Med thumb screen shot 2017 07 17 at 5.46.21 pm

Every summer, I leave the States to spend a month with my relatives in Xi’an, a 3,000-year-old city in central China that was once the starting point for the Silk Road. Visiting my family comes with the standard do-you-have-a-boyfriend questions and a nonstop supply of homemade grub (not that I'm complaining). But there's something else I've come to expect from family reunions in Xi'an: shuteye problems, courtesy of jet lag and a sleep environment that hardly resembles the American one I’ve grown up with.

Without fail, my yearly trips to China begin with days of drowsiness and nights of fitful sleep. But, by the time I’m ready to go home to North Carolina, I’m sleeping like a local. And my experience sleeping in China makes sense from an evolutionary standpoint: Humans are hardwired to adapt to sleeping in new places.

My family and I usually land in China around dinnertime. Each year, my routine is similar: I stumble into my grandma’s apartment with a sore butt from 24 hours of air travel. After some jian bing, a Chinese-style crepe, and an episode of the latest Chinese soap, I’m ready to call it a night. My stiff bed never looks inviting, but, by this point, I’m too tired to care where I collapse. So I lie down and let my head sink into the pillow, a cloth cushion stuffed with buckwheat hulls (similar to the Zafu meditation pillow), and try to get comfortable.

Chinese beds are the polar opposite of what you’d find in America. The mattresses are made of thin cotton-like material and customarily topped with bamboo mats, or liang xi, for maximum coolness. One Quora commenter compared bamboo mats to kitchen floor tiles: “Have you ever been so hot you envied your dog for sprawling out on the kitchen floor tiles? [It’s] like that, but for your bed.” Interestingly enough, the character for “bed” in Chinese (床) contains “wood” (木), perhaps alluding to its rigid nature.

My first night sleeping in Xi'an is always a restless affair. But this is normal. The first night in any new environment triggers what’s known as the First Night Effect (FNE), when one hemisphere of your brain stays vigilant to monitor for suspicious noise or activity — it’s essentially a protective mechanism.

I'd rather enjoy my day than go for round two in my hard bed. So my default move is pretending I feel alert, which is apparently a science-backed trick. And, thanks to willfull ignorance, I can typically hold it together through lunch. But, after I take my last bite of yang rou pao mo, a Xi’an delicacy consisting of steamed bread and meat cooked in lamb broth, it's time for a Karaoke bar. And I start fading, fast.

And so begins the biological tug-of-war: the light outside that signals daytime vs. a circadian rhythm that tells me it’s way past my bedtime. My body hasn’t had enough time to adjust. It’s no surprise, though, because studies have found that it's more difficult to adjust to eastward travel than westward travel (especially jumps of more than 8 time zones, and China is 12).

I can force myself to cheer on my cousin’s off-key rendition of “...Baby One More Time,” “whoo-ing” and tapping a tambourine through fits of yawning. But I'm relieved when it’s time to funnel into taxis and head home. Last year, my need for sleep was extreme enough to inspire an entry in my journal app. At 9:46 pm, Xi'an time, I wrote: 

After we got back around 5 pm, I knocked out and slept until around 9:30, woke up and felt very energetic, and then ate a little bit. Around midnight I went back to bed and slept until 6:30 am, so I consider last night a success in terms of jet lag. Usually I always get so sleepy in the afternoon and sleep from 4 or 5 until 2 or 3 am, which is the worst.

Adapting to sleep in China isn’t just about battling buckwheat pillows to find that sweet spot for your head, it’s also about balancing wake and sleep schedules. Outside of traveling to China, I don’t have much experience flipping my sleep-and-wake schedules. And that’s a good thing, as Fred Coolidge, a psychology professor at the University of Colorado Colorado Springs, reminded me.

"For people that continually have to change their sleep habits…it’s really psychologically upsetting. It’s also physiologically upsetting,” said Coolidge, who went on to explain that "while it may only take several days for superficial adjustments to occur (aligning your sleep schedule to the local time), it takes two weeks for physiological changes, such as blood pressure, to return to normal."

But, like most travelers, I make myself stay awake during my biological night to keep up with the daily rhythms of my temporary home. Humans are the only species that willingly delay sleep. We put ourselves through this circadian anguish because we can. And even if it’s tough at first, I eventually don’t need to force myself to delay sleep. Within a week or so, I acclimate to my new time zone and decidedly un-plush bed.

In my mind, I adjust because I don’t have another choice. But here’s an evolutionary explanation: We can thank Homo erectus, our oldest human-like ancestor, for our ability to sleep in far-away lands somewhat easily.

"Our evolutionary predecessor has been likened to a 'weed' species, that is, able to adjust to a wide variety of climates, altitudes, temperatures, catastrophes, etc.,” said Coolidge. “[Homo erectus] kept evolving. Coming out of Africa, essentially going out into Asia and Europe. And I think that ability to travel those long distances, and adapt to those new environments, was very important. And I think that gives us some of that behavioral flexibility now.”

And, by the end of a month in Xi'an, my weed roots reliably come through. Not only does it become possible for me to fall asleep on stiff bamboo, I actually start enjoying the hard mattress and find myself waking up earlier and more refreshed. But, of course, this happens just as it's time to pack up and get re-acquainted with my American mattress. 

Not everyone is as inclined as I am to switch back and forth, and embrace conflicting definitions of comfort. I've come across accounts from both Chinese and American expats describing years-long struggles to get cozy in foreign beds. I wonder if the problem is that they truly can't acclimate or that they don't want to let go of their own culture's approach to sleep. The answer, of course, is that it depends on all sorts of factors. But, as Coolidge noted, "genes play the major role in whether we are good sleepers, bad sleepers, flexible sleepers, inflexible sleepers, etc."

I'll be sure to credit my genes (and whatever else contributes to my flexible sleep habits) in a few weeks, when it's once again time for buckwheat hulls and bamboo mats.