Seldom Bucket
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When the first sponge genomes were sequenced in the early 2000s, researchers were surprised to find that sponges not only have roughly as many genes as humans and other complex creatures but also have many of the same genes. Sponges are among the earliest branching lineages on the evolutionary tree of animal life; their simple bodies don’t even have a pattern of symmetry or a set number of parts. The presence of those genes implied that the genetic information for functions like muscle contraction and the differentiation of neurons was much more ancient than muscles or nervous systems themselves.
But what were those genes doing in an animal without neurons or muscles? Researchers could only make educated guesses and investigate expression patterns on a painstaking gene-by-gene basis.
Sponge Genes Hint at the Origins of Neurons and Other Cells | Quanta Magazine
A new study of gene expression in sponges reveals the complex diversity of their cells as well as some possibly ancient connections between the nervous, immune and digestive systems.
www.quantamagazine.org