As we all know, time travelers have to be very careful when they visit the past, because their evolved immune systems allow them to harbor pathogens that the olde timey people are defenseless against. One careless bowel movement, a single badly timed cough, a bit of blood spilled, and whole civilizations are in pandemic peril.

Surviving to the future means adapting to the risks of the past. Our ancestors harbored vulner­abilities that bounce off of us, and yet our lives are no easier than theirs, because the predators and parasites we contend with have adapted to us, just as surely as we have adapted to them. The predator carves the prey, the prey carves the predator in turn.

Our ancestors’ defenses were pitiful by contem­porary standards. Consider the ghost ad, on the sides of old brick buildings, in fading paint and ornate serif script: USE PEAR’S SOAP FOR THE SKIN AND COMPLEXION 5¢.

Use Pear’s Soap! Once upon a time, “Use Pear’s Soap” drove customers to the five and dime and the dry-goods store, clamoring for their own supply. Today, we sell soap like this: AXE BODY SPRAY WILL MAKE YOU IRRESISTIBLE TO WOMEN WITH THE BODIES OF FITNESS MODELS AND THE FACES OF ANGELS. BUY AXE BODY SPRAY OR YOU WILL DIE A VIRGIN. USE MORE AXE BODY SPRAY, ASSHOLE. NO, MORE THAN THAT. KEEP GOING. MORE. I SAID MORE!

It seems impossible that “Use Pear’s Soap,” ever sold a single cake of the stuff, but it must have, because slogans like this are all over the fossil record of our advertising, printed in 10-foot tall letters on the sides of old buildings, pictured in delicate engravings in old numbers of Collier’s and the Saturday Evening Post.

Over time, though, through repetition, through disappointments, through experience, we stopped responding to “Use Pear’s Soap.” We became inured to it. Adapted.

Remember Farmville? One day there was no Farmville, and then there was, and all your friends wanted you to water their cows and fertilize their chickens. Your kids – your spouse! – threw money at the game, trapped in a (seemingly) escape-proof limbic dopamine loop.

And then, poof, no more Farmville. I mean, it exists, and there’s a die-hard audience for it, but it is no longer a social phenomenon, no more than Beanie Babies or Pokemon Go is. Zynga’s share-price fell off a cliff in 2012 and it never came back. It’s not coming back.

Farmville is an unregulated, low-yield casino game. Casino games use cognitive traps that we’re all susceptible to at first, and that some small number of us never adapt to. The first time you played a slot machine, you probably found it weirdly, irresistibly compelling. A few dollars (penny slots) or few grand (dollar slots) later, you probably started to find slots weirdly, terribly boring. Not everyone has this reaction, of course: people in the fifth or sixth sigma of slot-machine susceptibility go out and buy adult diapers and gloves to prevent blisters, mortgage their houses, raid their kids’ college funds, and hock their mothers’ wedding rings.

Slots are very high-yield, so the slot machine industry can sustain itself by exploiting the vulnerability of a tiny minority of the population, because those whales will pump so much money into the machines that they make up for all the rest of the world who quickly adapt to the slots’ siren song, until it is damped down to a distant refrigerator hum.

But slots are regulated: there are cognitive tricks that slot machines are not allowed to play, games they could pull with the payouts and odds.

By contrast, Zynga games like Farmville have no limits on the tricks they can pull. They’re “games,” not “gambling,” so they can pull out all the stops. However, Zynga games are also very low-yield. Zynga’s ability to deploy the whole palette of addictive dark design patterns may net it a few more players who opt for the online equivalent of adult diapers (empty magnum bottles of Mountain Dew strategically placed near by the computer chair, I’m guessing) but as the vast majority of us develop callouses over the soft attentional tissue that Zynga figured out how to tickle, Zynga is left without the ongoing funds to pay the kinds of R&D talent it takes to locate and exploit new soft spots, and their existing diehards either run out of money, develop resistance, get poached by better-heeled competitors, or hang in there in dwindling numbers as Zynga circles the drain (I advise selling your Zynga stock now).

When a new attentional soft spot is discovered, the world can change overnight. One day, every­one you know is signal boosting, retweeting, and posting Upworthy headlines like “This video might hurt to watch. Luckily, it might also explain why,” or “Most Of These People Do The Right Thing, But The Guys At The End? I Wish I Could Yell At Them.” The style was compelling at first, then reductive and simplistic, then annoying. Now it’s ironic (at best). Some people are definitely still susceptible to “This Is The Most Inspiring Yet Depressing Yet Hilarious Yet Horrifying Yet Heartwarming Grad Speech,” but the rest of us have adapted, and these headlines bounce off of our attention like pre-penicillin bacteria being batted aside by our 21st century immune systems.

There is a war for your attention, and like all adversarial scenarios, the sides develop new countermeasures and then new tactics to overcome those countermeasures. The predator carves the prey, the prey carves the preda­tor. To get a sense of just how far the state of the art has advanced since Farmville, fire up Universal Paperclips, the free browser game from game designer Frank Lantz, which challenges you to balance resource acquisi­tion, timing, and resource allocation to create paperclips, progressing by purchasing upgraded paperclip-production and paperclip-marketing tools, until, eventually, you produce a sentient AI that turns the entire universe into paperclips, exterminating all life.

Universal Paperclips makes Farmville seem about as addictive as Candy­land. Literally from the first click, it is weaving an attentional net around your limbic system, carefully reeling in and releasing your dopamine with the skill of a master fisherman. Universal Paperclips doesn’t just suck you in, it harpoons you.

I lost a half-day to Universal Paperclips, then, abruptly, its spell was broken. The attentional callous had developed and the tender spots that Lantz had targeted with his proof-of-concept had been armored against these particular attacks.

The attention wars have real consequences for our daily lives. The entire fake news/Facebook ad/Twitter bot scandal is but a skirmish in the wider attention war, albeit one with global geopolitical (and potentially thermo­nuclear) consequences.

But today’s weaponized attention is tomorrow’s ghost ad. Cambridge Ana­lytica, the persuasion/manipulation company backed by billionaire Trump supporter Robert Mercer, claims it used Facebook targeting to deliver both Brexit and the 2016 presidency, and many people take them at their word.

I’m more relaxed about Cambridge Analytica than most of my friends. First because I always take sales brochures with a grain of salt, and when Robert Mercer, who is in the business of taking money in exchange for changing the minds of large populations, announces, without proof, that large shifts in public opinion are attributable to his product, that is a sales pitch. It may be true, but it’s about as unbiased as an Axe Body Spray ad.

But even if Mercer is right, we don’t know how long he’ll be right for. Cambridge Analytica may have stumbled on an attentional tender place, but there’s no reason to suspect that it is any more enduring than Upwor­thy headlines. There may be a rump of voters who’ll remain susceptible to Mercerism and its persuasion tactics, but you don’t win elections with a rump of voters.

Now, perhaps Mercer’s R&D labs will develop new tips for their attentional harpoons, ones that can puncture the callouses we’re developing even now. If they don’t, someone surely will, because there’s a lot of money and power for anyone who successfully punctures our defenses, while it lasts.

But history is littered with armies of seemingly invincible attention warriors who were out-evolved by their prey, and could not overcome the counter­measures that were begat by repeated exposure to their once-undefeatable tactics.

I’m not counseling apathy here, just perspective. It’s not that there won’t be evil billionaires trying to manipulate turkeys to vote for Christmas after Robert Mercer is a footnote in the history of persuasion, and I have no idea what new tactics they’ll use to get past our defenses – but I do know that we’ll have defenses, and today’s devastating superweapon will be tomorrow’s stone axe.