Thursday, February 20, 2020

A Taste for the Beautiful by Michael J. Ryan

Source of book: Borrowed from the library

In case it wasn’t obvious, I have been fascinated with science since I was a kid. This led to a lot of internal conflict between the militant Young Earth Creationism that was part of the Fundie homeschool culture I grew up in, and the obvious falsehoods that were necessary to believe for that viewpoint to work. My dad, at least, wasn’t committed to a young earth, so I felt that I had some freedom. As I got into my teens, I realized that I couldn’t believe in a timeline which didn’t match observed reality, and started a journey away from that. Eventually, in part because of my continued extensive reading on scientific topics, and in part because of my discovery of the rich tradition of non-literalist approaches to Genesis (dating back...before Christ, actually…), I came to peace with an acceptance of the truth of mainstream science. 

One of the fun things about accepting that there is overwhelming evidence in favor of evolution, even if we don’t have all the details (it’s amazing we have as much as we do, given the time scales), is being able to explore what we know and have learned even just in the last few decades about how life develops and changes. A great many things just make more sense that way, to be honest, including the wacky and often inefficient ways that traits work. 

A Taste for the Beautiful is about sexual beauty and attraction, and how it evolved in specific (and interesting) cases. The author is a researcher who has studied various animals - most pertinently, amphibians in Central America and their calls. (This forms a good bit of the book, which is a good thing.) 

The central idea of the book is that scientists often focus primarily on the males of the species they study, which means a focus on how the traits that attract females function and develop. In Ryan’s view, this misses a lot of the point, because beauty is in the eye of the beholder. Thus, it is more illuminating to examine why the beholder finds things beautiful - from there, it becomes somewhat more obvious how the “beautiful” trait evolved. 

Ryan takes a look at some basic ideas first. A central one to understanding life on Earth is that evolution and natural selection do not result in perfection. A trait need not be perfect to survive. It just has to be good enough. It is easy to see this in nature. Everything is a compromise. There is no such thing as a creature with endless endurance, high speed, and deadly reflexes. (If there was, it would likely devour everything else, then die of starvation…) Rather, you see creatures which have just enough fitness for their roles, enabling them to survive long enough to reproduce. 

I have heard this described elsewhere as the inherent “kludginess” of evolution. The human brain is a marvelous example of this. We actually do not have particularly “powerful” brains, if you think about it. A pocket sized calculator can do math far faster than we can, mechanical devices have better precision, and our memories...well, they are no great shakes. What human brains DO have, however, is a set of kludges - shortcuts - that enable us to think flexibly, think in analogies, and leverage our limited memory and processing speed in ways that solve the particular problems we encounter using what we have. It’s pretty impressive when you think about it. 

Everything in nature is like this, though. All vertebrates share a basic bone architecture, which is adapted for all kinds of locomotion, from swimming to flying to running to standing erect. If an engineer were to design a creature from the ground up, it is unlikely that it would look like anything currently in existence - let alone look strikingly similar despite widely different functions. 

When Ryan applied this basic idea to that of sexual beauty, he found that the eye (or nose or ear) of the beholder didn’t respond to sexual attraction in a sui generis way - it didn’t require unique traits used solely for sexual response. Rather, the pathways tended to be already used for something else - more basic stuff like finding food or avoiding being eaten. 

A great example of this is something most of us never think about: why do we universally, across cultures, as far back as history records, use the color red as a signal to stop, and green as a signal to go? (It’s crazy but true - this didn’t originate with the industrial revolution - it goes back to prehistoric times.) Ryan notes that most animals have vision that is either monochromatic, or a dichromatic version of color. (In that case, one could tell the difference between red and violet, but not see a significant difference between, say, green and yellow.) Humans, however, along with many of their primate relatives, have trichromate color - which allows a full rainbow experience. (At least in the visible color range - other animals vary in the wavelengths they see.) The ability to distinguish quickly and easily between green and red turns out to be hugely important to many primates. Why? Well, leaves are green...and fruit is red or yellow. Hey, that makes sense! We speed past the trees, but the fruit catches our eye. (Not in this book, but in other sources I have read, is the observation that animals that eat fruit in the New World and in Oceania don’t tend to have this, in large part because native fruits are more likely to be green, and thus the ability to see red isn’t as important.) 

From this ability to see color, humans found they were able to do other things. Humans (rather uniquely among animals), express emotion through blushing, to give one example. 

Color is just one, though. Ryan looks at pattern, which is pretty interesting. Cats are highly sensitive to patterns, particularly certain shapes and edges. This helps them avoid falling off things. But it also means that they have some...interesting reflexes. Hence the “cats and cucumbers” videos. I presume that oblong fruits remind cats of snakes, at least at first glance, and the reflex takes over before they think. For what it’s worth, our cat doesn’t care. But certain noises or motions can occasionally spook her - and she has a solid four foot vertical leap when startled. 
Starting from this framework, Ryan makes a case that the specifics of sexual beauty don’t come out of the blue, but utilize traits already present. The ear is already sensitive to a frequency that aids in hearing predators, so that frequency is used in frog calls. Patterns that already mean food or danger can be repurposed as attractiveness. 

This is kind of the central theme of the book, but it is far more detailed and varied than just that. Ryan spends a chapter each on sight, sound, and smell; and looks at the downsides of beauty - it can also attract predators, or make a creature less fit in some other way. It is, so to speak, a fight between reproduction and survival, with plenty of tradeoffs. Also quite fascinating was the chapter on how preferences can be fickle, and often change rapidly. 

Throughout, the book is well supported by research (much of which was done by the author), and avoids going beyond what can be seen from the results. Like all good science writers, Ryan is realistic about what we can and cannot know, and what we do and do not know. He doesn’t try to make a case he cannot adequately support by evidence. 

I think, however, that he does shed an interesting light on the evolutionary specifics of how traits develop. This book makes a good companion book to Sex on Six Legs, which more specifically looks at insects, but without the depth of information on the evolutionary details.   

A Taste for the Beautiful strikes a good balance between detail and readability, and is both fascinating and informative. Ryan clearly loves his topic, and makes it come alive.

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