Darwin and the Galapagos
Six hundred miles from the Ecuadorian coast, the Galapagos archipelago rises from the Pacific. It’s an evolutionary laboratory, shaped by primordial forces, providing us with clues to the origins of life. The birth of the islands was set in motion five million years ago, as a geological hotspot travelled across the ocean floor, bubbling up lava through cracks in the crust as it went. The oldest of the volcanoes are now being reclaimed by the sea, where only crescent shaped rims of the ancient craters remain. On the youngest islands, beaches are still composed of fragments of shells, coral and bone, not yet old enough to be crushed down into sand by the pounding of surf.
The only species that reside here are those that were able to travel by air or by sea, making it a mecca for sea birds and marine creatures. The cool waters of the Humboldt Current upwell nutrients to create an environment rich in plankton, the foundation of a vibrant food chain. Lumbering galapagos tortoises inhabit the land, along with bizarre land and marine iguanas, species found nowhere else in the world. With no natural terrestrial predators, the unique species here seem to live largely without fear when on land. They would have been easy pickings when Spanish explorers first arrived. The name Galapagos derives from the Spanish word for tortoise. Tortoises brought from the islands became a valuable source of food on long voyages. They would be placed on their backs within the hulls of ships, able to survive six months without food or water. That resilience helped the tortoises’ ancestors to float here from the mainland, where they then began to increase in size.
In 1835, Charles Darwin arrived here upon the five-year voyage of the HMS Beagle. The ship had sailed from England to chart the coast of South America. Darwin had been invited to join the expedition as a naturalist, documenting the various flora, fauna and geology they encountered. During his travels, he witnessed many uncategorized new species, including discovering fossils of the extinct megatherium and toxodon. Back in England, it was already becoming widely accepted within the scientific community that the fossil record indicated that there was a succession of species through time, with the extinct somehow giving way to new species. But the mechanism by which this occurred was still unclear. These islands would provide essential clues.
During his time in the Galapagos, Darwin noticed closely related animals on each island, but each population had their own unique adaptations. For example, the islands have their own distinct species of giant tortoise. In areas with plentiful rain and more ground vegetation, they have short necks and low wrapping shells. But in the dryer regions, where the tortoises feed on tall cactuses, they have high upward arched “saddleback” shells with long necks for reaching up to the vegetation. It appeared, through their long periods of isolation, each island had subjected their animal inhabitants to unique constraints, somehow causing their form to shift based upon the necessity of the environment.
Further evidence came upon Darwin's return to England, when an ornithologist did a closer examination of his various bird specimens collected from the Galapagos. What he thought to be a variety of different genera were 12 related species of finch (now technically classified as Tanagers). Those from certain islands had developed narrow beaks for feeding on insects. Others had thick beaks for cracking open seeds. Another species had developed behavior to feed on the blood of seabirds. As finch populations diverged, so too did their beak colors and patterns.
It had become clear to Darwin that these species weren't fixed and unchanging, which was the claim historically asserted by traditional religious orthodoxy. Rather they were somehow morphing to adapt to their environments. But how? In 1838, all the evidence Darwin had observed started to coalesce into his theory of Natural Selection. In 1859, after two decades of further research, he released On the Origin of Species, expounding upon his theory. The book has since fundamentally changed the field of biology and, more broadly, our understanding of life on earth.
It proposed that the planet's species had morphed and diverged into an ever-evolving tree of life, where it was the struggle for existence within a competitive environment that drove species towards greater adaptation. This evolutionary branching perfectly explained the tree like taxonomic structure which was already used by naturalists to categorize species (kingdom > phylum > class > order > family > genera > species).
The theory of Natural Selection can be broken down as follows:
1. Each population of a species tends to produce more offspring than will survive to maturity.
2. Since there's a competition for survival, and a variety of traits within a population, those offspring with more favorable traits have better odds at surviving.
3. Through inheritance, those advantageous traits will tend to then propagate and be amplified within later generations, slowly shifting the population towards a new and modified form.
