The Times They Are A-Changin': What Punctuated Evolutionary Equilibrium Means for the Anthropocene

What do you imagine when you think of a native ecosystem? Plants and animals living side by side harmoniously thanks to millions or billions of years of eco-evolution? Butterflies perfectly adapted lifecycles to pollinate flowers, birds with beaks just the right size to chow down on the fruits of a native tree? 

The primary argument we hear advocating for native-exclusive ecosystems revolves around the concept of co-evolution. The narrative usually goes something like this, “Native plant species are inherently ecologically superior because they have co-evolved over millions of years with other plants, fungi, insects, and animals."

But what if that narrative isn’t telling the whole story?

What is being described is a process by which native plants became what they are today. But, contradictorily, conservationists simultaneously assert that a native plant is an established, unchanging entity. 

The parts missing in this story is that part that examines that process of co-relational development; the story of how native species interacted before they got familiar with one another, and the part that acknowledges that relationships can continue to grow and shift and change. These are the breadcrumbs that lead us to where we are today and ever forward into the story that comes next, the one that will determine the fate of future ecosystems in the Anthropocene.

Co-Evolutionary Timescales

We’ve been told that biota have evolved together for millions of years, and their co-evolutionary relationships took those millions of years to form. But that is only a partial truth. Honestly, when applied as a broadbrushed statement about the general evolutionary behavior of organisms, I’d call it a lie by omission. This leaves us to believe that a co-evolutionary relationship requires millions of years to change, and that on a deep-time scale these relationships are slow and arduous to build. It also gives us the impression that the relations are in some “final” form, as opposed to a continually evolving process (partly due to the idea that because these changes occur so slowly, they are essentially frozen in time by our very limited relative experience of their evolution). 

The reality is that this is not how much of evolutionary progression takes place. Historically, the earth has undergone very long periods of minimal change and ecological pressure. Occasionally, a large-scale disturbance event or a cascade of effects from a variety of factors would occur. Early evolutionary theory also developed before scientists could directly observe genetic change in real time, meaning most evidence for evolution came from fossils, comparative anatomy, and long historical inference rather than direct observation. As a result, gradualism became the dominant public narrative: small changes accumulating steadily over immense spans of time. Since that time, scientists have observed evolutionary change in the span of a human lifetime and scientific understanding of the fossil record has progressed. If we look at the fossil record, we can see evidence of these long periods of homeostasis, and then boom, an explosive change in pace of evolutionary traits. In the early development of evolutionary theory, this was thought to be the result of missing fossils as opposed to repaid diversification. But now it is well accepted that evolutionary rates are highly variable, and ecological disruption or opportunity can compress major evolutionary change into relatively short windows of time. This is called punctuated equilibrium, a term coined by paleontologists Niles Eldredge and Stephen Jay Gould in 1972.

“Ecologically significant evolutionary change, occurring over tens of generations or fewer, is now widely documented in nature. These findings counter the long-standing assumption that ecological and evolutionary processes occur on different time-scales, and thus that the study of ecological processes can safely assume evolutionary stasis. Recognition that substantial evolution occurs on ecological time-scales dissolves this dichotomy and provides new opportunities for integrative approaches to pressing questions in many fields of biology… Recent studies suggest that fluctuating selection and associated periods of contemporary evolution are the norm rather than exception throughout the history of life on earth. The consequences of contemporary evolution for population dynamics and ecological interactions are likely ubiquitous in time and space.”

 CARROLL, S.P., HENDRY, A.P., REZNICK, D.N. and FOX, C.W. (2007), Evolution on ecological time-scales. Functional Ecology, 21: 387-393. https://doi.org/10.1111/j.1365-2435.2007.01289.x

