Chapter VIII - Instinct
Darwin noted that many instincts are so wonderful and their origins so mysterious that a discussion of them would appear to "overthrow my whole theory" (Page 233). Notwithstanding the obvious difficulty of explaining the origin of behaviors of animals, Darwin made the effort. He started out by not defining the subject: "I will not attempt any definition of instinct" (Page 233). He then proceeded in his usual rambling manner to discuss what he refused to define and to compare it with "habit". "Habit" was considered a behavior that an organism acquired by changing its behavior in response to changes in its environment or changes in its body or perhaps by some chance event, or because the organism itself exercised personal judgment. Once repeated and acquired/fixed, the physiological changes produced by changes in "habit" could pass to the parent organism's offspring in some mysterious fashion, but always by some "law" of nature.
Animals, even primitive ones, illustrate some judgment and make decisions though they often behave to their benefit without knowing the purpose of their actions. When an organism behaves in a certain way without knowing why it does so, that organism acts by instinct.
Habit and instinct are related. Humans, for example, may memorize a song and sing that song. If interrupted in the middle of the song, the person often has to go back to the beginning of the music piece to recall all the words and finish the song. In a comparative way, a caterpillar that is in the process of making a "hammock" is taken out of the "hammock" and placed into another one at a different stage of completion, forgets where it is in construction and starts from the beginning. Darwin reported from his "experiment," that the caterpillar "was much embarrassed" (Page 234) in its confusion.
Instincts are acquired by the offspring through the changing of habits of the parents. Habits are heritable; however:
It can be clearly shown that the most wonderful instincts with which we are acquainted, namely, those of the hive-bee and of many ants, could not possibly have been acquired by habit (Page 234).
Complicated behaviors vis-à-vis instinct develop piece-meal over long periods of time:
No complex instinct can possibly be produced through natural selection, except by the slow and gradual accumulation of numerous slight, yet profitable, variations (Page 235).
Because instinctual behaviors are important to the individual's survival, natural selection works on instincts and eliminates those that are not beneficial and assures the continued development of beneficial instincts. Thus, natural selection produces complex instincts but the organism can develop habit through individual changes in behavior; sometimes through willful changes. But no organism develops instincts nor habits except for self-benefit:
Again, as in the use of corporeal structure, and conformably to my theory, the instinct of each species is good for itself, but has never, as far as we can judge, been produced for the exclusive good of others (Page 235).
To illustrate the latter point, Darwin preformed an experiment with ants and aphids. He observed the ants stroke the aphids with their antennae in order to stimulate the release by the aphids of "sweet excretion" devoured by the ants. Subsequently, Darwin removed the ants and similarly stoked the aphids with a hair. The aphids did not, however, release the excretion eaten by ants. Next, he replaced an ant among the aphids and the aphids began to release the viscous excretion for the ant to eat. Darwin concluded from his experiment that the release of the "sweet excretion" by the aphids "was instinctive, and not the result of experience" (Page 236). He further concluded that the ants benefit from the food source provided by the aphids and that the aphids benefit from ridding themselves of the viscous excretion. Summarized:
Although there is no evidence that any animal performs an action for the exclusive good of another species, yet each tries to take advantage of the instincts of others, as each takes advantage of the weaker bodily structure of other species (Page 236).
Natural selection has numerous variations of instincts to act upon, even within the same species. For example, some birds of the same species build different kinds of nests in the northern and southern parts of their range. And, animals of the same species differ in how much they fear man. Those individuals with little or no exposure to man show little fear for man and those persecuted by man are more fearful. Such observations illustrated variations within species upon which natural selection acts to improve the survivability of instincts within species. Darwin ended this chapter with:
But I am well aware that these general statements, without the facts in detail, will produce but feeble effect on the reader's mind. I can only repeat my assurance, that I do not speak without good evidence (Page 237).
Critique
A lot of animal behaviors appear to be genetic/automatic. Most animals also appear to have abilities to learn, and thereby alter their behaviors. The origin of the tremendous amounts of chemically coded information required for an organism to function at the molecular and cellular level remains unknown. Certainly, in his time, Darwin's attempts to explain such phenomena as animal behavior and thought processes in materialist terms lacked merit.
On Page 234, Darwin said that a caterpillar, disoriented when taken from its partially completed "hammock" and placed into one built to a more advantaged stage, "was much embarrassed". He failed to explain how he determined the emotional state of this larva.
Darwin said that the instinct of no species exclusively benefit's the survival of another species. Perhaps, in Darwin's day there were no governmental laws aimed at the protection of rare and endangered species? Possibly, people in Darwin's day did not hang bird houses and bird feeders in their back yard?
