Wikipedia:Reference desk/Archives/Science/2009 March 8

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March 8

King Faisal's Dream

Bodies of 2 Sahaba removed from the grave in iraq ,This event held ,when king Faisal see a dream about this .[1] Can any body tell me about facts .How this event was happened .Any thing which we can not explain by every day science about this event. —Preceding unsigned comment added by True path finder (talk • contribs) 01:40, 8 March 2009

Well, if you follow the links back to the source, you arrive at this: http://www.themajlis.net/Sections-article139-p1.html - which is from some journal called "VOICE of ISLAM" published in South Africa. There appears to be a bunch of articles in every edition - each containing a rather sketchy description of some kind of miraculous Islamic happening (of which there appears to be a very great number). In this case, the entire text is:

"SHAHEED SAHAABAH

In 1932, the Sahaabi Hadhrat Huzaifah (radhiyallahu anhu) in a dream instructed king Faisal of Iraq to relocate their graves elsewhere since water from the river was seeping in.

The king issued orders for the bodies of Hadhrat Huzaifah (radhiyallahu anhu) and Hadhrat Jaabir Bin Abdullah (radhiyallahu anhu) to be exhumed. The exhumation was done in great style and pomp. Thousands of people witnessed the event. When the bodies were removed, it seemed as if they were buried o­nly a couple of hours ago inspite of the lapse of almost 14 centuries. The bodies were fresh and glittering with Noor.Thousands witnessed the exhumation and many non-Muslims who were present embraced Islam."

This exact same story (word-for-word) occurs in some other places such as this.

So what we have here is that in 1932 King Faisal of Iraq claims to have had a dream. OK - there were two kings of Iraq named Faisal. Faisal I of Iraq died in 1933 - Faisal II was born in 1935. So it must have been Faisal I. There is no mention of this miraculous event in our article about him - so we first have to wonder where is the evidence that he claims to have had the dream. We'll never know whether he truly DID have it - because even if we have primary evidence, it's just his claim. There is no scientific evidence that he truly did have the dream.

Then we are told that as absolute monarch - he demands that some bodies are dug up, with great ceremony - and we're told that the bodies are in surprisingly good condition considering their claimed age. Well, firstly, how do we know that these really were the right bodies? If they'd been there for 14 centuries - then records of their precise burial location would have to be sketchy at best. So if Faisal wanted to do this to make himself seem more self-important, he could EASILY have framed the whole thing. Had two recently deceased men buried at dead of night - then invited an entire crowd to come see them dug up again just hours later. His motives for doing this would have been strong. He was very interested in uniting the people and forwarding a 'pan-arab' agenda - and being told stuff in a dream and then pulling off a miracle could easily be his idea for making that happen! We're told that a ton of people came to watch - so evidently there was HUGE publicity value here. Given that it happened in the very same year as the independence of Iraq - this would not be at all surprising if he faked the whole thing.

Then there is the issue of whether - even if the event were genuine - did the reporting of the freshness of the bodies get exaggerated in the retellings? Certainly the claims of the intactness of Shaheed martyr's bodies is claimed all over the place (just try Googling the term!) - so this result was certainly expected. Mummification would have been well known in 500 AD when these martyrs are claimed to have been buried - so it's perfectly possible that they were in more reasonable condition than observers might expect - and it's EASY to imagine a simple "Wow! They're amazingly well preserved for a 1400 year old body." to gradually turn into "as if they were buried only a couple of hours ago" after many re-tellings and hype.

"Noor" is an arabic word meaning "light" - so the bodies were "glittering with light". I'm not sure what that proves - maybe they were still wet from the ingress of river water?

So that's the range of possibilities. Anything from a 'miracle' to a corrupt politician working the minds of the public to meet his ends of unification to a simple progressive exaggeration of a somewhat surprising - but not earth-shattering event.

The scientific view is that we don't overturn all of science and suppose a 'miracle' if there is a simpler explanation. I think we have two explanations that are each VASTLY simpler than that some godlike or miraculous event magically preserved bodies and caused a king to have a dream.

Hence, I have to say to our OP - categorically: No. Science cannot not regard this as anything in any way out of the ordinary - because there are MUCH simpler explanations than those claimed in the "Voice of Islam" article. If a proper, controlled scientific examination of the bodies had been possible - then perhaps some other conclusion might be arrived at - but "Extraordinary claims require extraordinary evidence" - this is most certainly an extraordinary claim...and there is essentially zero evidence - so science isn't going to jump to that conclusion.

SteveBaker (talk) 07:28, 8 March 2009 (UTC)

When saints were exhumed hundreds of years ago in europe by monks, it was also sometimes reported that they looked as if recently buried. I recall there might be a scientific reason for this, or it could be that since the abbeys earnt a lot from pilgrims, they may have distorted that facts one way or another. 89.243.46.238 (talk) 14:04, 8 March 2009 (UTC)

It's the same deal though. When the people doing the exhuming have a stake in the results - you can't expect a balanced view of the ensuing event. SteveBaker (talk) 17:02, 8 March 2009 (UTC)

Excellent response by SteveBaker, who, however, did not emphasize the most obvious explanation. Is "The Majlis (the Voice of Islam)" the most reliable source, or might one consider its articles to be on the level of the fictional accounts one finds in supermarket tabloids? Is there any independent source for this story which, supposedly, occured 77 years before the posting? Without one, we can doubt this tale from top to bottom.

Let us consider three of the statements.

