{"id":83792,"date":"2025-07-22T17:52:10","date_gmt":"2025-07-22T17:52:10","guid":{"rendered":"https:\/\/www.europesays.com\/us\/83792\/"},"modified":"2025-07-22T17:52:10","modified_gmt":"2025-07-22T17:52:10","slug":"we-might-have-been-wrong-about-where-spiders-came-from","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/us\/83792\/","title":{"rendered":"We Might Have Been Wrong About Where Spiders Came From"},"content":{"rendered":"<p>Technically speaking, every living thing on Earth can trace its origins to the sea. Some of these earliest creatures crawled onto land, evolving to become many different kinds of animals and insects\u2014including, scientists believed for a long time, spiders and their relatives.\u00a0<\/p>\n<p>A new study published today in <a href=\"https:\/\/dx.doi.org\/10.1016\/j.cub.2025.06.063\" target=\"_blank\" rel=\"noopener\">Current Biology<\/a> challenges the popular conception that spiders first emerged on land, instead suggesting that these arachnids and their relatives originated and evolved in the ocean. The team reached this conclusion by investigating the fossilized central nervous system of Mollisonia symmetrica, a long-extinct animal from the Cambrian era (between 540 and 485 million years ago), thought to be the ancestor of horseshoe crabs. Mollisonia\u2019s brain structure closely resembled that of modern spiders and their relatives, not their supposed crab descendants.\u00a0<\/p>\n<p> <img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2000632556\" src=\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/07\/mollisonia-graphic.jpeg\" alt=\"Attack Of The Arachnida! 7 5 25c\" width=\"700\" height=\"408\"  \/>Illustration of what the Mollisonia animal would have looked like at the time it lived, more than 500 million years ago. Credit: Nick Strausfeld <\/p>\n<p>\u201cThe discovery of an arachnid brain in such an ancient creature as Mollisonia suggests that the major groups of arthropods alive today were already established then,\u201d <a href=\"https:\/\/neurosci.arizona.edu\/person\/nicholas-strausfeld-phd\" target=\"_blank\" rel=\"noopener\">Nick Strausfeld<\/a>, study lead author and neuroscientist at the University of Arizona, told Gizmodo in an email. He added that this \u201ccasts a fresh view on the question: Where did arachnids first evolve?\u201d<\/p>\n<p>Until now, scientists had assumed\u2014based on the external features of arachnid-like fossils found in sedimentary rocks formed on land\u2014that modern spiders and their relatives evolved on land. For the study, however, Strausfeld and his colleagues looked inside a well-preserved fossil of Mollisonia, which they did using an optical microscope and other imaging techniques to investigate its cerebral arrangements in higher detail.\u00a0<\/p>\n<p> <img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2000632559\" src=\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/07\/mollisonia-brain.jpg\" alt=\"Mollisonia Brain\" width=\"850\" height=\"743\"  \/>Advanced imaging techniques allowed the research team to identify key anatomical features in the fossilized remains of the Mollisonia specimen. Credit: Nick Strausfeld <\/p>\n<p>The team uncovered several similarities between modern spiders and Mollisonia, but the most striking feature was that of the creatures\u2019 central nervous system. Unlike insects, arachnid brains have a strange backward structure, in which the \u201cforebrain lies on top of circuits that control the movement of the legs,\u201d Strausfeld explained. It\u2019s this that makes spiders and their relatives so \u201cincredibly versatile in their movements.\u201d As the new research shows, \u201cthe backward organization is enough of a \u2018tell\u2019 to demonstrate [that] Mollisonia\u2018s brain arrangement typifies those of living arachnids,\u201d he said.<\/p>\n<p>Other common features the team found included external resemblances, such as jointed limbs or pincer-like claws. They bolstered their hypotheses by running a statistical analysis comparing 115 anatomical traits across both living and extinct arthropods (which includes arachnids), which placed Mollisonia as a \u201csister\u201d to modern arachnids, the authors reported in the study.<\/p>\n<p> <img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2000632557\" src=\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/07\/comparison-mollisonia.png\" alt=\"Comparison Mollisonia\" width=\"1920\" height=\"1429\"  \/>A side-by-side comparison of the brains of a horseshoe crab (left), the Mollisonia fossil (center) and a modern spider (right) reveals the surprising findings of this study: The organization of Mollisonia\u2019s three brain regions (green, magenta, and blue) is inverted when compared to the horseshoe crab and instead resembles the arrangement found in modern spiders. Credit: Nick Strausfeld <\/p>\n<p>\u201cThis is very interesting, but we do not yet know how it relates to the vast array of arachnids other than spiders,\u201d said <a href=\"https:\/\/www.paulselden.net\/\" target=\"_blank\" rel=\"noopener\">Paul Selden<\/a>, a paleontologist and arachnologist at the University of Kansas who wasn\u2019t involved in the new work, in an email to Gizmodo. \u201cClearly, their conclusions on the phylogenetic [study of evolutionary history using visual cues] placement of Mollisonia are fascinating but merely mark the start of further investigation.\u201d<\/p>\n<p>It\u2019s probably premature to declare spiders as spawns of the sea, but the good news is that Strausfeld and his colleagues already seem to be on the case.\u00a0<\/p>\n<p>\u201cMost Cambrian fossils look very different from modern species, so it is really exciting when such outward appearances reveal something inside them\u2014a fossilized brain and nervous system\u2014that tells a different story,\u201d Strausfeld said. \u201cArachnids are a crucial feature of our biosphere, and we should pay attention to what they contribute to our well-being.\u201d\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"Technically speaking, every living thing on Earth can trace its origins to the sea. Some of these earliest&hellip;\n","protected":false},"author":3,"featured_media":83793,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[16278,45951,831,56883,25054,159,929,67,132,68],"class_list":{"0":"post-83792","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-evolution","9":"tag-fossils","10":"tag-neuroscience","11":"tag-paleobiology","12":"tag-paleontology","13":"tag-science","14":"tag-spiders","15":"tag-united-states","16":"tag-unitedstates","17":"tag-us"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@us\/114898163777049389","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/83792","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/comments?post=83792"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/83792\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media\/83793"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media?parent=83792"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/categories?post=83792"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/tags?post=83792"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}