One of the most dramatic examples may be the rise of flowering plants (angiosperms) and pollinating insects. For long periods, terrestrial ecosystems were dominated by non-flowering plants; conifers, ferns, and cycads. Then, during the Cretaceous period, flowering plants diversified remarkably quickly in geological terms. Darwin famously called this sudden diversification the “abominable mystery.” It is hard to pin down precisely what drove these changes in the Cretaceous period, but we know that this period was not environmentally stable. There were shifting climates, high atmospheric CO₂, tectonic fragmentation, rising sea levels, and volcanic activity.  Some researchers think flowering plants were initially especially successful in disturbed habitats such as floodplains and recently opened areas. New reproductive strategies may have helped them move into and thrive in unstable environments. Over time, they expanded outward into more stable ecosystems. We also know that intense coevolution between flowering plants and insects helped drive this explosive diversification. Plants evolved specialized pollination features, including color, scent, nectar rewards, and specialized flower structures. Their pollinators evolved specialized mouthparts, pollen-carrying adaptations, and synchronized life cycles. Positive co-evolutionary feedback loops of selection pressures from both plants and their pollinators accelerated diversification on both sides. But it is important to note here that the fossil record suggests that these shifts were gradual. They occurred in rapid bursts, followed by longer periods of relative ecological stability. 

Nature finds what works, adapts, and then conserves energy until more change is needed.

"Darwin's finches"

For much of the twentieth century, Darwin’s finches were presented mainly as a historical illustration of evolution, with multiple species diverging gradually over long stretches of time. The work of Peter and Rosemary Grant help to change that narrative. Through decades of field research in the Galápagos Islands, the Grants demonstrated that evolution was not merely a slow historical process visible only in fossils, but something directly observable in real time. By carefully measuring finch populations across changing environmental conditions, especially during severe droughts, they showed that natural selection could rapidly alter beak size and shape within only a few generations as food availability shifted. Their work revealed evolution as dynamic, responsive, and ecologically intertwined, helping transform Darwin’s finches from a static symbol of gradual evolution into one of the clearest modern examples of rapid adaptation, eco-evolutionary feedback, and evolution occurring on ecological timescales.

Black cherry (Prunus serotina) provides an example of how feedback loops create co-evolutionary changes amongst introduced species. Originally native to North America, black cherry has been introduced to parts of Europe, where it often spreads in disturbed forests, plantations, and forest edges. In these novel environments, the cherry encounters a community of herbivores, fungi, and competing plants with which it does not  have a co-evolutionary history. Native insects and mammals gradually begin to feed on the trees, while the black cherry populations undergo selection for traits such as stronger chemical defenses and altered growth strategies. Over time, this creates a feedback loop in which herbivores adapt to the new resource and the plant responds to increasing pressure. It is an ongoing eco-evolutionary change, where species interactions reorganize over relatively short timescales and both ecological structure and evolutionary trajectories continue to adjust after initial establishment. The black cherry was introduced to Europe in the 1600s with major spread in the 19th to 20th centuries. Depending on the region, this means only a handful of generations over a few hundred years resulted in ecological integration. Will those relationships become refined over millions of years, even if ecological pressure wanes? Of course, because change is the only constant in nature. 

Modern Consequences

Evolutionary rates are not constant. High-pressure periods can compress major changes into short times. Right now, in the anthropocene, we are in a pressure cooker. The scale of modern human disturbance regimes creates the conditions needed to compress evolutionary change into very short timeframes. This is nothing new; there are twenty-two official geological time periods in the earth’s history, shifts primarily driven by mass extinction events and the emergence of new, dominant species in the fossil record. We are currently in the Cenozoic Era, which has spanned the last 66 million years, and Holocene Epoch, which began 11,700 years ago. The difference now is the level of influence at which humans are affecting the earth, which is intense enough that some scientists have suggested we have crossed over the geological boundary from the Holocene Epoch into the Anthropocene Epoch. The scale of change is global, and its core drivers are accelerating at an exponential rate. 

Menno Schilthuizen has become well known for showing how rapid evolution occurs in human-altered environments, especially cities. His book Darwin Comes to Town argues that urban environments create intense new selection pressures like noise, pollution, heat, fragmentation, artificial light, new predators, new food sources. Large cities have only existed in the U.S. for about a hundred years, and yet they still are biodiverse, lively ecosystems. How is that possible? Because the organisms living there responded, fast. Birds changed song frequencies, insects and fish evolved pollution tolerance, and mammals changed their behavior. Microbes evolved resistance almost immediately. There are an abundance of examples of both adaptation and evolution on the genomic level. 