Darwin observed ants caress aphids' abdomens with their antennae. In each case, the aphid raised its abdomen and excreted a "sweet juice," which the ant consumed. Next, Darwin removed the ants and caressed the aphids with a hair to see if the aphids would similarly excrete. They did not and Darwin concluded that the positive response of the aphids to the ants showed that the interaction was "instinctive and not the result of experience". I suppose that what Darwin meant by "experience" was that the ants and aphids did not develop the apparently mutualistic interaction by a process of learning?
My question is: what kind of evidence on the origin of aphid-ant interactions could Darwin possibly derive from his caressing aphids with a hair, whether the aphids responded positively or negatively to his experiment? Perhaps his earlier decision to not define the subject (instinct) of his discussion added to the confusion? His conclusions from such observations and rationale appear to me to lack merit in spite of his assurances that "I do not speak without good evidence" (Page 237).
Inherited Changes of Habit or Instinct in Domesticated Animals
Under this general topic, Darwin discussed the behaviors of domestic animals, including dogs and cats. He cited the various behaviors of bird dogs, retrievers, and herding dogs. He believed that these different breeds of dogs developed because man selectively bred dogs for specific, different behaviors. He also stated that man caused changes in the behaviors of dogs by rewarding desired behaviors and punishing undesired behaviors. Additionally, the environments of domestic animals removed them from exposure to dangers in the wild and the domestic animals lost their natural fear of predators. Changes in the habits of domestic animals, whether environmental or man-induced, were inherited by the offspring of those domestic animals. Thus, domestic animals developed because of man's selection among "spontaneous variations" (Page 237) and because the offspring of domestic animals inherit habitual behaviors learned by their parents:
Hence, we may conclude, that under domestication instincts have been acquired, and natural instincts have been lost, partly by habit, and partly by man selecting and accumulating, during successive generations, peculiar mental habits and actions... (Page 239).
Critique
To say that man's selective breeding of animals explained the origin of behaviors in domestic species is incorrect. Selective breeding, a microevolution
ary process, to produce breeds of dogs from a parent stock provided no information on the origin of behaviors and thought processes in the wolf nor ultimately in the various breeds of dogs.
Darwin's idea that the offspring inherit, through some Lamarckian evolutionary process, new behaviors initiated by their parents fell under his category of the "law of habit". He believed that "habit" could produce or diminish natural instincts. His views on the subject of instinct, which he refused to define, were speculative.
Special Instincts
Under this topic, Darwin discussed the gradual development of instincts in the cuckoo, the "slave-making instinct of certain ants," and the "cell-making power of the hive bee" (Page 240).
Instincts of the Cuckoo
It is supposed by some naturalists that the more immediate cause of the instinct of the cuckoo is, that she lays her eggs, not daily, but at intervals of two or three days... (Page 240).
Darwin took this anecdotal information and further speculated about the disadvantages associated with the rather random laying behavior of the European cuckoo. If the female bird incubated the eggs as they were laid, the young would hatch at different intervals and some would mature before the others and the female would leave with the more mature young and the male bird would be left to tend and feed those remaining by himself. To avoid this circumstance, the female hit upon the habit of laying one egg at a time in the nests of other species of birds.
The European cuckoo lays only one egg per parasitized nest, lays relatively small eggs, and the newly hatched cuckoo has the practice of pushing its foster siblings out the nest so it is the only baby bird left to be tended by its foster parents. One Australian species of cuckoo illustrates evolving steps toward the laying of one egg in the host nest because it on occasion lays more than one egg per nest. In the case of egg size, "In the Bronze cuckoo the eggs vary greatly in size, from eight to ten times in length" (Page 241). In addition, a "Mr. Ramsay" stated that two of the Australian cuckoos select to lay their eggs in the nests of other bird species with eggs of similar color. "Mr. Ramsay" also noted that the Australian bronze cuckoo produced eggs of various colors to accommodate this egg-placement behavior. Thus, Darwin said of these observations: "natural selection might have secured and fixed any advantageous variation" (Page 242).
Insofar as the instinct of the baby European cuckoo to expel its foster siblings to their deaths from the nest, Darwin observed:
I can see no special difficulty in its having gradually acquired, during successive generations, the blind desire, the strength, and structure necessary for the work of ejection; for those young cuckoos which had such habits and structures best developed would be the most securely reared (Page 242).
Darwin argued that early on, a young bird developed an "unintentional restlessness" (Page 242) and this habit was passed on to its offspring who acquired the instinct at a younger age.
Darwin then proceeded to compare parasitic egg-laying behaviors in the genus Molothrus (cowbirds). Three species of cowbirds vary in the degree they successfully parasitize the nests of other species. Darwin believed the varying degrees of nest parasitism among species of the same genus showed gradations in evolutionary development, with one species being superior to the others.
