Wikipedia:Reference desk/Archives/Science/2016 October 7

= October 7 =

Age and Height: 2 to 3 Yards Tall
How exactly does one's life expectancy decline with height, for people who are between two and three yards tall (i.e., between 1.8 and 2.7 meters) ? Or, alternately, what is the tallest human height achievable, so that the person in question might have a `very big chance` of living into their early 70s, or late 60s ?

I ask this because:


 * the tallest credibly-documented humans who have ever lived were less than 3 yards (~2$3/4$ meters) tall.
 * no human above 8 feet (~2$1/2$ meters) has lived more than about 55 years, with those towards the end of the spectrum dying in their 20s or 30s.
 * even among those (slightly) below 8 feet (2$1/2$ meters), only a (significant) minority lived into their 60s or 70s.
 * the tallest human who did not suffer from gigantism reached a natural height of almost 7$2/3$ feet (~2$1/3$ meters), and lived into his early 80s.
 * people up to about 6$3/4$ feet (2 meters) seem to have average life spans.

— See list of tallest people.

I therefore logically assume that the cut-off point for an `average` or `convenient` life span (65 to 75 years) is somewhere in between 7 and 8 feet (2.15 and 2.45 meters). But where exactly ? — 86.127.61.109 (talk) 19:46, 7 October 2016 (UTC)


 * See cum hoc. There may very well be a correlation between height and life expectancy, but this does not imply a causal relationship between them. Tevildo (talk) 21:10, 7 October 2016 (UTC)


 * The fact gigantism and acromegaly create severe health problems has already been well established. — 86.125.206.37 (talk) 23:35, 7 October 2016 (UTC)


 * Correlation alone may not prove causation, but we have other elements here:


 * 1) First, the order is quite clear. The height occurs first, then the premature death (would be difficult to occur in the other order, wouldn't it ?).


 * 2) Second, we know some of the mechanisms by which height may cause early death, such as more strain on the cardiovascular system.


 * Of course, we can also argue that a third factor causes both, like the genetics that lead to gigantism, but that rather seems like splitting straws. StuRat (talk) 22:17, 7 October 2016 (UTC)


 * Your first point is great demonstration of Post hoc ergo propter hoc. You may also be interested in learning a little about proximate and ultimate causation. SemanticMantis (talk) 22:26, 7 October 2016 (UTC) SemanticMantis (talk) 22:23, 7 October 2016 (UTC)


 * Again, it's only a logical error if that is the only link in the chain of causation. When the chain is complete, it's no longer a logical fallacy. StuRat (talk) 22:48, 7 October 2016 (UTC)

There is a very strong negative correlation between height and lifespan. This holds true across ethnic groups and over time (at least the last 90 years). You can read that article to come some specific numbers. Someguy1221 (talk) 22:19, 7 October 2016 (UTC)


 * Thank you. I am already well aware of that article, as well as others in the same vein. I was hoping for something a bit more precise and substantial. — 86.125.206.37 (talk) 23:35, 7 October 2016 (UTC)

How same elements form different compounds
In a nutshell, how exactly just three chemical elements like carbon, hydrogen and oxygen and, broadly, CHON can form such a vast array of chemical substances with different properties? For example, lactose, malic acid and testosterone which are formed only by carbon, hydrogen and oxygen. Aside from different numbers in molecular formulae, is it chemical bonds that make lactose a lactose, etc or it's something else? And where do such compound-forming factors come from? --93.174.25.12 (talk) 22:15, 7 October 2016 (UTC)


 * Structure is a major factor. Just as you can assemble Legos to make many different things, the same is true in chemistry.  For example, the same chemicals can spiral to the right or left, and this results in different properties.  See levolorotary and dextrorotary. StuRat (talk) 22:22, 7 October 2016 (UTC)


