Unveiling the Dance: A Deeper Dive into Behavior's Role in Shaping Evolution

The narrative of evolution, once envisioned as a rigid procession dictated by chance mutations and environmental pressures, is undergoing a metamorphosis. The notion that behavior, far from being a passive passenger, actively participates in shaping its own evolutionary journey is no longer relegated to the fringes of scientific discourse. "Evolution ‘on purpose’: how behavior has shaped the evolutionary process"  delves into this captivating subject, offering a tapestry of insights that challenge our traditional understanding of how life unfolds.

The article embarks on a historical expedition, tracing the ebb and flow of this concept over two centuries. We encounter Jean-Baptiste Lamarck, a visionary who dared to propose the inheritance of acquired traits, laying the groundwork for the notion that behavior could influence evolution. However, the ascension of Darwin's theory of natural selection shifted the focus to random mutations and environmental pressures, leaving behavior's role somewhat muted. The 20th century witnessed whispers of revival with concepts like Baldwin's "Organic Selection" and Simpson's "Baldwin effect", but it wasn't until recent decades that behavior truly reclaimed its rightful place as a potent force in shaping the evolutionary narrative.

This resurgence can be attributed to a confluence of factors. Multilevel selection theory shattered the individual-centric view of evolution, acknowledging that traits benefit not just single organisms but also groups, creating an avenue for behavior to exert its influence. The remarkable phenomenon of epigenetic phenotypic plasticity underscores this notion. Organisms are no longer seen as passive recipients of their environment; they actively fine-tune their behavior in response to external cues, demonstrating their agency in shaping their surroundings. Furthermore, niche construction theory adds another layer of complexity. Organisms aren't merely inhabitants; they are architects, modifying their environment in ways that create feedback loops and influence the very selection pressures that drive evolution. The industrious beaver, diligently constructing dams that reshape landscapes and create ecosystems that favor their own kind, serves as a powerful testament to this.

But how does mere behavior translate into lasting evolutionary change? The article introduces the concept of "constrained purposiveness". Organisms, through the relentless process of evolution itself, acquire behaviors that enhance their survival and reproduction. These behaviors are not driven by conscious planning but rather by the choice of traits that have proven adaptive over generations. This subtle distinction is crucial, for it emphasizes that organisms are not passive pawns but active participants in their own evolutionary journey.

The article then dives into captivating examples that illuminate the power of behavior in shaping evolution. Consider the chimpanzees' remarkable tool use. Their ability to craft and utilize tools expands their resource access and survival chances, potentially influencing the development for cognitive abilities and dexterity. In the realm of mate choice, individuals select partners based on a variety of criteria, such as plumage, strength, or nurturing behavior. This, in turn, drives the evolution of traits that attract mates, shaping the course of populations over generations. Social learning provides another potent example. By sharing knowledge and skills within groups, organisms enhance their collective survival, potentially favoring genes associated with learning, cooperation, and communication. The intricate dance between cleaner wrasse and their larger fish clients exemplifies this beautifully. The wrasse keep the fish free of parasites, a behavior that benefits both parties and has likely shaped their evolutionary trajectories.

Beyond the Examples:

While the article highlights fascinating examples like tool-wielding chimps and cooperative cleaner wrasse, the influence of behavior on evolution extends far beyond these. Consider the intricate mating rituals of birds, with their elaborate displays and dances, shaping the evolution of plumage, song, and behavior itself. Or the social hierarchies of wolves, where dominant individuals suppress the reproduction of others, influencing gene selection and population dynamics. Even seemingly mundane behaviors like food choice can have profound consequences, shaping the gut microbiome and potentially influencing susceptibility to disease and even brain development.

The Epigenetic Dance:

The conversation doesn't end with genes and behavior. The emerging field of epigenetics adds another layer of complexity, revealing how environmental factors can influence gene expression without altering the underlying DNA sequence. Imagine a population of birds facing a harsh winter. Birds exhibiting shivering behavior to conserve energy may be more likely to survive and reproduce, passing on not only the genes for shivering but also epigenetic tags that predispose their offspring to shiver as well. This creates a fascinating interplay between genes, behavior, and the environment, weaving an intricate tapestry of evolutionary change.

Unveiling the Human Story:

As we delve deeper into the intricate interplay between behavior and evolution, we are not only enriching our understanding of the natural world but also gaining profound insights into ourselves. For we, too, are products of this remarkable dance. Our language, culture, and social interactions are all behaviors that have shaped our evolution as a species.

Behavior as an Evolutionary Driver: Challenging the Modern Synthesis 

The article "Evolution ‘on purpose’ argues for a renewed appreciation of behavior's impact on evolution, challenging the dominance of the Modern Synthesis. Here's a summary of its key points:

Historical Context:

• The idea of behavior influencing evolution has a long history, with proponents like Lamarck (inheritance of acquired traits) and others.

