A herd of wildebeests, a shoal of fish, a flock of birds. Many animals gather in large groups that are among the most wonderful spectacles in the natural world. But why do these groups form? The common answers include things like seeking safety in numbers or hunting in packs or gathering to mate or breed, and all of these explanations, while often true, make a huge assumption about animal behavior, that the animals are in control of their own actions, that they are in charge of their bodies. And that is often not the case.
Čreda gnujev, jata rib, jata ptic. Mnoge živali se zbirajo v velikih skupinah, ki so med najčudovitejšimi prizori naravnega sveta. A zakaj se te skupine oblikujejo? Običajni odgovori vključujejo stvari, kot so iskanje varnosti v množičnosti, ali lov v krdelih, ali zbiranje zaradi parjenja ali razmnoževanja, in vse te razlage, čeprav pogosto držijo, vsebujejo veliko predpostavko o obnašanju živali, in sicer, da živali nadzirajo svoja dejanja, da imajo nadzor nad svojimi telesi. A temu pogosto ni tako.
This is Artemia, a brine shrimp. You probably know it better as a sea monkey. It's small, and it typically lives alone, but it can gather in these large red swarms that span for meters, and these form because of a parasite. These shrimp are infected with a tapeworm. A tapeworm is effectively a long, living gut with genitals at one end and a hooked mouth at the other. As a freelance journalist, I sympathize. (Laughter) The tapeworm drains nutrients from Artemia's body, but it also does other things. It castrates them, it changes their color from transparent to bright red, it makes them live longer, and as biologist Nicolas Rode has found, it makes them swim in groups. Why? Because the tapeworm, like many other parasites, has a complicated life cycle involving many different hosts. The shrimp are just one step on its journey. Its ultimate destination is this, the greater flamingo. Only in a flamingo can the tapeworm reproduce, so to get there, it manipulates its shrimp hosts into forming these conspicuous colored swarms that are easier for a flamingo to spot and to devour, and that is the secret of the Artemia swarm. They aren't sociable through their own volition, but because they are being controlled. It's not safety in numbers. It's actually the exact opposite. The tapeworm hijacks their brains and their bodies, turning them into vehicles for getting itself into a flamingo.
To je artemija, solinski rakec. Verjetno ga bolj poznate pod imenom morska opica. Je majhen in navadno živi sam, a se lahko zbira tudi v takšnih velikih rdečih rojih, ki se raztezajo več metrov. Ti pa se oblikujejo zaradi zajedavca. Ti rakci so okuženi s trakuljo. Trakulja je v bistvu dolgo, živo črevesje, z genitalijami na enem koncu in kljukastimi usti na drugem. Kot samostojni novinar, sočustvujem. (smeh) Trakulja srka hranljive snovi iz artemijinega telesa, a počne tudi druge stvari. Kastrira jih, njihovo barvo spremeni iz prosojne v svetlo rdečo, podaljša jim življenje, in, kot je odkril biolog Nicolas Rode, jih pripravi do plavanja v skupinah. Zakaj? Zato ker ima trakulja, tako kot mnogi drugi zajedavci, kompliciran življenjski cikel, ki vključuje mnogo različnih gostiteljev. Rakci so samo en korak na njeni poti. Njen končni cilj je ta, veliki flamingo. Trakulja se lahko razmnožuje samo v flamingu, zato, da bi prišla do njega, zmanipulira svoje gostitelje rakce, da oblikujejo te roje vpadljive barve, ki jih flamingo lažje opazi in požre, in to je skrivnost rojev artemij. Niso družabni po lastni volji, ampak ker jih nadzirajo. Ni varnost v množičnosti. Dejansko je ravno nasprotno. Trakulja ugrabi njihove možgane in njihova telesa ter jih spremeni v vozilo, s katerim pride do flaminga. Tu pa je še en primer zajedavske manipulacije.
And here is another example of a parasitic manipulation. This is a suicidal cricket. This cricket swallowed the larvae of a Gordian worm, or horsehair worm. The worm grew to adult size within it, but it needs to get into water in order to mate, and it does that by releasing proteins that addle the cricket's brain, causing it to behave erratically. When the cricket nears a body of water, such as this swimming pool, it jumps in and drowns, and the worm wriggles out of its suicidal corpse. Crickets are really roomy. Who knew?
To je samomorilski čriček. Ta čriček je pogoltnil ličinke gordijskega črva ali žive niti. Črv je v njem zrastel do odrasle velikosti, vendar mora za parjenje priti do vode, to pa naredi z izločanjem beljakovin, ki zmedejo čričkove možgane, da se začne obnašati neobičajno. Ko se čriček približa vodi, kot je ta bazen, skoči vanjo in se utopi, črv pa privijuga ven iz njegovega samomorilskega trupelca. Črički so res prostorni. Kdo bi si mislil?
