by PATRICK MCNAMARA
In dreams; a beach-roamer, Germany, 1933. SOURCE/Herbert List/Magnum Photos
Gritty, emotional, smelly and dirty: new evidence supports Freud’s long-debunked theory that sex fuels our dreams
Yet even if dreams are all about sex, how would that explain why we put ourselves at so much risk just to run the late-night reel? For REM sleep is profoundly dangerous: the major antigravity muscles of the body are inhibited or paralysed, and the thermoregulatory reflexes of the body are suspended, making it impossible to produce much internal heat. REM is also associated with intense autonomic nervous system (ANS) ‘storms’ or instabilities. The ANS is the system that regulates key physiological processes such as the heartbeat; instabilities during REM explain why there are so many heart attacks in the wee hours of the morning when sleep is rich in dreams.
In short, every 90 minutes during sleep, we enter this dangerous twilight zone called REM sleep. The reward centres of our brains are activated, and our sexual systems are turned on – yet our bodies are partially paralysed so we cannot move to take advantage of these activations. Instead, as key physiologic systems collapse, we are forced to watch these things we call dreams. Why would evolution impose this risky system on us? When we are paralysed, we are vulnerable to predation. When we are unable to generate internal heat, we are vulnerable to disease. When our ANS becomes erratic, we are vulnerable to heart attacks, and so forth. So whatever REM sleep and dreams are doing for us it must be quite important, given the dangers they usher in. But what could that extremely important function be?
It wasn’t until I came across Charles Darwin’s book The Descent of Man, and Selection in Relation to Sex (1871) that I began to understand why the paralysis and the heart attacks might be worth the risk. Darwin’s theory of natural selection concerns the evolution of new species by selection of traits that adapt to the environment across generations. But his theory of sexual selection concerns the emergence of traits and behaviours that enhance the ability to find a mate and reproduce.
Darwin’s theory of sexual selection was, in fact, an answer to critics of his theory of evolution, who pointed out that not all traits helped individuals survive. Darwin explained the phenomenon by pointing to the peacock’s brightly coloured tail and the reindeer’s elaborate antlers, with their unwieldy and dangerous exfoliations. How could such risky accoutrements make these animals fit enough to outcompete predators in the struggle for existence? Their very adaptations, those glaringly identifiable tails and those massively unwieldy antlers, seemed to hinder them in escaping their predators – not to mention the energy requirements these traits impose.
However, 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. Any peacock whose genes could support such a costly tail must be fit indeed! 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. The goal was to intimidate your competitors enough that they would give up the fight for access to a fertile female and you would then win the chance to mate with her. The pressures of sexual selection made it imperative that males develop weapons such as aggressiveness, antlers, body armour, muscles, and stingers to fight other males for access to females as well as elaborate adornments to attract females. Thus, the costly, apparently non-adaptive traits were explained.
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