Wikipedia:Reference desk/Archives/Science/2013 June 23

Science desk
< June 22	<< May | June | Jul >>	June 24 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 23

Are there any human societies that...

Do we know of any human society with a significant number of people (> 100) that:

1. cannot control fire?
2. does not have a language that can express a nearly-infinite number of ideas?
3. cannot make stone or metal tools?
4. doesn't understand that sex causes impregnation?
5. does not have a religion or know about other religions (so atheists in a modern state don't count)?

I suspect the answer to all of these is "no", but I'd be very interested in reading about any counterexamples. --50.125.29.131 (talk) 02:35, 23 June 2013 (UTC)

Define religion? As for your other questions, there is evidence from Lake Mungo that Australian Aboriginals, the people separated from the rest of the human race for longest, used fire and stone tools when they arrived in Australia at least 40,000 years ago. Given that the rest of the human race interacted with each other after that, there's not much doubt that everyone else had those skills. (That excludes many modern western humans who wouldn't know how to manage a fire or make a decent stone axe even if their life depended on it.) As for language and sex, I'll leave that to others. HiLo48 (talk) 02:54, 23 June 2013 (UTC)

To borrow the basic premise of James Burke's Connections series', the average human as recently as a couple of centuries ago knew everything they needed to know in order to survive. Everyone was a generalist. Thanks to the industrial age and the technology explosion, now everyone's a specialist, some to the point that they couldn't pour water out of a boot even with the instructions written on the heel. But as you suggest, all 5 of the OP's questions were addressed many thousands of years ago. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:02, 23 June 2013 (UTC)

Language and sex are instincts, things written into our genetic code. I'm not so much speaking about specific languages and sex acts (say, "English" or "69"ing which are cultural and must be learned/taught). But this is birds and bees stuff. Birds always speak bird language to each other, and animals naturally know how and why to mate. It's part of being an animal.

On a somewhat related topic, I did read a book that said there are some societies that haven't figured out that a child has only one biological father. They believe that if a female's womb is fertilized by a number of men, the child will take on the characteristics of all the "fathers". For this reason, they believe it is advantageous for a woman to mate with a number of desirable men, so that the child will inherit all their best qualities. It also helps strengthen the group's social bonds because all the "fathers" feel a responsibility to protect the child and assist in its upbringing.--Jerk of Thrones (talk) 05:04, 23 June 2013 (UTC)

Cats (and apparently a small number of humans) sort of work that way. "Triplets" can have three fathers, but each kitten, of course, only one. InedibleHulk (talk) 13:30, 23 June 2013 (UTC)

The exact mechanism of human reproduction, as with other technological discoveries, is only fairly recently known, and more primitive peoples may not have heard about it. But the association between sex and reproduction has been known for countless thousands of years. The mechanism was thought to be the man planting a seed in the woman, like in a flowerpot, hence the terms "sperm" and "semen", both of which mean "seed". ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:09, 23 June 2013 (UTC)

Most societies have a hard time controlling fire, even if they know how to use it to their advantage. See List of California wildfires or, more generally, List of fires. InedibleHulk (talk) 13:22, 23 June 2013 (UTC)

Our article states that there is no evidence that the Sentinelese use fire. However, most details about these people are pretty uncertain. 129.234.53.163 (talk) 19:43, 23 June 2013 (UTC)

Currently, I don't know, but I vaguely remember that isolated pockets of aborigines in Tasmania had lost the ability to /make/ fire and didn't use fish traps when first contacted and then wiped out by the enlightened Europeans. Things haven't much progressed over there. Greglocock (talk) 00:38, 24 June 2013 (UTC)

