An Immense World

By Ed Yong
Random House, June 2022

This book is about your point of view. Not your opinions or politics, but the way you view and perceive the world. It is also about the point of view of others: other species that have very different points of view from you and your fellow humans. This notion is called ‘umwelt’, a word of German origin that means ‘the world as perceived by a particular organism’^[1]. The human umwelt is rich and complex, but as the author points out, if we look at the range of umwelts of other species we find that our view of the world is quite limited: other species may perceive light and sounds in frequencies we can’t perceive or have senses we don’t possess. 

If we consider the vast range and configuration of senses possessed by all the different species on the planet, we find that the combined umwelts represent an immense world. As stated in the introduction, “…every animal can only tap into a small fraction of reality’s fullness. Each is enclosed within its own sensory bubble, perceiving but a tiny sliver of an immense world.”

The author explores this ‘immense world’ through the example of numerous animals focusing on various aspects of the senses. The scope of the book ranges over various senses: familiar ones such as smell, taste, sight and hearing; aspects of perceptions such as the sense of heat, the feeling of vibrations, the distinction of colors, the experience of pain and the awareness of the balance and position of the body (“proprioception”). Then there are the senses that are alien to humans: the awareness of the earth’s magnetic field (that birds use to guide migrations) and the detection of the electric fields of other animals (that sharks use to find fish lurking in the mud). Also, there are aspects of senses that are beyond human experience as when bats or dolphins transmit carefully sculpted sounds and use the echoes of these sounds to locate prey or to create a three-dimensional picture of the world when there is little or no light (“echolocation”).

The author gives us a guided tour of this immense world, emphasizing that human consciousness represents only a very small slice of a larger sensory world. Other creatures may have a much more acute version of a sense than we possess: elephants have 5 times the sensitivity of smell than humans and an eagle’s vision is several times more acute than that of humans. However, many species have poorer smell or sight than humans or lack a certain sense altogether (e.g. deep ocean fish living in total darkness are often blind). A creature’s sensory world is thus molded by evolution to closely fit what is required for survival. As a result, its umwelt (although very specific) is adequate and complete in its own right. There is no sense of one umwelt being superior to another one. Each is totally sufficient for the needs of a particular being. 

The various modes of experiencing the world are illustrated by touring a vast array of examples from our shared evolutionary history. This tour has many surprises. The octopus has taste and touch receptors on each of its 8 tentacles. These receptors lead each tentacle to respond to the world independently and without input from a central brain. This calls into the question the notions of awareness and individual identity. The brittle star is a starfish that has light receptors on each of its legs. This affords the creature the most elementary of visual acuity but enables it to scuttle away from light towards the safety of dark crevices. It accomplishes this with no brain, in effect functioning as an individual without a central nervous system. As with the octopus, this challenges common notions of agency and identity. In another profile we are introduced to Zipper, a Big Brown bat who is a research subject at Boise State College. In a completely dark room, high speed infrared cameras are employed to determine how bats use echolocation to catch prey. Zipper earns his name as the fastest and most accurate hunter among those being studied. 

The author employs many other examples to illustrate, in concrete detail, the different ways the world is perceived and experienced. These examples are entertaining and engaging.

A huge amount of detail is presented in this book, along with much scientific detail. But we are swept along by the intensity of the journey and the personal connection with many scientists and creatures. All of this makes it well worth the effort.

Frank Jenkins is a retired statistician. He is interested in climate change, ecology, weather, artificial intelligence and quantum computing.

^[1] Coined by zoologist von Uexkull in 1909, derived from the German word for ‘environment.’