The tapeworm and the Gordian worm are not alone. They are part of an entire cavalcade of mind-controlling parasites, of fungi, viruses, and worms and insects and more that all specialize in subverting and overriding the wills of their hosts. Now, I first learned about this way of life through David Attenborough's "Trials of Life" about 20 years ago, and then later through a wonderful book called "Parasite Rex" by my friend Carl Zimmer. And I've been writing about these creatures ever since. Few topics in biology enthrall me more. It's like the parasites have subverted my own brain. Because after all, they are always compelling and they are delightfully macabre. When you write about parasites, your lexicon swells with phrases like "devoured alive" and "bursts out of its body." (Laughter)
Trakulja in živa nit nista edina. Sta del celotne kavalkade zajedavcev, ki nadzirajo um, glivic, virusov, črvov in žuželk ter drugih, ki so vsi specializirani za spodkopavanje in nadvladovanje volje njihovih gostiteljev. Za ta način življenja sem prvič slišal v "Preizkusih življenja" Davida Attenbourgha pred približno 20 leti, kasneje pa še v čudoviti knjigi "Zajedavec Reks", ki jo je napisal moj prijatelj Carl Zimmer. In od takrat naprej pišem o teh bitjih. Ni veliko tem v biologiji, ki bi me bolj očarale. Kot da bi zajedavci sprevrgli tudi moje možgane. Konec koncev so vedno neustavljivo privlačni in čudovito strašljivi. Ko pišete o zajedavcih, je vaše besedišče polno fraz, kot so "živ pojeden" in "izbruhne iz njegovega telesa." (smeh)
But there's more to it than that. I'm a writer, and fellow writers in the audience will know that we love stories. Parasites invite us to resist the allure of obvious stories. Their world is one of plot twists and unexpected explanations. Why, for example, does this caterpillar start violently thrashing about when another insect gets close to it and those white cocoons that it seems to be standing guard over? Is it maybe protecting its siblings? No. This caterpillar was attacked by a parasitic wasp which laid eggs inside it. The eggs hatched and the young wasps devoured the caterpillar alive before bursting out of its body. See what I mean? Now, the caterpillar didn't die. Some of the wasps seemed to stay behind and controlled it into defending their siblings which are metamorphosing into adults within those cocoons. This caterpillar is a head-banging zombie bodyguard defending the offspring of the creature that killed it.
A gre za več kot zgolj to. Sem pisec in kolegi pisci v občinstvu bodo vedeli, da imamo radi zgodbe. Zajedavci nas vabijo, da se upremo privlačnosti očitnih zgodb. Njihov svet je poln zasukov v zgodbi in nepričakovanih razlag. Zakaj, na primer, ta gosenica začne nasilno mlatiti naokrog, ko se katera druga žuželka približa njej in tistim belim kokonom, ki jih očitno straži? Ali morda ščiti svoje brate in sestre? Ne. To gosenico je napadla zajedavska osa in vanjo izlegla jajčeca. Mlade osice so se izlegle in gosenico živo pojedle, preden so izbruhnile iz njenega telesa. Vidite, kaj mislim? Gosenica ni umrla. Nekaj os je očitno ostalo in so jo nadzirale, da je branila njihove brate in sestre, ki gredo skozi preobrazbo v odrasle v tistih kokonih. Ta gosenica je z glavo udarjajoč zombi telesni stražar, ki brani potomce bitja, ki jo je ubilo.
(Applause)
(aplavz)
We have a lot to get through. I only have 13 minutes. (Laughter)
Veliko snovi imamo za predelat. Imam pa samo 13 minut. (smeh)
Now, some of you are probably just desperately clawing for some solace in the idea that these things are oddities of the natural world, that they are outliers, and that point of view is understandable, because by their nature, parasites are quite small and they spend a lot of their time inside the bodies of other things. They're easy to overlook, but that doesn't mean that they aren't important. A few years back, a man called Kevin Lafferty took a group of scientists into three Californian estuaries and they pretty much weighed and dissected and recorded everything they could find, and what they found were parasites in extreme abundance. Especially common were trematodes, tiny worms that specialize in castrating their hosts like this unfortunate snail. Now, a single trematode is tiny, microscopic, but collectively they weighed as much as all the fish in the estuaries and three to nine times more than all the birds. And remember the Gordian worm that I showed you, the cricket thing? One Japanese scientist called Takuya Sato found that in one stream, these things drive so many crickets and grasshoppers into the water that the drowned insects make up some 60 percent of the diet of local trout. Manipulation is not an oddity. It is a critical and common part of the world around us, and scientists have now found hundreds of examples of such manipulators, and more excitingly, they're starting to understand exactly how these creatures control their hosts.