(1) "...the lapse of almost 14 centuries." But 1932 was 1300 AH, and we're being told that they'd been buried for almost 1400 years. The numbers don't add up.

(2) "The exhumation was done in great style and pomp." What does this even mean? What kind of "style and pomp" can be involved with digging two holes in the ground? They had a marching band? A catered banquet brought in from Paris and Vienna? Planes flying overhead in the Missing Man formation?

(3) "... many non-Muslims who were present embraced Islam." Sure, there must have been hundreds present as Muslims are always delighted to have kafirs around for their religious events. ("Hey, honey, look we got an invitation to the exhumation!" "Wow, let's bring the children and really make a day of it!") ... And running it the other way around: if some RC bishop claimed he had a dream that two saints' should be disinterred from his cathedral, and they were 'fresh,' would Muslims convert to Christianity on the spot?

---

Ased.

---

Well I was still looking for the so called "Scientific Fact" above only to find opinions. BUT no opinions as to the cause .... what can cause a body to remain 'fresh' (not just preserved) for even a decade doesn't matter the person was Jew, Muslim or Christian.

One has to remember that it was 1930s not 2010 so the point of having it examined (with what and for what) to find the cause does not seem like a genuine argument.

Sure the writer must have exaggerated (e.g. pomp & style .. South African English) but I can understand the point he is trying to make.

Graves of 2 well knows companions of the Prophet Muhammad were to be dug up and relocated (not going into reasons as to why or how come), so there has to be justification (not going into True or False)and with reasoning and hence a kind of show ... for reasons that should be obvious (can you guess without mongering angry hateful remarks) .. So that answers what the writer called pomp and style.

I don't know the exact story, the sources of stroty, facts, but do know that in every exaggeration there is some truth and people do exaggerate.

Tim was born in 1980 and in 2008 he was alomst 30 years old --- sounds like a correct statement. SO 1400 years is a common term used in this century to describe the era of early islam ... it could be 1200 or 1300 or in between, so lets not go into it was 1395 or happened in 1210 and six months ago not 1400 years ago

MY POINT.. a lot of BIAS with some anger and maybe hate camouflaged under so called scientific argument, with questioning as to why no effort been made to make similar Christian stories look (attempt atleast) silly as well. And by the way the word Kafir only means disbeliever

Crystal structures in Anza Borrego (California) State Park

End view of lines of crystals

A few days ago I noticed these crystals embedded in a stream bank in Anza-Borrego Desert State Park in California. At first I thought they were shells, as the area is the former delta of the Colorado River. They're 6"-12" in diameter and located in a dirt/sand matrix. The bank is 12'-15' high.

The light-colored crystals faces can be seen arranged in several lines in the accompanying picture, especially in the upper-right. While there was stratification of the dirt/sand, there didn't seem to be any major difference in the composition/texture of the strata near the lines of crystals. Just these things in (very dry) mud.

Section of crystal

There were several pieces that had fallen from the bank. The one in the picture is (ahem) fresher than the others. Each was roughly cylindrical. The exposed parts of the crystals in the bank were nearly horizontal and roughly parallel, although only a few inches of each were exposed. It is a natural area with a high tourist load, so (ahem, much) excavation was out of the question.

There is no obvious ring structure such as found in stalactites, except for the outer 1/4" or so which is darker.

I asked a ranger at the visitor center and he started going off about "concretions". So I stopped asking.

What process would lead to formation of such crystals in a river delta? Is this a form of caliche?

Thanks. Saintrain (talk) 01:53, 8 March 2009 (UTC)

I'm just guessing here - but it looks to me like a chunk of fossilised tree. If the tree were to be surrounded by the sand/sandstone up to some depth - then gradually, a few inches of the wood in the trunk would be dissolved away by water soaking through it - and replaced by whatever material is in these rocks. I think you could probably describe that as a 'concretion' - and it would certainly explain the smooth shape. SteveBaker (talk) 06:47, 8 March 2009 (UTC)

I'm with the ranger on this, look like concretions to me, the area is well known for them apparently [2]. Concretions can be extremely smooth and regular, our article has some nice examples. Mikenorton (talk) 10:47, 8 March 2009 (UTC)

I agree with Mikenorton that they appear to be concretions. The way that the exposed ends appear to be weathered away in the outcrop makes me wonder whether the cementing material mightn't be something more water-soluble than the more usual calcite—gypsum, perhaps? Deor (talk) 20:09, 8 March 2009 (UTC)

The first time I scrolled past the photo today I thought it was a pork pie - I had to stop and look more closely. Just now I scrolled past, and thought of scotch pies. Must be hungry. Gwinva (talk) 06:23, 9 March 2009 (UTC)

Thanks all. My apologies to the ranger. I had confused concretion and conglomerate. The rows of horizontal cylinders still intrigues me. Plant roots as nuclei, maybe. Saintrain (talk) 15:04, 10 March 2009 (UTC)

I think it probably just reflects how water flowed through weaknesses in the bedding planes of the surrounding material. See the "Elongate concretions" section of the "Concretions" article. Deor (talk) 13:11, 11 March 2009 (UTC)

destroy the copper

BSM(=bismlah alrahman alrahim). We want to destroy a copper screw in a brass plate, fast with a chemical reagent and without damaging to brass. what is the way?unsigned post by 94.101.128.70 (talk) 05:38, 8 March 2009 (UTC)

• What's "BSM"? One of these? --Anon, 20:31 UTC, March 8, 2009.

