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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Effect of 2,3-bisphophoglycerate (2,3-BPG) on haemoglobin

When 2,3-bisphophoglycerate (2,3-BPG) binds to haemoglobin, a higher partial pressure of oxygen is needed to bring about 50% saturation of with oxygen. What is the physiological significance of this ...
user avatar
5 votes
3 answers
5k views

Is sex a spectrum?

At the moment I'm especially interested in the question of whether biological sex is really a spectrum. Unfortunately I could not find any good answers on the Internet. Therefore I hope that some of ...
Tetragrammaton's user avatar
2 votes
3 answers
173 views

Is there any disease in common between human and insects?

I am not asking about disease transferred by insects. I am wondering is there any disease that commonly make both human and insects sick?
KathySpider's user avatar
0 votes
1 answer
130 views

At what saltiness will water simply pass through us?

If water has a low salt content, it hydrates us. When water has too high salt concentration, like sea water, it drains water out of us instead when we drink it. At what salt concentration would water ...
Etheryte's user avatar
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49 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
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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
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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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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
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
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29 votes
2 answers
7k 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
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
25 votes
2 answers
38k views

How do the brain and nerves create electrical pulses?

The information between the brain and peripheral nerves is sent via electrical pulses or signals, How then does a non-metallic human cell manage to conduct an electrical signal?
johnny1bucket's user avatar
24 votes
2 answers
61k views

How many human cells are there in our body, on average?

How many human cells are there in our body, on average? Wikipedia says 1013: Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in ...
Sklivvz's user avatar
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24 votes
9 answers
23k views

Why have humans evolved much more quickly than other animals?

Humans have, in a relatively short amount of time, evolved from apes on the African plains to upright brainiacs with nukes, computers, and space travel. Meanwhile, a lion is still a lion and a ...
Matt Cashatt's user avatar
20 votes
4 answers
88k views

What is the armpit hair for?

Modern human beings, especially women, cut their armpit hair. It seems to me the armpit hair is trivial/useless. Shortly speaking, what is the armpit hair for?
kiss my armpit's user avatar
19 votes
3 answers
651 views

Are human fetuses more likely to be male? [duplicate]

Question: From a physiological point of view, when sex is determined in a human fetus, is it equally likely to be male or female? Studies in this area typically measure age at birth, where the data ...
Douglas S. Stones's user avatar
19 votes
3 answers
30k views

Can one die from pain?

Is it possible that a human or any other creature can die from pain? I googled and found different answers. Some articles say Yes while others say No.
Mayank Jain's user avatar
19 votes
4 answers
23k views

Why is the brain dependent on glucose?

The strict dependence of the (human) brain on glucose has always been puzzling to me. While ketones can substitute for a portion of the brain's energy needs, it cannot substitute completely: blood ...
Roland's user avatar
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18 votes
1 answer
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How fast can a human run?

I'm a runner (cross country) and I'm always amazed at how fast Olympic sprinters are. There's a lot of hype about those in the 100-meter dash being the fastest in the world, and we're constantly ...
HDE 226868's user avatar
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18 votes
4 answers
15k views

What is the evolutionary reason behind the fragility of teeth?

Almost all organs in the human body have a rather large threshold within which the organ or tissue is capable of repairing itself using materials supplied by the body, whether it's made from organic ...
Sir Quill's user avatar
  • 283
17 votes
4 answers
8k views

What causes the development of antibiotic-resistant strains of bacteria?

I understand bacteria have become resistant to antibiotics due to selection pressures, but how do resistant bacteria process antibiotics when exposed to it, compared to non-resistant bacteria. Also, ...
harpalss's user avatar
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17 votes
1 answer
4k views

Do we actually get more sick (flu/cold) during winter?

The word flu derives from the Italian phrase "influenza de freddo" meaning "influence of the cold". Indeed it is that time of the year when my colleagues seem to have the flu/cold more often than not....
hello_there_andy's user avatar
17 votes
2 answers
13k views

Will humans and animals be harmed by frequencies outside their hearing range?