With the exception of groups of deaf people who were not exposed to sign language until late in life, every human society has language. It would seem that all humans have ancestors who made fire, though I suppose there may be a few small "uncontacted tribes" who have lost the art. There are, or were until recently, societies without stone or metal tools (nothing more complex than a broken rock for temporary use like a chimp might use; in Hadza country there is no archeological evidence that there ever was a stone-tool technology), but AFAIK they've all had wood or bone tools that served the same function, so that's more a detail of material than of tool technology. There are traditional societies that essentially don't know or care much about religion, and many have no belief in an afterlife or maybe even in gods, but all seem to have some belief in unseen (supernatural) forces, so that's a question of how you define "religion". (An anthropologist would define religion as belief in the supernatural rather than specifically in God.) I don't know about sex. I've certainly read claims that some peoples did not (and maybe still do not?) understand the link between sex and procreation, but as with any claim for a negative, that would be difficult to demonstrate. I'd be interested in anyone who can elaborate on that. The results might not be what we'd expect: Medieval Europeans didn't understand how malaria was transmitted, for example (thus mal aria "bad air"), while some stone-age societies understand it to the point that they use the same word for malaria and mosquito. — kwami (talk) 01:20, 24 June 2013 (UTC)

• cannot control fire?

No, although this was alleged of the Tierra del Fuegans.

• does not have a language that can express a nearly-infinite number of ideas?

Unequivocally, no.

• cannot make stone or metal tools?

Unequivocally no, for stone; many for casting metal before Columbus or other modern contact. (Seee chalcolithic and iron age.

• doesn't understand that sex causes impregnation?

doubtful, but the question is too complex to address in less than a book.

One interesting fact is that the bow and arrow are known indigenously on every continent and subcontinent, including New Guinea, but excepting Australia, where the boomerang, unknown elsewhere, was used.

μηδείς (talk) 02:40, 24 June 2013 (UTC)

Not every society had shaped stone tools like fluted arrowheads that would be visible in the archeological record, though everyone in history has probably banged something with a rock. I'm not sure that's what anon. meant by stone tools, however. — kwami (talk) 06:03, 24 June 2013 (UTC)

Yes, but there is a huge conceptual difference between using a tool and making a tool. For example, there are species of birds that will drop a rock or use one as a hammer against a snail in order to break the shell. Those birds are using a tool - but they aren't making one. Chimpanzees have been observed stripping leaves from twigs in order to use them to poke into termite mounds...that is making a tool (albeit a very simple one). Even more, I doubt that a significant proportion of the members of our modern society have ever made a stone or metal tool. But even that isn't the question - the issue is whether they could do so if they needed to - not whether they actually do that. Technically, these people don't even have to know how to do it - within the scope of the question, it's enough to ask whether they could hypothetically figure it out. It's plausible to imagine a small village in the USA of 100 perfectly knowledgeable, well-educated people, none of whom has ever made a stone or metal tool in their entire lives. However, if they had to make a simple stone or metal tool - I'm pretty sure they could figure it out. It's really hard to imagine a society that couldn't do it if it had to. So I'd give this one a definitive "No!". SteveBaker (talk) 18:40, 24 June 2013 (UTC)

Boomerangs unknown outside Australia, Medeis? Not according to boomerang: places like Egypt, California, Arizona, India and Poland are mentioned. -- Jack of Oz ^[Talk] 06:19, 24 June 2013 (UTC)

Didn't suspect that. μηδείς (talk) 16:55, 24 June 2013 (UTC)

Regarding question #4 - The general conceit that a society doesn't "understand" the role of sex leading to babies is one with a long history in anthropology. For example, Bronisław Malinowski claimed in The Sexual Life of Savages in North-Western Melanesia that the people of the Trobriands did not believe or understand that babies were the result of sex. The problem is, outsiders often run into a problem of misunderstanding the difference between what is known and what the official story is; a bit like claiming Catholics truly think they drink blood and eat human flesh at church. That's... kind of the story, but only in a facile sense. Later researchers did not come to the same conclusion as Malinowski; they knew very well where babies came from, but the official story was that they were created by spirits of some kind (I'm a little rusty here). Anthropology is or was rife with something called bongo-bongo-ism, which was a belief that the people a researcher was studying were always "the most isolated" or "the most primitive" and thus had the weirdest or most exotic ideas and lack of knowledge of procreation was a gem. So, it's also possible that Malinowski was on some level aware that what he was writing was wrong, but kept it in anyway because it was a juicy bit. It did not, of course, hurt that he was writing about "dark-skinned savages" who of course might believe anything. On such clear consciences was the foundation of anthropology built. :) Matt Deres (talk) 01:17, 25 June 2013 (UTC)

