mixed habitat & densely vegetated hiding places

"The majesty of nature," Ed Yong writes, "is not restricted to canyons and mountains. It can be found in the wilds of perception."

The truth of this statement is amply demonstrated on every page of An Immense World, as Yong takes us on a guided tour through Earth's perceptual diversity, examining the sensory abilities of spiders, dogs, ticks, elephants, octopuses, flies, birds, fish, whales, and many more creatures.

But Yong makes it clear up front that this isn't about childishly ranking which species have the "best" senses—each one, after all, has senses that are well-calibrated to what it needs to know to survive—but rather about challenging ourselves to imagine how others experience the world. From ultraviolet and infrared, to the Earth's magnetic field, to rippling wakes that seals can sense in the water long after the fish that left them has gone... there is so much that humans can never directly perceive, no more than a sighted person can see into the visual void behind their own head.

Yong is also quick to point out that humans don't all have the same sensory world, and he is wonderfully careful to be inclusive in how he writes and what he writes about. In his discussion of echolocation, he doesn't limit himself to bats and dolphins, but also explores how some blind people have taught themselves to echolocate, and can teach others—though, as one echolocator mentions, some blind children who attempt this are discouraged by adults who are concerned that the clicking noises they are making with their mouths or canes will make them seem "weird". Of course, sensory innovation has always been a part of human life, as we've used our technology to extend what we can perceive down to microscopic particles and out to the most distant stars.

The scientific process is centered throughout the book, explaining not only what we know, but also how we know it and what's still a mystery, as well as introducing us to many of the people doing this research. I noticed that a significant proportion of the scientists Yong quotes and interviews are not men (many are women and at least one is nonbinary), and I'm not sure how much of that is down to the demographics of this field and how much is the author making an effort to find diverse interviewees, but either way I appreciated it.

Yong is also sensitive to issues with animal experimentation, acknowledging both ethical concerns about the animals' welfare as well as the problem of getting skewed results from stressed-out test subjects. I am probably about as touchy about animal suffering as it is possible to be, and if I could get through this book okay, I'd think most anyone can.

The book wraps up with a discussion of sensory pollution in the environment, particularly in the form of light and noise. This is much more easily fixed than many other kinds of pollution, but first we have to know there's a problem and care enough to do something about it. Having nights dark enough to see the stars is good for the mental health of many humans, but for some animals that evolved in darkness and are blinded by human light sources, it's a matter of life and death. Yong also offers a new perspective on why biodiversity matters: once a species is lost, its unique perceptual world is also lost. (This reminded me of a similar point that's often made about endangered languages—each language represents a unique window on the world that can't be replaced once it's gone.)

Human are animals, and our sensory worlds are just as valuable and awe-inspiring as those of any other species. But what makes us truly special is not our senses, it's our ability to imagine what the world is like to someone other than ourselves. We can try to imagine what it is like to be a bat, but a bat (probably) can't try to imagine what it would be like to be a human. This is the ability we desperately need to make sure we are using, not only to understand our fellow animals and how to treat them, but also to empathize with our fellow humans.

This is an outstanding work of popular science, and it would be an amazing resource for anyone writing about aliens, mutants, or fantasy creatures and wanting to do something interesting with their sensory abilities. I highly recommend it.