The human ear (for example) is sensitive to frequencies from 20Hz to 20kHz. Any sound beyond that limit would not be heard by us naturally. Will it harm us (effect our ability to hear) when we hear ...
Santosh Kumar's user avatar
16 votes
1 answer
61k views

At what age do babies begin to synthesize their own antibodies?

When babies are first born, they receive their antibodies from their mother (I assume because they do not yet have the capacity to synthesize their own). So my question is, at what age do babies ...
Whitney's user avatar
  • 161
15 votes
2 answers
2k views

Is the 'fluttering feeling' when under stress neurological or physical?

I'm sure that everyone is familiar with the sensation commonly known as "butterflies in the stomach". It is commonly experienced during periods of anxiety or stress (e.g. before high stakes job ...
Rory M's user avatar
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15 votes
3 answers
1k views

Athletes: nature vs. nurture?

Having watched a lot of olympians the last few weeks, I was struck by how many of them have actually spent their wholes lives/careers training for their one event (be in running a marathon, or ...
Luke's user avatar
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14 votes
4 answers
2k views

During starvation, does the human body do anything to prioritize which organs receive nutrients?

When food is scarce, the body slows its metabolic rate to conserve energy. Are there any other systems or processes that prioritize which organs receive nutrients?
Gabriel Fair's user avatar
  • 4,509
13 votes
5 answers
22k views

Why is the opposite of plantar flexion called "dorsiflexion"?

Why is the action of flexing the foot so that the toes move anteriorly/superiorly (i.e. in the direction opposite that which they move during plantar flexion) described as "dorsiflexion?" In the same ...
senshin's user avatar
  • 241
13 votes
1 answer
36k views

What senses are active while sleeping?

During sleep, our body activity decreases. I am wondering on the extent of the lowering of this activity regarding our five senses. Clearly, the sense of touch is still very efficient since shaking a ...
Taladris's user avatar
  • 245
12 votes
2 answers
22k views

Why can all animals swim in water without learning to swim but humans cannot?

I had a question since I was a child. I was always curious about the fact that all animals can swim in water. They don't need any training or to learn swimming. But humans need to learn to swim. Why ? ...
Balaji Birajdar's user avatar
12 votes
1 answer
29k views

Why does the ring finger not move independently?

Why is it that we need to move little finger in order to move ring finger with it? For example, put your palm on a table and fold your middle finger inside. You won't be able to move your ring finger ...
dudethisismyemail's user avatar
12 votes
3 answers
10k views

What is happening when we get a tan?

Almost everyone nowadays wants that nice summer tan, but what exactly is going on beneath the skin? I've heard a few different theories about tanning - such as a tan is nothing but the pigmentation in ...
SolarLunix's user avatar
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11 votes
1 answer
17k views

Why do humans seem so much more prone to disease than animals? [closed]

It seems like when we observe animals in the wild, the occurrence of noticeable disease in adult individuals is much lower than in humans. Why? There are a number of reasons that this could happen, ...
technitaur's user avatar
11 votes
1 answer
5k views

Which sex has higher variance of reproductive rate in modern societies - male or females?

Who has a more varied reproduction rate in modern western societies - men or women? The average rate is the same of course, but I wonder which sex have higher variance - higher variance means that ...
Qbik's user avatar
  • 230
11 votes
3 answers
12k views

How much weight/volume do microbes occupy within the human body?

Microorganisms constitute the bulk of all the biomass on Earth. I weighed myself yesterday, and wondered how much less I would weigh if I were completely free of bacteria and microbes, inside and out. ...
LanceLafontaine's user avatar
10 votes
2 answers
7k views

Why do organisms excrete nitrogenous wastes?