Darwin compared this process of Natural Selection to what he coined as Artificial Selection, when a gardener or farmer selectively breeds crops and animals to exhibit certain traits. He consulted with many farmers and breeders as to their experience with domestication. They observed that from a single plant or animal, they all exhibit a great variety of offspring, even with a single male providing fertilization. For example, they may vary in size, color, thicknesses of coat, flavor of fruit or tenderness of meat, or varying in behavior. From this variety of offspring, farmers would choose to breed certain individuals with specific traits, to amplify those characteristics within the next generation. Over time, those slight changes compound, with the new trait becoming characteristic of the breed. This ability for traits to slowly morph through reproduction cycles is innate. So, if species can evolve and morph via domestication over just hundreds or thousands of years, as the many dog breeds have descended from wolves, then how far could the constraints of nature shift species over the course of millions of years?
The way in which Natural Selection guides this process of change is mostly the same as with Artificial Selection. But in this case, it's the competition amongst environmental pressures that selects which traits are rewarded or penalized. Nature itself will favor those individuals with traits that incrementally aid in eating, evading predators, resisting disease, weathering harsh climate, and gaining mating opportunities. More of those individuals will survive and pass on their genes to the next generation, thus being Naturally Selected without requiring any intentional guidance.
For an example of this in action, we can look to the Galapagos marine and terrestrial iguanas. Their jungle ancestor is thought to have been carried here on the Humboldt Current from the South American mainland upon floating debris, flushed out of a river during an inland storm. A single pregnant female is all that would have been required. But the ecosystem here was very different than on the mainland, with very little vegetation to feed upon. Some of the new arrivals focused on eating cactus, and others ate seaweed. And over time the population diverged, each pursuing their own distinct survival strategy.
Those feeding on the water's edge faced intense competition over the limited food supply. Individuals that successfully ventured a little further into the water to feed were rewarded with more nutrition and subsequently more offspring, while those that couldn't starved. Over many generations, this algae eating population became increasingly adapted for the marine environment. Those with slightly shorter snouts were able to feed more efficiently on short algae growing close to the volcanic rock. Those with longer, sharper claws were able to cling onto rocks better within the crashing surf. The young with darker skin would be more camouflaged upon the black volcanic rocks from predatory birds. And those that could hold their breath for longer could go deeper into the water to feed. And through the millennia, the population incrementally shifted to morph into the new species of marine iguana, one that can now spend fifteen minutes at a time underwater, feeding within the surging ocean.
The terrestrial iguana uniquely morphed on each island too, most notably with the males of certain regions developing distinct colorations. This sexual dimorphism between the male and female of a species is due to a specific kind of Natural Selection that Darwin named Sexual Selection. Here the bright colors of male iguanas don't give it some advantage in terms of its own survival. Quite the opposite, it became more conspicuous. This might explain why the iguanas of Santa Fe Island lack this distinct coloring, since the predatory Galapagos Hawk frequents there. Rather, bright colors and bizarre ornamentation in males have typically evolved to attract the attention of the opposite sex. These can act as a display of health, or the aesthetic trait can be genetically tied to the occurrence of some other more advantageous trait. Sexual Selection can also take the form of males battling for dominance. This is also evident with these iguanas, where males are consequently significantly larger than females. Battles are costly though, and are typically avoided via posturing, exhibited through vigorous head nodding when challenged.
In both types of Sexual Selection, whether it's ornate displays or fights for dominance, successful males are rewarded with mating opportunities with females. Both the sexually dimorphic characteristic of the male and the preference for that trait by the female are passed on to offspring, each becoming stronger with successive generations. This growing sexual preference for unique characteristics has the effect of wedging clear divisions between varieties within a population, allowing other advantageous traits to become more concentrated, and encouraging divergence into a clearly defined new species. And for this reason, unique mating displays of this kind are particularly common in birds, where mating boundaries could otherwise easily overlap. We see it manifested in the Galapagos with the inflatable red throat pouch of the great frigate bird, distinguishing it from the magnificent frigate birds, or with the distinctive courtship dance of the waved albatross. Note too that the trait being selected for via Sexual Selection doesn't necessarily have to be exhibited only by the male. In the case of the blue footed booby, both sexes will display the same distinctive characteristic, but only those males with a certain vivid shade of bright blue will be given the opportunity to mate. In all cases, the sexually selected traits will typically develop only after the individual reaches breeding age, as a signal that it's ready to mate, prior to which, the young are typically more camouflaged.