When small children have not had "The Facts of Life" talk (even in my generation where there was no sex on TV or in movies that kids might see) - they often make guesses about this. They can tell, just from observing the world around them - that most children have (or had) both a mommy and a daddy. So while they can't know about the details of the sex act - they tend to guess that "getting married" or "lots of hugging and kissing" or "living in the same house" or "falling in love" is what spurs women to get pregnant. This is certainly an inaccurate view of things - but it's not SO inaccurate that it doesn't have some predictive value.

Even in spectacularly primitive societies, you'd expect adults to be able to deduce this fact at least as well as small children do in our society. That's especially true in societies with formulaic rules about when intercourse is allowed. Let's face it, some societies rigidly disallow sex before marriage and insist that a marriage is consummated before it becomes legal and final...in those societies, it would be almost impossible to distinguish whether getting married or having intercourse is the cause of pregnancy.

But pretty soon, people would start to notice things like if the man becomes impotent then no babies appear after that. It's really hard to imagine a society in which the true cause of pregnancy isn't obvious after just a couple of generations of observation and shared knowledge.

SteveBaker (talk) 16:39, 25 June 2013 (UTC)

But aren't you assuming that every society has such a thing as a "father" and "mother", who live together with their children in a segregated house? If everyone is having sex all the time (as implied by Sex at Dawn), with no concept of marriage, how will anyone associate sex with children? Not every society is monogamous. In fact, I think most are not. --50.47.81.232 (talk) 05:47, 26 June 2013 (UTC)

I think that in those kinds of more open society, it would be even easier to deduce that no girls ever get pregnant until they first have sex. When everyone knows who does what and to whom - this kind of thing would be even clearer. SteveBaker (talk) 19:31, 26 June 2013 (UTC)

Well, I don't think it's necessarily an obvious thing. For example, absent repression from adults, pre-adolescents engage in various forms of sex and sex play without conceiving a child. Married couples may have sex dozens of times without conceiving (or alternately have sex once and conceive triplets), and of course some people simply cannot conceive at all. This is all complicated by humans' concealed ovulation. The thing is, sex is not the kind of thing a society can possibly do without, unlike wheels, paper, plows, etc that might also seem equally obvious. Eventually, the penny will drop. Matt Deres (talk) 02:16, 27 June 2013 (UTC)

There's a bit of an overview here. Based on my readings and understanding, humans are generally monogamous in principle. Places where you find polygamy or polyamory are nearly always under special circumstances due to environmental or financial pressure, or involve only a select few members of the population (cv. the imperial incest of Ptolemaic Egypt. Here again, anthropology sometimes provides a skewed view; if 99.9% of a population makes do with a normal old spousal arrangement and a select few engage in sibling incest or brotherly co-husbands or some other juicy topic, do you think the 99.9% will be the part that gets written about? Not a bit of it! It's like studying pair bonding by reading Hollywood tabloids; the neat stuff gets publicized and the boring stuff is relegated to an appendix somewhere. Matt Deres (talk) 02:34, 27 June 2013 (UTC)

Why can we only eat living things (or things that use to be alive)?

How come the only edible things are plants and animals? I mean to a certain extent you can eat minerals like salt, but only in tiny amounts. Like I could eat a pound of steak or a pound of bananas but not a pound of salt. Plus I don't think salt has any calories.

But wouldn't something flammable like gasoline have calories? Yet I'm sure gasoline is poisonous and not very nutritious.

