Charles Darwin and the Theory of Natural Selection

Charles Darwin’s book, The Origin of the Species (1859), was “‘one long argument’ . . . for evolution and natural selection” (Brown, 2007, p. 68). Darwin had provided biology with its principal theoretical backbone, the evolution of organisms by means of natural selection. Of course, it took time before biologists and other scientists came to accept his conclusions. One reason for that lag was the state of biology before Darwin.


By the end of the 18th century, biologists struggled to interpret the new evidence accumulating yearly. Some argued that the close fit between organism and environment could only result from divine design. Others countered that organisms changed but did so in order to better match the requirements of their unique environments. Lamarck famously argued that species changed according to their own efforts during their lifetimes and then somehow passed those improvements onto their offspring. For example, he held that as ancestral giraffes stretched their necks more and more over many generations in order to eat higher and higher vegetation they somehow passed those successive neck stretchings from parent to offspring. Embryologists discovered the process of differentiation: early embryonic forms of many obviously divergent species closely resembled each other. But, as they developed, they diverged sharply from each other until they closely resembled their adult forms.
Darwin was well aware of the current state of knowledge about nature, physical and biological, before he ever set foot on the HMS Beagle. After he returned to England nearly five years later, he was still far from ready to set down any coherent thoughts about evolution. The idea for natural selection did not come to him until after he had read Thomas Malthus’s essay on how the external limiters (e.g., wars and famines) to unchecked human population growth. Darwin quickly realized that all animals and plants, too, were subject to similar limits. Competition, or what he termed natural selection, was the key to organismic evolution. How he gradually arrived at that conclusion is the next topic.

Biography: Darwin was born in Shrewsbury, England. His father was a physician. His grandfather, Erasmus Darwin, was an early naturalist whose work anticipated evolutionary theory. Charles Darwin showed little early promise as a scholar. He attended the University of Edinburgh hoping to study medicine only to leave after two terms. He could not stand to observe the grisly operations. Anesthesia was not yet part of medical practice, so patients screamed in pain during their surgeries. Darwin then went to Christ’s College, Cambridge, intending to become a minister. There, he was still not much of a student but developed a close relationship with a botanist, John Stevens Henslow. After Darwin graduated, Henslow helped arrange a place for him on the HMS Beagle, a small naval ship about to map the coastlines of South America and make soundings for depth charts. The Beagle’s captain, Robert FitzRoy, was looking for a gentleman to accompany him on the voyage to serve as a naturalist and companion. The previous captain had committed suicide on its last mission, apparently due to loneliness combined with the strain of command. The rules and regulations of the Royal Navy prohibited captains from engaging in any personal interactions with officers and crew. Because naval captains were the supreme authorities on their vessels, the British Admiralty believed that any personal relationships would undermine discipline. Darwin (or any other civilian) was exempt from that regulation. In fact, Darwin and FitzRoy were amiable dinner companions throughout the Beagle’s years at sea.


At first, Darwin’s father objected to the trip, believing that his son had already wasted enough of his life, but relented after Charles’s maternal grandfather, Josiah Wedgewood, recommended the trip. The Beagle left England in 1831 and did not return until 1836. During that time it sailed to South America, the Galapagos Islands, New Zealand, Australia, South Africa, and back to South America before setting for home (see Figure 8.1). Darwin collected thousands of specimens of animals and plants during the voyage and shipped them back to England whenever the Beagle made port. It is a myth, however, that Darwin came to some grand revelation about his theory of evolution during the trip, or that he realized the importance of his Galapagos Islands specimens at the time (Waller, 2002).


Contributions: Once back in England, Darwin struggled to make sense of his observations. He believed that species changed over time but could not come up with a mechanism that was neither God given (e.g., creationist) or directive (e.g., one that led inevitably toward humans as the pinnacle of evolution). After reading Malthus, however, the mechanism did come to him; he called it natural selection. Malthus had argued that human populations could grow much more quickly than could their food supply. Thus, people had to compete with each other in order to stay alive. Darwin applied the same logic to all creatures when he wrote, “This preservation, during the battle for life, of varieties which possess any advantage in structure, constitution, or instinct, I have called Natural Selection” (Darwin, 1868, p. 6). In a stroke, Darwin had discovered a mechanism for how species could change over time that did not depend on a creator. Furthermore, the method was random, not directed. Changes in animals and plants happened via some mechanism yet unknown to Darwin. But, if those changes turned out to confer an advantage to their possessor, no matter how slight, then it would outcompete others of the same species. After he had thought up natural selection, he saw that it explained much in biology. The only other thing natural selection required was time; at least 300 million years, Darwin estimated.

