The Evolutionary Biology of Dreams, Explained

Dreams might be a whole lot sexier than we thought – but not because of their narrative content. Neurologist Patrick McNamara's theory links the biological changes in our brains during sleep to human's inherent desire to procreate.

Carl Jung battled his one-time friend and mentor, Sigmund Freud, on a number of topics, though perhaps none as perniciously as dreaming. An entire cottage industry of depth psychology and journaling workshops grew out of Jung’s theories of individuation—integrating the conscious and unconscious. To Jung, dreams—the primal material of the unconscious—unlocked humanity’s archetypal code, revealing more than they concealed, in direct contradiction to Freud’s ideas.


Freud was rather simplistic in comparison: dreams are about sex.

Not that sex is simplistic, nor is tunneling the depths of one’s undiscovered psyche. Jung’s intensive survey of mandalas and writings on mythological landscapes fueled generations of thinkers enamored with the idea of a subconscious primordial glue binding together humanity with the cosmos through this secret language of dreams.

By contrast Freud, though hugely influential therapeutically, has always been in and out of vogue, usually simultaneously. Ernest Becker posthumously won a Pulitzer for his 1973 book, The Denial of Death, which was essentially his shadowboxing with Freudian theory. He could not come to terms with the simplicity of Freud’s death wishes:

It was becoming difficult to maintain the casuistry of the dream theory that all dreams, even anxiety dreams, are fulfillments of wishes.

While later Becker ceded to Freud some of his discontent, wish fulfillment and anxiety are unapologetically bound up with the propagation of our species. Of course, the mechanism by which this occurs is sex, an act conflated and celebrated by our ingenious imagination. Could such a simple and complex act really inform our nightly picture show? Patrick McNamara says yes.

The associate professor of neurology and psychiatry at Boston University School of Medicine has spent decades decoding the hidden language of dreams, first influenced by his brother’s psychedelic poster of Freudian ideology in the sixties. By the time McNamara was working in the medical field a decade later Freud was so out of fashion as to be laughable, but the researcher in him never surrendered.

Fast forward to fMRI, the noninvasive breakthrough in wrapping our heads around what is inside our heads. McNamara spent hours studying dream reports by a wide range of men and women, noting peculiar patterns: in both genders strategies for partnership and procreation kept emerging. More tellingly, during the morning hours when REM sleep dominates, a cocktail of sex-related hormones—prolactin, oxytocin, testosterone—is served up in our midbrains, where circuits for pleasure and sex reside.

McNamara took it a level deeper. He split groups into those in relationships and those without—half the participants didn’t have to hunt for sex, the others did:

The anxious, preoccupied group was far more likely to recall dreams than the securely attached; they took less time to enter REM sleep and had many more dreams featuring aggression against competitors. But both the anxious and the securely attached recalled more dreams than avoidant participants. That is precisely the pattern one would predict if dream sleep were directly related to long-term sexual strategies.

A follow-up study with electroencephalogram (EEG) technology on college students confirmed these results, adding yet another nuanced layer: when in non-REM sleep (NREM), the dreamer was aggressive in only 29 percent of dreams, compared to 58 percent during REM sleep, the time believed to unite sexuality and inner cinema. Friendly interactions—sans sexual aggression—flipped that script, with 71 percent of NREM dreamers and 42 percent of REM sleepers reporting peace and love—agape, not eros.

All this research left McNamara to ponder one more peculiarity. REM sleep is marked by both a paralysis or inhibition of muscles and a suspension of the body’s thermoregulatory reflexes—the heat of passion is a bit cold at this time. The autonomic nervous system, responsible for our fight-flight-freeze reactions, is also unstable which, as he explains, is the reason more heart attacks occur during these hours.

Discovering reasons for evolutionary behavior requires reverse engineering, what philosopher Daniel Dennett describes as moving from how come to what for. Dennett encounters confusion between the two when debating religionists with a vested interest in theological narratives; the distance between them is critical in understanding evolutionary behavior. While Jungians get caught up in the mythology of dreaming, McNamara’s Freudian updates satisfy an even more incredible tale. As Dennett writes in his forthcoming book

A mystery solved is even more ravishing than the ignorant fantasies it replaces.

Like Dennett, McNamara turns to Darwin for insight. Why, for example, would nature endow peacocks with colorful plumage that adds no physical advantage in battle, or in the case of reindeer’s unwieldy antlers, are biologically expensive? McNamara speculates:

Darwin pointed out that many features of sexually reproducing species can boost reproduction rather than survival in the environment per se. The peacock’s tail advertised its fitness to peahens, and so they tended to mate with the male who had the most extravagant tail in the group … Similarly, the reindeer’s antlers were used as weapons in the fight against other males of the same species for access to females. The more elaborate the antlers, the more forbidding the buck.

Like weightlifters puffing their chests, showmanship trumps defense. Or rather, showmanship is the first line of defense. Applying this to dreams, McNamara suggests that a drop in body heat promotes sleeping in close quarters with others, increasing opportunities for procreation. It also makes sense that during a period in which aggressive behavior is being played out in the theater of dreams you would not want to attack the person you’re cuddling with; hence, physical paralysis during mental stimulation.