Since brass is an alloy of copper and zinc - any reagent that would dissolve the screw would also dissolve the copper in the brass - thereby greatly damaging it. So although I'm not a chemist - I'm going to go out on a limb and predict that it's not going to be possible. SteveBaker (talk) 06:41, 8 March 2009 (UTC)

EC.: Beat me to it. Can't you just take a drill and drill it out? 76.97.245.5 (talk) 06:50, 8 March 2009 (UTC)

There are tools specifically for this, see drill bit#Screw extractor. SpinningSpark 09:34, 8 March 2009 (UTC)

Yeah - and they actually work...about one time in three! But if this genuinely is a copper screw as opposed to a copper-plated steel screw - then it'll be very soft and prone to shearing off. I'd be very surprised if a screw extractor would get it out without snapping it. By all means give it a shot - but I'm pretty sure you'll wind up drilling it out. But this must be a pretty special situation - copper is not a metal usually used for making screws. Screw#Materials_and_strength doesn't mention copper being used for making screws (because, mechanically, it makes no sense!). Would our OP care to divulge what exactly this is all about? SteveBaker (talk) 17:30, 8 March 2009 (UTC)

I'd guess it's a copper-based alloy; some of them, like some bronzes, are the same color as copper but stronger. Since the brass and the bronze are both mostly copper, the problem that the same reagents will attack both still applies. I presume a penetrating oil like WD-40 has already been tried? Then I think you're stuck, no pun intended, with a mechanical approach. --Anon, 20:34 UTC, March 8, 2009.

It will also help if you know the alloy numbers[3] of each material. Machine copper is weird stuff, I think it's only something like 50% or 70% copper. A screw made of "copper" would most likely be made of machine copper. It's designed not to be so soft, so that it can hold things like a screw-thread. Normal copper sort of sluffs off like playdoh if you try to mill it or work it in any way. Nimur (talk) 03:57, 9 March 2009 (UTC)

For example, this company actually classifies CDA936 as a "bronze" (though I'm pretty sure I've seen it marketed as a copper - it's been awhile since I did anything close to the metalshop). They specifically state that it is particularly resistant to acid and chemical corrosion. Nimur (talk) 04:14, 9 March 2009 (UTC)

By the way, BSM is Basmala. Polypipe Wrangler (talk) 11:58, 9 March 2009 (UTC)

A solution of vinegar and salt will remove copper oxide quickly, and probably also etches copper very slowly. It might be that it would attack oxide of both copper and brass that is part of what is making the screw get stuck, and help you get it loose while also not etching brass much.Ccrrccrr (talk) 15:00, 14 March 2009 (UTC)

Strange Lamarckian studies...

I was recently listening to an episode of BBC's In Our Time on Trofim Lysenko (I have a weird fascination with communist agricultural policies, whether they be Chinese or Soviet). In that very interesting episode, they go on a short tangent about how very recent studies have indicated that some aspects of Lamarckism/Lysenkoism might actually be real (they also made it perfectly clear that Lysenko was a nutcase, it's not like they were defending him). They talked about how people who lived through famines tended to pass some sort of genetic imprint of that famine (as an example they said that the grandchildren of people who had lived through a famine in Holland were shorter than the average person).

Is this true? Can someone link to one of these studies, or direct me to the appropriate Wikipedia article? I mean, this seems shocking to me, and I would like to find out more about it. Belisarius (talk) 13:30, 8 March 2009 (UTC)

Check out Epigenetics. --98.217.14.211 (talk) 14:48, 8 March 2009 (UTC)

(After EC) You're probably hearing about epigenetic changes that can be transmitted transgenerationally (see [4]). These examples are quite different than classical Lamarckism or Lysenkoism, which postulated that adaptive changes acquired by an individual could be passed down (the classic example being the giraffe, who stretches its neck by reaching for higher leaves and then "passes down" a trait for a longer neck to its offspring).

Epigenetic changes, in contrast, do not change the DNA sequence but rather alter the characteristics of gene expression (the best example being methylation of certain DNA nucleotides) that can persist across many cell divisions (and in some cases across generations). In the example I linked to, it is shown that famine conditions in the 1940's led to DNA methylation changes -- within the growing fetuses -- that persisted into adulthood. There's quite a lot of research on the effects of in utero nutritional exposure and later onset of obesity, diabetes, etc. but less is known about the transgenerational persistence of these traits.

The epigenetic changes reported in the "famine offspring" could be adaptive if the next generation became slighly smaller because of the altered gene expression and were therefore able to survive better in the famine conditions. However, this is hardly classical Lamarckism... it isn't as though individuals exposed to famine changed genetically in order to be able to survive the famine and then passed on those genetic changes to their offspring. --- Medical geneticist (talk) 15:17, 8 March 2009 (UTC)

I don't understand how "the grandchildren of people who had lived through a famine in Holland were shorter than the average person" proves anything other than an entirely normal, predictable evolutionary pressure. Prior to the famine, some people were taller than average and others were shorter than average. If we believe that height has a genetic component then the famine strikes - the tall people need more nutrition so die off in larger numbers than small people. The "tall" gene is selected against and the "short" gene survives in larger numbers. Guess what? Two generations later, you have kids of below-average height. Why the heck do we have to invoke Lamarkism to have this work? SteveBaker (talk) 17:42, 8 March 2009 (UTC)

