The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning (11 page)
Authors: Daniel Bor
BOOK: The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning
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MUTANTS, SEX, AND DEATH
The first, most obvious means of injecting new ideas into DNA code is through mutations. Although DNA is an immensely robust molecule, DNA machinery isn’t perfect, and occasionally errors do arise. For instance, for bacteria, one mistake occurs every 10 million letters. If you only have 100,000 letters to spell your entire recipe, that means there will only be a single mistake in a single letter for every 100 bacteria. Some of these misspellings won’t even make any difference, as they will just be a new spelling of the same word. Others could radically alter the protein made—probably causing serious problems for the cell’s functions. But there’s also a slim chance that it will be an improvement, a better idea for how to survive and reproduce in the current environment.
With mutations being the mainstay of innovation in all organisms, manipulating this mutation rate is one way that creatures can increase the frequency of potential new ideas in order to match a more volatile world. Some species do indeed utilize this trick: When the situation looks grim, and survival is strained, random mutation rates are increased in some bacteria. Yeast react to stress not by reshuffling letters, but entire chromosomes, for the same inventive result.
An interesting analogy to this is in primate innovation. Those primates with the lowest social standing tend to exhibit innovative behaviors far more often than their higher-ranking compatriots, in the hopes of chancing upon some strategy that will raise them up the social ladder. There are many human analogues to this, such as the technological leaps that tend to occur in or around wartime.
Animals, however, with similar mutation rates to bacteria, but a far greater investment in complexity and size, have a serious problem: Since they reproduce up to half a million times slower than bacteria, their genetic creativity has taken a massive hit. This makes many animals terribly vulnerable to certain changes. The 10-kilometer-wide asteroid that crashed into the earth 65 million years ago was devastating for many animals, especially the dinosaurs, partly because they couldn’t adapt fast enough to the climate changes it brought. Seventy-five percent of all animal species were made extinct by this event. Although it’s impossible to collect such ancient data for bacteria, their extinction rate would very likely have been a very tiny fraction of this. Evolution would have been spoiled for choice to pick new forms of bacteria within most species, as they would have quickly adapted to thrive in the hellish conditions that arose after the asteroid’s catastrophic arrival.
To attempt to compensate for this serious limitation (slow replication), animals reproduce sexually. Sex is in many ways the first port of call for new strategies. Although bacteria normally simply divide, preserving every gene in the process, they can also perform an analogy to sexual reproduction by combining with another bacterium, even of another species, and swapping a section of genetic code with their ephemeral lover. But for animals, sexual reproduction has to be very much the rule, rather than the exception.
From a “selfish gene” point of view, indulging in sexual reproduction, instead of simply cloning oneself, is a minor disaster, since only half of an animal’s genetic identity is passed to the next generation. But the reward—genetic creativity—is very much worth it. Heavily mixing an animal’s genes with its partner’s throws up new genetic ideas in their offspring, helping them cope with the world’s many threats. This compensation for slow reproduction is so useful that almost all animals exploit it.
One animal has been definitive in demonstrating the utility of sexual reproduction, the lowly nematode worm. One nematode species,
Caenorhabditis elegans
, is a favorite model of genetic research. Because these worms are very simple animals that rapidly create offspring (every four days or so), the case for sexual reproduction is marginal.
C. elegans’
response to this is to keep their options open, so they can either reproduce on their own or have sex with others.
Caenorhabditis elegans
, is a favorite model of genetic research. Because these worms are very simple animals that rapidly create offspring (every four days or so), the case for sexual reproduction is marginal.
C. elegans’
response to this is to keep their options open, so they can either reproduce on their own or have sex with others.
From an information-processing point of view, if the worm’s world is a safe paradise, replete with abundant, choice morsels, it may as well reproduce asexually, since its genetic ideas about how to survive in the world are accurate and successful. But if there are mortal dangers, then its DNA could do with a shake-up for the next generation, of the kind that sexual reproduction can offer, to see if its rather different children will chance upon a better genetic recipe to cope with this harsh world. In fact, this is exactly how
C. elegans
behaves. Patrick Phillips and colleagues have shown that, when faced with some threat, such as a bacterial infestation, these worms are more likely to forgo the default of self-fertilization and instead have sex with others, and because of this, the family line is more likely to survive. The cauldron of sexually induced genetic diversity is beneficial at those times. In contrast, any that are forced to self-fertilize, despite the same threats, simply cannot cope, and they are soon wiped out after only a handful of generations.