Najbrž nekateri od vas sedaj obupno iščete nekaj tolažbe v ideji, da so te stvari nenavadnosti naravnega sveta, da so osamelci, in takšno stališče je razumljivo, saj so zajedavci po svoji naravi precej majhni in veliko svojega časa prebijejo v telesih drugih stvari. Z lahkoto jih spregledamo, vendar to ne pomeni, da niso pomembni. Pred nekaj leti je Kevin Lafferty skupino znanstvenikov odpeljal v tri kalifornijske estuarije in stehtali, secirali in zabeležili so vse, kar so lahko našli, in kar so našli, je bilo skrajno izobilje zajedavcev. Še posebej pogosti so bili metljaji, majhni črvi, ki so specializirani za kastriranje svojih gostiteljev, kot je ta nesrečni polž. Posamezen metljaj je mikroskopsko majhen, vendar pa so vsi skupaj tehtali toliko, kot vse ribe v estuarijih in tri- do devetkrat več kot vse ptice. In se spomnite žive niti, ki sem vam jo pokazal, tisto s čričkom? Japonski znanstvenik, Takuya Sato, je odkril, da v nekem potoku, te stvari poženejo toliko čričkov in kobilic v vodo, da utopljene žuželke predstavljajo 60 odstotkov prehrane lokalnih postrvi. Manipulacija ni nenavadnost. Je ključen in običajen del sveta okoli nas in znanstveniki so odkrili že na stotine primerov takšnih manipulatorjev, kar pa je še bolj razburljivo, začenjajo razumeti, točno kako ta bitja nadzirajo svoje gostitelje.
And this is one of my favorite examples. This is Ampulex compressa, the emerald cockroach wasp, and it is a truth universally acknowledged that an emerald cockroach wasp in possession of some fertilized eggs must be in want of a cockroach. When she finds one, she stabs it with a stinger that is also a sense organ. This discovery came out three weeks ago. She stabs it with a stinger that is a sense organ equipped with small sensory bumps that allow her to feel the distinctive texture of a roach's brain. So like a person blindly rooting about in a bag, she finds the brain, and she injects it with venom into two very specific clusters of neurons. Israeli scientists Frederic Libersat and Ram Gal found that the venom is a very specific chemical weapon. It doesn't kill the roach, nor does it sedate it. The roach could walk away or fly or run if it chose to, but it doesn't choose to, because the venom nixes its motivation to walk, and only that. The wasp basically un-checks the escape-from-danger box in the roach's operating system, allowing her to lead her helpless victim back to her lair by its antennae like a person walking a dog. And once there, she lays an egg on it, egg hatches, devoured alive, bursts out of body, yadda yadda yadda, you know the drill. (Laughter) (Applause)
In to je en od mojih najljubših primerov. To je Ampulex compressa, smaragdna osa, in univerzalno sprejeta resnica je, da si smaragdna osa, ki ima oplojena jajčeca, mora želeti ščurka. Ko ga najde, ga zabode z želom, ki je tudi čutni organ. Do tega odkritja smo prišli pred tremi tedni. Zabode ga z želom, ki je čutni organ, opremljen z majhnimi zaznavnimi izboklinami, ki ji omogočijo, da otipa značilno teksturo ščurkovih možganov. Tako kot oseba, ki na slepo tipa po vreči, najde možgane in jim vbrizga strup v dva točno določena skupka nevronov. Izraelska znanstvenika, Frederic Libersat in Ram Gal, sta odkrila, da je strup zelo specifično kemično orožje. Ščurka niti ne ubije, niti ga ne uspava. Ščurek bi lahko odkorakal ali odletel ali stekel, če bi se tako odločil, a se ne odloči za to, ker strup uniči njegovo motivacijo za hojo in samo to. Osa v bistvu odstrani kljukico iz kvadratka pobegni-pred-nevarnostjo v operacijskem sistemu ščurka, kar ji omogoči, da svojo nemočno žrtev vodi nazaj do svojega brloga s svojimi antenami kot človek, ki sprehaja psa. Ko sta enkrat tam, nanj izleže jajčece, jajčece se izleže, živega poje, izbruhne iz telesa, bla, bla, bla, zdaj že veste, kako to gre. (smeh) (aplavz)
Now I would argue that, once stung, the cockroach isn't a roach anymore. It's more of an extension of the wasp, just like the cricket was an extension of the Gordian worm. These hosts won't get to survive or reproduce. They have as much control over their own fates as my car. Once the parasites get in, the hosts don't get a say.