Organisms excrete nitrogenous wastes in the form of urea, uric acid or ammonia. But isn’t that a bit of a waste? There is a shortage of biologically available nitrogen in the ecosystem, and plants ...
Gerard's user avatar
  • 361
10 votes
2 answers
682 views

How is human biological clock modelled in modern science?

Im an engineer by education and i program a lot, so the question sounds weird to people from other disciplines. Im trying to better understand the human biological clock. Yet i do not really know ...
Alex Stone's user avatar
  • 6,515
10 votes
1 answer
308 views

Which part of human eyes is getting tired?

It's a thing of common sense that if you read, drive or look at computer screen for too long your eyes will get tired. They burn, itch and try to close all the time. But I was wondering which part(s) ...
Tomáš Zato's user avatar
  • 1,096
10 votes
1 answer
2k views

In humans what is the last metabolic process to cease after death?

After death which of our body's metabolic processes will continue functioning for the longest?
Ben's user avatar
  • 1,131
10 votes
1 answer
1k views

How does laser surgery correct accommodation problems?

When someone undergoes laser surgery to improve eyesight, how does it correct accommodation problems? Why does it not help presbyopia?
Gabriel Fair's user avatar
  • 4,509
9 votes
3 answers
2k views

Is homosexuality an adaptation in humans?

Homo sapiens have menopause - as some other mammals (e.g. some Cetacea) - a phenomenon where older females live for decades after the end of their own reproduction. Perhaps homosexuality, that looks ...
Rodrigo's user avatar
  • 1,300
9 votes
1 answer
60k views

What is the optimum length of abstinence for maximum ejaculation volume in humans?

There have been papers discussing this, and whether the abstinence period should be 1 week, 2 weeks or other [1, 2]. Some think the time to maximum ejaculation volume is even longer than this. doi: ...
user16234's user avatar
9 votes
1 answer
2k views

How quickly can the human heart rate rise and fall?

How quickly can the human heart rate rise and lower? For example lets say a human heart rate is rested and is at 60BPM and that person is suddenly scared to trigger their fight or flight reaction. ...
Scott's user avatar
  • 193
9 votes
1 answer
1k views

What causes Paresthesia (Pins and Needles) at a cellular level?

I've looked it up in plenty of places like the Wikipedia page and such, and it is clear that the most common cause of Paresthesia is either a fair amount of pressure on a specific patch of skin ...
Ethan's user avatar
  • 193
8 votes
2 answers
3k views

How does the brain know where a signal came from? What is the addressing system

I am an electronic engineer so I am thinking about this from an electronics outlook. How does the addressing system work, As I see it, the nervous system is small parallel branches attached to larger ...
Shasam's user avatar
  • 83
8 votes
2 answers
9k views

Why can't we grow more teeth?

A similar question but about teeth healing themselves is Do teeth have the capacity to heal?. So I understand that teeth have the capacity to heal themselves to a certain degree. It appears to be ...
TheLethalConstant's user avatar
8 votes
2 answers
1k views

Would exposure to a strong magnetic field have deleterious effect on the human?

This article states of a 25T magnet, ".. If are ever caught in one of these devices, let’s just say you probably won’t live to tell the tale." Is the above statement in order? What effect would ...
Everyone's user avatar
  • 3,863
6 votes
1 answer
2k views

Getting goosebumps at will

I can get goosebumps at will, regardless of the environment. Its mostly visible on my arms, and I can feel it on my head. It requires some level of concentration to achieve this. My questions are : ...
l0r3nz4cc10's user avatar
6 votes
2 answers
778 views

How significant is the genetic component of homosexual behaviour?

From some basic googling, I found that nobody has ever proven that people are born gay and that environment plays a great part in homosexuality. I wish to know if there is a genetic component to ...
Luca's user avatar
  • 77
6 votes
3 answers
95k views

Is it possible for a child to grow taller than their tallest parent?

I have heard that offspring can't grow taller than either of their parents but I've also heard that sometimes some gene activation can skip generations. Is it possible for a child to grow taller than ...
max's user avatar
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