Darwin was in no great hurry to publish his theory. For one thing, he realized that its publication would cause much criticism. So, he anticipated many possible attacks against his ideas by conducting detailed research on barnacles, investigating how breeders altered the morphology and behavior of domestic pigeons, and reading extensively. He hoped eventually to publish a massive tome while answering all possible objections. Unfortunately for Darwin, the arrival of a letter written by a younger biologist, Alfred Russel Wallace, changed those plans. The letter asked Darwin to evaluate Wallace’s own independent ideas about organismic evolution. The letter shocked Darwin, for he immediately realized that he could lose scientific priority to Wallace. The ideas in the letter were nearly identical to his. He showed the letter to his scientist friends, Lyell and Hooker. Their solution was to invite Darwin and Wallace to present jointly summaries of their theories at a meeting of the Linnean Society in 1858. That way both would share priority. The meeting took place; others read the papers, neither Darwin nor Wallace attended the meeting (Boakes, 1984). Immediately afterward, little public notice ensued.


Over the course of the next few months, Darwin worked feverishly to put together a shorter version of the big book he had planned to write. That book, published in 1859, was The Origin of Species by Means of Natural Selection. It forever changed biology and, eventually, came to have a major impact on early psychology as well. The book was an instant success; the first printing of 1,250 copies sold out in one day. From that point on, Darwin’s life changed too. Many biologists and scientists quickly accepted his conclusions. However, many did not. One who did not was Lord Kelvin, the most prominent physicist of the time (for one thing, he had discovered the Second Law of Thermodynamics). Kelvin had calculated the age of the earth based on the assumption that it had cooled from molten rock to its present state. The age he calculated was far less than Darwin’s 300 million years. This was a serious problem for the successful operation of natural selection, and was only removed after the discovery of radioactivity in the late 19th century. Kelvin’s calculations had not taken into account the fact that radioactivity added heat to the earth. Another objection raised by many was the problem of complexity. How could an organ as complex as an eye have evolved from the minute changes Darwin had proposed? Darwin answered that question by pointing out there were many different kinds of light-gathering organs in the animal kingdom, ranging from simple to complex. Thus, he argued, the eyes of mammals were highly evolved and had originated from earlier and simpler precursors.
The issue of how the changes of natural selection were passed on from generation to generation was also incomplete. The emergence of genetics and its subsequent synthesis with evolutionary theory still lay in the future. Darwin himself waffled over Lamarck’s idea of acquired characteristics. By the last edition of his book he had reintroduced Lamarck’s idea as another possible evolutionary mechanism. Fortunately for Darwin, others, including Thomas Huxley (known as “Darwin’s Bulldog”) took up the fight to preserve, promote, and revise his theory.

After biology’s modern synthesis, the union of genetics and evolution, and after much research filling in gaps in data, evolution came to hold the central position in biology that it continues to occupy today. Evolution, however, was only one of the advances in biology important to the emergence of psychology. Also playing major roles were two other new biological areas of study: neuroanatomy, the study of the structure and organization of the brain and nervous system, and psychophysics, the study of the relationship between physical stimuli and their detection and interpretation by the conscious and unconscious mind.

DARWIN’S INFLUENCE ON BIOLOGY AND PSYCHOLOGY

creationism: the belief that God created all things in substantially the same form as they presently exist and that they did not evolve from distant ancestors.

natural selection: the competitive process by which organisms that are better adapted to survive the environmental conditions around them survive, and thus, reproduce more successfully leaving more offspring, and gradually altering the population characteristics of their own species.

