Why Do Pirates Love Parrots? (31 page)

I
n
Why Do Dogs Have Wet Noses?
, we chronicled how Boeing decided to assign the 700s to its commercial transport jets, and that the marketing department decided that for its first foray, 707 had a better ring to it than 700. The 717 was skipped because the Dash 80, temporarily called the 717, lost its designation when it became an Air Force plane, known as the KC-135.

Boeing has been a beehive of 7-7 activity of late, and a stalwart
Imponderables
reader and Boeing employee, Ken Giesbers, makes sure we’re updated. While the 707, 727, and 757 are currently out of production, the Boeing 777 has proved popular, particularly among international carriers; the 777-200LR Worldliner set a record for the longest nonstop flight ever (from Hong Kong, flying east, to London’s Heathrow Airport).

Next on tap is the 787 Dreamliner, formerly known as the less mellifluous Boeing 7E7. In its continuing game of cat and mouse with the European consortium’s Airbus, the Dreamliner is Boeing’s attempt to launch the most fuel-efficient jumbo jet in the sky.

But the big news from the Imponderables front is that the Boeing 717 is back, at least for a while. After Boeing merged with McDonnell Douglas in 1996, one of the planes it acquired from MD was the 100-seat MD-95, which Boeing re-branded as the 717. While the slightly bigger 737 has been the best-selling jet in history, the 717 hasn’t been competitive, and Boeing has announced that production of new 717s will end this year. You can’t keep track of Boeing’s sevens without a scorecard.

T
he answer to this Imponderable from
Why Do Clocks Run Clockwise?
is as dated as the clothing on
That ’70s Show
. Only geezers probably remember that originally all M&M’s were brown—it wasn’t until 1960 that red, green, and yellow M&M’s were added. The red M&M’s were pulled in 1976 because of a scare about the safety of Red Dye No. 2, even though the dye was never used in the candy. In
Clocks,
we mentioned the color distribution of M&M’s twenty years ago:

I
n
Why Do Clocks Run Clockwise?
, we might have overstated how universal this phenomenon is. Yes, horses have the physiological equipment to sleep standing up, and in the wild, sleeping on all fours could provide for a quick getaway in case they were threatened by a predator.

But new research indicates that horses lie down more often than we suggested. Most horse owners and researchers have observed their horses standing while sleeping, a relaxed, passive posture for them because of the ligament and tendon structure that we detailed. But when horses enter REM (rapid eye movement) deep sleep, their legs often buckle. In the middle of the night, horses usually catch their REM sleep and lie down on their sides for two to four hours at a stretch. If they cannot spread out completely to sleep, a common affliction in stables, horses often lean against a wall or any sturdy object nearby.

The
New York Times
Q&A column tackled this Imponderable several years ago and quoted Dr. Katherine A. Houpt, a physiologist at the Cornell University College of Veterinary Medicine. Although conceding that horses sleep less in the wild, she’s not so sure that they stand for defensive purposes, proposing that it

According to Houpt, when wild horses do lie down, a single horse stays on all fours as a sentry, allowing its compatriots to catch REM zzz’s.

S
peaking of sleep and REMs, it turns out that some mammals are joining fish in the burning-the-candle-at-both-ends game. A team led by Jerome Siegel, head of the Siegel Lab at the Center for Sleep Research at UCLA, reported in 2005 that newborn bottlenose dolphins and killer whales don’t get any shuteye in their first month of life. Perhaps in exasperation, their mothers also forgo sleep during this period.

This finding astounded sleep specialists because the prevailing theory has been that REM sleep is necessary for brain development in mammals, and that hormones crucial for growth are released during sleep. While human babies sleep like, well, babies, and their mothers take every opportunity to catch some sleep, Siegel speculates that whales and dolphins might have developed this mechanism so that the babies can evade predators when they are most at risk. But wouldn’t the same be true of any animal? Siegel proposes that “in the water, there’s no safe place to curl up.”