As Dennett suggests of evolutionary adaptations, these are profound responses to complex behaviors, which does nothing to detract from the wondrous mythology of dreaming. Jung might not have been wrong in suggesting that archetypal keys are uncovered during night flights, but at the foundation biology wins out. In this case, Freud just might emerge victorious.

Here's Michio Kaku explaining why Freud still has credibilty in this field: 

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Derek Beres is working on his new book, Whole Motion: Training Your Brain and Body For Optimal Health (Carrel/Skyhorse, Spring 2017). He is based in Los Angeles. Stay in touch on Facebook and Twitter.

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The image of an undead brain coming back to live again is the stuff of science fiction. Not just any science fiction, specifically B-grade sci fi. What instantly springs to mind is the black-and-white horrors of films like Fiend Without a Face. Bad acting. Plastic monstrosities. Visible strings. And a spinal cord that, for some reason, is also a tentacle?

But like any good science fiction, it's only a matter of time before some manner of it seeps into our reality. This week's Nature published the findings of researchers who managed to restore function to pigs' brains that were clinically dead. At least, what we once thought of as dead.

What's dead may never die, it seems

The researchers did not hail from House Greyjoy — "What is dead may never die" — but came largely from the Yale School of Medicine. They connected 32 pig brains to a system called BrainEx. BrainEx is an artificial perfusion system — that is, a system that takes over the functions normally regulated by the organ. Think a dialysis machine for the mind. The pigs had been killed four hours earlier at a U.S. Department of Agriculture slaughterhouse; their brains completely removed from the skulls.

BrainEx pumped an experiment solution into the brain that essentially mimic blood flow. It brought oxygen and nutrients to the tissues, giving brain cells the resources to begin many normal functions. The cells began consuming and metabolizing sugars. The brains' immune systems kicked in. Neuron samples could carry an electrical signal. Some brain cells even responded to drugs.

The researchers have managed to keep some brains alive for up to 36 hours, and currently do not know if BrainEx can have sustained the brains longer. "It is conceivable we are just preventing the inevitable, and the brain won't be able to recover," said Nenad Sestan, Yale neuroscientist and the lead researcher.

As a control, other brains received either a fake solution or no solution at all. None revived brain activity and deteriorated as normal.

The researchers hope the technology can enhance our ability to study the brain and its cellular functions. One of the main avenues of such studies would be brain disorders and diseases. This could point the way to developing new of treatments for the likes of brain injuries, Alzheimer's, Huntington's, and neurodegenerative conditions.

"This is an extraordinary and very promising breakthrough for neuroscience. It immediately offers a much better model for studying the human brain, which is extraordinarily important, given the vast amount of human suffering from diseases of the mind [and] brain," Nita Farahany, the bioethicists at the Duke University School of Law who wrote the study's commentary, told National Geographic.

An ethical gray matter

Before anyone gets an Island of Dr. Moreau vibe, it's worth noting that the brains did not approach neural activity anywhere near consciousness.

The BrainEx solution contained chemicals that prevented neurons from firing. To be extra cautious, the researchers also monitored the brains for any such activity and were prepared to administer an anesthetic should they have seen signs of consciousness.

Even so, the research signals a massive debate to come regarding medical ethics and our definition of death.

Most countries define death, clinically speaking, as the irreversible loss of brain or circulatory function. This definition was already at odds with some folk- and value-centric understandings, but where do we go if it becomes possible to reverse clinical death with artificial perfusion?

"This is wild," Jonathan Moreno, a bioethicist at the University of Pennsylvania, told the New York Times. "If ever there was an issue that merited big public deliberation on the ethics of science and medicine, this is one."

One possible consequence involves organ donations. Some European countries require emergency responders to use a process that preserves organs when they cannot resuscitate a person. They continue to pump blood throughout the body, but use a "thoracic aortic occlusion balloon" to prevent that blood from reaching the brain.

The system is already controversial because it raises concerns about what caused the patient's death. But what happens when brain death becomes readily reversible? Stuart Younger, a bioethicist at Case Western Reserve University, told Nature that if BrainEx were to become widely available, it could shrink the pool of eligible donors.

"There's a potential conflict here between the interests of potential donors — who might not even be donors — and people who are waiting for organs," he said.

It will be a while before such experiments go anywhere near human subjects. A more immediate ethical question relates to how such experiments harm animal subjects.

Ethical review boards evaluate research protocols and can reject any that causes undue pain, suffering, or distress. Since dead animals feel no pain, suffer no trauma, they are typically approved as subjects. But how do such boards make a judgement regarding the suffering of a "cellularly active" brain? The distress of a partially alive brain?

The dilemma is unprecedented.

Setting new boundaries

Another science fiction story that comes to mind when discussing this story is, of course, Frankenstein. As Farahany told National Geographic: "It is definitely has [sic] a good science-fiction element to it, and it is restoring cellular function where we previously thought impossible. But to have Frankenstein, you need some degree of consciousness, some 'there' there. [The researchers] did not recover any form of consciousness in this study, and it is still unclear if we ever could. But we are one step closer to that possibility."

She's right. The researchers undertook their research for the betterment of humanity, and we may one day reap some unimaginable medical benefits from it. The ethical questions, however, remain as unsettling as the stories they remind us of.