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Questions tagged [human-biology]

This tag is for questions about the general biological features of human beings (as opposed to the biology of non-humans).

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308 votes
3 answers
287k views

Why do I only breathe out of one nostril?

I was just sitting with my hand next to my nose and I realized that air was only coming out of the right nostril. Why is that? I would think I would use both, it seems much more efficient. Have I ...
David says Reinstate Monica's user avatar
124 votes
4 answers
7k views

Is there a reason why human eyesight and plants make use of the same wavelength of light?

The accepted range for the wavelengths of light that the human eye can detect is roughly between 400nm and 700nm. Is it a co-incidence that these wavelengths are identical to those in the ...
Rory M's user avatar
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94 votes
6 answers
38k views

How could humans have interbred with Neanderthals if we're a different species?

To be clear, I'm not doubting that Homo sapiens and Homo neanderthalensis did interbreed: of that much I'm convinced. Within the past few years I've seen an upcropping of pop-sci articles discussing ...
Dave Kennedy's user avatar
  • 1,043
89 votes
6 answers
32k views

Are humans the only species who drink milk as adults?

I was drinking a glass of milk the other day and that got me thinking that no other animal to my knowledge drinks milk past their infant stages. One could argue that cats might but it isn't good for ...
ggiaquin16's user avatar
84 votes
4 answers
138k views

Death because of distilled water consumption

One of my friends said that I would die if I drank distilled water (we were using it in a chemistry experiment) I gave it a go and surprisingly did not die. I did a bit of Googling and found this ...
The-Ever-Kid's user avatar
  • 1,169
74 votes
1 answer
56k views

Why do Humans not produce Vitamin C like other mammals?

Why do most mammals produce their own Vitamin C? Why do Humans not?
Gabriel Fair's user avatar
  • 4,529
73 votes
3 answers
16k views

How does the brain's energy consumption depend on mental activity?

What is the impact of mental activity on the energy consumption of the human brain? I am most interested in intellectually demanding tasks (e.g., chess matches, solving a puzzle, taking a difficult ...
Piotr Migdal's user avatar
  • 1,935
64 votes
2 answers
8k views

Why does it hurt the next day after doing significant exercise?

I think this is a fairly common observation that if one does some significant amount of exercise, he/she may feel alright for the rest of the day, but it generally hurts bad the next day. Why is this ...
user1995's user avatar
  • 927
57 votes
4 answers
41k views

Why do the fastest runners tend to be black?

If you watched the last Olympics like me you probably also observed that most medallists in running events were black. Why is that? I discussed this with university grad friends and researchers and we ...
Mud Warrior's user avatar
54 votes
5 answers
3k views

Human perception of time depending on age

From what I can tell and what thus far all people with whom I discussed this subject confirmed is that time appears to "accelerate" as we age. Digging a little, most explanations I found basically ...
back2dos's user avatar
  • 883
50 votes
1 answer
12k views

What causes morning wood?

Sometimes men wake up with an erection in the morning. Why does this happen?
I J's user avatar
  • 1,236
50 votes
1 answer
58k views

Why Does Salt Water Help Sore Throats?

I am having some trouble understanding how salt water, a simple solution, could so effectively remove the pains of a sore throat. I do believe that the answer is closely related to hypo/hyper-tonic ...
nmagerko's user avatar
  • 611
49 votes
4 answers
257k views

What's the maximum and minimum temperature a human can survive?

This is a question that has been in my mind since I was a kid. I'm not a doctor, nor even a biology student, just a curious person. What is the minimum and maximum temperature a human body can stand ...
Bugster's user avatar
  • 691
48 votes
1 answer
8k views

Why do human females have periods?

Why do human women have periods when most animals don't? It is known that the unfertilized egg needs to be shed from the uterus. But why shed the whole endometrium? Why didn't evolution put ...
Harini's user avatar
  • 615
44 votes
4 answers
33k views

Is there any advantage to one blood type over another?

All humans can be grouped into ABO and Rh+/- blood groups (at a minimum). Is there any advantage at all to one group or the other? This article hints that there are some pathogens that display a ...
Rory M's user avatar
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42 votes
5 answers
56k views

Why is cold water more refreshing than warm water?

Obviously, the temperature of water does not affect its chemical composition. At least not in the ranges we are likely to drink it in. Yet it is clearly far more pleasant and refreshing to drink cool ...
terdon's user avatar
  • 12.9k
41 votes
4 answers
8k views

Are there biological reasons why life expectancy is lower for men in most countries of the world?

I've been checking life expectancy figures for men versus women in many countries of the world and the figures for men sometimes are terrifying. Countries like Russia have a 12 years gap in disfavor ...
Pablo's user avatar
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40 votes
4 answers
15k views

Can a person survive on blood in place of water?

