The Cultural Influence on Evolutionary Development

Two years prior to Charles Darwin's groundbreaking expedition to the Galapagos Islands, another notable naturalist, Jean-Baptiste Lamarck, was nearing the end of his life. Despite his many contributions, he is often remembered for his controversial ideas about the inheritance of traits. Lamarck suggested that the physical abilities an organism developed during its lifetime could be genetically transmitted to its offspring. He illustrated this with the giraffe, claiming that stretching to reach higher leaves led to longer necks, which were then inherited by the next generation.

In contemporary understanding, it is largely accepted that personal fitness routines do not enhance the physical attributes of one's children, although some epigeneticists might argue differently. Most genetic research now affirms that exercise alone does not alter the genes passed on. However, culture—something you can indeed pass down—can significantly influence the physical and mental development of future generations.

Culture has long been associated with what makes us distinctly human, including language and tool use. Yet, recent studies on animal behavior have challenged the notion that such traits are exclusively human. Jane Goodall’s observations of chimpanzees using tools introduced a new perspective on "man as the tool maker." Her findings showed that these skills were not only present but also passed down through generations, suggesting that culture is not solely a human trait.

While sexual selection is widely recognized as a crucial factor in evolution, many complex animal behaviors are often attributed to the vague concept of “instinct,” which sometimes serves to oversimplify the explanation.

For instance, migratory waterfowl are said to rely on instinct for their lengthy seasonal migrations. Yet, there are numerous examples of migratory birds that choose to settle in certain areas year-round. The film "Fly Away Home" illustrates how a girl and her father taught a group of goslings to migrate, using methods derived from wildlife rehabilitation techniques for endangered whooping cranes.

These instances underscore the idea that migratory behaviors are learned, likely through the guidance of older flock members. If "instinct" were the sole motivator, these birds would not stop to graze on my golf course throughout the year.

Years ago, the book "Born Free" recounted Joy Adamson and her husband George's journey of raising and releasing an orphaned lion cub, Elsa, back into the wild. While the cub may have displayed inherent feline behaviors like chasing and pouncing, integrating into a wild pride proved to be a complex challenge.

It’s rare to find an animal in a complex environment that doesn’t undergo some form of learning from parents or social groups. Behaviors such as cooperative hunting, seasonal migration, and territorial claims exert substantial selective pressure on those populations. I would argue that these learned behaviors could be powerful enough to drive speciation.

The early giraffe that began stretching for higher leaves likely discovered a previously untapped resource or ecological niche. It is probable that this behavior was taught to her offspring and herd members, initiating a cascade of behavioral selection.

As more individuals focused on reaching higher foliage, those with longer necks and legs had greater foraging success. According to traditional natural selection theories, this advantage would lead to enhanced reproductive success. Consequently, the genetic traits responsible for height would be amplified over generations, similar to the selective breeding practices seen in pigeon breeding.

The competition became a race between increasingly taller giraffes and the acacia trees they fed upon, with each side exerting selective pressures on the other, driving evolutionary changes.

Seals are believed to have evolved from dog-like ancestors, raising questions about how they transitioned from land-dwelling hunters to adept swimmers. In a gene-centered hypothesis, genetic variations would have led to a shift towards aquatic living. Conversely, a culture-driven hypothesis posits that behavior preceded adaptation. It’s conceivable that an individual recognized a slight advantage in swimming and subsequently adopted a marine lifestyle, although this scenario seems less likely than one driven primarily by learned behavior.

Most animals lack the analytical capacity to first recognize a beneficial trait in themselves or others and then apply that knowledge to adapt to new environments. Each member of a pack or herd typically plays a learned role in cooperative activities. The random emergence of a physical trait suited for different tasks might go unnoticed or be deemed disadvantageous within the established social culture.

