Do We Understand Our Instincts?
Does evolution or environment shape learned behavior?
Stranger Danger
A mother holds her infant and a strange man approaches making friendly cooing sounds. The infant bursts into tears and is inconsolable until the embarrassed man moves away. “I’m great with kids,” he mumbles. Well if the man was great with kids, he would know that stranger anxiety is a normal phase of instinctual fear that most children go through at a certain stage of their development.
Thousands of miles and a continent away, the Brazilian National Congress debates a controversial bill aimed at eradicating the indigenous practice of child-killing. The Yanomami are one of a few indigenous peoples of Brazil who engage in infanticide and killing of certain older children including the disabled. Other tribes also target children of single mothers, and twins.
The Yanomami are famous not only for retaining indigenous cultural practices we find horrendous. They also represent a culture that anthropologists view as a holdover of our prehistoric ancestral condition. The Yanomami have been described, controversially, as being in “a state of chronic warfare”. A part of this endemic violence is directed at children.
In 1937, Helena Valero was kidnapped from a Christian missionary by Yanomami warriors when she was eleven years old. She witnessed many acts of violence by rival tribes targeting especially boys. Valero recalls a woman pleading for the life of an infant boy, saying that he was one of the warrior’s sons. The warrior paused to consider the new information, then rejected it, grabbed the infant by the feet and dashed him against the rocks.
If the Yanomami represent our ancestral human behavior, we can infer an evolutionary survival advantage for infants who express fear and anxiety of unfamiliar adult males. That fear has been bred into them over hundreds of thousands, perhaps millions of years of brutality.
The fear that infants and young children automatically feel and express upon meeting unknown adult males may represent an instinctual response — a complex behavior that is not learned but is innate, and which is genetically programmed rather than programmed by experience.
Or is it?
Pioneering Studies of Instinct
One of the pioneers of our modern understanding of instinct was Konrad Lorenz, one of the founders of the field of ethology, or the study of animal behavior. Lorenz shared the 1973 Nobel Prize in Physiology or Medicine with Nikolaas Tinbergen and Karl von Frisch for his work.
Lorenz is most famous for his study of the imprinting of goslings, where he described hatchlings bonding instinctively to the first moving object they saw. Many have seen images of a line of new hatchlings following Lorenz around as if he were their mother. Lorenz was able to hijack their imprinting instinct by making sure that he was the first thing these goslings saw, and they dutifully followed him around.
Lorenz met Nikolaas Tinbergen in 1936 at an international symposium on instinct. The two become good friends and colleagues, where together they studied the behavior of geese and established the field of ethology.
The key points Lorenz and Tinbergen made were that instinctual behaviors in animals were innate, hereditary, built-in instructions on how to act in given circumstances and that were independent of experience and learned behaviors. Lorenz pointed out important characteristics of instincts:
- The behavior is standardized, constant, predictable
- It is characteristic for the whole species
- It appears even when the animal is raised in isolation (it isn’t learned)
- And it appears fully developed even though the animal had no chance to practice it
However, Lorenz’s approach ultimately came under tremendous criticism for failing to prove that the behaviors were indeed innate, and for failing to dissect the mechanisms and development behind the behaviors he observed.
Ultimately, Lorenz was among the last of the great observational, descriptive biologists, in the tradition of Darwin. Both Lorenz and Darwin suffered from a failure to get to the mechanisms, the underlying genetics behind the behaviors, and the evolution they observed.
Darwin’s work long predated the blossoming of Mendelian genetics, but Lorenz did not have that excuse. Lorenz continued publishing until his death in 1989, so his career spanned most of the development from classic mendelian to modern molecular genetics and the mechanistic understanding of biological processes.
Today, field biologists in Lorenz’s tradition collect samples for DNA and other molecular analysis. Observational field biology has been immeasurably enriched by the use of molecular tools and the resulting deep genomic understanding of individuals and populations of animals in their native habitat.
A Modern Understanding of Instinct
Today, there is much more rigor and an attempt to get at the molecular and developmental mechanisms driving behavior and instinct. Even Lorenz’s famous gosling imprinting instinct has been broken down into distinct processes:
- A chick’s natural attraction toward the shape of a mother’s head and neck shape
- Learning, even while in the egg, about the mother’s calls and sounds.
We now know that there is no rigid dichotomy between instinct and learned behavior. Instead, we understand that behavior falls into a broad continuum from highly malleable to rigid, with many behaviors having a combination of genetic and learned components.
A key breakthrough in the genetic understanding of behavior came with Seymour Benzer’s classic work in the 1960s using the fruit fly Drosophila melanogaster to tease apart behaviors like courtship and sleep. Benzer is the subject of an excellent and very readable book called Time, Love, Memory, by Jonathan Weiner. Benzer was among the great migration of physicists who came into biology in the 1950s and began the molecular biology revolution which gave new power to the field of biology. But his most compelling contributions were to the field of behavioral genetics.
Behavioral genetics was a field started by Francis Galton in the late 19th century and was discredited by association with his other major “contribution”, eugenics. Eugenics, the belief in improving the genetic quality of the human race, mostly by excluding certain individuals and populations, led directly to the horrors of genocide and the Holocaust in the early 20th century. This is what stained the field of behavioral genetics.
Despite Galton’s dubious contributions with eugenics, he nonetheless was a genuine polymath. In 1869, 10 years after his cousin Charles Darwin published On the Origin of Species, Galton published Hereditary Genius where he showed that the rate of “eminence” was highest with the closest relatives of eminent individuals. It was in this work that Galton introduced multivariate analysis and the beginnings of Bayesian statistics. But Galton’s founding of the eugenics movement and its ultimate association with Nazi genocidal atrocities has dimmed Galton’s contributions, including behavioral genetics.
Nonetheless, Benzer brought new analytical and experimental methods to bear on the problem of understanding behavior.
Benzer and another giant in the field, Jerry Hirsch, found themselves at opposite ends of their field. Hirsch felt that behavior was far too complex to be reducible to one or a few genes. This perspective, for the most part, is true. However, Benzer was able to make tremendous advances in doing genetic screens to find mutants in specific behaviors. He found genes specific for fly behaviors including circadian rhythm, sexual function, and memory (thus the title of the book about his work).
Where Are We Today?
Today, we still at the very beginning of our exploration of behavior and instinct. Behavior, instincts, and learning are very complex and difficult phenomena to dissect and understand at a basic, mechanistic level. The fundamental problem is how to untangle the influence of genetics from the environment, despite the contributions of scientists like Benzer. As far as we know now, evolution acts through both genes and the environment to shape behaviors that affect survival. Behaviors once thought to be purely instinctual are now known to have both a genetic component as well as an environmental or developmental component.
For example, the stranger anxiety which we opened this article with, is a phenomenon that is known to develop at a characteristic age and to fade a few years later during early childhood. Although we label stranger anxiety as a childhood instinct, there is no way to separate and dismiss environmental effects, a learned component to this childhood anxiety.
Thank you for reading. I want to thank Anthony Lawrence for challenging me to tackle this topic. This article is my first installment in exploring instinct and memory.
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