June 8th, 2014
The Mass Extinctions
250 million years ago, something very bad happened. Our best guess is that a huge volcanic region in what is now Siberia began releasing vast amounts of lava, gas, and ash, and thus made a huge cloud that spread over much of the earth’s surface, triggering what we might now call a “nuclear winter”. With little sunlight reaching the earth’s surface, temperatures plunged. Plants died due to lack of sunlight, and shortly thereafter the animals that fed on them starved to death. The entire biosphere was clobbered, but apparently there was enough resource to sustain a fraction of life. 96% of all marine species perished; so did 70% of all terrestrial vertebrates.
Consider this graph of the number of thousands of genera of marine species over the course of the last 500 million years:
The author has fitted a trinomial to it, fitting the data quite nicely. It shows a rise, a slight slump, and then a steep rise. I would characterize this overall shape as representing how the biosphere “learned” to capture an increasing fraction of the negentropy pouring all over the earth from the sun. Over the course of time, new ecological niches were created and filled with new genera. That’s the big-picture message of this graph.
But there are finer details to consider. I cannot address the slump; it remains a mystery to me. But there’s another aspect of this graph that I think deserves serious consideration. I refer to the mass extinctions, which appear in the graph as a sudden dip in the number of genera. I count nine of these, the most severe being the Permian extinction 250 million years ago, although the most prominent is the Cretacious extinction 65 million years ago. What strikes me about this graph is that most of the periods between extinctions do not follow the shape we might expect. Since the overall shape of this graph is one of general rise in the number of genera, we’d expect that general rise to show up in the segments between extinctions. This would yield a sawtooth shape, like this:
Look closely at the match between the black sawtooth and the gray data. There’s a consistent error in it. I can point out that error by labeling the graph differently:
The blue triangles mark the peaks attained prior to the extinctions. The key point I want to make is that those peaks are not sharp, as you would expect from the sawtooth graph. Instead, they are lopsidedly rounded; while the extinction phase sometimes shows a sharp fall, the phase prior to extinction clearly shows that the rate of creation of new genera was falling prior to the extinction. Life did not increase in complexity linearly; although the immediate recovery from an extinction was usually rapid, things always slowed down.
What was going on here? Why did evolution slow down? Here’s a pairing of graphs that throws some light on the process:
The lower blue graph charts the number of genera that went extinct. Thus, where there’s a mass extinction, the upper graph shows a dip in the total number of genera and the lower graph shows a spike in the number of extinctions of genera.
What’s striking about the blue graph is the fact that the spikes don’t stick out in isolation. If these were solely the result of some grand catastrophe — an asteroid hitting the earth or a massive volcanic eruption — then we’d expect it to look like a bolt from the blue, with the extinction event standing in isolation. Instead, what we see is something like anticipation of the extinction. Look at each of the three later mass extinctions, at 250 million years, 200 million years, and 65 million years. Each one shows a rise in extinctions well before the actual extinction.
Did species decide that, since they were doomed in another 20 million years or so, they might as well get it over with and go extinct immediately? How could they know that there was an asteroid out there with their name on it?
Evolutionary biologists are fully aware of this and I have read essays in which they discuss the factors at work behind these “anticipatory extinctions”. However, I would like to offer another possible explanation which includes some elements taken from others.
Finding local optima
The biosphere is a system that attempts to maximize utilization of negentropy from the sun. This is not a purposeful strategy; instead, subsystems that do not maximize are outcompeted by subsystems that do maximize. But this process of optimization is subject to a pitfall arising from what are called ‘local optima’. Consider this simple expression of the concept:
The horizontal axis represents some physiological variable such as length of legs, aggressiveness of the immune system, or metabolic rate, while the vertical axis represents the degree of fitness conferred by that physiological variable. In other words, longer legs might well permit you to run faster, but there are some ideal lengths, represented by points A and B, that represent really useful lengths. Notice that point B is better than point A, but each is still better than the points in its immediate neighborhood.
Now suppose that a given species finds itself at point X. It’s going to evolve by slow changes towards either point A or point B. But it cannot see ahead; it cannot know in advance what the ideal leg length is. All it can do is carry out trials with different individuals and evaluate the statistical results through reproduction. Some creatures are born with slightly longer legs, and some are born with slightly shorter legs.
But look — there’s a flaw in the scheme! The individuals with longer legs are LESS fit than the ones with shorter legs, so the ones with shorter legs win the competition and the species slowly evolves towards point A. That’s what’s called a local optimum — it’s the best place in the immediate neighborhood, but it’s not the best place overall.
The same concept applies to the biosphere as a whole. It’s creating and destroying species in a pattern that moves towards optimal utilization of solar negentropy. But it can get stuck in a local optimum. Indeed, the real world sparkles with local optima. Here’s a two-dimensional representation of the idea:
In fact, the reality has not just two dimensions but millions of dimensions, so we’re talking about an extremely complex situation, so it’s no wonder that the huge experimental laboratory that is the biosphere takes millions of years to explore all those possibilities.