However, if behavior comes first—say, if a group discovers an abundant food resource along the coast—the dynamics of selection shift. Dogs are particularly adept at recognizing and utilizing food resources, even in unfamiliar situations. If a group finds a rich food source, the benefits of diving in could outweigh the drawbacks of inadequate adaptation for the task.

The ability to learn and navigate complex environments can yield substantial benefits when opportunities arise. When a new habitat offers increased resources, it can broaden the fitness spectrum by allowing more varied individuals to thrive. A generous resource base can facilitate the survival of diverse traits, thereby increasing variation and reinforcing these traits through reproduction.

Expanding the fitness bell curve enables novel pairings of individuals that were previously overlooked in breeding. These combinations can reinforce and amplify unique physical characteristics within the population, leading to significant shifts in their physical traits.

The critical element required to drive substantial divergences in form and create distinctly new species is abundance. Darwin's theories on the origin of species were largely founded on scarcity and competition for limited resources. Upon arriving in the Galapagos Islands, Darwin encountered a relatively harsh environment characterized by seasonal droughts and limited food availability.

What he failed to recognize was the relative abundance that awaited the first finch settlers. The islands, rich with seed-producing plants but devoid of finch-type feeders, offered numerous open niches and opportunities for adaptive radiation. The initial years of finch colonization likely involved resource exploration and creative adaptation, allowing for the emergence of distinct forms and breeding populations.

Darwin viewed animals as mechanistic beings largely driven by unconscious instincts and limited by their physical traits. He attributed little significance to intelligence or creativity, focusing instead on a gene-driven model of divergence. His theory emphasized the marginal advantages conferred by genetic traits in driving individual behavior.

Research on the Galapagos finches has highlighted forced divergence among competing populations, noting that while competition spurred divergence, it only occurred within a narrow range of physical traits. During periods of abundance, these populations shared resources, becoming more specialized only during times of scarcity.

To achieve dramatic changes in form, such as the transition from dog-like creatures to seals or from browsers to giraffes, substantial rewards are likely necessary.

It's conceivable that early giraffes evolved from slightly taller individuals capable of reaching higher leaves. Competition with other grazers may have spurred the upward search for untapped resources. However, given the ability of most animals to observe and mimic the strategies of their peers, it seems improbable that only those with slight height advantages would seek out new resources when opportunities arose.

More likely, the initial innovators among giraffes drove the selection process by adopting a new feeding strategy that yielded rich rewards, thereby creating a new selective environment. As parents taught this new strategy to their offspring, the taller individuals enjoyed greater success. As these successful tall individuals bred, they passed on their genetic predispositions for height, including longer legs, necks, and enhanced circulatory systems.

The breeding practices of pigeon fanciers provide a useful comparison. When breeders select slightly different individuals with unique traits for interbreeding, those traits can become exaggerated far beyond their original expression. There’s no reason to assume this selective amplification is limited to pigeons or dogs. The success of taller proto-giraffes paired with similar mates may not have been driven by conscious selection, but it could have occurred just as rapidly and effectively.

Fossil evidence supports instances of punctuated equilibrium, indicating rapid physical changes, much like the significant divergences seen in domesticated animals. The factors that could alter the behavior of early giraffes or seals likely include changes in climate or weather patterns prompting migration to new areas. Such events are now hypothesized to have influenced the evolution of modern humans approximately 70,000 years ago, when a prolonged drought in Africa drove a population of early hominids to the coast, where they found abundant food resources and settled into a smaller area.

This newfound bounty is thought to have spurred a creative explosion in language and cultural practices, possibly leading to the emergence of art and aesthetics, alongside physical changes characteristic of modern humans. This group is believed to have subsequently migrated across Africa, Europe, Asia, and into the Pacific, sometimes interbreeding with Neanderthals along the way.

Similar scenarios have likely unfolded numerous times throughout Earth's history. For giraffes, this could have meant moving into savannah-like environments with scattered trees that encouraged upward grazing. For the ancestors of seals, it might have involved young adults venturing into new territories that included rich tidal zones.