 * You may wish to read Isomer and Chemical compound, although you may be just confused by the latter! Combinatorial chemistry give a clue as to why there are so many compounds. Graeme Bartlett (talk) 12:41, 8 October 2016 (UTC)
 * Already with CHON you have a great deal to work with. First, you have the basic skeleton, the arrangement of the carbon atoms, which can loop or branch. Some of these may not be C–C single bonds, but C=C double bonds or C≡C triple bonds which act as concentrated regions of negative charge that can react with electron-seeking electrophiles. Hydrogen atoms are added so that every carbon makes four bonds. But once you add O and N into the picture you can add an untold number of functional groups to give a molecule its personality, so to speak. (For this reason C=C and C≡C are also considered functional groups.) For example, you can have C=O (the carbonyl group), where the oxygen has a higher electron density, and so the carbon bears a partially positive charge and can be attacked by electron-rich nucleophiles. Or you can have hydroxyl (–OH, gives alcohols; easily forms hydrogen bonds), alkoxy (–OR, gives ethers), amino (–NH2, gives amines, usually smelly), nitro (–NO2, famous for exploding), carboxyl (–CO2H, gives carboxylic acids, from which come the the sharp flavours in many fruits), amide (–CONH2, most famously in proteins). There's more, but these cover your examples and already go beyond them. As for how all of this works, much of it boils down to the differing electronegativities of C, H, O, and N. Double sharp (talk) 14:39, 8 October 2016 (UTC)


 * Oh, boy, this one is a doozy. Damn decent question to ask, though.  Part of it is that CHON are low-numbered common elements.  Look at nucleosynthesis - they're some of the absolute top abundance elements in the cosmos.  Hydrogen was around as soon as nuclei became stable; CNO are some of the lightest elements that can be fused in small and large stars.  This matters because the chemistry we know is tinged by what we have available to play around with.  On the other hand, some elements (like He) are common but just don't play well with others.  The same is true of many alkali metals that mostly turn up in boring salts.
 * Very true – I forgot to mention that. Boron has an amazingly rich chemistry that rivals carbon, I daresay the richest in the inorganic realm, but stars cannot effectively produce it and so there's just not enough of it to play around with. Thus, no boron-based life. (Though there are other reasons, one among them being that boranes have a tendency to explode in an oxidising atmosphere like Earth's today.) Double sharp (talk) 14:05, 9 October 2016 (UTC)
 * Maybe, but the early Earth had a reducing atmosphere, not an oxidizing atmosphere as it does now, so that would not have been a barrier to boron based life if boron had been available in sufficient quantities. Given that production of oxygen was caused by changes to life itself which then evolved to cope with it there is no reason to suppose that boron based life would not do the same, or perhaps would not have created the oxygen in the first place. SpinningSpark 14:55, 9 October 2016 (UTC)
 * That's very interesting! Thank you! Double sharp (talk) 04:08, 10 October 2016 (UTC)
 * There's something to be said for the first period over the others also. I think it tends to like multiple bonds more than the others.  In some ways this makes for simple-looking compounds (N2, O2) that wouldn't be formed by phosphorus or sulfur.  But it also leaves us with conjugated double bonds and lots of other fun stuff.
 * This is actually a rather well-known observation called the double bond rule. For example, carboxyl groups (C=O) are very common, yet silanones (Si=O) are of only fleeting existence. You get restricted rotation around C=C double bonds, but not about Si=Si bonds because that pi bond is weak and easily broken. Admittedly, this is of dubious truth for P and S. Double sharp (talk) 09:50, 9 October 2016 (UTC)
 * Definitely electronegativity is part of it. The pure geometry of the Schroedinger equation translates into an idea that there is a "shell" of eight electrons to be added between helium and neon and that all the elements, regardless of their nuclear charge, are being pushed toward trying to get that shell filled.  Yet ... CHON doesn't actually include strongly electropositive elements.  C and H are sort of neutral, N and O are more electronegative but not so much as fluorine.  Still, that doesn't mean you can't get a positive charge, since -NH2 can end up as -NH3+.  When electronegativity is extreme (-COOH, which can be stable as just -COO-) you can get a negative charge.  It's kind of finicky - oxygen has extra electrons that could take an H+ just like a nitrogen, but it rarely will do so; -OH2+ is rarely seen even in transition structures.  The extra H's are also critical for hydrogen bonds.  We can make strongly hydrophilic compounds by having some components that have a partial charge on them and/or engage in hydrogen bonding, and hydrophobic compounds that are simply symmetric (CO2) or unadorned with electronegative components (CH3-CH2-CH3).


 * Higher order complexity is also a part of it. The difference between starch and cellulose seems to have to do mostly with how they crystallize and self-associate, AFAIK.  Proteins are all about secondary structure, without which they'd just be a bunch of amino acids in a row.