But what happens when it gets stuck on a local optimum? Small perterbations won’t be enough to jog it loose so that it can explore other, possibly better arrangements. So is it doomed to remain forever on some local hilltop, never able to ascend the mountaintops?
The only way out of this trap is the rare catastophe that wipes the decks clear and permits the biosphere a fresh start. A huge volcanic eruption or a rampaging asteroid are just what the doctor ordered to clear out the accumulated genetic gunk and get the old evolutionary motor revving again.
Of course, each time this happens, the biosphere doesn’t start from scratch: it retains a goodly portion of the genetic legacy it has built up. True, the pathetic survivors of the catastophe aren’t much to look at, but their genes contain lots of genetic tools well-honed by millions of years of development. The survivors of each catastrophe start from a higher base than those of previous catastrophes.
This large-scale process began about 200 million years ago. I don’t know why it didn’t start earlier; perhaps the biosphere was still too primitive. But there’s no question that biodiversity starts accelerating at that point, and continued to accelerate despite setbacks at 150 million and 65 million years ago.
Thus, catastrophes are a way to escape from local minima.
fill this in later
This was certainly a disaster for the existing species, but I argue that it was beneficial for life in general. The Permian had seen the global biosphere approach an equilibrium situation in which every ecological niche was filled and the global ecosystem was in balance. In such a system, there is no need for evolution to proceed. In a sense, when the global ecosystem is fat and happy, nothing changes.
The Permian extinction wiped the board clean and forced life to start over. However, this time it was starting over from a higher base: the survivors had large, complex genomes that gave them plenty of elbow room to expand into new ecological niches. The result was the rise of the dinosaurs, which by any measure are more complex and interesting species than the ones they replaced.
There was another exinction event, the Triassic extinction, around 200 million years ago; it was nowhere near as bad as the Permian extinction, wiping out only about half of all species. However, the survivors retained the best of the ancient genomes, and so they started from a more advanced state than their Permian ancestors. This triggered another fast round of evolutionary progress, replacing more primitive dinosaurs with more complex creatures which went on to dominate the terrestrial environment.
(By the way, I want to clarify an important point here. I am not falling prey to the old “great chain of being” line that saw all of evolution leading up to Homo Sapiens as the pinnacle of evolution. Instead, I am claiming that the genetic complement of species steadily grew over the course of millions of years, so that the complexity of life forms steadily expanded.)
Things were fairly stable for the next 135 million years, but 65 million years ago, an asteroid hit what is now Yucatan, spreading a vast cloud of ash over the planet. This Cretacious extinction was pretty bad: it wiped out 75% of all species. It annihilated the terrestrial dinosaurs. But in the process it opened up new ecological niches for mammals to expand into. With a few dozen million years, mammals had gone wild, enthusiastically colonizing those new ecological niches. Once again we see that the destruction of a stable system led to dramatic changes that built upon the previous genomes.
The overall conclusion I draw is that the mass extinctions played a crucial role in the development of life on earth. The biosphere as a whole expanded, reaching into every possible ecological niche, then reached an optimal state and stabilized. Once stability had been achieved, very little change took place. Had there been no mass extinctions, the earth would probably still be populated by trilobytes, crinoids, ammonids, giant dragonflies, very large amphibians — and no reptiles, birds, or mammals.
The catastrophe at the end of the Bronze Age
Around 3200 years ago, the civilizations in the Middle East had reached a kind of equilibrium. The Mycenaens, Egyptians, Mesopotamians, and Hittites had carved out their respective territories; things were stable. They fought wars that never really changed anything.
But then, out of nowhere, came the Sea Peoples. These were naughty people: they ravaged the Middle East, burning, looting, and destroying. They wiped out the Hittites and Mycenaens, devastated all the coastlines, and even gave the Egyptians a run for their money. Then they disappeared. They left behind smoking ruins and depopulated zones.
The Asian littoral quickly recovered, primarily because of colonists from the interior, who simply rebuilt the same types of social structures used previously. But the Aegean areas did not recover so easily. Their cultural slate had been wiped clean, and so they started from scratch. As I explain in The Bronze Age Collapse, The Achaens, and The Greeks, these people built a new civilization from scratch — a more complex civilization that sported many advantages over the ancient Middle Eastern civilizations. This new civilization, the Greek civilization, changed everything. They invented rationalism and geometry and explored a huge range of ideas, leaving a mark that impresssed people from other cultures for thousands of years. Even today, we talk about “The Glory that was Greece”.
This development is directly analogous to the mass extinctions: a broad catastrophe cleared the decks sufficiently for something completely new and distinctly better to emerge.
But only so much progress can be made in a single jump. The Romans inherited the Greek culture, embraced it, and even managed to extend it somewhat. But they didn’t take it far; Roman civilization quickly reached a kind of cultural equilibrium and social evolution slowed to a crawl.
Although Rome had stopped advancing, the same cannot be said for the Germanic peoples living in northern Europe. They continued the advance of their own primitive cultures and grew so powerful that they overran the Roman Empire. This constituted a cultural mass extinction of vast scale; the Dark Ages began. For hundreds of years Europe stagnated. It started to revive under Charlemagne, but then the double whammy of the Viking and Saracen attacks brought the revival to a brutal end.