ANIMAL INTELIGENCE AND COMPARATIVE PSYCHOLOGY


One of the main controversies inspired by the Darwin-Wallace theory of evolution was the issue of continuity. The theory of evolution made human beings just another species rather than the final, perfect product of Aristotle’s scale of nature. The adoption of continuity by scientists late in the 19th century opened up the door to the study of animal psychology. Darwin himself had pioneered that subfield following the publication of his 1872 book, The Expression of Emotions in Man and Animals. George Romanes, a younger follower of Darwin, popularized the idea of studying animal intelligence through his books on the subject. C. Lloyd Morgan, in turn, followed Romanes and revised much of his work through careful observation along with a much more thorough and skeptical approach to the field. Unlike Romanes, Morgan discounted nearly completely the anecdotal reports from untrained observers to which Romanes had become enamored of late in his life and career. Romanes, for example, had bought a monkey for his sister to raise. When the monkey learned how to unscrew a bolt, Romanes inferred that it had learned the mechanical principles behind threaded screws. Morgan, while not doubting that the animal could indeed screw and unscrew bolts, interpreted the monkey’s behavior more cautiously; it had learned that turning the bolt one way or another led to a predictable outcome. Morgan went on to suggest what he called his canon (Morgan, 1894, p. 53):


"In no case may we interpret an action as the outcome of the exercise of a higher psychical faculty, if it can be interpreted as the outcome of the exercise of one which stands lower in the psychological scale."

Morgan intended for his canon to put animal psychology on a par with human psychology by providing a rule for interpreting animal minds scientifically (Costall, 1993). Morgan did not wish to disallow comparison between human and animal intelligences. In fact, he believed that such comparisons were legitimate; they just had to be made carefully (Karin-D’Arcy, 2005). However, a completely different result ensued. The comparison of animal intelligence and human intelligence disappeared as a psychological topic until its revival late in the 20th century. Thus, comparative psychology was part of early psychology that grew out of its border with biology. Today, the situation is not much different for the subfield. While comparative psychology reappeared within psychology, it has gradually become a rarer course in the psychology curriculum.

Abramson (2018, p. 3) in an article supporting comparative psychology’s importance in the face of generalized neglect by the rest of psychology stated:
"In my view, there is no psychology as important as comparative psychology. The skills and perspective of a comparative psychologist would make them a highly valued member of any research team. Comparative psychology should be taught not only at the college level but in high school as well."

Remarkably modern psychology has all but ignored a pioneer in the study of animal cognition, Charles H. Turner. He was an African American psychologist who conducted experimental research in animal cognition on insects, birds, and reptiles. Despite publishing important research results including three articles in Science, only a handful of his contemporaries were aware of his contributions. Today, in his honor, the Animal Behavior Society gives an annual travel award to members of underrepresented groups (Dona & Chittka, 2020).

Continuity

Controversial idea a the time: all life forms are related in some way

In other words: Humans: just another species

Aristotle's scale of nature posited different categories:

God--Angels--Men--Women--Beasts

Continuity alllowed scientists to study animal psychology as well

Darwin's (1872) book was an early example:The Expression of Emotion in Man and Animals

Lorenz's later example of dog fear and aggression. Fear rises on Y axis and aggression rises on X axis

Look at the nine dogs. Which one is not afraid of you? Which one is most afraid of you?

George Romanes popularized the idea of studying animal intelligence

ANIMAL COGNITION
Bräuer et. al (2020) reviewed the field of animal cognition and concluded that in the past researchers had been too anthropomorphic and had neglected to take (p. 2) “ the biological context of behaviors” into account. They complained that all too often researchers assumed that one general and overall form of cognition was sufficient to explain all cases. While many researchers still consider humans as possessing the ultimate form of cognition, Bräuer et al. provide many counterexamples where animals outperform humans including the ability of many birds to classify objects and remember cached locations of food over long periods. They point to how researchers failed to use the proper sensory modality when testing for animal cognition. They cite the paucity of studies in dog behavior that assess that species’s (p. 12) “most relevant sense,” olfaction. Researchers, however, should take care to consider animal cognition in its own context to avoid anthropomorphic interpretations and be aware that they are not studying a general form cognition but rather are studying a wide variety of cognitions in a Darwinian sense. Bräuer et al. (p. 29) argued that considering each case by itself:

"allows us to reveal the evolutionary, developmental, and environmental conditions that foster the growth of certain unique abilities in the young of a species, or the convergence of skills shared among species."


Modern psychology animal cognition, too, is an active area of research and has re-emerged phoenix-like from Romanes’s overtly anthropomorphic origins and it near-banishment by classical Behaviorism.

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