Critique
"It is supposed by some naturalists..." (Page 240). To support a theory with suppositions and found discussion on anecdotal information is beyond or beneath the realm of science but well within the realm of advocacy. Darwin repeatedly used such "information" and speculations to provide "evidence" of the truth of his theory of the gradual evolution of all species from a common ancestor; that is, bacterium to mathematician. One is prone to wonder how some bacteria decided to remain in their class while others proceeded toward the evolution of mathematician.
Darwin discussed the variations among several species of cuckoos in egg size, number of eggs per parasitized nest, and colors of eggs. He noted that all these different characters provided natural selection ample opportunity to work upon and fix "advantageous variation". In addition, the variation among and within the cuckoo species showed the evolutionary advancement of species and individuals, illustrating the gradual development of new and advanced characters in the living birds. Rather, I suggest, ecologically speaking, each species possesses specific characters that enable it to better survive within its specific living situation than other members of the same genus. There are good reasons for the differences among the species of cuckoos. We cannot assume, as Darwin did, in order to support his theory of gradualism, that some species of cuckoos are more advanced along the scale of evolution than others. The yellow-billed and black-billed cuckoos in America, for example, are sympatric (co-exist spatially) in much of their ranges. Because no two species can successfully occupy the same niche, we must assume that each is adapted to different living situations, not that one species is at some lower step of phyletic evolution as Darwin would have us believe.
Darwin also noted in this section that the female cuckoo laid eggs in the nests of other birds because if she laid eggs daily in the same nest and began incubation with the laying of the first egg, the young would hatch and mature at different times. Farm boys know that the wild and domestic birds they observe do not begin incubation until the full clutch of eggs is laid. What was Darwin thinking?
Slave-making Instinct
Darwin described the slave-making behavior in the ant species Formica sanguinea and F. refescens. These species of ants, found in western Europe, collect the pupa of other species of ants in their genus and raise them as their own offspring. They prefer to enslave members of the species F. fusca. Observations suggested that F. refastens requires the service of its slaves to perform all the work of the group, including the building of the nest, carrying out migrations, collection of food, and feeding and care of young and adults. By contrast, slaves of F. sanguinea merely assist in such activities.
Darwin guessed at how the slave instinct may have developed gradually in a step-wise manner. He speculated that the master ants originally robbed the pupae from the nests of related species for food. They subsequently failed to eat all the foreign pupae and some developed into adults and followed their own instincts to serve their hosts.
Critique
One guess is as valid or invalid as another with such surface observations. The real question might be to ask how at the molecular level, information changes developed to program slave-making behaviors in certain species of slave-making ants.
Cell-making Instinct of the Hive-bee
Darwin described nest-building by the humble bee (bumble bee), the Melilpona (stingless bees), and the hive bee (honeybees). In his mind, he believed that the "hive bee" made complex nests that required highly evolved behaviors, that the humble bee made relatively crude nests, and that the Melilpona constructed nests of moderate complexity. The humble bees:
...use their old cocoons to hold honey, sometimes adding to them short tubes of wax, and likewise making separate and very irregular rounded cells of wax (Page 248). ...The Melilpona itself is intermediate in structure between the hive- and humble-bee, but more nearly related to the latter; it forms a nearly regular waxen comb of cylindrical cells, in which the young are hatched, and, in addition, some large cells of wax for holding honey (Page 248).
Darwin then proceeded with an excess of 3,000 words to describe his observations and the observations of others to conclude that the making of the hive by the honeybee was complex but understandable and therefore not too complex to show that such complexity could evolve through gradual steps. The nest-building of the above bee species showed gradations in the complexity of nest-building and therefore the gradual evolution of bee nest construction.
Critique
When Darwin tried to illustrate the development of complex behaviors or structures in species by assigning some as "primitive" and others as more advanced on the scale of evolutionary development, he violated fundamental ecological principles. No two species can occupy the s
ame ecological niche (living situation) because the better adapted species will replace the less adapted one. Thus, because the honeybees, the bumble bees, and stingless honeybees coexist in time and space, each is best adapted to survive in its specific ecological niche. Because each species is most fit to survive in its own living situation, it would be erroneous to assume that the body plans and/or behaviors of one species of bees were more advanced on some evolutionary scale than those of the others.
Objections to the Theory of Natural Selection as Applied to Instincts: Neuter and Sterile Insects
Darwin was concerned about the origin of sterile female workers in some social insects; e.g. some ants and bees. What could be the reproductive advantage of producing sterile offspring? Darwin also believed that species changed because their new behaviors affected their structures and their offspring inherited these changes or "habits". But sterile members of species could not pass their Lamarckian-acquired "habits" to the next generation:
For peculiar habits confined to the workers or sterile females, however long they might be followed, could not possibly affect the males and fertile females, which alone leave descendants (Page 261).