C. elegans
behaves. Patrick Phillips and colleagues have shown that, when faced with some threat, such as a bacterial infestation, these worms are more likely to forgo the default of self-fertilization and instead have sex with others, and because of this, the family line is more likely to survive. The cauldron of sexually induced genetic diversity is beneficial at those times. In contrast, any that are forced to self-fertilize, despite the same threats, simply cannot cope, and they are soon wiped out after only a handful of generations.
Another injection of creativity into evolutionary hypothesis testing may well be death itself. Some people believe that research departments benefit from forcing crusty old professors to retire at sensible ages, so that stubborn, old-fashioned theories and habits aren’t perpetuated so forcefully in the community, and new ideas from younger, more dynamic scientists have more space to flourish. Likewise, in nature it’s possible that the existence of death helps species to avoid the buildup of outdated hypotheses. It’s true that organisms just wear out. It’s also true that any fatal genetic illness that materializes after the creature has successfully had children is not something that evolution is particularly interested in removing. But this isn’t necessarily the whole story.
For instance, death can be held at bay, seemingly indefinitely, in some cases. Some bacteria can survive, in stasis, in the cold wasteland of the Antarctic, for hundreds of thousands of years, if necessary. What’s more, all organisms so far tested, from yeast to worms to humans, can, on average, have their lives extended by at least a third simply by eating less. It’s therefore quite possible that this is an important biological mechanism by which to hang around for longer, until food becomes plentiful again and the environment is ripe for babies once more. So death, to some extent, seems programmed and flexible, and possibly for good reason.
I would speculate that without age-related death, genetic creativity across a species would become increasingly polluted by outdated ideas. If an older generation persists, then its offspring with genuinely useful innovations are less likely to flourish, as they have greater competition from their own family. If this situation continues for many generations, then the good ideas will increasingly become diluted and the species will be far more sluggish in response to changes. And when some crisis looms, for which the creatures with this excessive longevity have no solution, the species will be far more fragile than it would have been with a rapid turnover of creatures across the generations.
A similar reason exists for why we don’t, as a rule, remember everything we experience in our lives. Holding on to an increasingly irrelevant bank of information would drastically interfere with our daily functioning, and we would eventually be mentally crippled. One particularly striking case of near perfect memory is that of Solomon Sherashevski. Sherashevski was born around 1886 and grew up in a small Russian Jewish community, eventually, in his late twenties, ending up as a journalist.
It was as he began this profession that Sherashevski’s extraordinary mental skills were revealed to the outside world. His editor was having his usual morning meeting with the staff to portion out all the instructions necessary for the reporters to go about town to do their daily jobs. Everyone was industriously taking notes—except Sherashevski. He, in stark contrast, didn’t even have a pencil and paper at the ready. Assuming that Sherashevski was being lazy, the disgruntled editor called him up on his behavior. Sherashevski explained that he didn’t need to take notes, as he simply remembered absolutely everything, all the time. Disbelieving, the editor asked him forthwith to prove this wild assertion, which he duly did, by quoting back with perfect fidelity every word that the editor had said that morning.
In fact, to this remarkable man, it was incomprehensible that other people
didn’t
do exactly the same thing—
why on earth would someone immediately forget these important facts? What’s the point of that?
At this stage, it was clear to outsiders that Sherashevski was far from normal. He was soon sent to a famous Russian psychologist, Alexander Luria, who studied him extensively over a period of thirty years.
didn’t
do exactly the same thing—
why on earth would someone immediately forget these important facts? What’s the point of that?
At this stage, it was clear to outsiders that Sherashevski was far from normal. He was soon sent to a famous Russian psychologist, Alexander Luria, who studied him extensively over a period of thirty years.
