Recent Reading: An Immense World by Ed Yong

An Immense World is a great book about the sensory worlds of nonhuman animals.

This book was recommended to me by another panelist at the Philosophical SF workshop – the neurobiologist Ben Kinney,  unsurprisingly – and I’m so glad because it’s fascinating and just plain fun to read.

I hardly know what to say about it, except that the book is quite long and therefore the 10% sample is definitely extensive enough to show you whether you want to read the whole thing. I definitely did. I’m only about 20% of the way through, but I couldn’t wait to tell you about this book. Only then I couldn’t think how to describe it. So, fine, I’ll just provide a handful of paragraphs that particularly appealed to me. These are not in order from within the book, by the way. I started with a sentence that I especially liked and then took little fragments from here and there. Choosing which paragraphs to include here was … I started to say, not easy. But it would be more correct to say, practically random. This is just a delightful book!

So, here:

I am staring at a jumping spider, and even though its body is pointing away from me, it is staring back. Four pairs of eyes encircle its turret-like head, two pointing forward and two pointing sideways and backward. … Jumping spiders “are the only spiders that will turn and look at you routinely,” says Elizabeth Jakob, whose lab in Amherst, Massachusetts, I am currently visiting. … Humans are such a visual species that those of us with sight instinctively equate active eyes with an active intellect. In their flitting, darting movements, we see another curious mind investigating the world. In the case of jumping spiders, this is not unwarranted anthropomorphism. Despite their poppy-seed sized brains, they really are surprisingly smart. The Portia species are famed for planning out strategic routes when stalking prey or flexibly switching between sophisticated hunting tactics. …

This made me think of a praying mantis I encountered not that long ago. Talk about an arthropod that will turn and look at you! I love praying mantises.

But back to the jumping spider:

These [the pair of central eyes] point straight ahead and are the largest of the four pairs. They are also the sharpest. Despite being just a few millimeters long, they can see as clearly as the eyes of pigeons, elephants, or small dogs. … The central pair may be sharp and mobile, but their field of view is very narrow. If they were all the spider had, its vision would be like two flashlights sweeping around a dark room. The secondary eyes on either side of the central pair compensate for this shortcoming with a much broader field of view. Though they are themselves immobile, they are highly sensitive to motion. If a fly buzzes in front of the spider, the secondary eyes spot it and tell the central eyes where to look. And here’s the truly bizarre part: if the secondary eyes are covered, the spider cannot track moving objects. … [To us,] these tasks – sharp vision and motion detection – feel inseparable. And yet jumping spiders have separated them so thoroughly that they exist within different sets of eyes. The central ones recognize patterns and shapes and see in color. The secondary ones track movements and redirect attention.

This is remarkable to think about, but we didn’t start with sight. We started with smell and taste, and then got into vision with a description of the weird way that vision almost count as a chemical-based sense. This made me think of Project Hail Mary, by the way, and what animals would look like if sight had never evolved, and what that might really be like.

But this tidbit about taste also caught my eye:

The most extensive sense of taste in nature surely belongs to catfish. These fish are swimming tongues. They have taste buds spread all over their scale-free bodies, from the tips of their whisker-like barbels to their tails. There’s hardly a place you can touch a catfish without brushing thousands of taste buds. … in the mid-1990s, when Caprio tested the marine hardhead catfish, he was shocked to learn that almost half its taste buds react to D-amino acids. [The D forms of amino acids are incredibly rare.] … He eventually learned that several marine worms and clams can flip L-amino acids into their mirrored D opposites.

This book isn’t exactly about weird senses. It’s about the different sensory worlds nonhuman animals live in, and about the exercise of imagination it takes to try to put ourselves into those worlds. Here’s how the book actually starts:

Imagine an elephant in a room. … Now imagine a mouse has scurried in too. A robin hops alongside it. An owl perches on an overhead beam. A bat hangs upside down from the ceiling. A rattlesnake slithers along the floor. A spider has spun a web in a corner. A mosquito buzzes through the air. A bumblebee sits upon a potted sunflower. Finally … add a human. Let’s call her Rebecca. …

The elephant raises its trunk like a periscope, the rattlesnake flicks out its tongue, and the mosquito cuts through the air with its antennae. All are smelling the space around them, taking in the floating scents. The elephant sniffs nothing of note. The rattlesnake detects the trail of the mouse and coils in ambush. The mosquito smells the alluring carbon dioxide of Rebecca’s breath and the aroma of her skin. It lands on her arm, ready for a meal, but before it can bite, she swats it away – and her slap disturbs the mouse. It squeaks in alarm, at a pitch that is audible to the bat but too high for the elephant to hear. The elephant unleashes a deep, thunderous rumble too low-pitched for the mouse’s ears or the bat’s, but felt by the vibration-sensitive belly of the rattlesnake. Rebecca, who is oblivious to both the ultrasonic mouse squeaks and the infrasonic elephant rumbles, listens instead to the robin, which is singing at frequencies better suited to her ears. But her hearing is too slow to pick out all the complexities that the bird encodes within its tune.

The robin’s chest looks red to Rebecca, but not to the elephant, whose eyes are limited to shades of blue and yellow. The bumblebee can’t see red either, but it is sensitive to the ultraviolet hues that form a bullseye at the heart of the sunflower, which grabs the attention of both the bird and the bee. The bullseye is invisible to Rebecca, who thinks the flower is only yellow. … The seven creatures share the same physical space, but experience it in wildly and wondrously different ways. …

But when we get to sight, we get back to this stuff about ultraviolet and different color perceptions. You’ve probably all encountered this before, but Yong writes about this with more verve than your typical biology textbook:

If bees were scientists, they might marvel at the color we know as red, which they cannot see, and which they might call “ultrayellow.”

[A] bird’s color vision is a pyramid, with four corners representing each of its four cones. Our entire color space is just one face of that pyramid, whose spacious interior represents colors inaccessible to most of us. If our red and blue cones are stimulated together, we see purple – a color that doesn’t exist in the rainbow and that can’t be represented by a single wavelength of light. These kinds of cocktail colors are called non-spectral. Hummingbirds, with their four cones, can see a LOT more of them, including UV-red, UV-green, UV-yellow, and probably UV-purple (which is red + blue + UV). At my wife’s suggestion … I’m going to call these rurple, grurple, yurple, and ultrapurple. … These non-spectral colors and their various shades account for roughly a third of those found on plants and feathers. To a bird, meadows and forests pulse with grurples and yurples. … Many supposedly “white” bird feathers reflect UV and wouldn’t look white to birds.

Apparently it turns out that for most bird species where we think the males and females have the same plumage? They don’t. They look very different – if you include ultraviolet. Ditto for butterflies that mimic each other. To us, the mimics look the same. But they don’t look the same to each other.

I could go on forever, even from the 20% of the book I’ve read so far. This is just a wonderful book, and I want to go back and suggest panel topics based on this for WorldCon and Archon and so forth. Too late for that this year, but maybe next year! In the meantime, I’m considering how to turn this into an out-of-class project for my biology students, if I turn out to need that kind of project. The sample is so extensive that it should be easy to design some sort of project that can be done on the basis of the sample alone. And probably just about everyone has a phone capable of getting the Kindle app? We’ll, we’ll see.