In the case of Darwin’s finches, a storm may have blown a flock off course to an archipelago populated with plant life but lacking finch-type seed feeders. Their adaptive radiation to exploit various seeds, insects, and cactus flowers would have been influenced by the existing genetic variation in their founding population and the rate of natural mutation within those traits. More critically, the extent of their adaptive radiation would have been constrained by the availability of reliable and rich niches to exploit.

When Darwin initially studied the finches, he overlooked the subtle differences between the birds from various islands, mistakenly assuming each island was home to a distinct species. These differences, which have since led biologists to classify the birds into numerous species, were likely influenced by the limitations imposed by their environment.

In contrast, the Hawaiian Drepanididae evolved into over 40 distinct and easily recognizable species, making up more than half of Hawaii's endemic species prior to human intervention and the introduction of non-native species, which led to many extinctions. The Galapagos Islands host roughly a third of the endemic species found in Hawaii, with half of those being variations of finches so similar that only experts can differentiate them.

The disparity in species density and variation between the two archipelagos appears to correlate with the richness or scarcity of the habitats available to colonizing populations.

Hawaii's Drepanididae exhibit remarkable variations in coloration, bill structure, size, and feeding habits, reflecting the reliable and diverse food sources available there, free from the extreme droughts characteristic of the Galapagos. A finch migrating to Hawaii would encounter a wealth of seeds and flowers, allowing for specialization without the risk of sudden food scarcity.

Conversely, in the Galapagos, specializing to exploit a specific resource could have dire consequences if that resource became scarce due to environmental shifts. This periodic scarcity necessitated more conservative strategies. For instance, sexual selection manifests differently in the two regions. The Galapagos finches show minimal color variation, with breeding readiness indicated merely by darkening feathers and bills, while Hawaii's Drepanididae display vibrant breeding colors, a luxury made possible by their abundant environment.

Not only has specialization been richly rewarded in Hawaii, but it has also allowed species to invest heavily in sexual displays to attract mates. In contrast, the finches of the Galapagos could not afford such extravagance, as it would likely become a perilous investment during lean times.

While the beaks of Galapagos finches serve as the primary distinguishing features of the various species, their differences are often mere fractions of a millimeter. Taxonomists and the birds themselves recognize these variations, but to the untrained eye, they can be deceptively subtle. In comparison, the beaks of Hawaii's Drepanididae have diverged dramatically, with many exhibiting long, curved bills specialized for nectar feeding, a trait unseen in Galapagos finches.

Thus, the models of adaptive radiation and significant morphological divergence are exemplified in these two archipelagos: one characterized by fierce competition for limited resources, leading to minor variations; the other driven by the exploitation of abundant wealth, resulting in pronounced divergences. Darwin’s model of scarcity and competition fits the conditions of the Galapagos, resulting in only slight variations among the finches, while the wealth-driven divergence in Hawaii utilizes and amplifies genetic variation.

It's undeniable that the inhabitants of both archipelagos engage in sentient and culturally transmitted behaviors to thrive. The nectar feeders in Hawaii did not wait for a bird with an unusually long bill to start seeking nectar. The Galapagos nectar feeders developed only slightly varied beaks for sipping, still versatile for gathering other food sources. In contrast, the Hawaiian nectar feeders possess highly specialized beaks that serve little purpose beyond nectar feeding. It seems more probable that both island chains were initially populated by generalist birds, but only Hawaii provided the ecological conditions necessary for such divergent specialization.

Neither Lamarck nor Darwin had access to substantial information about the nature of genes, genetic variation, or the cellular mechanisms of reproduction. Our understanding of animal behavior has also undergone significant transformation over the past few decades. It’s difficult to predict how either scientist would have integrated this new knowledge into their theories, but I can envision Lamarck being particularly intrigued by recent findings on animal cultural behaviors. He might argue, "See, the act of stretching for leaves does lead to offspring with longer necks… just not in the way I originally envisioned."