There are a number of implications of this in terms of how we view the modern composition of our ecosystems. The already wobbly ground that invasion ecology stands upon becomes even more tenuous when we apply the potential of rapid dynamic co-evolutionary evolution. It undermines the older assumption that “non-native” organisms are ecologically “fixed” species entering a static native system. The traits of “native” and “non-native” plants are as dynamic as the ecosystems they exist in, and can evolve in as little as few generations if enough ecological stress exists. The transient dynamics of the introduction of catalyst species dynamics does not predict long-term outcomes. The long term outcome is dependent largely on underlying factors of disturbance pressures (i.e. human interaction), and whether these changed ecosystems move into evolutionary stabilization, repeated cycling and upheaval is a larger question than just which species exist in those locations. Climate change, pollution (including noise and light pollution), watershed distribution,  land use and “resource” extraction, habitat fragmentation, soil compaction and depletion, herbicide-driven microbial shifts, pesticide-driven insect population decline, eutrophication, fire management, etc. are some of the underlying disturbance pressures that determine whether an ecosystem will stabilize or remain unstable. If you keep picking at a scab your body will just keep making another. 

First Impressions… Don’t Matter?

Contrary to popular belief, most plants that are introduced to a new ecoregion do not take hold. Less than 10% of introduced species survive without intentional cultivation, and about 1% become highly prolific. Being tossed into a new ecosystem without the buffers of gradual movement, parent populations, and seedbanks make it hard for plants to establish themselves. The newcomers are actually far more disadvantaged in terms of survival than established residents of an ecosystem. This is why the ones that survive tend to be more "aggressive" in nature. Regardless of the type of species which arrives, and introduced species undergoes a series of processes thereafter, from establishment, ecological integration, evolutionary adjustment, and ultimately long-term reorganization (or, at any point along the way, it could fail to establish itself and die out, until the next time if and when that species is reintroduced). There are a multitude of factors that affect each part of those steps, such as founder effects (when a new population starts from a small number of individuals with small sample of genetic diversity), selection (individuals with advantageous traits in relation to this environment tend to survive), drift (random genetic changes), and hybridization (individuals from separate species interbreed). These factors, and addition to the synergy created by them,  continually reshape both non-native and native gene pools after establishment. So called “invasions” can actually generate new genetic diversity, not just reduce it. These changes may be small, and hard to notice (especially when the current paradigm means we willingly ignore any positive impacts or integration of pre-Colombian species), small changes can make big ecological ripples. A tiny evolutionary change can mean the difference between survival and extinction, and can be all that is needed for an entire resource-web system to shift into equilibrium. These small changes are happening all the time, with nature dynamically poised for greater movement in any given direction.

“Half a millimeter can decide who lives and who dies.” -Jonathan Weiner, The Beak of the Finch

Kudzu (Pueraria spp.)  is often used as a textbook example of biological invasion, but it also illustrates a more modern view of invasion ecology as a dynamic, time-dependent process rather than a simple case of a plant overwhelming a passive ecosystem. Introduced from East Asia into the southeastern United States, kudzu initially spread explosively in disturbed landscapes such as abandoned fields, roadsides, and logged forests where ecological resistance was low and competition was reduced. It didn’t invade intact, stable ecosystems. 

Kudzu Pueraria montana

Its rapid growth created the impression of an unstoppable invader, but over time the system has shown more complexity: climate limits restrict its northern expansion (for now, this will shift with climate zones), forest regrowth increases shading that constrains it, and native species interactions and emerging natural enemies gradually alter its dominance. It remains highly prolific in disturbed areas, i.e. areas highly visible to humans, like roadsides and private residences, and therefore it is still perceived as a dominating species and ecological threat. But kudzu demonstrates how disturbance, ecological opportunity, and time-dependent feedback loops shape invasion outcomes in ways that can’t be understood from early snapshots of the phase before there has been time for relationship adaptation. 