This question: Can you get enough water by eating only fish? asks if a person could survive on fish alone. Can a person survive on fish and/ or blood alone of any species if stuck at sea or animal ...
Muze's user avatar
  • 1
40 votes
2 answers
8k views

What actually happens when my leg 'falls asleep'?

Most people have experienced the temporary loss of feeling and tingling in their leg resulting from sitting in an abnormal position for a short while. Usually you get a loss of feeling in your leg ...
Gordon Gustafson's user avatar
39 votes
2 answers
20k views

What do ants do with human finger nails?

There is place in my house where I cut my nails. Here, there is an ant hole where an ant colony is seen. Whenever I cut my nails from here, they take my nails inside their hole. I was wondering what ...
Aishwarya Shiva's user avatar
39 votes
1 answer
67k views

How does laughing gas (N₂O) work?

Laughing gas (N2O), well, makes people laugh. How does just a gas make us do that, there has to be some hormones at work... So, I wanted to know how this works? What is the mechanism?
Ashu's user avatar
  • 783
39 votes
5 answers
2k views

Why do we age? or Do we have a theory of senescence?

There seem to be a number of ideas about why we age. Hypotheses include the gradual accumulation of cell metabolic products affecting organism function and the reduction of telomere length during cell ...
Poshpaws's user avatar
  • 7,302
38 votes
6 answers
46k views

Why do the two hemispheres of the brain control the opposite sides of the body?

Why does the left hemisphere control the right and the right hemisphere control the left? I googled it but didn't find a good answer regarding this. Could someone explain? Does this adaptation help ...
lmathl's user avatar
  • 739
36 votes
3 answers
2k views

Why don't teeth glow?

Hydroxyapatite is the main component of tooth enamel. It contains phosphorus in the form of phosphates, pyrophosphates etc. that are found to exhibit the the property of phosphorescence. But why don't ...
Stp30's user avatar
  • 549
34 votes
5 answers
5k views

Is there an advantage to antibacterial soap?

There are plenty of different hand soaps out there, as well as hand sanitizers. Is there an advantage to soaps that claim that they're antibacterial vs soaps that just say soap? In particular I'm ...
SolarLunix's user avatar
  • 3,084
34 votes
3 answers
4k views

How and where, in the human brain, are memories stored?

Background I am a computer programmer who is fascinated by artificial intelligence and artificial neural networks, and I am becoming more curious about how biological neural networks work. Context &...
Matt Cashatt's user avatar
34 votes
1 answer
12k views

How long do your eyes need to adapt to darkness and reach full contrast?

I heard you should wait some time until your eyes adapt to darkness and are able to see smallest luminosity differences, otherwise you might overlook faint objects in the ocular. Are there any rules ...
Hauser's user avatar
  • 923
33 votes
1 answer
22k views

What do you see when your eyes are closed?

If you are in pitch black and you close your eyes, you sometimes can see strange shapes of various colors. A lot of the time these shapes and colors change as you observe them. This phenomenon still ...
JonHerman's user avatar
  • 532
32 votes
2 answers
5k views

What makes a cancer contagious?

Most human cancers are not (very?) contagious (perhaps besides a couple of incidents). But the Tasmanian devil seems to have a form of cancer which is contagious. Now what makes the difference between ...
Marijn 's user avatar
  • 2,765
32 votes
3 answers
161k views

Why do mammalian red blood cells lack a nucleus?

How did the red blood cell in humans get to lose its nucleus (and other organelles)? Does the bone marrow just not put the nucleus in, or is it stripped out at some stage in the construction of the ...
John Smith's user avatar
  • 2,798
31 votes
3 answers
9k views

Can humans ever directly see a few photons at a time? Can a human see a single photon?

I am not asking the following question: Can humans ever see a photon in the same way we see a chair? My question is: Can a human retina respond to a single photon? If so, how does this happen and why ...
Daniel Mera's user avatar
30 votes
7 answers
7k views

Human evolution: Where *exactly* did the first human come from, whose parents were not?

Layman here. So I have never really quite understood this facet of human evolution, (or any other for that matter), in that, I understand the evolutionary process, but I get lost on the 'border' cases....
Spacey's user avatar
  • 583
30 votes
3 answers
9k views

Can a cancerous cell from outside cause cancer in a healthy person?

If a cancerous cell enters the body of a healthy person from someone else's blood or something, will that healthy person get cancer? In human beings.
Poin's user avatar
  • 503
30 votes
1 answer
16k views

What is the human energy consumption by organ?