Please explain.--Jerk of Thrones (talk) 04:49, 23 June 2013 (UTC)

Oh, I guess gasoline is also made up of things that use to be alive. When I was in school, they told us oil was made out of dead dinosaurs. In fact, Sinclair_Oil_Corporation's logo is a dinosaur. So maybe that wasn't the best example of possible caloric foods that aren't made up of plants and animals. Still, I would like an answer to my question.--Jerk of Thrones (talk) 04:54, 23 June 2013 (UTC)

Petroleum could theoretically be dinosaurs, but more likely large animals like that were eaten or decomposed before they had a chance to be buried in sediment. Mainly made of the little corpses which floated to the sea floors unnoticed, like zooplankton, algae and tiny fish. I don't think there's any way to tell what a given sample is made of, though, this far along. InedibleHulk (talk) 13:03, 23 June 2013 (UTC)

The Nutrition article might be a good start. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:57, 23 June 2013 (UTC)

(edit conflict) Your body is not able to digest and extract energy and building materials out of anything. Inside your body are substances (mostly enzymes) and processes (things like the Kreb's cycle, which are carefully tailored towards utilizing certain substances, either for their ability to provide energy, or for their ability to provide material your body can use to build itself up. Macronutrients is the term for these substances, which make up the bulk of what you eat (micronutrients include things you need, but only in trace amounts; basically vitamins and minerals). There really are only three classes of macronutrients: carbohydrates, which are your primary dietary source of energy, though your body gets energy from other macronutrients, what it doesn't get from carbohydrates is anything except energy. There are lipids, which also provide energy (at a much higher energy density, but lower absorbtion rate, that carbohydrates), though many lipids also provide building blocks (cholesterol, for example, is present in cell walls and is used by the body as a source of the basic steroid structure vital to many hormones and other compounds in your body). Proteins also provide energy, at roughly the same density as carbohydrates, but proteins are also very important as a source of amino acids which your body uses to build other proteins, which are much of the primary structural and functional components in your body. While you can make some amino acids from scratch, there's a bunch of essential amino acids you must consume, since your body cannot make them. The thing is, this is essentially all your body can metabolize for energy and building material. You can't just eat any substance that burns, your body has no way of dealing with it, because you lack the compounds and processes to effectively use it. You've got those three, and that's about it. And those things are only made by other living things (technically, any of them can be created in a "man-made" way from first principles without starting with living material, but the process is so inefficient and expensive, there's really no point). You can't get protein from a rock. --Jayron32 05:02, 23 June 2013 (UTC)

Well, you're made up of carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus. You drink water freely, you breathe oxygen, and N, S, P are normally thought of as mineral supplements more than food. That leaves carbon. There is a close relationship between organic compounds as carbon-containing and life-derived, because by and large living things get their paws on every bit of carbon in the cycle, so there's nowhere much else to take it from. Even the CO2 in the air comes from formerly organic sources, and you'd have to be photosynthetic to 'eat' it. Wnt (talk) 06:25, 23 June 2013 (UTC)

Just a point of order: You get sulfur, nitrogen, and phosphorus from living sources: sulfur and nitrogen you get from proteins; I'm pretty sure you get all of the nitrogen you need from proteins, and probably also sulfur. You get phosphorus from stuff like nucleic acids. Most dietary minerals can be gotten from living sources as well (iron is plentiful in food with blood, like black sausage, as well as many vegetables like broccoli, iodine from seafood, etc. The only stuff you need to get from outside of your food (that is, consuming the bits of other recently living beings) is oxygen. --Jayron32 12:44, 23 June 2013 (UTC)

Oh, certainly; I didn't mean to suggest that you couldn't or didn't get them from living sources, only that with some gaming of the rules I could probably think of some contrived artificial diet which provides them separately in a form that can be incorporated (though due to essential amino acids not all of them). For phosphorus and sulfate that is easy - for nitrogen (other than nitrate), much more tricky - maybe you could connive to reverse the glycine cleavage system? But in any case we think of nitrogen as a waste product from all the things people have to eat, rather than as a needed foodstuff in itself. Wnt (talk) 18:02, 23 June 2013 (UTC)

