var pgAd = ''; pgAd += "<"+"script src=\"https://www.googletagservices.com/tag/js/gpt.js\">googletag.pubads().definePassback(\"/149443272/254539272\", [300, 250]).setTargeting(\"pgpro\", \"12\").setTargeting(\"pgpid\", \"https%3A%2F%2Fwww.nature.com%2Farticles%2Fd41586-018-05857-9%C3%BE%C3%BEutm_source%7Cbreakingnews%C3%BEutm_medium%7Cemail%C3%BEutm_campaign%7Cnnp.\").setTargeting(\"pgiid\", \"157049821173491280755331169httpswwwnaturecomarticlesd41586018058579utmsourcebreakingnewsutmmediumema\").setTargeting(\"pgzid\", \"169\").setTargeting(\"pgpub\", \"14\").setTargeting(\"pgscrh\", 768).setTargeting(\"pgscrw\", 1024).setTargeting(\"pgtrgtype\", \"content\").setTargeting(\"pgtrgtime\", \"1570498211734\").setTargeting(\"pgjour\", \"Nature\").setTargeting(\"pgpubadunit\", \"/270604982/nature/nature/articles\").setTargeting(\"pgpubparam\", \"%7B%22articleid%22%3A%5B%22%2Farticles%2Fd41586-018-05857-9%22%5D%2C%22collectionid%22%3A%5B%22false%22%5D%2C%22logged%22%3A%5B%22n%22%5D%2C%22path%22%3A%5B%22%2Farticles%2Fd41586-018-05857-9%22%5D%2C%22pos%22%3A%5B%22MPU1%22%5D%2C%22tile%22%3A%5B%222%22%5D%2C%22type%22%3A%5B%22fronthalf%22%5D%7D\").display();<"+"/script>\n"; document.write(pgAd);