When older dolphins and whales do sleep, they usually float on the surface of the water or lie on the floor. But these newborns swim continuously, and don’t start sleeping as much as adults until they are four or five months old.

Unlike fish, dolphins have eyelids, so they can close their eyes when they sleep. But dolphins sleep with one eye closed. Sleep researchers have never found any proof that they experience REM sleep at all, and the best evidence is that only one hemisphere of the dolphin brain is experiencing the restfulness associated with sleep.

Just as some have suggested that fish might actually be sleeping (with their eyes open), perhaps whale and dolphin babies might be enjoying some form of sleep that we haven’t identified yet. And just as fish seem to go into a trance when the water is dark, maybe these marine mammals indulge in some brief periods of sleep in the midst of swimming. Unlikely, but possible.

W
e solved this Imponderable in
When Do Fish Sleep?
, but almost twenty years later, scientists have just discovered why crickets aren’t going deaf. If you think cricket chirping is loud, you are right—their singing can reach 100 decibels (louder than an idling bulldozer, slightly quieter than a leaf blower at full blast), enough to cause hearing damage to humans. How can the tiny cricket’s nervous system hold up to the barrage?

Humans are not deafened by their own screaming because of a phenomenon known as “corollary discharge signaling.” Neurobiologists have long maintained that when your brain signals to the muscles in your mouth and throat to speak (or scream), a copy of that signal is sent to your auditory system, so it can prepare to withstand the noise.

Two zoologists from the University of Cambridge in England, James A. Poulet and Berthold Hedwig have identified the two neurons in crickets that carry corollary signals to the auditory center. They discovered that at exactly the moment at which crickets move their forewings to chirp, their auditory neurons are inhibited, so the crickets do not respond as sensitively to the noise.

In a
New York Times
article about the discovery, reporter Henry Fountain asks Poulet what implications the study might have for humans:

For a short but more technical explanation of Poulet and Hedwig’s work, see http://www.zoo.cam.ac.uk/zoostaff/hedwig/discharge. html.

W
e answered this Frustable in
When Do Fish Sleep?
The consensus almost twenty years ago was that this “photic sneeze response” was likely a hereditary condition, caused by the sun (or other bright lights, such as from lamps) irritating the nerves that control sneezing. At the time, we contacted Winnipeg, Manitoba optometrist Steven Mintz, who had been a valuable source to us in the past. He couldn’t help us with an answer then, but ever vigilant, he has since mailed us an article called “The Photic Sneeze Response: A Descriptive Report of a Clinic Population,” published in the
Journal of the American Optometric Association.

Much to our shock, the article cites the first report of PSR in an English book by W. S. Watson in 1875! But very little hard research has been done on PSR. The three authors of this article conducted the second-largest study ever. They received 367 completed surveys, and 122 ( just under one-third) were from “self-recognized photic sneezers” (at the high range of 25 to 33 percent that we estimated in
When Do Fish Sleep?
). Most of the people did not sneeze every time when looking at the sun. Nearly two-thirds estimated that they sneezed very rarely or, more commonly, only once in a while, when exposed to sunlight. Only 15 percent reported sneezing “almost every time.”

The survey of Doctors Semes, Amos, and Waterbor also confirmed another much-asked Imponderable that we mentioned in our write-up—many PSRs are serial sneezers. When asked how many successive sneezes were caused by sunlight, only 39 percent reported one sneeze. Forty percent claimed two sneezes and 28 percent answered three. Two percent of the respondents bragged that they typically sneezed nine or more times in a row! The vast majority of the serial sneezers took zero to twenty seconds in between sneezes, but a few claimed that there was usually at least a minute between sneezes.

While most PSR subjects started “sunlight sneezing” at a young age, only 13.6 percent reported sneezing before the age of ten. Ten to fourteen was the most common starting point, and more than 10 percent said that PSR didn’t start for them until after the age of thirty. These findings indicate that while there still seems to be a hereditary predisposition to PSR, it may also be an acquired trait. Smokers seem to have a slightly elevated chance of acquiring PSR, but the most likely candidates of all: folks who have a deviated septum.