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18

To elaborate on A random zoologist's answer, the problem is that the human digestive system does not contain any cellulase enzymes. Cellulases are a class of enzymes that break down cellulose, the chief structural component of plants. You might be able to obtain a small amount of nutrition from grass or other cellulose-rich materials, but as the plant cell ...


12

While poison affects not every organism equally, plants did develop some poisons to avoid being eaten. However, if you look at the great multitude of so-called secondary metabolites, most of them are poisonous to either viruses, bacteria, fungi or other microorganisms, or insects, or even other plants. Plant evolution just hasn't had time to adapt to humans. ...


12

Of course eggs are not vegetarian. Eggs are, well, the eggs of chickens (usually). Chickens are animals so their eggs are animal matter as well. Whether or not the egg has been fertilized is completely irrelevant, eggs are chicken just as much as drumsticks are. The color of the egg has nothing at all to do with it. All eggs are, by definition, animal ...


11

The basic reason is osmosis, the tendency of solutes to move from an area of high concentration to one of low concentration across a permeable barrier. So, ingesting large amounts of salt results in a high sodium concentration in the blood stream. This in turn causes water to enter the blood vessels by osmosis. More water in the blood means a greater volume ...


10

During putrefaction of animal tissue, lysine is decarboxylated into cadaverine and arginine is decarboxylated into putrescine. These compounds are deemed to be toxic. A serving of meat contains 8 g of protein, corresponding to 640 mg lysine and a little bit less of arginine. Let's go straight and say that a spoiled meat serving contains 640 mg cadaverine ...


9

I wouldn't be suprised if no one has hard data on this. In any case there is more than one answer to this question. Niches are defined more than one way. In the narrowest definition, the niche might be defined as the ability of the different trees to grow in different terrains or be eaten by different animals in the same environment. I can't comment on ...


7

Evolution is not that simple. There is no selective pressure for a feature if it does not ultimately in some way benefit reproduction or the offspring. Vegetables are healthy for us now because we live much longer than we used to in an environment not dominated by us, and they contain many nutrients which help to sustain a healthy body beyond, say, 50. ...


7

Shortest answer: there's nothing special in human biology, you could totally make it Short answer: Bachelor chow! I would totally buy this stuff if they made it. The closest I have now to bland, flavorless, zero thought/effort food is Wheaties. longer answer: Seriously though, dogfood for humans wouldn't be that hard to make. If you just took everything ...


6

Yes. Rob Rhinehart has developed what he refers to as "a food substitute intended to supply all of a human body's daily nutritional needs, made from powdered starch, rice protein, olive oil, and raw chemical powders" which he calls Soylent. It was developed and tested largely in 2013, crowdfunded late 2013, and is expected to start shipping in 2014. Tests ...


6

Here is a website that presents very accuerately the tree of life: tolweb.org/tree Yes, they have a common ancestor just like any other living things! How closely related are they? Both species are: Eukaryotes (cells with a nucleus) Archaeplastidae (plants) Angiosperms (flowering plants) Then, they split their way! Here is the tolweb.org page that ...


6

Well, humans can eat grass, but it will not be digested. Cause to digest grass our body needs different kind of enzymes, which lack in humans so they can't digest grass directly although humans can eat grass, but not recommended. Similarly our body has different enzymes to digest wheat and beans etc. Also remember rice, wheat and beans are fruit, not plant. ...


6

Wheat and other grasses are very significant sources for human nutrition. Grass seeds are digestible; seeds have to digest themselves to sprout, with very little biochemical machinery. Human civilization is founded on the ability to cultivate grass to eat. It is due to pepsin that a cellulase supplement would not help to digest grass stems and leaves. ...


6

The reason for this is the oxidation of phenol residues in the banana (for example in the yellow color) which get oxidized by the enzyme Polyphenol oxidase (PPO) to melanins. The scheme (the image is from this website on food browning) looks like this (you can of course also use more complicated substrates): For further information, see these references: ...


5

Quite a bit can be absorbed through the mouth. Most commonly, starches are broken down to maltose (two glucose molecules formed by a condensation reaction) and are easily absorbed by the bloodstream. A lot of other factors balance into this, ie pH, lipid solubility, and molecular weight. Generally, if a substance is easily dissolved in saliva, it can be ...


5

As mentioned by nico in his comment, this infographic is very misleading in that it presents quite uninteresting data in a way as if it was a sensation. It claims the average meal drink has been soda which has increased by 6 times in size. Then it claims most of the volume is water. This is of course true. But while a substance solved in water barely ...


