The traffic in front of him came to a standstill. “Darn it,” he exclaimed, and continued less loudly, “I’ll be late for the morning meeting, and I will get in after Brigitte, that lazy woman. Just imagine the look on her face if I walk in after her.” The traffic started to move again, on a stop-and-go basis. “Getting up early also means retiring early. You can see this in town, where everything closes before people in Berlin even get ready to go out for the evening,” he thought. “Berliners don’t get up early and still attract good business.” At that point, the traffic jam dissolved as quickly as it had formed. About fifteen minutes later he parked his car in front of the building where GoEast had rented a suite of offices.
When he entered the conference room everyone was already there, including Brigitte, who gave him a broad smile. Olaf opened the meeting. “Has anyone had a breakthrough idea for the state PR campaign overnight?” To his chagrin Brigitte was the first to raise her hand.
“Did anyone hear the cool story on this morning’s news?” she asked. “It was about a study which found that the people of Saxony-Anhalt are the first to be up every morning.”
Olaf waved his hand in a dismissive gesture: “Yes, I heard it. It’s quite pathetic, really.”
“But on the contrary,” replied Brigitte, “Olaf, leave behind your ‘Wessie’ prejudice and think of how you would have reacted if they had found our state to be the last up every morning!” She had always thoroughly disliked her boss’s two-faced attitude. On the one hand he thought that East Germans were a bunch of losers, and on the other he was one of the first to realize that there was a lot of money to be made in the East. Not to mention the fact that he had bought the most beautiful old mansion for a bag of peanuts. “Your reaction would have been similarly negative. ‘Typical,’ you would have said, ‘who would have thought anything else?’” Brigitte now had the full attention of everyone in the room.
“This is our big chance! This morning’s newscast has solved all our problems. It has delivered our campaign slogan on a silver platter. Here is what I suggest: ‘Saxony-Anhalt—we get up earlier!’” In an instant, a whole firework of ideas, images, and action items exploded in the morning meeting. Getting up early is more than just getting out of bed—it is a mentality that is reflected in the state’s long and successful history. Getting up early is the mindset of a state that is eager to be the best, ready to move ahead. Saxony-Anhalt is Germany’s early bird that catches the business.
Even Olaf started to see the posters and the TV ads. This was it! There was no doubt that his company would win the competition, and that his idea, his campaign would change the face of Saxony-Anhalt. Olaf was convinced that he had brought the campaign’s central idea into this morning’s meeting, and he was very proud. Still, from then on, he was oddly hesitant to treat Brigitte with the same disdain that he had ever since this Magdeburg-born woman had started to work for GoEast.
When you drive on the highway from anywhere in the southwest of Germany toward Berlin, you quite likely will pass through the state of Saxony-Anhalt. The signs announcing the entry into this state carry the slogan, “Saxony-Anhalt—welcome to the country of early risers.”2 This campaign has been the cause of many comments and jokes on the internet. One of them says, “If I still lived in Saxony-Anhalt, the early-riser record would collapse since my daily habits would completely mess up the average.” Another one refers to the fact that workers in Saxony-Anhalt had, on average, such a long commute to their workplace compared with workers in other German states that they simply had to get up earlier. A third comment, written by someone who had recently moved there, asks: what makes the people from Saxony-Anhalt rise earlier? And someone answered with a smiley: “They think of their dogs, who want to go and ‘read’ their ‘morning paper’ at the crack of dawn.”3 This joke probably comes closest to the truth.
The poll mentioned in our story is real. It had apparently asked two thousand Germans when they get up. Although this poll is not very representative (it averages to no more than 125 individuals per federal state), its results are remarkably close to what you will read about in this chapter. A couple of years ago, I approached the question of whether the human clock is synchronized by the light–dark cycle—like the circadian clock of other animals—or whether humans are an exception whose clocks are predominantly synchronized by social cues. In a first approach, I conducted an experiment together with colleagues in India. We collected thousands of chronotype questionnaires in two cities: Chennai, on the east coast of the Indian subcontinent;4 and Mangalore, a city at the same latitude on India’s west coast. The first results showed that the average chronotype in Chennai is clearly earlier than that in Mangalore, indicating that the light–dark cycle is the main zeitgeber for the human body clock—the sun rises earlier in the east than in the west. When I presented these preliminary results at a conference in Florida, a British colleague came up to me after the session and said, “Beautiful data, but I bet you this is India—I’m sure you won’t find anything like this in Europe!”