Can you point to any evidence that tall people die disproportionately during famine, or is that just conjecture? On the flip side, recent experience suggests height increases within 1-2 generations of shift to higher-calorie diet, and I don't think that's because increases in calorie intake kill the short people. --Scray (talk) 17:58, 8 March 2009 (UTC)

Well, the taller you are the more calories you need, so it makes sense that taller people would do less well in famines. --Tango (talk) 18:34, 8 March 2009 (UTC)

I understand the basis of the specific assumptions being made. It's also possible that tall people would be able to compete effectively for food that is in short supply, depending on how food is distributed. So, rather than make these assumptions, I was wondering if this is anything more than speculation. --Scray (talk) 00:03, 9 March 2009 (UTC)

Yeah - please don't go away with the idea that I'm saying that it's DEFINITELY evolution. I'm merely pointing out that evolution could quite easily produce this effect. There are any number of other possible causes (maybe people wore shoes with thicker heels before the last remaining "thick shoe heel tree" died during the famine and now everyone just seems shorter!!)...I don't know that...I'm just trying to point out that we DO NOT have to assume the highly discredited theories of Lamarckism/Lysenkoism are true as a result of this finding about Dutch children. There are much easier reasons and extraordinary claims demand extraordinary evidence...which this finding is not. SteveBaker (talk) 00:52, 9 March 2009 (UTC)

I also believe it's well established that areas with little food produce dwarf animals, since the smaller versions require fewer nutrients (and the larger ones die off during periods of starvation). There's no reason to think that humans would be immune to this trend. As for people getting taller when there's more food, this probably isn't much due to short people dying, in the short term, but rather because their growth isn't stunted by periods of malnutrition, as it was for their ancestors. In the long run, being taller may have certain evolutionary advantages, such that people would eventually evolve to be taller in the presence of abundant food, but this effect would likely take thousands of years to become apparent. StuRat (talk) 21:08, 8 March 2009 (UTC)

I think we're saying the same thing - it's not clear to me that changes in height over a short period of time would have a genetic basis, but an epigenetic influence might well play a role. --Scray (talk) 00:03, 9 March 2009 (UTC)

Steve, I'm fairly sure they would only conclude it is an epigentic effect if the genome appeared to be basically unchanged but the expression of the given genes it in was affected. That's what epigenetics is about. It is not Lamarckism and it is not woolly-mindedness. Check out the article. Real chemistry and genes and everything. --98.217.14.211 (talk) 22:16, 8 March 2009 (UTC)

Responding to Scray's last: In the mid-19th century, the average height of Frenchmen was less than it was in 1800 despite improved nutrition. Napoleon barely passed the height requirement in the French Army, and such a large percentage of taller young Frenchmen were killed in the wars from 1879 to 1812, thus siring less children, that there was a noticable shortening in the next two generations. B00P (talk) 05:30, 9 March 2009 (UTC)

Why do cancers seem to have purposeful ways of spreading or resisting death, yet cannot have evolved?

Cancers do not have generations so cannot have evolved, yet they seem to exhibit purposeful 'behaviour' which promotes their spreading in the body (see for example http://news.bbc.co.uk/1/hi/health/7813072.stm ) or resisting anti-cancer treatment. Why is this, what is the reason? Is it perhaps just an illusion, rather like a chess computer that simultaneously plays moves at random with millions of skilled opponents, so that those very few games which it wins seem to be the result of cleverness? Or what? 89.243.46.238 (talk) 15:56, 8 March 2009 (UTC)

The trick is in your very first phrase. Cells within a tumor divide, and so there are 'generations' of malignant cells. Many of the mutations which permit uncontrolled cell division also inhibit or disable the cell's mechanisms for detecting and repairing DNA damage. Consequently, every time a malignant cell divides, there are copy errors: additional mutations.

Many of these mutations will have no effect or will render the daughter cell less fit for its environment, but a few will aid the survival of the cell. External selection pressures – the body's immune system, chemotherapeutic agents, etc. – will encourage the survival and proliferation of cells best able to resist those challenges. The parallels with species evolution are evident.

We have an article at Somatic evolution in cancer which goes into the matter in much greater depth and takes a more technical approach. TenOfAllTrades(talk) 16:15, 8 March 2009 (UTC)

Thank you for the explaination, now I understand. 89.241.34.62 (talk) 17:31, 8 March 2009 (UTC)

Also note that, while we think of cancer as a disease people sometimes get, we probably all have multiple cancers inside us all the time. However, the vast majority of them aren't very efficient at spreading, and are easily dealt with by our immune systems long before they become noticeable. One piece of evidence for this is the case of the bubble boy, who lacked an immune system. When he receive a bone marrow transplant from his sister, this resulted in hundreds of cancerous tumors as a result of her Epstein-Barr virus. However, his sister showed no signs of cancer. It's logical to conclude that this virus also caused as many cancerous tumors in her, but which were wiped out immediately by her fully functional immune system. StuRat (talk) 20:59, 8 March 2009 (UTC)

Excellent answer. It's also worth note that we consider some extremely non-malignant cancers "normal," like warts. The virus that causes them belongs to the same family of viruses that cause a few different types of cancer. arimareiji (talk) 22:10, 8 March 2009 (UTC)