5

The ancestral apple is thought to originate in what is now Kazakhstan. See this report from the USDA on this topic. Those early apples were small and likely eaten more often by non-human species. Pears: From Wikipedia: The genus is thought to have originated in present-day western China in the foothills of the Tian Shan, a mountain range of Central Asia, ...


5

There is a very plausible explanation here. Basically, it explains that meat colour is due to the protein myoglobin (a haem-containing protein related to haemoglobin). There are two types of skeletal muscle: fast-twitch and slow-twitch (Wikipedia). Slow-twitch muscle is red muscle because it contains lots of myoglobin. Fast-twitch muscle is white muscle, ...


5

I would think added preservatives are the most likely candidate, for example, Azodicarbonamide is frequently added to bread in the US, but banned in Ireland and most of the rest of the EU. Since it has a preservative effect it is a reasonable candidate for a specific causal factor. But as Keegan points out there are an awful lot of possible factors so it's ...


5

Earwax, also called cerumen, is slightly acidic (1), with a pH of about 6, and acidic foods or substances taste sour. The composition of earwax, upon which its taste depends, is related to its functions. Earwax aids in cleaning and lubrication of the ear canal and has an antimicrobial effect. The antimicrobial effect is in part attributed to its acidity, ...


4

Much like Daniel Standage suggests, I think "edible" is more inferried than defined, sort of like looking at a black hole - its absence is defined by the activity around it. Human bodies are capable of metabolizing lots of compounds that become poisonous pass some threshold. In medical terms there are LDmin and MLD and LD50: miminum Lethal Dose, Median ...


4

As far as I know, edibility (wow, I'm surprised that passes the spell checker!) is not a strictly defined term, biologically or otherwise. Humans have been around eating and drinking stuff long before the scientific method was around to study this question rigorously, and before there were regulatory agencies charged with approving new products as "safe." As ...


4

The likeliest culprit here is fermentation carried out by bacteria present in the milk. Fermentation of a sugar, for example glucose, releases carbon dioxide (a gas) : C6H12O6 → 2 C2H5OH + 2 CO2 Since this reaction produces a gas, the gas builds up in the milk carton causing it to bulge. This is not, generally, a good sign, make sure to smell the milk ...


4

Yes. I think it would certainly be possible for raw sawdust to be made digestible by humans through some sort of fermentation process with some kind of microbe or another. Pickling (as is done with kimchee and cucumbers and lots of other fruits) uses naturally occurring bacteria that are artificially selected for by using a strong brine solution so that ...


4

For what concerns amino acids, mice rapidly reject meals that are not balanced in essential amino acids and continue to look for other kind of foods. This behavior is called aversion response and it is an adaptive phenomena that can be observed already 20 minutes after exposure to the unbalanced food. The mechanism involves brain sensing of uncharged tRNAs. ...


4

In fact, being lactose tolerant is the mutation. Adult mammals are normally not lactose tolerant, only the still milk drinking babies have the lactose gene activated. Humans developed this mutation earliest in the Neolithic. Lactase persistence (LP), the dominant Mendelian trait conferring the ability to digest the milk sugar lactose in adults, has risen ...


4

The lactose intolerance Wikipedia page explains the problem fairly well, so I'll refer you to that for a more detailed explanation. Briefly, the most common cause of lactose intolerance is primary lactase deficiency, which affects the majority of the world's population. This only affects adults: the majority of people do not produce lactase as adults. ...


4

Yes, they are behaving differently because of the lack of nutrients, including lactose, and possibly because of the presence of other chemicals in soy milk that aren't in dairy. Kefir grains are a complex community of different types of lactic acid bacteria and yeasts which metabolize (eat) various nutrients/chemicals in their environment. Because soy milk ...


4

1 billion hives (at 10,000-50,000 bees/hive this is 10-50 trillion bees) Managed: 100 million hives Based on country-level data from FAO, supplemented for a few countries with Apiservices, in 2011 there were about 80 million managed hives. Because FAO lacks any data for some countries, and other countries under-report (for instance US figures don't ...


3

Ara H 1, Ara H 2, and Ara H 3 are the three main peanut allergies. AH1 and AH2 are typically higher-acuity anaphylactic type reactions. The molecular cause for this is that some Immunoglobulin E develop a serum sensitivity and bind directly to vicilin and conglutin (the active proteins in AH1 and AH2). There are actually 7 or 8 Ara H complexes, but it is ...


3

Vegetables provide calories and don't kill you. For a hunter-gatherer, that's reason enough to eat them even if you don't like the flavor a lot. Finding nourishing foods "repellent" is a modern luxury. Additionally, the bitter flavors in vegetables may be less noticeable to people who were not raised from infancy with hyperpalatable, sugar-sweetened food.



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