I was quite shocked by this remark, but I owe my colleague a debt of gratitude for making me look for a way of proving him wrong. At home I had a database of chronotypes in Central Europe that contained at that time approximately 40,000 individuals. Since we had asked the participants to enter the postal codes of their current residence, it would be possible to create a map of Germany based on the coordinates corresponding to the postal codes. Back home, I immediately began to analyze the database and generated the map. When I finally looked at the finished product, I was astonished to find how well the database covered the entire country.
I decided to use only German entries for the analysis and not other countries for two reasons.5 First, they were by far the biggest contingent, and second, I would not have to defend the results against a critic who pointed to potential cultural differences. Germany is a big country and certainly not very homogeneous in its culture, but Berliners and Bavarians resemble each other more than, say, people from Baden-Baden and from Strasbourg. Each of the points shown in the map represents up to several hundred entries. Their underlying number strongly correlates with the population density of the respective location. There is no need to draw borders around the area of postal code coordinates—Germany’s shape is clearly represented (see small inserted map in gray). There are even some entries from people living on German islands in the North Sea.
Entries in the Munich ChronoType Questionnaire database represent all of Germany well. Reprinted from T. Roenneberg et al. (2007). The human circadian clock entrains to sun time. Current Biology 17(2):R44–R45, with permission from Elsevier.
Based on this result, all I had to do was cut Germany into longitudinal slices from east to west and determine the average chronotype in each of them. Each longitude represents one of the 360 degrees of the earth’s circumference, and the earth makes a complete turn every 1,440 minutes. The sun therefore takes four minutes to pass over each longitude. At its widest point, Germany extends over nine degrees of longitude, so that the sun rises thirty-six minutes earlier at the country’s most easterly point compared with its most westerly one. If the body clock of humans were entirely influenced by social time, all Germans should have, on average, the same chronotype at all longitudes because, unlike in bigger countries like the United States, Canada, or Russia, Germans all live in the same time zone. If, however, the human body clock were entrained by the light–dark cycle—by dawn, dusk, or simply by the sun’s highest inclination (at solar midday)—then the difference in chronotype should be four minutes later in every longitude from east to west. Because of all I knew about circadian entrainment in all kinds of different organisms, I would have bet that sun time also has an influence on the timing of humans. However, the clarity of our results was surprising, even to me. In the graph below, the horizontal axis represents the local time of sunrise for each longitude on the longest day of the year (this is just a point of reference—I could have chosen any other day of the year). The
vertical axis shows the local time of midsleep on free days (representing chronotype) averaged for all people in our database who live in a given longitudinal slice of Germany. The dashed diagonal line represents the east–west progress of sunrise. You can easily see that chronotype moves with the sun, becoming later by, on average, four minutes per longitude from east to west. Note that sun times are inverted on the horizontal axis, increasing from right to left, so that west is to the right and east is to the left, as they are on maps. These results show that the body clock of humans is no different to that of animals. It entrains to sun time—even in Europe.
It is a remarkable fact that every time I find evidence for a biological basis for human behavior, I am confronted by the conviction that the same results could be explained far better by cultural causes.6 The first time I presented these results, I was instantaneously confronted with the claim that this is a cultural artifact! The people in the former GDR always had to get up earlier than their fellow countrymen in the West.7 The social-explanation camp claims that our study merely shows a remnant of the cultural differences between people having grown up under either a socialist or a capitalist regime.
Chronotype in Germany moves with the sun, becoming later from east to west.
If this were true, the results should have looked more like what is shown in the figure below. Depending on the “mixture” of capitalists and socialists living in each of the longitudinal slices, the averaged chronotype should fall onto an S-shaped curve, with pure East Germany on the right, pure West Germany on the left, and some mixture of the two in the middle.
The German data show that the human clock is predominantly synchronized by sun time rather than social time. The curve here predicts average chronotype from west to east if social time was the dominant zeitgeber. In reality, average chronotype for each degree of longitude falls on a straight line, as shown in the previous figure.
However, the real data form a straight line parallel to sun time, which weakens the purely sociopolitical hypothesis. But to be sure that the systematic east–west changes in chronotype are not a sociopolitical artifact based on the transition between the former GDR and West Germany, we simply analyzed the southern regions of Germany, which have almost the same east–west expanse but were never ruled by a socialist government.8 The results were practically identical to those for the entire country. So, we finally were able to convince our critics that the human clock is predominantly synchronized by sun time rather than social time.
As you read in the introduction, time-zone time is the temporal reference that people have lived by since the late nineteenth century, when the world was subdivided into twenty-four time zones. Before that, the temporal reference was local sun time. It is quite remarkable that we find—in the first part of the twenty-first century—that our body clocks still live very much like those of our ancestors, namely by sun time, while our entire social life has to conform to a different schedule. We might think that—since each time zone is only one hour apart from the next—we would have to live, at most, only one hour away from the actual local sun time. And if a time zone spreads equally to the west and to the east, then the forced deviation would be only thirty minutes, which seems like an acceptable difference. After all, we change our reference time by a full hour twice a year when we change to and from daylight saving time.
