In this artwork, how is the Wonder, rationality, and man of the Barnett’s philosophy elucidated?
Barnett’s first few pages of the first part expound his philosophy of natural history. It begins in the classical tradition with wonder (Part I, LIFE p 85), a conventional motivation known as early as the Academics.  The peripatetics of the next generation elucidate further that wonder is a perplexity  eliciting feelings of ignorance. Barnett’s next assertion departs somewhat from the classical tradition. He supposes that wonder is the specific difference between men and animals, which in evolution "caused him to leave behind the animal forbears from which he sprang." From it "the questioning spirit of man was born."
Tradition had gone in a different direction. Aristotle (and students), author of the earliest surviving work on logic, or reasoning, had defined reason, or rationality, as the ability to apply logic. Furthermore, he asserted, it is the one property that distinguishes man from the other animals. Centuries later, in a study of one of Aristotle’s works, Porphyry recapped the definition of man as a mortal, rational, sensible, animate substance, which survived as the main definition into modern times. Descartes simplified it to rational animal (only to then vainly reject its usage), while Linnaeus devised the Neo-Latin name of Homo sapiens, "man the wise."
“Rationality” and “Wonder” are not necessarily mutually contradictory if both are regarded as potencies, or the powers to produce human behavior; that is, all humans have the power to act rationally or experience wonder, but they may not necessarily actually do so. Pythagoras said (reportedly):"in life, some grow up with servile natures, greedy for fame and gain, but the philosopher seeks for truth."But in traditional philosophy; specifically, The Theory of Act and Potency, the perceptible form of rationality is an act, an "accomplished fact", as opposed to a mere potency, or "possibility" hidden within something else. Some acts, however, retain something of potency about them. These are called active potencies. Those who seek fame and gain in Pythagoras are no doubt rational, and do wonder, but they choose not to pursue philosophic investigation, which is as yet only a possibility within them. Since wonder and rationality are the same type of object and serve the same purpose of being the specific difference of man, one might suspect that they are to some degree the same thing. Philosophy  is a rational undertaking and wonder, the source of philosophy, must be under the same umbrella.Whether of rationality or of wonder, Barnett’s definitions offer a logical problem: man becomes different from the animals because of wonder, but wonder is the difference. Some animal therefore must have wondered. The problem, however, belongs to the concept of evolution, rather than to Barnett.  The record of the rocks presents a stepped sequence of species already complete, but the concept of evolution requires continuous change. The transitions between steps are missing.
Their existence was proved subsequently. After the chemical structure of genes and chromosomes was deciphered by Watson and Crick and was  published in 1953, the ability to reconstruct parts of the genome, or genetic map of a species, ensued. The resulting field of cladistics compares genetic sequences to produce more accurate phylogenetic trees than were possible with only comparative anatomy. Knowing the true lines of descent, the paleontologists have been able to identify many more transitional fossils. Man’s closest living relative is the chimpanzee. The last common ancestor is dated to 6 mya.Intermediate fossils by the hundreds lie scattered along the evolutionary path from then to now. There is a gradation, suggesting that rationality did develop gradually.  It was the anthropologists of the 20th century who began to propose that the specific difference of man is only one or some subdivisions of rationality and that the animals have a share in others. The main suggestions have been culture, tool-using, language, adaptability. Barnett indulges in this sort of speculation himself at the end of the part on mammals, anatomically selecting the human brain (Part VI, LIFE p 109):"a convoluted mass of soft tissue which enables him to perceive the world around him with unique acuity and respond to stimuli with a subtlety and self-consciousness that sets him apart from all other living things. It invests him, moreover, with a power which no other creature ever possessed – the power to modify the environment, to govern and alter the very course of evolution ...."
The passage expresses a studied optimism, but, in the middle of the 2oth century, there is a certain degree of prophetic hypocrisy about it:“Of the more than one million species of animals on earth  man is capable of killing all but a few without recourse to the weapons he ingeniously contrives for his own destruction.”
This expression of unease about the outcome of the wonder story long after Barnett’s death would become shrill cries of warning concerning the human impact on the environment. Amidst doubts about how successful  rationality is as a strategy over geologic time, the theorists were finding increasing difficulty in defining it and discovering when it began. Each subdivision of rationality developed its counterpart in animal behavior studies:  animal culture, tool use by animals, animal language, and so on.
When all is said and done about rationality, we are left with the problem of finding a complex that is minimally present in some form in animals but gradually grows more complex in humans until it accounts for their great success and power . Apparently, rationality would seem to be  a pre-condition for the development of rationality. The  paradox is nothing new to evolutionary problems. The answer is generally pre-adaptation,  the pre-empting of a feature that evolved for some other reason,  such as the use of feathers, which evolved for thermal insulation, for flying. Otherwise, the feathers would present a problem, as they could only evolve in animals that already fly. There is, however, no clear pre-adaptive function of rationality. The differences between human and animal rationality or irrationality  are still being experimentally defined, a topic not covered by Barnett. His sequel to the human story in ‘’The Epic of Man’’ concentrates on anatomical development. He presumes, following anthropological tradition, that the growing skills of man are linked to the increase in brain size (a presumption often questioned and still not proved). The documentation of these skills, rather than any theory of wonder or rationality, is his main concern in that series.
adaptability transitional fossil phylogenetic tree Aristotle Neo-Latin evolution animal culture Homo pre-adaptation comparative anatomy Intermediate fossils The Epic of Man The Theory of Act and Potency logic Academics genome mya peripatetics specific difference wonder Linnaeus human impact on the environment tool-using culture animal language language Descartes chimpanzee gene chromosome Watson and Crick Homo sapiens tool use by animals Pythagoras left cladistics Porphyry rational animal