Sailors' sleep patterns are mostly dictated by their watch schedule. Different ships have different schedules (eg, three eight-hour shifts, or four six-hour shifts, etc) and basically you try to get sleep whenever possible.
I sailed on a ship that had six four-hour watches with three watch groups. That meant that one group would stand two 4-hour watches per 24-hour period (eg, 4am-8am then 4pm-8pm). With less than eight hours between watches, you had no choice but to sleep in two different blocks each day.
The effects of such a schedule and standing watch in a windowless engine room deep in the hull of the ship are quite interesting. For example, people (myself included) would completely forget whether it is PM or AM. If you occasionally go outside--rather than straight from the engine room to your bunk--you never knew whether to expect it to be light or dark out. I often went out expecting to reminisce under the star-laden sky, only to find out it's broad daylight out.
Not to detract from your main point, but I don't think Siesta is very common in Mexico and most other Latin American countries. I was born in Cuba, lived there for five years and lived in Mexico for about three or four. I don't know of a single person who regularly slept after noon.
In fact, I had an opportunity to live in Barcelona for three months and while a lot of businesses do close down from noon to three, I got the impression that people were not using that time to sleep, and that the idea of siesta in Catalunya is on the decline.
Ok, I did work for Bolivia for a time, and our Bolivian office closed for siesta, as did our main customer (the La Paz city council).
Same for a more rural area of Mexico (Toluca surroundings), they also did siestas there.
Googling a bit, acording to Time magazine, siesta was struck down in Mexico in 1944, so it's more a myth than reality now I guess (probably subsists in some more rural areas).
My impression was that siesta still persisted in some countries, but that it tends to disappear as they conform to western work hours, and, as the Time article states, it does involve four commutes instead of two, so it's not workable in urban areas (btw, people who siesta still work the same amount of hours, I'm not saying they work less).
Observation: In the Philippines, most parents force their kids to take a siesta. These are taken around 1 or 2 in the afternoon. However, some parents fail to wake their kids up after 3 hours of sleep. In this case, these kids are up till the wee hours of the night, making their sleeping habits more complicated than it should be.
Regarding the article, I guess one should just do what works for them (their body). Some people find it necessary to get 8 hours of sleep, and some are okay with six.
I don't see how your post could be "also" to the parent post: It's saying to be skeptical of the claims due to lack of evidence, while your post contrarily implies that this is already established knowledge.
I think he's saying that the conclusion from the historical study (people used to have bi-modal sleep patterns) isn't exactly revolutionary either. So it's in line with the parent post in that there's not really anything noteworthy in the article.
