By Giovanni Mussini
This article was originally published in The Oxford Scientist Michaelmas Term 2021 edition, Change.
In one of the last and most accomplished of his works, Giacomo Leopardi, the 19th century giant of Italian poetry, turns to the natural world to ridicule le magnifiche sorti e progressive–the magnificent and progressive fates–of humanity: as laid bare on the ash-ridden wastelands of the Vesuvian slopes, the fate of all life is to perish, leaving its struggle against hostile Nature as a silent legacy. A man whose disenchantment and sense of wonder went hand in hand, Leopardi criticised a once-voguish vision of universal progress. It was a vision that 20th century alienation and carnage did much to put to rest.
What’s more, the intrinsic purposelessness of Darwinian evolution has since been taken to provide the ultimate argument for cosmic pessimism. In biology lecture halls, progress is as close to a taboo as it gets. This holds true regardless of what Darwin himself–waxing lyrical about the production of ‘higher animals’–would add to the conversation.
The emergence of this consensus owes much to Stephen Jay Gould (1941-2002), the Harvard palaeontologist and formidable science populariser. Gould was a fierce critic of progress, which he dubbed a ‘noxious, culturally embedded, untestable, non-operational, intractable idea’. In a provocative 1996 article, he portrayed Earth as an eternal ‘planet of bacteria’. Bacteria–so the argument goes–are, and always have been, our planet’s dominant lifeform on ‘any reasonable or fair criterion’. Talk of progress would strike our microbial masters as a sure sign of vertebrate hubris.
Ironically, the number of Escrichia coli in a single human body can only exceed that of all humans that ever lived because of the metabolic opportunities opened up by that wondrous bioreactor–the animal gut.
Before putting Gould’s arguments to the test, let’s clear out some misconceptions. The failure of orthogenesis (the idea that individual lineages evolve according to intrinsic teleological forces) to explain patterns in the living world is not in dispute. It would also be foolish to deny that microbes surpass all other lifeforms in sheer numbers, antiquity, and biochemical exuberance. Whether these constitute the only ‘reasonable or fair’ criteria to assess evolutionary or ecological significance, though, is much less clear-cut.
The success of living bacteria rests in large part on their capacity to negotiate a world far more complex and varied than that of their Archean forebearers. Gould’s paean of microbial Earth falters on this all-important note. Ironically, the number of Escrichia coli in a single human body can only exceed that of all humans that ever lived because of the metabolic opportunities opened up by that wondrous bioreactor–the animal gut.
Animals embody cutting-edge terraforming technology. Over half a billion years ago the simplest of them all, sponges, may have precipitated a revolution in ocean ventilation through the pumping action of their feeding systems, which withdraw dissolved carbon and enhance the mixing of oxygen in the water column. In turn, this paved the way for the rise of more oxygen-hungry, active ecosystem engineers. Among them were the earliest bilaterally symmetrical animals. By irrigating marine sediments with oxygen and nutrients, burrowing bilaterians heralded the transition from a seafloor smothered by bacterial mats to the thriving, dynamic communities of today. Similarly, early land plants boosted rock weathering and nutrient release, inventing soil as we know it. In doing so they turned Earth’s continents from barren, UV-irradiated wastelands into the nutrient-rich canvas of today’s terrestrial biomes.
Similar feats of geoengineering attest to the power of biology to reinvent Earth as a more intricate, lush, and diverse place. All else being equal, this makes for a richer, more interesting planet to live on. Acknowledging this makes room for a subtler conception of evolutionary progress. Instead of being locked into competition for a fixed number of possible ‘niches’, life is drawn into novelty by the array of opportunities opened by other life, and there is no reason to think that the process is plateauing.
Instead of being locked into competition for a fixed number of possible ‘niches’, life is drawn into novelty by the array of opportunities opened by other life, and there is no reason to think that the process is plateauing.
The story of life’s progress also has a lot to do with intelligence. We may no longer think of ourselves as the pinnacle of creation, but this has no bearing on the fact that the world is home to big-brained cetaceans, elephants, capuchin monkeys, parrots, crows, caracaras, and octopi leading rich inner lives. Their complex minds evolved independently of each other. And yet, they exist now, sharing the planet with our lineage of tool-using apes. No such minds graced the Cambrian oceans, and the very concept of a mind has little to do with Archean stromatolites.
What are we to make of this wealth of intelligence, short of positing an ascent towards Teilhard De Chardin’s “Noosphere”? At one level, it is all a matter of baselines. As Gould himself acknowledged, given enough time, some lineages will tend to wander into complexity, even in an unperturbed random walk, in the same way as a drunkard’s floundering may lead him further and further away from a wall. If we visualise evolution as a blind search through a landscape of possibilities, the current scenery provides plenty of shortcuts to intelligence compared to what a younger Earth may offer. Today, a trekker on a random walk to human-like cognition could choose its starting point from a catalogue of brainy, tool-using vertebrates. On Precambrian Earth, the path would have been far fuller of twists and turns, and the probabilities of getting to the destination in a single step much closer to those of spontaneous brain self-assembly: for all practical purposes, nil.
If Earth is now in a better position to spawn technological intelligence than at any point in history, this should give us pause for thought. Unless our species wreaks irreparable havoc on the planet, the next few tens of millions of years may prove more intriguing than any chapter so far. The prospect of ‘sapient’ species blossoming on multiple branches of the tree of life no longer seems unfathomable. Rather than being exceedingly improbable, we may just be the first.
Unless our species wreaks irreparable havoc on the planet, the next few tens of millions of years may prove more intriguing than any chapter so far.
On a cosmic scale, though, this explanation wavers. Our galaxy hosts hundreds of billions of suns, many of them far older than our own. If technological intelligences become less and less of a miracle as biospheres mature, why should we be the first on the galactic stage? In this light, the Fermi Paradox–the puzzle of why we are yet to find intelligent aliens – appears even more problematic. However, we should never forget how clueless we are about extra-terrestrials. We do not even know if they have already paid a visit to our solar system, or, outrageously, to our own atmosphere. Perhaps we should be wary of excluding such exotic proposals. We should expect intelligent extra-terrestrials to exist, and this is a good enough reason to keep searching.
Whether or not evolution ever got a chance to sculpt ‘endless forms most beautiful’ elsewhere, one thing is clear: our Sun is ageing. Barring unfathomable feats of stellar engineering, life on Earth will ultimately perish like Leopardi’s titular Ginestra. And yet, the journey will have been worthwhile. For all those who value diversity, complexity, and intelligence, progress has occurred on every reasonable or fair criterion.