• However, the 20th century gene-centered view largely downplayed its role, focusing on random mutations and natural selection.

The Uprising of Behavior:

• Recent research highlights various mechanisms linking behavior to evolution:

• Phenotypic plasticity: Organisms adjust behavior via epigenetics in different environments, potentially leading to heritable changes.

• Niche construction: Organisms modify their surroundings, creating new selective pressures and opportunities.

• Gene-culture coevolution: Learned behaviors (culture) interact with genes, influencing adaptation.

• These mechanisms suggest behavior isn't just a passive response to selection; it can actively shape its own evolutionary trajectory.

Challenges to the Modern Synthesis:

• The Modern Synthesis emphasizes random mutations and natural selection on individual organisms.

• However, incorporating behavior introduces complexities:

• Selection can act on groups beyond individuals (multilevel selection).

• Behavior can introduce directedness into evolution, favoring specific outcomes.

• The focus shifts from purely genetic change to interactions between genes, behavior, and environment.

The "Purpose" Misnomer:

• The article clarifies that behavior isn't truly "purposeful" with conscious intent.

• Instead, it's shaped by evolved decision-making mechanisms that enhance survival and reproduction.

• This distinction avoids teleological pitfalls while acknowledging the active role of behavior.

The Future Landscape:

• Integrating behavior into evolutionary theory requires ongoing research.  The Modern Synthesis needs revision if not replacement.

• This new understanding could have broad implications for various fields, including ecology, conservation, and even understanding human evolution.

Snippets

The idea that behavior has played an important role in evolution has had its ups and downs over the past two centuries. Now it appears to be up once again.

Lamarck can claim priority for this insight, along with Darwin's more guarded view.

However, there followed a long ‘dark-age’, which began with Weismann's mutation theory and spanned the gene-centred era that followed during most of the 20th Century, although it was punctuated by various contrarians, from Baldwin's ‘Organic Selection theory’ to Simpson's ‘Baldwin effect’, Mayr's ‘Pacemaker’ model, and Waddington's ‘genetic assimilation’, amongst others.

Nowadays, even as we are reading genomes and using this information to illuminate biological causation and decipher evolutionary patterns, behavioral processes are more fully appreciated, with ‘multilevel selection theory’ providing a more ecumenical, multicausal model of evolutionary change.

Behavior has a purpose (teleonomy); it is ends-directed

Living organisms are not passive objects of ‘chance and necessity’ (as Jacques Monod put it).

Organisms are active participants in the evolutionary process (cybernetic systems) and have played a major causal role in determining its direction.

I call this agency ‘Teleonomic Selection’.

In a very real sense, our species invented itself.

For better and worse, the course of evolution is increasingly being shaped by the ‘Sorcerer's Apprentice’.

Darwin was scornful of this idea in his earlier years. ‘Heaven forfend me from Lamarck's nonsense’, he wrote to a friend in 1844

Yet, for obvious reasons, Darwin considered Lamarckian influences to be a minor subsidiary to natural selection.

in the process of rejecting the Lamarckian view of inheritance, the baby got thrown out with the bath water; the role of behaviour as an important causal factor in evolutionary change was also summarily rejected.

Lamarck, it seems, was on the right track regarding the fundamentally important role of behaviour in evolution. The evidence would appear to be overwhelming. Yet there is still some reluctance to incorporate this theoretical insight into the core explanans of evolutionary biology.

However, natural selection is not a ‘mechanism’. It does not do anything; nothing is ever actively selected (although sexual selection and artificial selection are special cases).

the term natural selection, as Darwin utilized it, is a metaphor (i.e. a label that identifies an aspect of the evolutionary process).

Thus, natural selection is a kind of umbrella term that refers to whatever functionally-significant factors are responsible in a given context for causing differential survival and reproduction.

The emergence of ‘multilevel selection theory’ in biology during the past two decades has been an important step in the right direction.

Teleonomy in living systems is today accepted without question.

The purposiveness of living organisms represents a major (emergent) causal agency in evolution.

Terms such as ‘phenotypic plasticity’, ‘norms of reaction’, and ‘reaction ranges’ are commonplace, and there are frequent references to the complex interplay of various factors via ‘epigenetic cascades’, ‘ontogenetic networks’, and similar terms.

It is clear that the traditional ways of portraying evolution, such as Monod's ‘chance and necessity’, Campbell's ‘blind variation and selective retention’, Mayr's ‘two-step, tandem process’, and Dennett's ‘blind algorithmic process’ (whatever that means), are inadequate and require modification.

In retrospect, it might have been more appropriate to call it ‘Neo-Lamarckian Selection’, as opposed to Darwinian Natural Selection.