Mankind is poised midway between the gods and the beasts. – Plotinus
Plotinus’ quote is symbolic of a fundamental biological principle illustrating that man is descended from some lowly organized form, and which serves as the backdrop to the discussions Carl Sagan (Figure 1) presents in The Dragons of Eden. In order to provide a description of nature, and human growth, Sagan begins by discussing this principle, one that distinctly identifies the field from other physical sciences, evolution by natural selection.
Let’s digest that last bit, piece by piece. The word evolution is commonly used to describe the gradual development of something, from a simple to a more complex form. In scientific terms, evolution is the change evidenced in hereditary characteristics that are carried over successive generations in biological populations. It is the fundamental process that has led to biodiversity within species, and individual organisms.
Natural selection was the brilliant discovery of Charles Darwin and Alfred Russell Wallace (Figures 2-3), detailed in the publication of their joint works in 1858. It is the theory that describes evolution, and is the preferential survival and reproduction of organisms that are by accident better adapted to the environment.
Natural selection is due to differences in the phenotypes of individual organisms. A phenotype is basically a composite description of an organism’s traits and characteristics including its physical and biochemical properties, as well as morphology, development, and behavior. An organism’s phenotype is a consequence of an organism’s genetic code, or genotype, along with environmental factors, and the collective influence and interaction of the two. It is important to differentiate natural selection from artificial selection, or selective breeding, where humans use animal and plant breeding to “select” for the development of particular characteristics by choosing which males and females of animal and plant species will sexually reproduce, and have offspring together.
In The Dragons of Eden, Sagan, much like Jacob Bronowski (Figure 4), best remembered as the presenter and writer of the 1973 BBC television documentary series, The Ascent of Man, wants to provide an account of how human beings and human brains “evolved” or grew up together. By understanding the evolution of human beings and human brains, Sagan intends to provide a platform from which he can speculate on the nature of human intelligence, its evolution, and its future.
For starters, he addresses the role of knowledge and learning in a species’ ability to survive, and adapt to its environment. In order for an organism to survive, it must have the basic ability to extract and manipulate information from the environment. Most organisms depend on their genetic information to survive, but in their lifetime, they can also collect extragenetic information. On the other hand, humans and mammals exclusively depend on extragenetic information.
Mammals are warm-blooded (maintaining a constant body temperature compared to the temperature of the environment), vertebrate (have a backbone or spinal column) animals distinguished from other animal classes by their possession of hair or fur, the birth of live young, and the secretion of milk by the females for the nourishment of the young.
While our genetic history does exert a significant influence in our behavior, our brains allow for us to interact at a higher level with what we learn from the environment. This has drastically enhanced the chances of survival of the human species. Human beings have also invented extrasomatic knowledge, or information that can be stored outside our bodies, writing being a notable example. As Sagan points out, our dependence on extragenetic, and extrasomatic information is crucial to the survival of our species. Since the timescales involving evolutionary or genetic change is far too long, we cannot depend on a process that may take place over hundred thousands to millions of years in order to keep up with the changes that we encounter in the world. In fact, we now live in a time where our world is changing at an unprecedented rate. To deal with an unknown and perilous future, Sagan insists it will be necessary for humans to actively consider the changes in our environment, and learn to adapt, control, and adjust our lifestyles accordingly. Our survival relies on the evolution, growth, and sensitivity of human intelligence, which has been a solution and a cause to the many problems and changes that afflict our species (Figure 5).
Sagan’s interests in addressing the evolution of human intelligence is also an extension of the work he accomplished at SETI (Search for Extraterrestrial Intelligence) as the insights we derive from an investigation of terrestrial intelligence will help in our search for extraterrestrial intelligence.
Both the existence of those other civilizations and the nature of the messages they may be sending depend on the universality of the process of evolution of intelligence that has occurred on Earth. – Carl Sagan, The Dragons of Eden
Ultimately, his treatment of the evolution of the brain will assume that its workings, or what can be called the mind, are a result of its physiology and anatomy. His primary goal in addressing the evolution of human intelligence is to dissect the various aspects of a subject that touches base with various other scientific fields. By understanding the evolution of human intelligence, he stresses the insight that can be gained from the interactions between brain physiology, anatomy, and human introspection.
With this approach, Sagan considers the “mind” to be the result of collective processes of the components of the brain, and chooses to not entertain the hypothesis of what is called the mind-body dualism (Figure 6). The mind-body problem deals with various arguments about how mental states, events, and processes can be related to physical states, and likewise, with the governing assumption that the human body is a physical entity, while the mind is non-physical. (The Stanford Enyclopedia of Philosophy is a wonderful primer’s read-through of this highly detailed topic.)
And that’s all there is to the introduction! While it may read as a book review, the introduction is a concise summary of what we will see later in the book. Now, to reiterate, Sagan’s work in The Dragons of Eden is presented against the backdrop of the theory of evolution. Since its induction in science, evolution has garnered its share of controversy, and disagreement. To all my readers, by reviewing this book, I am in no way forcing these views, and arguments on you. Science is not dogmatic, neither should it be in its endeavor to discover the nature of our world, and our place in it. It is an open stage, and thus, I leave it to you, my readers,to decide on the views you wish to accept, and decline in my review of the book.
- Sagan, Carl. The Dragons of Eden: Speculations On The Evolution of Human Intelligence. Ballantine Books, 1977.
- Wikipedia articles:
- Gould, Stephen Jay. “This View of Life: Darwin’s Untimely Burial.” Natural History, Vol. 85, pp. 24-30, October 1976.