Can You Really Evolve to Sleep Less?
Perhaps – if you’re like a cavefish.
Research done at NYU by Professor Richard Borowsky and company, reported last week in Current Biology, looks at a Mexican species of fish that has evolved to live in caves.
The cavefish version of Astyanax Mexicanus are also blind.
When brought back to the NY City labs, the cavefish clearly sleep less – a lot less. While the surface fish fall to the bottom of the tank, the cavefish take short sleeps, then patrol and patrol throughout the night.
So Borowsky took the surface fish and mated them with the cavefish. The hybrids showed variation in some major genes that probably help control sleep time.
But were the cavefish sleeping less because they need less sleep?
According to an interview in Science Centric, Borowsky thinks it’s the other way around-that they sleep less because they’re required to stay awake.
The cave environment has both less and more erratically appearing nutrients. He thinks the fish have evolved to have less sleep because they pretty much don’t have a choice – they need to stay awake to find enough food. They sleep less because they have to sleep less.
What about people?
The Long and the Short
As humans progress to short shrift rest in its many forms, much interest has now been laid on human short sleepers. Many a CEO claims to “hardly sleep at all” in their quest to create a better corporation, while some medical academics extol their ability to thrive through 36 hour shifts.
Are they lying, highly motivated, or telling the truth? What seems to be coming out is this:
1. Some people really are short sleepers. Some have variants of a particular gene seen in families where the normal time to go to sleep is after midnight and the wake up time is 4 AM. Most sleep physicians have met people like this – some of whom come in only to ask if it’s “okay” that their sleep needs are so low. I know one woman who still sleeps three hours a night as the always has – at the age of 96.
2. Such short sleepers are actually quite rare. Some estimates go as high as 1-3% of the populations, but people who study them, as reported by Melinda Beck in the Wall Street Journal, know only a handful themselves, despite years of research.
3. Many short sleepers are also very, very active people in the daytime – having many of the symptoms of manic-depressive illness, in terms of high energy, high productivity, happy or high mood, seemingly without most of the negative ones. Such people go under the rubric of “functional hypomanics” and do include in their number highly successful people in business and the professions. Just as there are people who are great basketball players or superb concert pianists, some people have more energy and push than others – along with a lower sleep need.
4. Most of the population who call themselves short sleepers are not – simply people who are sleeping less on work days and sleeping more than five or six hours on the weekends.
5. In times of great stress, people are capable of operating at low levels of sleep for surprisingly long periods of time. Medical interns and residents may make far more serious mistakes, but are capable of staying up and appearing productive for years at a time doing 36 hour shifts. Similarly, in wartime troops may operate for long periods with four hours or less of sleep.
6. Since sleeping less is associated with higher mortality; more high blood pressure and heart disease; more major depression; greater weight gain; and perhaps more tumors, especially in shift workers, sleeping less than what your particular body needs is not a good idea.
7. Sleeping less because of work demands may be even less of a good idea. Recent studies of British civil servants show that those working 11 hours or more each day had much greater risk of cardiovascular death.
Getting Less Sleep
You can fight nature for just so long. Mexican cavefish may have found a special niche for themselves that allows their species to expand its ecological footprint. Yet they are blind, and apparently constantly foraging for food – night and day.
Humans can shirk rest, too – especially when they perceive they have no choice. However, eventually the results will be felt – not just with lower mood and productivity, worsened relationships and bigger bellies, but with increased mortality.
Some of us are lucky in that we function well with far less sleep than average 7-8 hours. Yet most of us cannot emulate – and will hurt ourselves if we try.
Human evolution of less sleep may require many generations of electronic media that keep us up night after night – and then somehow become necessary for survival. Figuring out the genetics of sleep may come faster.
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