Post with 1 note
Reconstruction of Kerygmachela kierkegaardi. a Dorsal reconstruction of the head region with the central nervous system (orange), anterior neural projection (yellow), and muscular pharynx (blue). b Artistic reconstruction of K. kierkegaardi. el eye lobe, mo mouth opening, nap anterior neural projection, nb branching of nerve, nc nerve cord, nfa frontal appendage nervous tract, npc protocerebrum, nop optic nerve, phr pharynx. Artwork by Rebecca Gelernter, nearbirdstudios.com (The picture and this text are copied from the paper linked below)
As more fossils are discovered preserving the fine structure of the central nervous systems (CNS) of early forms of life (and we are finding more of these now because we know what to look for), we are gaining more insight into the evolution of the brain, and understanding the evolution of the brain is a necessary prerequisite for understanding the evolution of mind and consciousness.
Some time ago in How early a mind? I discussed the incredibly detailed fossil of
Chengjiangocaris kunmingensis; now the well preserved remains of
Kerygmachela kierkegaardi
are offering further insights into CNS evolution. We might call these and similar fossils the
Lagerstätten of the mind.
The paper detailing this most recent discovery is, as of this writing, freely available (download it while it’s available): “Brain and eyes of Kerygmachela reveal protocerebral ancestry of the panarthropod head” by Tae-Yoon S. Park, Ji-Hoon Kihm, Jusun Woo, Changkun Park, Won Young Lee, M. Paul Smith, David A. T. Harper, Fletcher Young, Arne T. Nielsen and Jakob Vinther.
The report on the discovery in Science magazine –
This ancestor of today’s insects, spiders, and crustaceans had a simple brain, but complex eyes, by Elizabeth Pennisi – caught my attention. By “simple brain” it was meant that this ancestor to insects did not have the tripartite brain that contemporary insects have, with each part of the brain associated with one of the segments of the body. However, the idea of a simple brain and complex senses immediately suggested a counterfactual to me.
Suppose that some early animal developed the locus of its CNS not in an independent organ, but attached to or integral with its major sensory organ. This would result in a brain even more dominated by a particular sense than the way in which the human brain is dominated by sight and the canine brain is dominated by smell. Suppose that our brains grew from the back of our eyes, with the retina integrated directly into the brain (but probably wired up like in cephalopods instead of the awkward inside-out nerves of the mammalian eye), and that this came about as a result of the locus of a CNS developing at or on a complex sensory organ.
This isn’t how brains evolved on Earth, and, significantly, this is not only a counterfactual for us, but a counterfactual across terrestrial forms of life, as true of arthropods and cephalopods as of vertebrates – perhaps this indicates an evo-devo tendency in Earth life to evolve a separate brain. Although it didn’t happen here, it could happen elsewhere. Sensory organs are natural clusters of nerves, and it wouldn’t take much of an evolutionary nudge for these clusters of nerves to grow into a brain, especially in an early form of life in which there is relatively little differentiation of nervous tissues.
What might it be like for an animal to evolve with a “smart” sensory organ? What is the sensory signals from you other organs had to pass through another sensory organ on their way to being processed by the brain? How differently would such an animal perceive and conceive the world as compared to life on Earth?
Above is another Anomalocaris fossil, not associated with the paper discussed above and the new discoveries it details.