A lot of the reason cancer is so difficult to treat isn't that the cancer cells are particularly adept at evading drugs, but that it's really bloody difficult to "hit" the cancer cells without hitting the normal ones. An explanation of the nature of drugs which kill cells might also help in understanding. If you're designing a drug to kill the disease-causing cells (foreign or malignant) in a patient, you have to make sure it's something that won't kill the good cells too. To use a crude analogy, think of it as if you were a police sniper - you can only shoot at parts of the bad guy that are exposed; you can't hit the hostage.
This is relatively easy for antibiotics, because there are huge differences between bacteria and human cells. There are a lot of cellular mechanisms in bacteria which don't exist in human cells, or are so radically different that a drug which stops XYZ process in bacteria won't have any effect on XYZ process in human cells.
But almost all of the cellular machinery is exactly the same for normal human cells and cancerous human cells. You can target cells which are rapidly dividing, but then you'll hit hair cells just for starters (one common side effect of chemo is for hair to fall out). You can target the out-of-control enzymes, but then you'll wreak havoc on general metabolism. And so on.
Usually, the only hope chemotherapy offers is to kill the vast majority of the cancer cells and hope the body will recognize and kill the rest. In my personal opinion, the only real hope for a long-term treatment for aggressive cancers is to help train the body to more easily recognize the cancer cells so it can kill them. Some therapies based on this are already in the works. (Full disclosure: I own stock in a company which works on one of these treatments. But I bought it after examining it closely and deciding it had high potential, not the other way around. ;-)
Does this help explain, or does it just make it more confusing? arimareiji (talk) 22:10, 8 March 2009 (UTC)

Rather than anthropomorphizing ("particularly adept at evading drugs", and the OP's "purposeful"), which is quite common and understandable, it might be more accurate to describe cancers as genetically unstable, large in population size, and therefore highly diverse. As a result, maneuvers that are reliant on genetically-determined traits (such as drug transport and metabolism) are unlikely to kill all cancer cells. Combine that with continual growth, and relapse becomes likely, without ascribing any organized intelligence or intent to the cancer cells. I don't mean this to be criticism - it's just a good habit to consider the process as it is. --Scray (talk) 22:39, 8 March 2009 (UTC)

Some people, led by Leigh Van Valen, have proposed that some cancers cells have evolved sufficiently to be classed as a new species (though most disagree): Helacyton gartleri. Rockpocket 02:05, 9 March 2009 (UTC)

Also of note here is the propensity of cancer cells to overexpress the genes for the ABC transporter, which seems to be a natural mechanism co-opted to pump anti-cancer drugs right back out of the cell; and the recently developed concept of cancer stem cells. These are cells that have escaped the normal controls on division frequency and genetic integrity, and continue to divide to produce the continuing stem cell and a "daughter" cell. The continuing stem cell line is already genetically compromised (by definition) and is thus prone to further genetic mutations. To that degree, cancer stem cells constitute a rapidly evolving population subject to selection pressure == evolution. See also The Selfish Gene - everything wants to survive.

And of course there is Devil facial tumour disease, which could conceivably be classed as a new species. Franamax (talk) 02:26, 9 March 2009 (UTC)

HDU

What can HDU stand for, please?

Since you asked at the science desk I'd bet you were looking for high density urethane. These [5] are other options. 76.97.245.5 (talk) 16:26, 8 March 2009 (UTC)

Urgh - our HDU page was a complete mess - so I've written a new one especially for you! Check it out! SteveBaker (talk) 18:39, 8 March 2009 (UTC)

Thanks to 76.97.245.5 for the first answer, and to SteveBaker for the vastly-improved HDU page. Much appreciated.

Doe anybody have the Book introduction to Biotechnogy By Thieman

I need chapter 6 and I don't have the book and I was wondering if anybody could copy the pages on the web so I can look over them and do my assignment for them

It would be most appreciated Mike0078 (talk | contribs)

It doesn't seem to be available for any preview. You might find it at a local library e.g. [6] or

Wikipedia:WikiProject Resource Exchange more specifically Wikipedia:WikiProject Resource Exchange/Resource Request might help. 76.97.245.5 (talk) 16:39, 8 March 2009 (UTC)

Copying them would be a fairly horrendous copyright violation. Not good. Check out the library. SteveBaker (talk) 17:52, 8 March 2009 (UTC)

Copying one chapter is often considered fair use, but I think only for personal use (so you can take it home from the library if it's a reference only copy, for example) - distributing it to someone else would probably be a violation. --Tango (talk) 19:57, 8 March 2009 (UTC)

Interpreting food nutritional value data

In tables which give you the nutrient content of 100 grams of each kind of food, are the numbers based on the only edible part of the foods? Particularly, in the case of fruits, is the "100 grams" number based on only the parts of the fruit that you eat (i.e. no peel, pits, etc)? Or is that 100 grams of fruit weighed intact? --173.49.9.169 (talk) 17:50, 8 March 2009 (UTC)

It's a pretty safe bet that it's based on only the edible portion, and it's also a pretty safe bet that with almost anything except melons the difference wouldn't be significant regardless. With most fruits and veggies, by far the more the better. arimareiji (talk) 21:03, 8 March 2009 (UTC)

Serving size has some info. arimareiji's statement is for healthy people. Individuals on certain restricted diets should consult their physician or dietitian. Those should be able to point you towards reliable information, calculation tables and the like. For unprocessed foods all information should be taken as "averages". Actual content does vary significantly. (E.g. onions grown in some parts are high in Selenium whereas those from parts with selenium poor soils have virtually none.) They don't withdraw a lab sample from each apple before they sell it to you :-)76.97.245.5 (talk) 00:15, 9 March 2009 (UTC)

