The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning by Daniel Bor

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.
    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