 * Life is also a part of it. There's nothing particularly exceptional about testosterone except that most people have an androgen receptor.  For those who don't, it's pretty much just another random collection of carbon rings. Wnt (talk) 18:50, 8 October 2016 (UTC)


 * The number-one thing is that carbon can bond in a bunch of different ways to itself and to other elements, because of its four valence electrons. Also those bonds are fairly stable. As our carbon article says, there are more compounds containing carbon than compounds of all the other elements combined (excepting hydrogen, because many hydrogen-containing compounds also contain carbon). Beyond that the different properties of organic compounds come from the overall molecular structure. The individual atoms aren't the determining factor; the important thing is that those atoms can be arranged in many different ways, similar to how you can build a bunch of different structures with the same bricks. When you get up to the size of proteins, whole amino acids can be changed often with little impact on the protein's structure or function—although not always! The article carbon-based life may be of interest. --47.138.165.200 (talk) 00:47, 9 October 2016 (UTC)


 * This is a good point - with either boron or nitrogen, there are effectively fewer valence electrons. But the difference is more pronounced than simply 3 vs. 4 - with nitrogen, it takes extreme pressure to permit something like tetranitrogen to form.  As that article explains, there is a difference between nitrogen, where a triple bond is more stable than three bonds, and carbon, where the reverse is true.  That said, I really don't know how interesting nitrogen chemistry could get at extreme pressures, such as in the atmosphere of a gas giant, so I'm not totally sure this isn't a parochial viewpoint. Wnt (talk) 14:25, 10 October 2016 (UTC)
 * In general, the problem is that N2 (g) has a very strong N≡N bond (as you said), and that the HOMO/LUMO gap is huge. Furthermore, there is no polarity and hence no opportunity for nucleophilic or electrophilic attack: hence the isoelectronic CO, CN−, and NO+ are substantially more reactive. You really do need high temperatures for it to react (there's a reason why it took so long to produce ammonia industrially).
 * Boron, on the other hand, is electron-deficient. It is really "one of a kind" in that it is the only non-metal which has less than half an octet. Essentially, what happens with B is that it is small and has a high ionisation energy, and has similar electronegativity to C and H (which is good for hypothetical boron-based life). Being [He]2s22p1 makes it predominantly trivalent. But since there are only 3 electrons to contribute, but 4 orbitals may be filled (s, px, py, and pz), it has unique properties such as being a Lewis acid (accepting electron pairs into the empty orbital) and for multicentre bonding. It also is very reactive with oxygen (so boron-based life had better figure out a way around that, or use the extensive borate chemistry to its advantage). Finally, boron is pretty small, so that it can form interstitial metal borides. As a result, you can almost think of five types of B compound that are really different from each other: metal borides; boranes and derivatives; trihalides, adducts and derivatives; oxo compounds; organoboron and boron-nitrogen compounds. Double sharp (talk) 15:35, 10 October 2016 (UTC)

breeds of cattle and their milk
Are there breeds of cattle whose milk are known to be better tolerated by humans who are lactose-intolerant? Are there any identified strains of cattle that are much like cattle from ancient times, and has the "tolerablity", if that's a word, of their milk been studied? Thank you!144.35.45.53 (talk) 22:27, 7 October 2016 (UTC)


 * That would imply either a lack of lactose or the presence of lactase, the enzyme needed to digest lactose, in the lactating bovine's milk. Either seems unlikely.  Here's a comparison of lactose content by each cattle breed, and, as you can see, there's little difference between them: .  However, the lactose content does go up the longer a pig lactates, and protein goes down.  In a Meishan pig it seems to have over 2.5 times as much lactose 3 weeks into lactation than at the start.  So, if the same is true of cows, that might help, especially if the object is to get your protein from milk (I calculate you would get 13.8 times as much lactose from a Meishan pig at 3 weeks into lactation, to get a given amount of protein from the milk, as you would on the first day of lactation).  But just adding lactase to the milk is a simpler fix.  StuRat (talk) 22:29, 7 October 2016 (UTC)


 * I found this while searching, but they seem to be conflating lactose intolerance with milk allergy, which is entirely different. As you're searching, be aware that the two concepts are often confused in the popular consciousness (including this). If the source starts talking about problems with proteins, they're almost certainly discussing the allergy. Incidentally, if you are interested in milk allergies, the milk of most other mammals tends not to affect sufferers as cow milk contains casein (which is the actual trigger, see references in that article). As far as the actual question goes, you might find this of interest, though it involves genetic modification rather than a breed developed the old fashioned way. Matt Deres (talk) 04:03, 8 October 2016 (UTC)