What are the lower limits for RDA for saturated fat

I've been keeping a record of the amount of fat I eat every day, and as I do not like junk food, am vegetarian, and cook my own food, then I eat very little fat every day. I might not be eating enough. What are the LOWER limits for the amount of saturated and other fats that should be eaten each day please? I've spent a while googling for this information without success. Thanks. 89.241.34.62 (talk) 19:57, 8 March 2009 (UTC)

The USRDA for saturated fat seems to be around 20 grams, but I take that to be a maximum. I'm not sure that there is a minimum requirement for saturated fat. Our Dietary Reference Intake article says the RDA for "saturated fatty acids" is "As low as possible". There does seem to be a minimum for fats, in general, though, but no requirement that any portion of them be saturated. StuRat (talk) 20:43, 8 March 2009 (UTC)

It's quite accurate to say that there is a minimum intake of fat, though that's rarely a problem in Western culture. ^_~ I've heard 10% of calories as one estimate, YMMV. Since fat calories are more "dense" than carbohydrates and protein (9, 4, and 4 kcal/g respectively), that would mean 4-5% of intake per gram. There are specific fatty acids that your body can't synthesize, but they're not saturated. This provides a decent synopsis. Sorry I can't be more specific, but this is already treading on thin ice wrt not asking or answering medical questions. arimareiji (talk) 20:56, 8 March 2009 (UTC)

Nutritional Q's like this are definitely not medical advice Q's. StuRat (talk) 23:48, 9 March 2009 (UTC)

Is This a Valid Concept in Evolution?

When speaking of evolutionary change, often only a single characteristic of a creature is considered. Similarly, only a single external influence affecting a creature is considered. But, of course, there are many characteristics in each member of a species that relate to evolution (fitness to survive), and many external influences have an effect on evolutionary change.

Furthermore, each member of a species is unique. It differs from other members of the same species in many small ways. The totality of the characteristics held in common, the unique characteristics, and external influences, determine a member's survivability and longevity, and hence its direction of evolution. (Long life normally results in more offspring being produced. Members with the most offspring will come to prevail in numbers over other members of the species, and will establish the evolutionary trend. This assumes that at least some unique characteristics are inheritable.)

Each unique characteristic will vary in its potency in relation to longevity. Also, the degree of potency may vary from one generation to the next, or even disappear from a new generation. External influences which affect longevity may also vary in potency from generation to generation. To clarify the principle being described, it will be assumed in this discussion that the potency of a unique characteristic, and the potency of environmental factors, remain unchanged over generations.

For any particular member of a species, the various unique characteristics that aid longevity can be expressed, respectively, by the capital letters A, B, C, …. The unique characteristics that hamper longevity can be expressed by the letters a, b, c, …. The total effect of all unique characteristics (U) on longevity can be expressed as U = A+B+C…. – (a+b+c ….).

Characteristics held in common that affect longevity can be expressed as C.

The external influences that aid longevity can be expressed by the Italic capital letters A, B, C, …. The external influences that hamper longevity can be expressed as a, b, c, …. The total effect of all external influences (I) on longevity can be expressed as I = A+B+C…. – (a+b+c ….).

The combined effect of unique characteristics, common characteristics, and external influences on longevity (L) can be expressed as L = U + C + I.

The above considers only an individual member of a species, and its descendents that breed true. Other members have their own unique characteristics and will have their own survivability and longevity. There will be unwitting competition between members with regard to which member will have the most true-breed descendents. The true-breed descendants of a member that has the highest L will eventually prevail over all other descendants. The descendants of other members will eventually become extinct because they will be in competion for food with increasing numbers of high-L (long-lived, more offspring) members.

Complicating the matter is the fact that unique characteristics, common characteristics, and external influences are not quantifiable in their effect on longevity. Indeed, some of the characteristics and influences would probably be unknown to science. Therefore, while the above formulas express general principles, they cannot give specific results.

A further complication is that nearly all species of living things reproduce sexually. Therefore, species members may interchange any unique characteristics that can be passed on by sexual reproduction. None of the resulting half breeds will have maximum longevity.

Maximum L may be only very slightly longer than other values of L. But over thousands of generations it will make a big difference in the numbers of members that will survive.

A single species member that by chance had an extra long life, and its descendents which inherit that capability, will determine the direction of evolution of the species. Shorter lived members, with their uniqe characteristics, will die out.

With regard to a single member of a species determining the direction of species evolution, I remember reading something about that for humans. The effect is indicated in cells and in the female line of descent. – GlowWorm.

External influences are not inherited, so what you are saying makes no sense. How well a particular organism reproduces depends on how well its inherited characteristics suit the environment it is in and a generous dose of luck. Over a long enough time the influence of luck reduces and those organisms which best suit the environment will prevail over the others. That is evolution. The environment is continually changing (both due to changes over time and due to organisms moving from one place to another), so evolution is a continuous process. One key part of the environment is other living organisms (of the same and different species), which are also subject to evolution, which means you get all kinds of complex interactions making the whole thing rather chaotic and unpredictable. --Tango (talk) 23:42, 8 March 2009 (UTC)

I did not say external influence is inherited. I said it affects evolution. Also, earlier on this thread I mentioned that other living things may be considered part of the environment. – GlowWorm.

You said "A single species member that by chance had an extra long life, and its descendents which inherit that capability", that's just not the case. Its descendants only inherit the genetics, which is only one component in determining longevity. (And longevity isn't the only thing to consider - number of offspring that reach breeding age is related to longevity, but it isn't directly proportional.) --Tango (talk) 00:12, 9 March 2009 (UTC)

So many errors - so little time!