Trdil bi, da ko ga osa enkrat piči, ščurek ni več ščurek. Je bolj kot podaljšek ose, kot je bil čriček podaljšek žive niti. Ti gostitelji ne bodo preživeli ali se razmnoževali. Nad svojimi usodami imajo toliko nadzora kot moj avto. Ko zajedavec enkrat vstopi, gostitelji nimajo več besede.
Now humans, of course, are no stranger to manipulation. We take drugs to shift the chemistries of our brains and to change our moods, and what are arguments or advertising or big ideas if not an attempt to influence someone else's mind? But our attempts at doing this are crude and blundering compared to the fine-grained specificity of the parasites. Don Draper only wishes he was as elegant and precise as the emerald cockroach wasp. Now, I think this is part of what makes parasites so sinister and so compelling. We place such a premium on our free will and our independence that the prospect of losing those qualities to forces unseen informs many of our deepest societal fears. Orwellian dystopias and shadowy cabals and mind-controlling supervillains -- these are tropes that fill our darkest fiction, but in nature, they happen all the time.
Seveda tudi ljudem manipulacija ni tuja. Jemljemo zdravila, da bi spremenili kemijo v svojih možganih in svoje razpoloženje, in kaj so argumenti ali oglaševanje ali velike ideje, če ne poskus vplivanja na um nekoga drugega? Toda naši poskusi tega so preprosti in nedodelani v primerjavi s fino specifičnostjo zajedavcev. Don Draper si lahko le želi, da bi bil tako eleganten in natančen kot smaragdna osa. Mislim, da je to tisti del, ki dela zajedavce tako zlovešče in tako neustavljivo privlačne. Takšno težo dajemo svoji svobodni volji in svoji neodvisnosti, da možnost izgube teh lastnosti zaradi nevidnih sil naslavlja naše najgloblje družbene strahove. Orwellovske distopije in senčne spletke in super zlobneži, ki nadzirajo ume - to so stvari, ki polnijo našo najtemnejšo fikcijo, v naravi pa se to kar naprej dogaja.
Which leads me to an obvious and disquieting question: Are there dark, sinister parasites that are influencing our behavior without us knowing about it, besides the NSA? If there are any — (Laughter) (Applause) I've got a red dot on my forehead now, don't I? (Laughter)
Kar me vodi do očitnega in zaskrbljujočega vprašanja: Ali obstajajo temačni, zlovešči zajedavci, ki vplivajo na naše obnašanje, ne da bi mi za to vedeli, poleg NSA (nacionalni urad za varnost, op. p.)? Če obstajajo - (smeh) (aplavz) Zdaj imam na čelu rdečo pikico, kajne? (smeh)
If there are any, this is a good candidate for them. This is Toxoplasma gondii, or Toxo, for short, because the terrifying creature always deserves a cute nickname. Toxo infects mammals, a wide variety of mammals, but it can only sexually reproduce in a cat. And scientists like Joanne Webster have shown that if Toxo gets into a rat or a mouse, it turns the rodent into a cat-seeking missile. If the infected rat smells the delightful odor of cat piss, it runs towards the source of the smell rather than the more sensible direction of away. The cat eats the rat. Toxo gets to have sex. It's a classic tale of Eat, Prey, Love. (Laughter) (Applause)
Če obstajajo, je to dober kandidat za njih. To je Toxoplasma gondii, ali na kratko, Toxo, ker si strašljivo bitje vedno zasluži ljubek vzdevek. Toxo lahko okuži sesalce, mnogo različnih vrst sesalcev, spolno razmnožuje pa se lahko samo v mačkah. Znanstveniki kot Joanne Webster so pokazali, da če Toxo pride v podgano ali miš, tega glodavca spremeni v raketo, ki išče mačke. Če okužena podgana zavoha prekrasen vonj mačjega scanja, steče proti viru tega vonja, namesto v bolj razumno smer, stran. Mačka poje podgano. Toxo lahko seksa. Klasična zgodba Jej, moli, ljubi. (smeh) (aplavz)
You're very charitable, generous people. Hi, Elizabeth, I loved your talk.
Ste zelo velikodušni, radodarni ljudje. Zdravo, Elizabeth, tvoj govor mi je bil všeč.
