Spider Silk

So, hi, if you happen to be my mom, you might want to stop reading now. As the title indicates, this is a review of a book that is all about spiders. SPIDERS!!!

My mother does not like spiders. She really, really does not like spiders.

But I do[1].

I approached Leslie Brunetta and Catherine L. Craig’s Spider Silk with hope and dread. Hope that I might learn a lot more about spiders. Dread that the authors would mangle evolutionary theory with over-simplification while trying to use spider silk to teach the general public about natural selection.

One of these emotions was unnecessary and wrong.

First the hope. Spider Silk is not just a compilation of all the cool trivia the authors could dig up about spiders. They present a metric ton of information at all levels of detail, from molecular and genetic to ecological and systematic, in the framework of a coherent narrative. There are a lot of facts, but none of them are superfluous.

As a biologist, I appreciated that the authors were willing to get into the molecular details of spider silk and how those details contribute to the properties of this fascinating material.

Throughout, Brunetta and Craig build your interest, encourage you to think, and then reward your curiosity. Numerous times I found myself thinking “What about this?” or “What if that?”. Invariably, the answer or a discussion on that topic would appear a chapter or two down the road.

For example, halfway through Spider Silk I found myself wondering what kind of spider silk (yes, individual spiders produce multiple types) Charlotte would have used to write “Some Pig” in EB White‘s Charlotte’s Web. In the second to last chapter, the authors not only told me which type EB White had Charlotte using[2], but also which type a real spider would probably use.

Now the dread. When popular science writers set out to educate the general public about evolution through an exciting example like spider silk, many things can go wrong. They can completely conflate the entirety of evolutionary theory with natural selection. They can get the details of natural selection wrong. They could present examples that are not actually good examples of natural selection, or just resort to just-so stories.

Spider Silk had its weaknesses for me; but it was not written for professional biologists with a deep understanding of evolutionary theory. They succeed on several fronts.

First and foremost, Spider Silk may contain the best and most complete explanation of natural selection I have seen written for a general audience. It is clear. It is concise. It describes how directional action emerges from random events. You can hear Leslie Brunetta give this explanation in her own voice during her Skeptically Speaking interview.

The example they use to illustrate natural selection, spider silk, is a phenomenal example of natural selection. Natural selection is undoubtedly the primary evolutionary force that has driven the evolution of spider silk. Not only is this true, but the authors do not hesitate to give the reader the details. Their efforts to explain the different mutational processes and how they contributed to the evolution of spider silk stood out to me.

And historically, they actually give Alfred Russell Wallace his due in his contributions to natural selection, rather than reducing his influence to a letter that got Darwin off his gentleman scientist hindparts for narrative simplicity. They also point out how wrong, and inconsistent, Darwin was about the mechanisms of inheritance and mutation. The geneticist in me always enjoys taking a little bit of the stuffing out of the great man himself, especially in the service of emphasizing the importance of Gregor Mendel‘s work.

Finally, Brunetta and Craig do an excellent job of continually pointing out that both the environmental context of adaptation and the history of adaptation are critical to what can happen in the evolutionary future.

I am, however, a professional biologists with a deep understanding of evolutionary theory and a tedious pedant. So, I am going to take this opportunity to discuss what I felt were the book’s two biggest weaknesses.

WARNING: What follows is tedious biological pedantry –

Their approach is to explain natural selection and then illustrate the technical explanation through the evolution of spiders and their silk. As a biologist, I would have preferred a description of the evolution of spiders and their silk followed by a discussion of why we think natural selection drove these processes.

This “weakness” is entirely based on this reader not actual being a member of the authors’ target audience. They are trying to educate. I am wanting to ask if can you present convincing evidence that a result of evolution was primarily driven by natural selection, rather than one of the other evolutionary force. General public. Biologist. You need to pick and know your audience. In my opinion, they chose wisely on the first, and I think they did well on the second.

Which brings us to the second weakness. Natural selection is not the only force that can drive evolution. Because Spider Silk is so focused on teaching its readers about natural selection, almost everything within the book is discussed within that paradigm. I would have preferred to see greater mention of the forces of drift and migration mentioned more prominently as alternatives to natural selection or possible explanations for phenomena that are not readily explainable by natural selection. Again, to be fair, these processes are mentioned in passing, but I would prefer to see them more prominent to help the general public build a more complete understanding of evolutionary theory.

Of course, a book about spider silk, which is, without doubt, primarily a product of natural selection, is probably a poor place for that particular crusade.

– end pedantry

I admire the clever choice to put spinnerets on the cover instead of a spider, which makes the book much more visually approachable to the casual arachnophobe. Still, I don’t think I’ll recommend it to my mother.

I can guarantee, come the spring, I’ll be testing out my new spider knowledge in the back garden with The Frogger and The Bell.

NOTES

1. Spider-Man was my favorite super-hero when I was a wee one.
2. Apparently, EB White consulted actual arachnologists before writing the book.