• When speaking of evolutionary change, often only a single characteristic of a creature is considered. - Well, in the simple examples quoted for simplicity in text books and such - but in reality, no.
• Similarly, only a single external influence affecting a creature is considered. - Again, not in practical applications of evolutionary theory.
• Furthermore, each member of a species is unique. - No, in many animals there are identical twins and in the case of creatures that reproduce asexually (an Amoeba, for example) - the offspring are essentially clones of the parent - except for DNA transcription errors and such.
• Long life normally results in more offspring being produced. - Not so - in fact most species are programmed to cease reproductive capability later in life. Female humans (for example) cease to be reproductively capable at about the same age all around the world - despite drastically different life expectancies.
• Members with the most offspring will come to prevail in numbers over other members of the species, - PROVIDING that the reason they were able to produce more offspring is (a) genetically heritable and (b) exposed to a similar set of environmental pressures. If (for example) a species is exposed to extreme drought - but ample food is available - then a drought-resistant strain that can more efficiently extract moisture from the food will survive into the next generation. However, if in ensuing years there is plenty of rain - but horrible food shortages - then the offspring of that successful earlier generation may suffer horribly.
• Each unique characteristic will vary in its potency in relation to longevity. - No. Longevity isn't everything - proclivity and reproductive success is very important. It's not as simple as you try to make it sound.
• To clarify the principle being described, it will be assumed in this discussion that the potency of a unique characteristic, and the potency of environmental factors, remain unchanged over generations. - That might clarify your explanation - but it's far from being true. When you look at very successful species, you come across animals like Wolves and Bears - which will eat almost anything - species which are HIGHLY adapted to (for example) eat just one food or hunt in just one way or which can only produce young if they swim up some highly specific river to spawn...those are very fragile...and a tiny change in the environment can wipe them out. Response to change is a vital part of why evolution works. Consider sexual versus asexual reproduction: Species that reproduce asexually can reproduce much more efficiently - but the problem is that there is very little genetic variation - so they are unable to change rapidly when the need arises. The evolution of sex itself is in response to the somewhat abstract evolutionary pressure - which is the ability to respond rapidly to changes in evolutionary pressure!
• For any particular member of a species, the various unique characteristics that aid longevity can be expressed, respectively, by the capital letters A, B, C, …. The unique characteristics that hamper longevity can be expressed by the letters a, b, c, …. The total effect of all unique characteristics (U) on longevity can be expressed as U = A+B+C…. – (a+b+c ….). - I disagree - it's more likely to be something like U = A x a + B x b + C x c. If you have the gene for 'B' (ability to survive a drought, say) and the environmental pressure 'b' is zero because it rains a lot - then B has no benefit so it's contribution is zero. But in reality it's going to be a VASTLY more complex equation U = ( A + B ) x ( a + b ) + A x C x c ...or something.
• The combined effect of unique characteristics, common characteristics, and external influences on longevity (L) can be expressed as L = U + C + I. - but Longevity isn't it - it's ability to reproduce...which is not at all the same thing.
• The descendants of other members will eventually become extinct because they will be in competition for food with increasing numbers of high-L (long-lived, more offspring) members. - Not always. The Origin Of Species (to coin a phrase) requires that sometimes the members with the new and novel genetic makeup may be geographically separate (eg stuck on an island) or may have evolved to exploit a different ecological niche. Hence there are now two species where there was once one - and hence there may be no extinction involved.
• A further complication is that nearly all species of living things reproduce sexually. - Is that true? I really doubt it. Bacteria, many plants, fungii, worms...lots of species do not.
• Therefore, species members may interchange any unique characteristics that can be passed on by sexual reproduction. None of the resulting half breeds will have maximum longevity. - That's nonsense. If some individuals of the (say) anteater species have a gene for longer noses - and other individuals have a gene for longer tongues - then neither of them may be able to reach into the deepest termite mounds. But a lucky breeding might produce an anteater with both the gene for long noses and the gene for long tongues - and therefore succeed where neither of it's parents could. The resulting "half breed" (poor choice of terminology...but whatever) has only characteristics that were present in the general population - yet is better than any of them.
• A single species member that by chance had an extra long life, and its descendents which inherit that capability... - No - if they lived longer by CHANCE then there is nothing to pass on genetically. Only those that reproduce more efficiently BECAUSE of their genes will pass that on to their offspring. The Zebra that happens not to meet any big lions (because it lives in a zoo) will have offspring that are no more 'lion-resistant' than their parent - and if returned to the wild will do no better than all of the other zebras.
• With regard to a single member of a species determining the direction of species evolution, I remember reading something about that for humans. The effect is indicated in cells and in the female line of descent. - all humans are descendants of a single person - all animals are descendants of a single animal. There are characteristics (in humans at least) that are carried on X chromosome. Women have two X chromosomes - men have an X and a Y instead. If a child is born that gets the X chromosome from the man (and, inevitably, an X from the mother) - then it must have two X's and therefore be female. If it gets the Y chromosome from the father, it will be a boy and his X chromosome will be from the mother. So X information carried on the X chromosome follows the female line because a father cannot pass his X chromosome onto his son(s). But that's a small minority of genes - and it's not true in all species.