First impressions do certainly matter, as public opinion and even scientific opinion can be swayed by the anticipation of potential unknown outcomes. But we cannot base our projections of how an introduced plant will behave in an ecosystem in the beginning stages, especially without a clear and unbiased understanding of why they demonstrate such behaviors or the dynamics of ecosystems over time, whether that be five years, fifty, or five thousand. We also have to observe these plants in the context of our own disturbance on the land in a holistic and interconnected fashion. Plant behaviors are responsive to human activity. Isolating “bad” plants and trying to remove them from an ecosystem where they have established themselves without changing our impact on that ecosystem is nothing short of Sisyphean. Our energy would be better spent elsewhere.

The ecosystems that we are observing are already undergoing some stage of destabilization. The inevitable outcome of a destabilized ecosystem is restabilization (i.e. reintroduction of prior disturbance regime), which results in a stable system. A stable ecosystem is one that is still dynamic, undergoing inevitable change, but slowly and somewhat predictably. The alternative is collapse. The ecosystem is changed in big ways, and adapts to the new disturbance regime in a way that means it no longer looks like the ecosystem it did prior, but is stable relative to its needs. This is called a novel ecosystem. An “invasive” species that moves into a destabilized area of disturbance will likely contribute to the restructuring of that ecosystem. I call these catalyst species. Due to the exponential increase and everchanging “progress” of modern development, it is hard for our ecosystems to find even footing, and so we are in what feels very much like a fixed state of ecological purgatory. Change is hard for humans, I get it. It’s especially hard when there is no light at the end of the tunnel, or in our case, when the tunnel is growing in front of our eyes like a bad dream. Scarier still  if you don’t understand why you’re in a tunnel in the first place. 

The initial shock of the introduction of a catalyst species can make it hard to envision a future returned to equilibrium. Another example of this is the Spotted Lanternfly, where the effects weren’t even realized, but projected. The hysteria around these insects came from scientists' concerns of potential damage to native species and economically important crops, not their actual observation of such events. The media took off running with it and after a few years when researchers indicated that the actual observed effects were actually pretty minimal, and that Lanternflies were nothing to fear, we were knee-deep in bug-stomping propaganda and no one was really paying attention. 

Spotted Lanternfly Lycorma delicatula

Emma Marris discusses this pattern of initial intensity during an introduction or ecological change. She calls this the “boom and bust” pattern, describing how many ecological systems naturally go through cycles of rapid expansion (“booms”) followed by crashes or reorganization (“busts”), rather than settling into a single, stable equilibrium state. Dynamic change is the normal, with varying degrees of oscillation depending on disturbance regimes. From this perspective, so-called “invasive” species or sudden population explosions are not necessarily signs of ecological failure, but expressions of normal ecological variability under changing conditions like climate shifts, land use change, or nutrient inputs. Marris uses this framework to argue that conservation goals focused only on restoring historical baselines may miss the reality that ecosystems are continually reorganizing, and that managing for resilience and function may be more realistic than trying to freeze nature in a single “ideal” state. The ideal state is one of dynamic flow in which humans exist in contextual relationships, not a strapped and stationary purse of resources for extraction or a “pure” visionary landscape that excludes us or quarantines us to some “other” place and isolates sacrifice zones of resources for our exploitation. 

“I don’t think “naturalness” is valuable. But I do think the autonomy of individuals is.” - Emma Marris

If we want to stop seeing these frightening upheavals and unfamiliar shifts in ecological homeostasis, we need to stop putting our foot on the gas. We are driving our ecosystems in unfamiliar territory through capitalist imperialism. Through terrible unsustainable agriculture practices that don’t even feed our population and are reliant on government subsidies and are not climate resilient. Through asinine watershed distribution like we see with the Colorado river and wetlands that are still to this day being drained to accommodate agriculture and infrastructure. Through technology-driven environmental catastrophes like AI and data centers. Through mind-boggling highways of rapid production, consumption, and waste. Through the fracturing of accountable, interdependent communities and the subsequent reliance on outsourced and imported means of subsistence. 

Change doesn’t happen overnight, but if the overwhelming weight of the complex web of cause and effect of ecosociopolitical conditions has led you to believe that change is not possible, take a hint from your phylogenetic ancestors. Rapid change is possible with resilient, adaptive individuals leading the way under high pressure systems. And the pressure is on.