Also the fruits and vegetables themselves like the aforementioned bananas are not living organisms, so you eat non-living stuff as well. Brandmeister^talk 10:31, 23 June 2013 (UTC)

Well, it's part of a living organism. That you don't eat every organism whole doesn't seem to be the trouble the OP is having; he seems to be having trouble understanding why food has to come from other living organisms (including parts we slice off of them) as opposed to substances which are either non-living, or so far removed from living as to contain no recognizable nutrients, like petrochemicals. --Jayron32 12:33, 23 June 2013 (UTC)

The lack of digestibility of petroleum products and coal, like the indigestibility of cellulose, seems like an evolutionary metabolic accident with some degree of chemical basis - in the case of fossil fuels, it is just harder to work with carbon compounds before some oxygens or nitrogens are brought in to activate them. Wnt (talk) 12:51, 23 June 2013 (UTC)

It's because we're at the top of the Food chain. There are plenty of organisms (plants, some bacteria, etc) that only consume the raw materials: Oxygen and CO2 from the air, water, nitrogen compounds from the soil, etc. However, we've evolved to let those other living things do all the work of turning those very basic materials into things like sugars and proteins - so we don't have to. If you think about it - it's much more efficient for us to eat an apple than it is to get those same nutrients by making them from scratch like the apple tree had to. We don't need that vast area of chlorophyll-filled leaves to gather sunlight to make sugars from CO2 in the air and water in the soil. Instead, we let the tree do all of that work - and just steal it's offspring at the end. Since other living things need all the same chemicals that we do, taking the life of a predator (even if only predating on plants) means that we get pretty much everything we need to survive from the things we prey upon. SteveBaker (talk) 13:24, 23 June 2013 (UTC)

• It might be useful to mention alcohol here -- ethanol, specifically. We don't usually think of it as a food, but it's actually a very strong source of calories. (By weight, it's nearly as calorie-dense as fat.) The ethanol that we consume if a byproduct of life, but not really part of a living thing. Looie496 (talk) 20:19, 23 June 2013 (UTC)

This source may suggest that some microbes "eat" something similar to "rocket fuel". I also find something that may be similar at Microbial corrosion. Bus stop (talk) 18:34, 23 June 2013 (UTC)

Microbes eat lots of odd things. In contrast, humans cannot digest cellulose - nor, apparently, can termites; except they have microbes in their innards which do the job for them. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:03, 24 June 2013 (UTC)

Well, plants eat CO2 from the air, if we're going outside the animal kingdom. Looie496 (talk) 01:28, 24 June 2013 (UTC)

• This has been answered clearly above. Basic life depends on the utilization of carbon and nitro-carbon compounds. Humans are top-scale apex predators that get the sugars, proteins, and lipids they need from basically every lower rung on the food-chain. That is what intelligence is for, selecting and taking advantage of the richest food sources. If the OP is unclear he should ask more specific questions. μηδείς (talk) 02:32, 24 June 2013 (UTC)

Sex ratios

I have learned that beach nourishment can cause the temperature of the beach sand to change,distorting the sex ratio of sea turtle populations (e.g cooler sand causes more embryonic sea turtles to become male). If you have an unbalanced ratio of females to males, would this cause the population of sea turtles in an area to decline?99.146.124.35 (talk) 17:17, 24 June 2013 (UTC)

Temporarily, but the few turtles who can still have male offspring in hot sand will have more grand-children than those that can only have female offspring, and therefore, over several generations, the genes that allow "making male in hot beaches" will become more common and the population can re-stabilise. Of course if the temperature variation is so wide that it prevents all males to be born, and it lasts for a long time, then this can cause an extinction. --Lgriot (talk) 08:37, 25 June 2013 (UTC)