Sherashevski’s memory was indeed incredible. He seemed to remember almost everything he came across entirely naturally. One example involved him being read aloud some stanzas of Dante’s
Divine Comedy
in its original Italian—a language he had no knowledge of. When given a surprise test on this content
fifteen years later
, he could recall the stanzas so completely that he even repeated the words with the same stresses and pronunciation as they were originally spoken to him.
Divine Comedy
in its original Italian—a language he had no knowledge of. When given a surprise test on this content
fifteen years later
, he could recall the stanzas so completely that he even repeated the words with the same stresses and pronunciation as they were originally spoken to him.
Although the ability for such vast, faithful recall seems a fantastic mental gift, there were prices to pay, both big and small. One drawback of his exceptional recall was an occasional inability to see the forest for the trees, to discover meaning, structure, or patterns in the stream of information he was busy encoding. For instance, while he could memorize long sequences of numbers, he would be completely oblivious to any simple structure within them, such as ascending numbers 1, 2, 3, 4.
But these unfortunate quirks of his mind were nothing compared to the emotional consequences of his superlative memory. For instance, his imagination was so vivid, so complete, that he often would mistake reality for a daydream. At the very least, imagination would corrupt reality so profoundly that he would struggle to get through something as mundane as a novel—every word in it would conjure up too many distracting images. For similar reasons, he struggled to overcome the crushing weight of his past. Sherashevski claimed to have near perfect memories from before he was one. These were so striking that he fought in vain to banish these carbon-copy recollections, since they also included the overwhelming intensity of these earliest feelings—the absolute terrors, or racking sobs of infancy.
As Sherashevski aged, the burden of this enormous memory became increasingly difficult to endure. He became desperate to find some effective strategy by which to forget things. He drifted from job to job, and unfortunately he died believing that he’d somehow wasted the mental opportunity he’d been given, and that he had never really amounted to much.
Examples like Sherashevski demonstrate that sometimes the fading and death of old information can help a person succeed. The person who forgets an optimal amount of old material can have a more accurate, organized view of what’s relevant in the world right now. Likewise, perhaps the death of older creatures can lead to a family or species with collective tools that are better honed for an ever-changing environment.
Replication has always been the driving force of evolution, with survival taking a back seat. But more than this, death as an evolutionary strategy might even be an example of how survival and replication can come to loggerheads, with replication not hesitating to abandon survival if there are gains to be made in terms of having a more accurate, up-to-date implicit picture of the relevant features of the world.
EVERY CREATIVE TRICK IN THE BIOLOGICAL BOOKMutations, death, and sex are by no means the only methods for potentially invigorating DNA sequences with useful new ideas, or tweaking the learning rate to reflect whether the microbe’s current world picture is successful or deeply flawed.
There is a large array of tricks that various simple organisms can exploit to discover new ways to successfully survive and reproduce, but one of the most intuitive is simply to try moving a sequence of code somewhere else in your recipe. After all, if much of this code is capturing something useful—perhaps it already creates a functional protein—then its shift to another part of the genome could create a similar protein that might be even more beneficial. So, compared to making changes in a painstaking way, letter by letter, this method is both more powerful and efficient: The potentially useful idea is already half-baked. Of course, mixing up code like this could be utterly disastrous, but there is also a chance that it might be not just a step, but a great leap in the right direction of advantageous innovation.
This mixing up of whole nuggets of ideas happens in various ways in the DNA code. Entire sections of genetic code (called transposons, or “jumping genes”) can jump around the genome, breaking off from one location and reattaching to another.
The source and behavior of these bouncing clumps of genetic letters is fascinating. Some of these jumping pieces of DNA might simply be a kind of life within a life—a ragbag collection of genetic letters that has chanced upon a way of surviving and reproducing, sometimes entirely within the dense, tangled forest of DNA strands. Just as an organism evolves through the generations, stumbling upon better beliefs about the environment, so are these jumping pieces of DNA code shaped by evolution—though their world is the cramped home of the set of DNA letters. But this isn’t the entire story: If these leaping sections of genetic code cause catastrophic failure in the function of their host, the organism, then they, too, will cease to exist. At the same time, if they can in any way aid their host, then they will have a greater chance of survival themselves.
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