PHEW! SteveBaker (talk) 00:30, 9 March 2009 (UTC)

Regarding your last point - the organelles all come from the ovum, so the mother, so things like mitochondrial DNA are inherited solely through the female line. Y-chromosomal DNA is inherited solely through male line. That doesn't mean we all get of mitochondria and Y chromosomes from the same individual, though. There isn't a single "first human" from whom everyone is solely descended. There are common ancestors of all the individuals in a species, but there are lots of them. See most recent common ancestor and identical ancestors point for more discussion of this. --Tango (talk) 00:46, 9 March 2009 (UTC)

• Actually, both chance and how well an individual is adapted to survive in its current environment play their part. Evolution is statistical mechanics in action.
  • Hypothetical: You have 100 zebras. 50 can run faster but need more food as a result (group A), and 50 zebras are "normal" (group B).
  • 7 A's and 4 B's die by random chance.
  • 8 A's and 4 B's starve to death.
  • 5 A's and 22 B's get eaten by lions.
  • All the rest reproduce, giving 2 offspring per individual.
• Next generation has 60 A descendants and 40 B descendants. If this pattern keeps up, soon B's will be a small minority. (But if food and/or lions become scarce, those proportions could easily change.) This also serves to illustrate why single genes are rarely the single determining factor in an individual's likelihood of reproducing. There's almost always a tradeoff for every "advantage," and the balance can easily shift depending on changes in the environment.
• I know the above is oversimplified, i.e. not taking into account that A's and B's can mate, dominant/recessive genes, multiple alleles, polygenic traits, etc. But I thought it might be illustrative.
• Finally, yeah - humans have 23 chromosome pairs. Only one is sex-linked. And don't even get me started about the plethora of ways gender is determined, and determines how genes get passed, in other species. XY isn't the only model, by far. arimareiji (talk) 01:08, 9 March 2009 (UTC)

If your model would hold water we'd have a hard time explaining why we still have genetic disorders that kill their carriers at a young age. Sickle cell anemia is one of the more commonly known, but not the only one. As it happens this trait offers its carriers some protection against Malaria. So, although longevity is very much curtailed, individuals have a higher chance of reaching reproductive age and reproducing. Fits evolution very nicely. One thing that often gets mixed up is that benefiting the individual and benefiting the survival of the species aren't the same. The world is full of examples of odd appendages, bright colors instinctive behaviors that serve no other function than to attract a mate. This can be and often is very detrimental to the individual. But as long as that individual manages to mate with more females than an individual without, the trait will get passed on. Looking around lots of short lived creatures from bacteria that live in your gut to cockroaches (Hopefully not under your floorboards:) to mice contradict your equation. A single mouse can spawn thousands of descendants in several generations in the time it takes a long lived human just to reach sexual maturity. Adding a couple of examples to Steve's list of asexual reproduction: many species of snails choose their sexual orientation when they meet. Female sharks can reproduce with or without males. 76.97.245.5 (talk) 02:25, 9 March 2009 (UTC)

"So many errors" that even the eagle-eyed SteveBaker missed an obvious one. The OP states, "Characteristics held in common that affect longevity can be expressed as C." However, he has previously defined C otherwise. He needs a different symbol. Here, try §.
— B00P (talk) 06:05, 9 March 2009 (UTC)

And one by SteveBaker, shock horror! Most animals are not programmed to cease reproductive activity later in life. That humans are is of great interest and there have been a number of putative explanations why. I'm not sure there's any other animals with such a definite menopause as opposed to just not being so fertile when very old, some apes and elephants probably are the closest with the way they lose fertility I'd guess. Dmcq (talk) 16:30, 9 March 2009 (UTC)

An easily misunderstood statement by SteveBaker as well: "all humans are descendants of a single person". Keep in mind that the transition from non-human to human was a smooth one, and that it is impossible to pinpoint a time when it occurred. If one were to make an arbitrary decision about when the transition occurred, there were thousands of persons living and interbreeding at that time, and more or less every one of them was an ancestor to every person alive today. When it comes to mitochondria, however, it is well established that all human mitochondria alive today descend from a most recent single common ancestor that lived in a woman in East Africa, about 140,000 years ago, the so-called Mitochondrial Eve. The most recent common ancestor of all humans alive today may have lived as recently as 3000 years ago, see Mitochondrial Eve#Misconception: The Mitochondrial Eve and Most Recent Common Ancestor (MRCA) are the same. --NorwegianBlue ^talk 19:48, 9 March 2009 (UTC)

"The most recent common ancestor of all humans alive today may have lived as recently as 3000 years ago,..." Ahem! A common ancestor of all Icelanders, Maoris, Khoi-San, and Japanese only 3,000 years ago? No. B00P (talk) 01:35, 10 March 2009 (UTC)

The statement from our article is, On the arbitrary assumption that people mate with a random individual drawn from the whole of the global population, the theoretical MRCA could have lived as recently as 3,000 years ago, citing a 2004 Nature paper as a source. Whether that arbitrary assumption is reasonable, may of course be questioned, but I assume it is discussed in the paper (which I haven't read, but I'll try and get a copy). --NorwegianBlue ^talk 08:03, 10 March 2009 (UTC)

Update: The abstract of the paper is here. The paper takes known migrations into account, trying to capture historical population dynamics realistically through Monte Carlo simulations. The authors conclude that "the genealogies of all living humans overlap in remarkable ways in the recent past. In particular, the MRCA of all present-day humans lived just a few thousand years ago in these models. Moreover, among all individuals living more than just a few thousand years earlier than the MRCA, each present-day human has exactly the same set of genealogical ancestors.". --NorwegianBlue ^talk 10:31, 10 March 2009 (UTC)