of years, or tens of millions of years) and the trophic pyramid takes shape again.

Some of these “sudden” transitions themselves took millions or years, or tens of millions of years, though the K-Pg extinction caused by the Chicxulub impact was a nearly instantaneous event. However, while the strike itself and its immediate effect in terms of a shock wave, tsunamis, and fires unfolded rapidly, the collapse of major clades (like the dinosaurs) still took time. Before the K-Pg impact, the apex predators were all dinosaurs, and no mammal held this ecological role. With the extinction of the dinosaurs and the vacating of their ecological niches, other lineages could fill these rolls, and so it is that we now live in a world in which the apex predators are mostly mammals, though there are also avian predators like the Harpy Eagle that are apex predators within their biome. Each of Earth’s major mass extinctions have been followed by a reshuffling of the trophic pyramid, as niches are vacated by one lineage and subsequently filled by another.

There has been occasional discussion of the possibility of an “intelligence niche” (called a “cognitive niche” by Stephen Pinker), which human beings fill on Earth, and presumably some other species would fill in some other biosphere that had attained what I called above an initial stage of maturity by establishing a trophic pyramid, but most of this discussion has been a rejection of the very idea of an intelligence niche.

Charles H. Lineweaver has been especially influential in this respect, formulating what he half-jokingly calls the “Planet of the Apes Hypothesis,” which has since by cited by others:

“The scientists who support Sagan’s view, subscribe to what I call the Planet of the Apes Hypothesis that goes something like this: There is a ‘human-like intelligence’ niche. There is selection pressure on other species (including our ancestors) to occupy this niche. In our absence (or on other planets) some species will evolve into that niche and develop technology. Carl Sagan has called the occupants of this niche the ‘functional equivalent of humans’.” (Cosmobiology: Our Place in the Universe)

Lineweaver’s treatment of the intelligence niche (which he prefers to call the “human-like intelligence niche”), while obviously unsympathetic, is a valuable discussion. Many of the points he makes are the same as points I have belabored in other contexts. However, Pinker also has made some good points in relation to his “cognitive niche” (I wonder if he introduced this alternative term to distinguish his argument from past uses of “intelligence niche”). I don’t think this debate is over. On the contrary, I think it has yet to fully play out, and the debate can only come to maturity with more contributions like those of Lineweaver’s and Pinker’s that explore the idea more fully, analyzing it into chunks small enough for science to productively attack the problem, while simultaneously developing the conceptual framework surrounding the problem. Impoverishment of the conceptual framework is the primary reason why questions like this linger in a kind of intellectual twilight, while other areas of inquiry pull ahead and generate new problem sets, keeping the research program vital and interesting, and attracting new minds to the field.

Sometimes the impoverishment of a conceptual framework is a simple function of interest: too few individuals are interested in a problem for that problem to be properly expressed and thus become the basis of a research program. This is not always the case, however. I often discuss civilization, and I often point out that not only is there no science of civilization, there isn’t even really a scientific research program into civilization, i.e., a research program that perhaps hasn’t produced definitive results, but is at least consistently working on the problem. Nevertheless, many people are interested in civilization, and a great many books and papers are written, but the field remains, as Samo Burja once said, “pre-paradigmatic.” It is possible that civilization is simply too difficult a problem for the present state of science, and that it would require a science brought to a higher stage of maturity to properly tackle the problem, and it might require science of an even higher stage of maturity to adequately resolve the problem. Social science notoriously lags behind the natural sciences, and it is amusing to pursue the thought experiment of a counter-factual civilization in which the social sciences are much more highly developed than that natural sciences, which latter always lag behind the former. Such a civilization, even if it is possible (which we cannot know), would be quite different from our own.

One might also posit Carlyle’s “Great Man theory of history” displaced into the sciences, such that no great man has come along to focus on the problem of civilization and thus laid the basis of a science that others could develop. This can also be given a formulation in terms of Kuhn’s distinction between revolutionary and normal science, such that no revolutionary scientist of civilization has come along to lay the foundations that other scientists could pursue as normal science, until the next revolution comes along. I think there is some truth to this, as it probably takes the right man at the right time — a confluence of many circumstances, some within the control of the individual, and some not in the control of the individual — to found a science.