The European recovery
The Europeans had to start from scratch and build a completely new civilization. Their poverty and low population had forced a primitive structure in which manors owned by lords were economically self-sufficient units, interacting only weakly with each other. From this nothingburger culture, Europeans fashioned a completely new and different civilization. One of the crucial elements was the development of cities unlike anything before.
In all other civilizations, cities were the seats of power. The king had a palace in the city from which his henchmen terrorized the local farmers to pay their taxes to keep the king and aristocracy in luxury. But in Europe, the seats of power were the manors, which were much smaller organizations. The feudal system organized all the manors into a hierarchy topped by a king — but this king was nothing like the kings elsewhere. He didn’t rule over the entire country; he had his own manors, but he had little control over the lords and their manors. He enjoyed some privileges as king but he simply could not command the country the way other kings did. He was usually engaged in continuous warfare with one or more defiant barons.
The cities arose as trading posts, but they lay outside the jurisdiction of the barons, and instead negotiated their legal status with kings or bishops. Realizing that these cities generated considerable wealth, kings were only too happy to grant special self-governing privileges to the cities.
This concept of charters granting special rights to selected communities caught fire and spread. Pretty soon there were guilds of artisans who had charters from their cities giving them special rights. Universities started off as guilds of scholars and students, and quickly grew into an institution unlike anything anywhere else in the world.
I won’t continue this history of European civilization in the Middle Ages — there’s too much. The point here is that the Germanic invasions that destroyed the Roman Empire cleared the decks for something completely new and substantially better.
The Islamic triumph
We see a smaller example of this process in the initial progress of the Islamic empire. The Arabs overran and wiped out the existing Persian, Byzantine, and Germanic areas in the Middle East and northern Africa, up to and including Spain. By wiping out old civilizations, they cleared the decks for something new and different, but they were too small in number to radically change the populations they encountered. Thus, the cultural leap they engendered was not as great as those of the Greeks or the Europeans, but nevertheless, the Islamic efflorescence of the 9th, 10th, and 11th centuries was an impressive period, with many contributions to humankind’s store of knowledge.
The stultifying stability of China and India
By contrast, neither China nor India ever suffered the kinds of catastophe that had shattered other civilizations. Yes, they had their wars and their terrible periods, the invasions of the Mongols, Moguls, and Manchus, and many other vicissitudes, but at no point was either civilization wiped out as a civilization. Invaders came and were assimilated into the local culture. In many ways, the continuity of these civilizations is impressive. A modern Chinese reader can understand Chinese documents written two thousand years ago.
But they never had the slate wiped clean. They never had to start over from scratch and build something completely new. Their underlying culture was never destroyed. Mao made a pretty good attempt at wiping out classical Chinese culture, but he failed. The British tried to westernize India, and they failed, too. Thus, the history of these civilizations is placid, peaceful — and devoid of the great leaps made by the Greeks and the Europeans.
The American and French Revolutions
We have smaller examples of this process in the American and French revolutions. The American revolution was not as profound a change, and so did not trigger any gigantic culture leaps, but it certainly did usher in changes that could not have happened under British rule, changes that took much longer for Britain to adopt.
The French Revolution, on the other hand, was definitely a catastophe of the first order. They wiped out the aristocracy and the entire governmental structure. They really did start from scratch in creating a new culture. In the process, they replaced the crazy-quilt French monetary system with a more rational decimal system; they created the metric system; and they made impressive innovations in governmental architecture. Sadly, the French Revolution got out of control and was subverted by Napoleon, but eventually the French sorted out their problems and developed a modern democracy.
The same ideas apply even at the small level of industries. Most industries creep along in a slow evolutionary process, but every now and then something radical changes everything — and that’s when we see the biggest leaps. The computer industry has provided us with a number of examples of this process.
Back in the 1970s, IBM ruled the computer universe. “Big Blue”, as it was called, dominated everything about computers and software. When microcomputers first appeared, IBM dismissed them as toys. But microcomputers blasted off, and despite IBM’s admirable attempts to catch up, it was never able to present serious competition to the companies that were born and raised in the microcomputer universe. Today, IBM is but a shadow of its former self, and companies like Apple and Microsoft that were babes back then are now the giants. What was a catastrophe for big computer companies like IBM turned out to be the breeding ground for new companies.
In the early 1980s, Atari ruled the world of home videogames. Lots of companies rushed in to cash in on the bonanza. Then in 1983 the videogame market collapsed, taking Atari and many other companies with it. But the aftermath of the videogame crash was a time of amazing creativity. All sorts of interesting ideas were bounced around. It took only a few years for the games industry to settle into happy stagnation. But for a brief time, creativity abounded.
Indeed, the phenomenon is now so widely recognized that there is a term for it: “creative destruction”. I think, however, that the term doesn’t quite capture the larger phenomenon that I’m describing here. Its focus is smaller, on single companies rather than entire industries. Still, it contains some of the sense of what I’m talking about.
Summary and conclusions
My point here is that systems always evolve to reach a point of relative optimization, in which