Book Review
Title: The Zoologist’s Guide to the Galaxy: What Animals on Earth Reveal about Aliens – and Ourselves by Arik Kershenbaum
Genre: Non-Fiction, Science
Rating: 3.75 Stars
The introduction of The Zoologist’s Guide to the Galaxy introduces the idea that intelligent life on Earth can predict what life on other planets might look like and their behaviour. The first chapter looks at form vs function, nature and evolution of life on Earth are points we can track fairly accurately and has reached a point where we can generalise about life on other planets. In order to do this, we need to establish some speculative biological laws which is a challenge within itself but one point we can look at is the dolphin and the ichthyosaur. Both of these creatures have the same lifestyle or function and so have a similar form despite there being no genetic or evolutionary link between them. This seems to explain how complex life forms can share similarities without an evolutionary link. However, explaining complex life is a challenge, far harder than it might seem at first. We have to remember that complex life exists in the face of the laws of physics. When searching for a good explanation for this, it must be self-contained without appealing to any external undefined processes.
Natural selection seems to be an explanation, but scientists are at a loss when it comes to proposing alternatives that are realistic. While mathematic analyses can give us a strong indication that natural selection may be the only explanation for life in the universe, much of our understanding of natural selection as the mechanism by which life evolved is mathematical in nature. It can show mathematically that the rate of change of a specific trait over time in a given population. For example, the rate at which descendants of animals get longer teeth depends on the covariance between the trait and the advantages it provides. This can be applied to every exoplanet in the galaxy as evolution seems to work similarly in similar environments.
On the reverse side, bat wings and bird wings perform the same function but are strikingly different in their form. Despite this the fact that the flight of birds and bats evolved quite separately yet are put to similar uses again shows how evolution and natural selection explain complex life. This demonstrates that similar solutions have evolved separately in distantly related species which is part of a phenomenon called convergent evolution. Another example of this is the thylacine, which is now extinct, it bears a strong resemblance to canids but is more related to the kangaroo than dogs. However, we can see that evolution depends on disastrous events. These events cause a boom in evolution and can cause similar forms to appear. There seems to be no doubt that organisms on other planets experience natural selection in a broad sense, because there is no other mechanism we know of that can spontaneously produce and maintain complex life. There are supplemental mechanisms and two are concerning, sex and family.
Evolution based on mating shows that traits can evolve to improve the chances of mating even if they seem to be problematic in terms of survival, which seems counterproductive. Natural selection is still occurring, but the emphasis is on competing for offspring rather than survival, this is called sexual selection. The other mechanism is kin selection, this is as simple as parents providing care for their offspring and this is important as it explains the evolution of social behaviour in general. Sexually reproducing animals are more diverse in both form and function than asexual reproducers like bacteria. While we can’t say for certain where those on alien planets will reproduce sexually or not, we can say that if they have complex life, it likely arose through some accelerated natural selection or similar process. This is also shown in the fact that bacteria have little in the way of interesting or social behaviour. It is exactly this complex network of conflicts of interest that generates the emergence of what we call sociality.
In order to look deeper into this we first need to define what is an animal and what is an alien which is more complicated answer than you might assume, and this is the focus of chapter 3. Humans seems to have an instinctive understanding that we share something in common with all animals and this bond of identity affects our attitudes towards them, both ethically and socially. Defining what is and isn’t an animal is an ancient problem and this is where we get the system of assigning hierarchical groupings to all life based on the similarities of their form and this basis structure remains in place to this day. The appeal of the structural/functional classification is strong but precise boundaries can muddy the relative importance of small differences. This all depends on what feature you consider more important, physiology vs behaviour.
For example, what makes mammals ‘mammals’ is their evolutionary heritage as they descended from mammal ancestors. This taxonomy develops a new emphasis on heritage not appearance. The technical question of should we classify aliens as animals is nothing compared to the ethical and emotional question of should we treat aliens as animals. The classification of life is never going to be simple since life is infinitely gradated and binary distinction are the exceptions rather than the rule. We have to remember that until the 1950s, it was generally thought that complex life began around 540 million years ago in what was called the Cambrian explosion. This tale of life is in some ways very specific to our own planet but in some ways, it is also very general. The problems facing animals on Earth are universal problems. It is also possibly that the range of evolutionary solutions we see on our planet is closer than we think to the range of solutions across the universe.
Chapter 4 is looking at movement and while on the face of it, understanding how aliens might move is a relatively simple question since movement is essentially a problem of physics and the laws of physics are universal. Forces like torque, friction and acceleration are the reality on every planet in every solar system. In total, there are three universally limited drivers of movement, and these are energy, space and time. While other planets might possess sources of energy unfamiliar to us, there is energy aplenty. We also know that once something starts consuming a stationary resource, it must learn to move in search of food or die. This is the simplest law of evolution, limited energy drives organisms to evolve in order to find new energy. We must also remember that the fundamental rule of natural selection is that there is always a cost-benefit trade off. Improving your abilities in one field must reduce your capabilities in another. On Earth, we can see numerous ways that animals are systematic and have some unique adaptations which they have evolved to overcome specific challenges. These examples give us an indication of what is possible on other planets and what conditions would be needed to make one type of motion more advantageous over another.