Darwin, as was his usual mode of operation, solved the apparent problem involving sterile offspring through the reasoning process called abduction. By abduction, one hypothesizes about possible events in the past, in the light of known processes, that could explain current observations/evidence. Darwin hypothesized that species of social ants experienced increased rates of survival by producing the sterile female workers.
The assumption here is the same that I made above: species are adapted and often fine-tuned to survive in their respective ecological niches, and therefore the characters they possess and reproductive strategies they display are functional and necessary for their reproductive success and survival, including the production of many sterile offspring.
Thereby, Darwin maneuvered about the reproductive advantage of producing non-reproducing offspring. The next problem he needed to explain was the observation that some ant species produced two distinct forms of sterile workers. How did natural selection accomplish this feat? Darwin speculated that long ago, fertile parents produced a wide array of forms of sterile offspring and those parents that produced more of the existing two forms had higher rates of survivability than those that produced more of the intermediate forms between the two extant forms. Progressively, over time there were fewer and fewer intermediate forms until only the two extant forms remained. Darwin believed that "division of labour" (Page 260) explained the benefits derived from the production of different forms of sterile offspring.
Darwin needed examples of ant species that produced different forms of intermediate worker ants. A colleague "Mr. F. Smith" assured him that the driver ant (Anomma) of West Africa produced "gradations of structures between the different castes of neuters in the same species" (Page 259).
Critique
Darwin hypothesized that some species of social ants experienced increased rates of survival by producing sterile female workers. This tautology means: some social ants that survive produce sterile offspring.
Darwin was correct in his assumption that the production of sterile workers benefits the colonies of some social bee and ant species. If sterile workers were not beneficial, they would not be produced on a regular basis. The ecological principle that most species are fine-tuned to survive in their relative ecological niches is generally sound. Darwin was not, however, consistent in the application of ecological principles when deriving "evidence" from extant species to support his theory of macroevolution. Repeatedly he stated that the characters and behaviors of some related, extant species showed gradations in evolutionary development; not that the behaviors and characters of each were fine-tuned to assure the survival of each in its own ecological niche. He repeatedly classified structure and behavior as "primitive" or "intermediate" or "advanced" to illustrate examples of step-wise gradualism in extant species and even within the structures of single individuals. These evolutionary classifications were out of sync with the ecological concept that species, their reproductive strategies, and behaviors are most often fined tuned and necessary to assure the survival of each species.
How did Darwin recognize which structures and behaviors in the sterile workers were more beneficial/advanced than others? One also wonders how the addition of worker ants with the minutest change in behavior or structure, recently inherited from parents, could improve the chances of survival of an ant colony? And, of course, the change had to reflect innumerable, minute changes because, otherwise, the alteration would represent a case of forbidden saltation. Cannot have that; rapid alteration of complex organs, behaviors, and structures approaches the unnatural and unscientific: "To admit all this is, as it seems to me, to enter into the realms of miracle..." (Page 232).
If Darwin had not been apprehensive about the implications of rapid changes, he might have been able to come up with other possible hypotheses to encompass the appearance of sterile ant castes. Perhaps the queen with mutation of her sex cells ... in one step, produced numerous sterile workers with the beneficial modification in behavior or structure? But she could only transfer that beneficial modification through her fertile offspring, not through her sterile offspring. Thus, rather quickly, numerous queen ants might appear within the species with the ability to pass on to their sterile offspring the beneficial modification. But how often would a slight/minute elongation of a sterile soldier's mandible, for example, occur? Would hundreds, thousands, or millions of such fortuitous mutations be required to establish the elongated mandibles found in some soldier ants? What is the probability of such repeated, cumulative, and favorable mutations in the same structure?
Mutation at a particular site along any chain of DNA occurs once in a hundred million births. If two or more mutations or a new protein-protein binding or two are required to produce a functionally improved mandible in an ant species, the probabilities of producing such cumulative modifications by blind chance could jump from the highly improbable to the virtually impossible; say, one blind chance in 1040 (Behe 2014:112-116,146). And, in concert with Darwin, if a larger, functionally improved mandible showed up all of a sudden, how would one explain such a fortuitous event?
Darwin struggled to incorporate the presence of specialized structures in sterile worker ants and bees into his gradualist model. One wonders what concoction of borrowed antidotal observations he would have come up with to accommodate the innumerable evolutionary steps required to produce complex one-celled organisms that reproduce asexually. Perhaps a bacterium would simply, in Lamarckian fashion, long to become a human mathematician and then would simply begin the long journey in that direction - in small steps of course. Lest we forget: "natura non facit saltum;" that is, "nature does nothing in jumps." Of course, a random mutation in a gene represents a non-Darwin leap.