The human brain uses about 25% of the human body's metabolic energy. How are the other 75% spent, in terms of portioning to its various systems? I thought this could be answered by a simple search, ...
MaudPieTheRocktorate's user avatar
30 votes
3 answers
1k views

Is telomere length a reliable measure of health/lifespan?

Several companies are commercializing tests for telomere length such as this one here. I understand the basic mechanism for why telomeres shorten during DNA replication, but how good is the evidence ...
Poshpaws's user avatar
  • 7,302
29 votes
3 answers
9k views

Can the dead be brought back to life by viruses?

Zombies have been a part of popular culture for decades. The living dead rising up to take over the world is a terrifying concept, worthy of Hollywood blockbusters and television hits. Some of those ...
Sajin Shereef's user avatar
29 votes
4 answers
29k views

Can humans eat grass?

Can a human eat grass and digest it? Could it be possible to use it as food just like other plants such as wheat or beans?
Xander Smeets's user avatar
29 votes
2 answers
9k views

Is it possible that by mutation a human could see infrared or other 'colours'?

Incoming light reacts with the several types of cone cells in the eye. In humans, there are three types of cones sensitive to three different spectra, resulting in trichromatic color vision. Each ...
Marijn 's user avatar
  • 2,765
29 votes
1 answer
8k views

Do we know all the possible human hair colors?

I occasionally see people with blue hair and I always assume it is dyed. I wonder how justified is that assumption. Have biologists determined all the possible human hair colors? Or is it possible ...
bimle's user avatar
  • 415
29 votes
2 answers
32k views

If a human takes antibiotics are all bacteria in the body killed?

From my basic understanding, antibiotics kill living things, bacteria for example. Do the antibiotics consumed by a human-being distinguish between what they kill? Or do they just kill every bacteria ...
Claus's user avatar
  • 399
29 votes
2 answers
8k views

Why is rabies incurable?

I'm still not sure about the mechanics that lead to rabies being incurable. I know that it can be treated before any symptoms show up, but why is it that once symptoms show the person is a dead man ...
thomasrive's user avatar
29 votes
5 answers
4k views

Are there any substance that are more dangerous at low dose than at higher dose?

It is commonly admitted that The dose makes the poison which means as a person, the more I take a substance, the more risk I take for my health. There is even an indicator called LD50 (see Median ...
JBE's user avatar
  • 423
29 votes
1 answer
6k views

Is kissing a natural human activity?

The word natural here is meant in contrast to it being a sociological construct. Is kissing in all its forms something natural for humans? Is it instinctively erotic? Or is it just a conventional ...
Nikolaj-K's user avatar
  • 595
29 votes
1 answer
1k views

Extremely rare occurence of Heart cancer?

The occurrence of Heart cancer (similar, but not the same as Rhabdomyosarcoma) is extremely rare, about 1 per year according to MayoClinic. The reason for this rarity is explained to be the post-...
stochastic13's user avatar
  • 4,689
29 votes
2 answers
22k views

What causes fingerprints to form and why is the pattern formed unique?

I've found research that suggests that the reason we develop fingerprints is because they aid us with feeling surfaces (Scheibert, et al. 2008) and not to increase friction and help with the gripping ...
Edoardo Pirovano's user avatar
28 votes
4 answers
10k views

Where does the 'C' in exhaled CO₂ mostly come from?

When a human being exhales CO₂, what is, by the numbers, the main source of carbon atoms exiting the body in this way? I mean what class of cells, or which tissues are the biggest on a pie chart of ...
mring's user avatar
  • 1,973
28 votes
2 answers
2k views

Why does looking at bright light trigger sneezing in some people?

Why does looking at bright light trigger sneezing in some people? Are there any recent studies that have found a cause for this Photic sneeze reflex? The Wikipedia article only references studies ...
luvieere's user avatar
  • 456
27 votes
5 answers
5k views

Why did scientists state that the Omicron COVID-19 variant was a reason to get a booster?

I was watching Vox’s video, Big questions about the Covid booster shot, answered, which references the New York Times article Omicron Prompts Swift Reconsideration of Boosters Among Scientists. In ...
hb20007's user avatar
  • 985
27 votes
3 answers
7k views

Is there any use of CO₂ in human body?

We all know CO₂ as a waste product of metabolism . Does CO₂ have any helpful role , apart from having a role in pH of blood ?
biogirl's user avatar
  • 8,621
27 votes
3 answers
3k views

Why was disease transfer to the Americas one-way?

It is well known that the European colonists brought many infectious diseases to the Americas, and that these had a deadly effect on the native populations, because they had no immunity to them. Were ...
TRiG's user avatar
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