Doubtful, Lgriot. Temperature-dependent sex determination is evolutionarily robust - the temperature ranges within which different genders arise may shift, but the system itself will most likely remain. To the actual question, it's possible that the shifting ratio of genders is actually of benefit to the turtles, and cancels out some harm caused by the non-optimal temperature. You may wish to read the article I have linked to. The actual purpose of temperature-dependent sex determination is only poorly understood, but it seems to have withstood the test of time, so it is probably good for something. Someguy1221 (talk) 08:44, 25 June 2013 (UTC)

(This question has just been re-asked...below...) SteveBaker (talk) 16:26, 25 June 2013 (UTC)

I have not said that the system would NOT remain, what makes you think that, Someguy? I do think however that the temperature range that a species can handle could shit up or down, due to obvious selection pressures, if the temperature change remains for many generations. And what I said about axtinction is for very wide variations (somethign crazy, like 25 deg celcius), minor variations (5 degrees or less) could simply lead to an adaptation. --Lgriot (talk) 09:08, 26 June 2013 (UTC)

Trees in the Piazza della Scala

Trees in the Piazza.

What trees surround the statute in the Piazza della Scala in Milan? It looks like linden trees, but I'm curious as to which species. Gabbe (talk) 09:08, 23 June 2013 (UTC)

Hard to be sure from the photo, but they look like Tilia cordata to me. Deor (talk) 12:09, 23 June 2013 (UTC)

Agreed. Alansplodge (talk) 14:12, 23 June 2013 (UTC)

Yup, as far as I know, that bracht bract is a distinguishing characteristic, and is clearly visible in the photo. In the US, we call these trees "little leaf linden." SemanticMantis (talk) 19:32, 23 June 2013 (UTC)

Would that be bract? Richard Avery (talk) 07:14, 24 June 2013 (UTC)

Yes, "linden" is probably the more sensible name, but a bit too Germanic for us Britons. Apparently, "lime" comes from the Middle English "lynde" which is not too far away.[1] As a small child, I was always hoping to find a lime on a lime tree - one of life's little disappointments. Alansplodge (talk) 13:00, 24 June 2013 (UTC)

Seed preservation mechanism

What is the mechanism that keeps a seed 'alive' for many years before it germinates? Is there any cell activity during that time? Is there any 'life' in the seed? Gil_mo (talk) 12:15, 23 June 2013 (UTC)

Have you read our article "Seed dormancy"? It seems to cover this in great detail. Evidently there isn't a single answer because different seeds handle this differently.

As a general observation, we humans tend to greatly over-estimate the amount of resources that plants and animals require to survive. That's because we're warm-blooded and our bodies consume large amounts of energy even if we're doing absolutely nothing - our brains alone consume massive amounts of oxygen and nutrients even when we're asleep - in order to get oxygen to power those heat generators and that big brain, we have to actively breathe - so our chest muscles are working all the time providing air flow and the heart has to beat at a reasonable rate to keep the oxygen flowing to where it's needed. We simply can't just shut down and do nothing.

This leads us to be amazed that cold-blooded animals, plants and many other living things can survive on incredibly small amounts of food and water because their bodies can more or less completely shut down. For example, a crocodile can live for an entire year without food...but we're in trouble after just a few days and probably dead within a month. Seeds are not doing any work - they aren't growing, moving, thinking, generating heat - nothing! So they use more or less zero energy and there are documented cases of seeds germinating after being stored in stone jars for 2000 years - using just the food and moisture stored inside the original seed when the parent plant dropped it.

SteveBaker (talk) 13:17, 23 June 2013 (UTC)

As David Attenborough once said (I think) "Ain't nature wonderful". Richard Avery (talk) 14:52, 23 June 2013 (UTC)

Thanks SteveBaker. Gil_mo (talk) 21:39, 23 June 2013 (UTC)