We know if you live surrounded by a single fluid, e.g. water or air, you need to exert a force against something that is not solid in order to achieve movement. This is also seen in animal flight and swimming techniques, as they alter the configuration of the force generating machine so that the forces don’t cancel each other out. While we can’t totally rule out the possibility of novel motion techniques on other planets, we can be confident that at least some of the techniques seen on Earth will occur on other planets as well. For example, legs are adapted for life at the interface between a solid and a fluid, and these became the most prominent in the arthropod species. However, human legs are built completely differently from spider or crab legs. These two evolutionary pathways came up with a similar solution to the problems of moving on a surface, using completely different mechanisms. Legs are essential in any surface ecosystem as they reduce friction and increase the speed of an animals and speed is essential when evading predators or catching prey. The form the legs will take depends on both the properties of the solid surface and of the fluid above which is why there is so much variation even just on Earth. In addition to their unique adaptations, most animals also use bilateral symmetry. There are some many advantages to bilateral symmetry that almost every animal known to us uses it, one example of a species that doesn’t is jellyfish. Due to this we can be confident that alien animals will be bilaterally symmetrical and that those living between a solid and a fluid will have legs that will most likely look familiar to us.
Jumping forward in the book I want to focus on specific chapters where the author discusses particularly important topics, starting with chapter 6 which looks at intelligence. The subject of animal intelligence has been highly fascinating especially in how it differs from human intelligence. However, finding an acceptable definition of intelligence has been difficult with some methods to measure intelligence being suspect. The study of animal behaviour of the past half century has given us some vital clues to understanding the commonality between our intelligences and possibly that of other creatures unknown to us. The argument that there is a single intelligence type that varies between species in degree rather than in type, comes from observation largely in human psychology. This testing has been used naively as we know that intelligent behaviour depends on some core abilities like learning, memory and decision making. Despite this, we do know that the ability to learn is widespread across animal species on Earth and that associative learning must be universal.
At its core intelligence evolves over time to fit specific needs and is not an inherited trait from the dawn of time, intelligence rose in response to learning. This convergent evolution of intelligence creates the possibility that different mechanisms may be operating in different species. However, it must be noted that general intelligence is more difficult to explain evolutionarily than specific abilities. Another issue regarding intelligence is that many of the behaviours we see as intelligent are based on separate and specific brain mechanisms, for example, birds are capable of learning at least two different types of skills which require different kinds of intelligence. In recent years, we have come to understand that the type of intelligence a species has comes from the route evolution took with that specific species. It is not unreasonable to think that animals on other planets will not evolve mathematical intelligence like us until they are faced with the need to do so. Through observation of animals with a spectrum of intelligent behaviours we can spot features of human behaviour that are not directly linked to problem-solving intelligence. For example, poetry and dance are just useful adaptive behaviours that have been co-opted for social purposes.
This leads into the second most important chapter I wanted to discuss which is focused on sociality. The notion of whether an alien species will be social or not will depend entirely on if they have advanced technology and this prediction was created by looking at sociality through an evolutionary perspective. In nature predation is universal because no ecosystem can exist for long without someone trying to eat someone else. This makes predation one of the most powerful drivers of adaptation. Likewise, the principle of herd dilution can be enough for animals to begin to form social groups. Predation can cause animals to aggregate, and these adaptations require cooperation on the animal’s part. In prey animals, these behaviours can be seen widely as sentinel behaviour and alarm calling. The key insight is these animals often live together in group that are related to each other bringing us back to the matter of kin selection. Alien species where relatedness is, for whatever reason, extremely high would almost inevitably be extremely social. However, we also see reciprocity in animal groups where relatedness is low, and these complex interactions show how powerful cooperation can be and is therefore likely to exist on other planets.
As the book draws to a close, we take a look at what it means to be human and legal personhood which are matters that would have to be considered if an intelligent, alien species was to come to Earth or be found on another planet. Legal personhood is not a universal property. It depends on culture and history and moral norms, and alien lawyers on other planets will have their own opinions on whether or not humans will be considered ‘people’. Personhood is not universal, because it is so closely tied up with cultural norms – to whom we give respect and rights, and from whom we withhold them. But humanity seems to be a more general concept, perhaps more clearly definable than personhood. For countless millennia we have assumed that humans are one species, distinct from all other life on Earth. Now some sophisticated DNA analysis on a tiny bit of fossil bone shows that we are not a monolithic species at all. With all the evidence that has been presented throughout the book we get a good sense of what an alien species might look like in comparison to our own. However, many ethical and legal issues arise from this possibility and these are questions we should be focusing on more than the search for intelligent life on other planets, as without good, solid answers to these questions we can predict our own actions as a species for if another intelligent species is found on another planet.
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