Elsevier

Developmental Biology

Volume 475, July 2021, Pages 181-192
Developmental Biology

A developmental perspective on the evolution of the nervous system

https://doi.org/10.1016/j.ydbio.2019.10.003Get rights and content
Under an Elsevier user license
open archive

Highlights

  • New trees and improved taxon sampling reject traditional views of neural evolution.

  • It is uncertain whether a nervous system evolved once or twice in animals.

  • Xenacoelomorpha sister to Nephrozoa supports a nerve net ancestral to Bilateria.

  • Nervous system development became restricted to the ectoderm in Bilateria.

  • AP and DV molecular arrangements were secondarily coopted into neural patterning.

Abstract

The evolution of nervous systems in animals has always fascinated biologists, and thus multiple evolutionary scenarios have been proposed to explain the appearance of neurons and complex neuronal centers. However, the absence of a robust phylogenetic framework for animal interrelationships, the lack of a mechanistic understanding of development, and a recapitulative view of animal ontogeny have traditionally limited these scenarios. Only recently, the integration of advanced molecular and morphological studies in a broad range of animals has allowed to trace the evolution of developmental and neuronal characters on a better-resolved animal phylogeny. This has falsified most traditional scenarios for nervous system evolution, paving the way for the emergence of new testable hypotheses. Here we summarize recent progress in studies of nervous system development in major animal lineages and formulate some of the arising questions. In particular, we focus on how lineage analyses of nervous system development and a comparative study of the expression of neural-related genes has influenced our understanding of the evolution of an elaborated central nervous system in Bilateria. We argue that a phylogeny-guided study of neural development combining thorough descriptive and functional analyses is key to establish more robust scenarios for the origin and evolution of animal nervous systems.

Keywords

Nervous system
Evolution
Homology
Blastopore
Fate map
Gene expression

Cited by (0)