How does the parasite control its host in this way? We don't really know. We know that Toxo releases an enzyme that makes dopamine, a substance involved in reward and motivation. We know it targets certain parts of a rodent's brain, including those involved in sexual arousal. But how those puzzle pieces fit together is not immediately clear. What is clear is that this thing is a single cell. This has no nervous system. It has no consciousness. It doesn't even have a body. But it's manipulating a mammal? We are mammals. We are more intelligent than a mere rat, to be sure, but our brains have the same basic structure, the same types of cells, the same chemicals running through them, and the same parasites. Estimates vary a lot, but some figures suggest that one in three people around the world have Toxo in their brains. Now typically, this doesn't lead to any overt illness. The parasite holds up in a dormant state for a long period of time. But there's some evidence that those people who are carriers score slightly differently on personality questionnaires than other people, that they have a slightly higher risk of car accidents, and there's some evidence that people with schizophrenia are more likely to be infected. Now, I think this evidence is still inconclusive, and even among Toxo researchers, opinion is divided as to whether the parasite is truly influencing our behavior. But given the widespread nature of such manipulations, it would be completely implausible for humans to be the only species that weren't similarly affected.
Kako zajedavec svojega gostitelja tako nadzira? V bistvu ne vemo. Vemo, da Toxo izloča encim, ki tvori dopamin, snov, ki je povezana z nagrajevanjem in motivacijo. Vemo, da cilja določene dele glodavčevih možganov, v ključno s tistimi, ki so povezani s spolno vzburjenostjo. Toda, kako se ti koščki sestavljanke sestavijo, ni takoj jasno. Kar je jasno je, da je ta stvar ena sama celica. Nima živčnega sistema. Nima zavesti. Celo telesa nima. A manipulira s sesalcem? Mi smo sesalci. Seveda smo bolj inteligentni od navadne podgane, a naši možgani imajo enako osnovno strukturo, enake vrste celic, enake kemikalije, ki se pretakajo skozi njih, in enake zajedavce. Ocene se precej razlikujejo, a nekatere številke nakazujejo, da ima en od treh ljudi na svetu v svojih možganih Toxo. Običajno to ne vodi v nobeno očitno bolezen. Zajedavec zelo dolgo ostaja v mirujočem stanju. Vendar pa je nekaj dokazov, da ljudje, ki ga prenašajo, dosegajo nekoliko drugačne rezultate na vprašalnikih o osebnosti, kot ostali ljudje, da imajo nekoliko večje tveganje za avtomobilske nesreče, nekaj pa je tudi dokazov, da so ljudje s shizofrenijo bolj verjetno okuženi. Mislim, da ti dokazi še ne zadostujejo in celo med raziskovalci Toxo-ja so deljena mnenja, ali zajedavec resnično vpliva na naše obnašanje. Vendar glede na razširjenost narave takšnih manipulacij bi bilo precej neverjetno, da bi bili ljudje edina vrsta, na katero ne bi imele podobnega vpliva.
And I think that this capacity to constantly subvert our way of thinking about the world makes parasites amazing. They're constantly inviting us to look at the natural world sideways, and to ask if the behaviors we're seeing, whether they're simple and obvious or baffling and puzzling, are not the results of individuals acting through their own accord but because they are being bent to the control of something else. And while that idea may be disquieting, and while parasites' habits may be very grisly, I think that ability to surprise us makes them as wonderful and as charismatic as any panda or butterfly or dolphin.
In mislim, da je ta zmožnost, da nenehno spodkopavajo naš način razmišljanja o svetu, tista, ki dela zajedavce neverjetne. Nenehno nas vabijo, da naravni svet gledamo postrani, in se sprašujemo, ali obnašanja, ki jih vidimo, naj bodo enostavna in očitna, ali begajoča in zapletena, niso rezultat posameznikov, ki se ravnajo po lastni volji, ampak so upognjena zaradi nadzora nečesa drugega. In čeprav je ta ideja lahko zaskrbljujoča in čeprav so navade zajedavcev lahko zelo grozne, mislim, da jih sposobnost, da nas presenetijo, dela čudovite in karizmatične kot katerakoli panda ali metulj ali delfin.
At the end of "On the Origin of Species," Charles Darwin writes about the grandeur of life, and of endless forms most beautiful and most wonderful, and I like to think he could easily have been talking about a tapeworm that makes shrimp sociable or a wasp that takes cockroaches for walks.
Na koncu knjige "O izvoru vrst" Charles Darwin piše o veličastnosti življenja in o neskončnih oblikah najlepšega in najčudovitejšega in rad si mislim, da bi z lahkoto lahko govoril o trakulji, ki naredi rakca družabnega, ali o osi, ki pelje ščurke na sprehod.
But perhaps, that's just a parasite talking.
Morda pa to govori le zajedavec.
Thank you.
Hvala.
(Applause)
(aplavz)