National Academies Press: OpenBook

In the Light of Evolution: Volume VI: Brain and Behavior (2013)

Chapter: Part I: EVOLUTIONARY ORIGINS OF NEURONS AND NERVOUS SYSTEMS

« Previous: Front Matter
Suggested Citation:"Part I: EVOLUTIONARY ORIGINS OF NEURONS AND NERVOUS SYSTEMS." National Academy of Sciences. 2013. In the Light of Evolution: Volume VI: Brain and Behavior. Washington, DC: The National Academies Press. doi: 10.17226/13462.
×

Part I

cth

EVOLUTIONARY ORIGINS OF NEURONS AND NERVOUS SYSTEMS

The first three chapters address the ancient history of neuron-related molecules and centralized nervous systems. In Chapter 1, Cecilia Conaco and colleagues review earlier findings that many of the molecules found in neuronal synapses, especially within the postsynaptic density, predate the evolution of neurons. The authors then use an analysis of gene coexpression patterns to show that these protosynaptic genes in sponges, which lack proper neurons, form several modules of interacting genes. With the evolution of neurons, these small modules fused into a larger module with a novel function, namely to build synapses. Thus, the research has moved beyond the relatively simple task of homologizing individual genes and begun to trace the evolution of complex and changing gene networks. An interesting, if as yet barely explored, implication of the idea that gene networks can change function is that the homologous gene networks may function in the development or function of nonhomologous structures (Striedter, 1998). This possibility is rarely acknowledged (Tomer et al., 2010).

In Chapter 2, Harold Zakon reviews the evolution of voltage-gated sodium (Na-v) channels. These channels probably descended from voltage-gated calcium channels, which were probably derived from voltage-sensitive potassium channels. Why did Na-v channels become the major driving force behind neuronal action potentials? The answer is probably because Na was plentiful in the ocean, where neurons first evolved, and because Na influx tends not to interfere with intracellular calcium signaling. Once incorporated into neurons, Na-v channels

Suggested Citation:"Part I: EVOLUTIONARY ORIGINS OF NEURONS AND NERVOUS SYSTEMS." National Academy of Sciences. 2013. In the Light of Evolution: Volume VI: Brain and Behavior. Washington, DC: The National Academies Press. doi: 10.17226/13462.
×

were modified in diverse, interesting ways. For example, they evolved regulatory sequences that allowed them to be clustered at the axon initial segment and at Nodes of Ranvier in myelinated axons. Additional modifications evolved after the ancestral Na-v gene was duplicated, once near the origin of vertebrates and then again (repeatedly) in several vertebrate lineages. One of the most interesting Na-v modifications is the evolution of resistance to TTX, which typically blocks Na-v channels, in pufferfishes and other species that use TTX to ward off predators.

Glenn Northcutt analyzes, in Chapter 3, when and in which lineages complex brains evolved. Favoring a cladistic approach, Northcutt concludes that the last common ancestor of all bilaterian animals, living 600–700 Mya, probably had a diffusely organized nervous system. Cephalic neural ganglia apparently evolved soon thereafter and were retained in many lineages. Truly complex brains evolved even later and did so repeatedly, in mollusks, arthropods, and chordates (including vertebrates). This conclusion contrasts sharply with the conclusions of other researchers, who are struck by similarities in developmental gene expression patterns among vertebrate, insect, and annelid nervous systems. To them, these similarities must represent homologies. That is, they argue that similar gene expression patterns must have existed in the last common ancestor of fruit flies, vertebrates, and worms. Northcutt begs to differ, arguing that the expression of these genes in brains is caused by convergent evolution, perhaps by the co-option of gene networks that predate brains. This debate will require more data for a full resolution.

Suggested Citation:"Part I: EVOLUTIONARY ORIGINS OF NEURONS AND NERVOUS SYSTEMS." National Academy of Sciences. 2013. In the Light of Evolution: Volume VI: Brain and Behavior. Washington, DC: The National Academies Press. doi: 10.17226/13462.
×
Page 1
Suggested Citation:"Part I: EVOLUTIONARY ORIGINS OF NEURONS AND NERVOUS SYSTEMS." National Academy of Sciences. 2013. In the Light of Evolution: Volume VI: Brain and Behavior. Washington, DC: The National Academies Press. doi: 10.17226/13462.
×
Page 2
Next: 1 Functionalization of a Protosynaptic Gene Expression Network--Cecilia Conaco, Danielle S. Bassett, Hongjun Zhou, Mary Luz Arcila, Sandie M. Degnan, Bernard M. Degnan, and Kenneth S. Kosik »
In the Light of Evolution: Volume VI: Brain and Behavior Get This Book
×
Buy Hardback | $69.00 Buy Ebook | $54.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

The central goal of the In the Light of Evolution (ILE) series is to promote the evolutionary sciences through state-of-the-art colloquia--in the series of Arthur M. Sackler colloquia sponsored by the National Academy of Sciences--and their published proceedings. Each installment explores evolutionary perspectives on a particular biological topic that is scientifically intriguing but also has special relevance to contemporary societal issues or challenges.

This book is the outgrowth of the Arthur M. Sackler Colloquium "Brain and Behavior," which was sponsored by the National Academy of Sciences on January 20-21, 2012, at the Academy's Arnold and Mabel Beckman Center in Irvine, CA. It is the sixth in a series of Colloquia under the general title "In the Light of Evolution." Specifically, In Light of Evolution: Brain and Behavior focuses on the field of evolutionary neuroscience that now includes a vast array of different approaches, data types, and species.

This volume is also available for purchase with the In the Light of Evolution six-volume set.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!