Unfortunately time-zone time and sun time rarely differ by just thirty minutes or less because politicians decide to which time zone their country’s citizens belong. Before I started to investigate the discrepancies between social and sun time, I was completely oblivious to how different midnight could be from its original meaning of “mid-dark.” The most extreme example is China. Its entire mainland territory, which extends over almost a sixth of the earth’s circumference, is fused into one single time zone referenced to Beijing sun time.9 When people in western China look at their watch and see that it is 10:00 P.M., it is actually only 7:24 P.M. by sun time, and if they had to get up at six in the morning to go to work, it would by local sun time be only 3:24 A.M. I have been told that the western Chinese population actually doesn’t orchestrate social life by Beijing time. For example, when they come together for an early evening meal (say at around 7 P.M. local sun time), they would arrange to meet at 11 P.M.
Similar though not quite so drastic differences exist even in Central Europe. By definition, mid-dark and midnight coincide, for example, in London, in Beijing, or in Prague.10 The Central European time zone is ahead by one hour compared with Greenwich, which corresponds roughly to the sun time in Prague, lying 15 degrees east of Greenwich. Thus, midnight occurs almost one hour before mid-dark in Paris and more than ninety-seven minutes earlier in Santiago de Compostela, the capital of the Spanish province of Galicia and the most western city of Spain. The difference between social time and sun time becomes even greater for more than seven months of the year when we live under daylight saving time. Then the time difference between midnight and mid-dark in Santiago de Compostela is as much as 158 minutes—two hours and thirty-eight minutes! When the clock in this Spanish town shows midnight, it is actually only 9:22 P.M. by sun time.
The large difference between social time and sun time in Galicia is especially interesting for our research because this Spanish province is very close to northern Portugal (and at the same longitude), yet the Portuguese population lives by Greenwich Mean Time. For that reason, I am trying to initiate studies that compare daily behavior between Galicians and northern Portuguese. When I mentioned this plan to a scientist from the northern Portuguese town of Porto, he responded without hesitation that such a study would be quite fruitless because of the strong cultural differences between the two populations. To underline his argument, he said, “In northern Spain, for example, they have dinner a whole hour later than we do in Portugal.”11 I am gradually beginning to get some fun out of this sociocentric view. In the case of adolescents, I argue that it is not the disco visits that make teenagers late chronotypes, but that discos are the only sanctuaries in our society where they can be loud at that time of night without waking up the rest of the population. With similarly reversed reasoning one could argue that some cultural differences result from the biology of the body clock. Although all live according to their social time, East Germans have their dinner first, followed by the West Germans, followed by the French, and finally followed by the Galicians. In the next chapter you will see that there are even body-clock reasons why people in the country have their dinner before the town folks.12
18
Constant Twilight
Sophie sat at her favorite spot in the alcove window overlooking the valley. After everyone else had gone to bed, she had switched off the lights to see the beautiful starry night outside. A full moon was just about to climb over the ridge of mountains, and its solar reflections bathed the valley in the most magical light. Her thoughts went back to those terribly confusing months when none of them had any idea about how to solve the gridlocked situation. Before everything had started to turn upside down and inside out, they had been a happy and normal extended family.
Joseph and Frederic were identical twins born thirty years ago on the family farm in the midst of the mountains. After finishing school, Joseph started to work full time on the farm with his parents. Six years ago they decided that it was time for the old folks to move into the small annex house. The farm was tucked away at the very end of a long, dead-end valley, about half an hour by car to the next small town, where Frederic worked in a small factory. The two were typical twins, walking the fine line between wanting to be separate individuals and wanting to do everything together. They had even met their future wives on the same evening at the annual dance of the local fire brigade!
The twins had danced with Sophie and Hanna all night, constantly exchanging partners. The two women were similar in looks and demeanor and shared the same sense of humor. As one might expect, the twins had very much the same taste in women, so it took them months to sort out who loved who
m more. In the end, those pairs that seemed to have more in common ended up together. Sophie had frequently gone to the farm to give Joseph a hand, whereas Frederic spent most of his lunch breaks visiting Hanna at the local grocery her parents owned. He then usually gave her a shopping list for the farm’s groceries. She had everything packed up by the time he came around in the evening to collect the supplies before driving up the long and winding road to the head of the valley.
Internal Time: Chronotypes, Social Jet Lag, and Why You’re So Tired Page 15