Someone might well produce a work of great merit in relatively isolation, and have it fall into obscurity. One could say that this was the fate of Ibn Khaldun’s Muqadimah. This work did not fall into complete obscurity, but it also could not have been said to have fallen on fertile ground, and it did not become the focus of a research program of a community of scholars. It appeared at a time when Islamic civilization was past its Golden Age, whereas if it has appeared some several hundred years earlier, things could have been different. When Aristotle was rediscovered in medieval Europe, it would be accurate to say that all aspects of Aristotelian thought became a research program. The very curricula of medieval universities was structured around Aristotelian texts.

We have since come to view this Scholasticism as a barren philosophical enterprise, but it is arguable that this outpouring of Aristotle scholarship was what made the scientific revolution possible. Aristotle provided a conceptual framework that could be inhabited, critiqued, revised, expanded, and even could serve as that against which intellectual rebels rebelled.

In any case, I came to these thoughts on the ecology of human beings by working on one of my projects, on which I made some progress this past week. I am working on is a series of talks (call it a curriculum if you like) intended to be a simple yet “big picture” review of the relationship between scientific knowledge and the “big questions” that were once the exclusive province of philosophy. I have two versions of this planned, one short, one longer. Here is the short version:

Science and the Big Questions

  1. Where are we?

2. When are we?

3. What are we?

4. How do we know what we know?

5. Where are we going?

And here is the longer version:

Science and the Big Questions

1. Where are we?

2. When are we?

3. What are we?

4. Who are we? (Why are we the way we are?)

5. How do we know what we know?

6. The Big Questions as We Understand Them Today

7. Where are we going?

8. The End of All Things

Of the above, the first is complete (at least as a draft), I have made substantial progress on the second, and worked significantly on the third this past week.

“Where are we?” describes our spatial location within the visible universe, starting with Earth. It is a very basic approach, not dealing with any controversies, but it sets the tone for the “big picture” treatment of very simple ideas — like the question, Where are we? — that will continue to play out in subsequent talks. “When are we?” has a similar structure, describing our temporal “location” within deep time — both the deep past and the deep future — but also going a bit further afield, gesturing toward more speculative aspects of science as it tests the limits of empirical knowledge. “What are we?” which I worked on this past week, continues this development, borrowing heavily from big history to trace the path from chemical elements to the tissues that make up our bodies, and our ecological role within the biosphere. Here there are a great many ways to pursue the theme, not all of which would converge, despite the common point of origin in contemporary science.

We can approach the question “What are we?” by means of biology, ecology, psychology, sociology, anthropology, and so on. Pushing the boundaries on any of these questions takes us into speculative regions where science cannot be clearly distinguished from philosophy. At present I am leaning toward developing the theme of human ecology, and starting to touch on some sensitive and controversial issues, and also some speculative issues, hence the discussion above of human ecology. Even the most “settled science,” when pushed to its limits, becomes something unsettled and forces us to rethink our scientific presuppositions root-and-branch.

Not included in the short version, no. 4 in the longer version will take up the question of evolutionary psychology, which will be largely skipped in “What are we?” where it could have been treated. “How do we know what we know?” will be a survey of the growth of human knowledge, and especially the growth of scientific knowledge, with a focus on the regulative principles of scientific thought rather than the scientific method (as it is usually understood), and “Where are we going?” will attempt to take a look at the human future insofar as that future is constrained by contemporary scientific knowledge, again borrowing heavily from big history and starting with relatively near-term events and moving on toward the longevity of our species and the possibility of successor species in the genus Homo.

In the longer version, “The Big Questions as We Know Them Today” will make the theme of the talks explicit, and will address how we went from answering these questions with religion, to answering them with philosophy, to answering them with science. Since this is a paradigmatically positivistic progression from religion to philosophy to science, it would be a good idea to put that idea of a progression under a microscope and examine its presuppositions in turn. And lastly, in the longer version, “The End of All Things” (Borrowed from Kant’s paper of the same title) will go beyond the end of human beings and look at the aging of the universe on the largest scales.

There isn’t much new in the above, except some of the treatments I will give of familiar themes might be somewhat novel. The focus is on keeping it simple at the same time as keeping big picture questions in view. This is a difficult tension to manage, as big picture questions often pull us into difficult science, while simple explanations imply that difficult questions are settled, which they are not. Simple ideas are, at the same time, fundamental idea, so that a simple idea pursued to its roots will reveal connections with other simple ideas, and therefore connections among disciplines usually separate. In this sense, simple ideas are also big picture ideas, and this is part of what I want to communicate in this project.