Today within the fields of biology and genetics, the theory of evolution has become almost universally accepted in the scientific community. The morphing of species within the fossil record is incomprehensible when taken out of an evolutionary framework. Darwin's theory was solidified in the 1930s when scientists discovered how genetic inheritance works, with dominant and recessive traits for example. And it's since been further strengthened with advancements in decoding DNA, which can now trace back shared gene segments to see how closely related species are. The Catholic Church even now acknowledges this. In 1996 Pope John-Paul II gave an address recognizing the evolution as “more than a hypothesis,” and a majority of Catholics now accept it (even if only about a quarter of Evangelicals do). Within South America, this subject doesn't appear to have been as politicized as it has been within the English-speaking world. Perhaps since Catholicism is a relatively new religion, merging and supplanting their various preexisting indigenous beliefs, their understanding of scripture might be a little less dogmatic.
Some within the religious community continue to express skepticism that such complexity can develop from what they perceive to be a random process, claiming that it can only be explained by the guiding hand of a creator. Creationists will sometimes give an example that a box full of random metal parts can't be shaken to form a functional watch. But it's important to note here that Natural Selection is not actually random. Those who claim so show a lack of understanding of the basic mechanism at play. While the gene mutations and shuffling of the genetic deck that cause variability are somewhat random, the Natural Selection process itself is actively testing each of those changes against the environment to determine whether they're advantageous. This could happen in myriad ways, from a predator picking off prey that's slower or less well camouflaged, harsh weather killing off those less able to regulate body temperature, or from amongst the same species when competing for food or mating opportunities. But in each case, it is aspects of the environment that are automatically determining which traits to keep and which to weed out of the population, not random chance.
The second problem with the watch analogy is that it implies complex organisms formed all at once. But that characterization misrepresents how life has evolved. Evolution has occurred by slowly ramping up the complexity, through very simple single cells to multicellular forms of life, over billions of years. New incremental changes are only favored if they are of immediate benefit, regardless of the final complexity its descendants may someday evolve. This is supported by what is evident in the fossil record, where the oldest layers of strata hold the simplest fossilized organisms.
This evolution-based understanding of how the species came to be doesn't necessarily disprove the very notion of God. It does show that the Book of Genesis to be something that should be interpreted metaphorically, not literally, as one of the many creation mythologies among the world's religions. However, for those who do believe in a higher power, if one holds more of a deist or pantheistic understanding of God, then natural selection could just be the process by which God's law allows for new forms life to arise and shift. The notion that a designer would create all of Earth's species upfront, in their final form, unable to improve with time or to adapt to changing environmental pressures, seems like a much less elegant design. Additionally, a system where new forms could not arise to fill the void left by extinctions would mean an ever-dwindling biodiversity of life on earth. So, one's religious faith shouldn't necessarily see an acceptance of evolution as conflicting with their wider beliefs. Acknowledgement of the reality of the process of evolution need not be the dividing line that ideological battles are fought over.
Throughout history, religion has tended to dualistically ascribe to God those unexplained phenomena which have causes yet unknown. Meanwhile we've seen that the universe is increasingly knowable by science. If supernatural explanations are really required to prove the existence of an all-powerful creator, then that God of the Gaps will forever be a shrinking one. There is however only one objective reality. If one is going to believe in God, then an accurate description of its true nature should also encompass all that is discovered scientifically. Once these laws that guide the creation of the universe are known, this shouldn't in any way lessen our awe and reverence of it, because it's still remarkable that it works as elegantly it does.
There are still unanswered questions. The big one is that nobody knows with certainty how the process of life first got started. But they're looking. It's an interesting field of research called abiogenesis. In the meantime, until there is a robust theory as to how the genetic replication process first began, religion can continue to ascribe the first spark of life to some supernatural miracle of the creator. But even if that too does someday become known by science, it shouldn't necessarily be seen as any less miraculous just because we're aware of how the creation of life on earth first unfolded, by whatever name you choose to call it.
