In response to my post on the endorsements for The Tangled Bank: An Introduction to Evolution, a lot of commenters had questions and reactions. I’ve responded in the comment thread here.
With all the talk of price in the comments I was expecting it to be very high, but apx $70 Canadian seems quite reasonable to me. I’m so looking forward to it, especially after reading all the great endorsements. If I haven’t already bought it for myself by then, it’s going on my Christmas list. (Love the new cover design by the way!)
On the Origin of The Nervous System
Greg Miller (science 325 pg 24)
“Peering back through the ages for a glimpse of the first nervous systems is no easy trick. In the seventh essay in Science’s series in honor of the Year of Darwin, Greg Miller discusses some tantalizing clues that scientists have recently gained about the evolutionary origins of nervous systems. They’ve found that some of the key molecular building blocks of neurons predate even the first multicellular organisms. By looking down the tree of life, they are concluding that assembling these components into a cell a modern neuroscientist would recognize as a neuron probably happened very early in animal evolution, more than 600 million years ago. Most scientists agree that circuits of interconnected neurons probably arose soon thereafter, first as diffuse webs and later as a centralized brain and nerves. But the resolution on this picture is fuzzy. The order in which early branches split off the animal tree of life is controversial, and different arrangements imply different story lines for the origins and early evolution of nervous systems. Scientists also disagree on which animals were the first to have a centralized nervous system and how many times neurons and nervous systems evolved independently.”
“Sponges don’t have a nervous system, or even neurons, but they do have a surprising number of the building blocks that would be needed to put a nervous system together. This sentence comes from one of a series of essays about Charles Darwin, this essay reviewing what is known about the origin of nervous systems in higher animals. For darwinists, the picture is deeply puzzling. “…Some of the key molecular building blocks of neurons predate even the first multicellular organisms.”
“The genome of one studied species contains the genes for proteins typically found on the receiving side of a synapse. “Yet electron microscope studies have failed to find synapses in sponges.” The same genome also contains genes for some neurotransmitter receptors, which sponges appear to lack. “Thus, the function of these synaptic scaffolding proteins in a sponge is a mystery….But we see a consistent story emerging. Many different studies find that essential genes existed before the evolution on Earth of the features they encode. In cosmic ancestry this is the required order of events. Finding genes for neurons in primitive species that lack neurons is an especially telling example.” – Brig Klyce
I hope there is ample space devoted in your book on how important mass extinctions have been in reshaping the Earth’s biodiversity not once, but at least five or six (and up to as many as eight) times in the past 550 – plus million years. How are you treating the “Cambrian Explosion”, as a real event, or more likely, as a metaphorical description of the first common appearances of skeletonized metazoans (I believe Derek Briggs might say that it is a real event, but I remain skeptical, only because of the amount of time involved – tens of millions of years – before we see representatives of every major metazoan phyla present within the marine fossil record.).
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Carl Zimmer writes about science regularly for The New York Times and magazines such as DISCOVER, which also hosts his blog, The Loom. He is the author of 12 books, the most recent of which is Science Ink: Tattoos of the Science Obsessed.