What is Human: Definition and 893 Discussions

Humans (Homo sapiens) are the most abundant and widespread species of primates, characterized by bipedality and large complex brains enabling the development of advanced tools, culture and language. Humans are highly social beings and tend to live in large complex social structures composed of many cooperating and competing groups, from families and kinship networks to political states. Social interactions between humans have established a wide variety of values, social norms, and rituals, which bolster human society. Curiosity and the human desire to understand and influence the environment and to explain and manipulate phenomena have motivated humanity's development of science, philosophy, mythology, religion, and other fields of knowledge.
Humans evolved from other hominins in Africa several million years ago. Although some scientists equate humans with all members of the genus Homo, in common usage it generally refers to Homo sapiens, the only extant member. H. sapiens emerged around 300,000 years ago, evolving from Homo erectus and migrating out of Africa, gradually replacing local populations of archaic humans. Early humans were hunter-gatherers, before settling in the Fertile Crescent and other parts of the Old World. Access to food surpluses led to the formation of permanent human settlements and the domestication of animals. As populations became larger and denser, forms of governance developed within and between communities and a number of civilizations rose and fell. Humans have continued to expand, with over 7.8 billion humans occupying almost all regions of the world in 2021.
Genes and the environment influence human biological variation in visible characteristics, physiology, disease susceptibility, mental abilities, body size and life span. Though humans vary in many traits (such as genetic predispositions and physical features), two humans on average are over 99% similar, with the most genetically diverse populations from Africa. The greatest degree of genetic variation exists between males and females. On average, men have greater body strength and women generally have a higher body fat percentage. Females undergo menopause and become infertile decades before the end of their lives. They also have a longer life span in almost every population around the world. The division into male and female gender roles has varied historically, and challenges to predominant gender norms have recurred in many societies.
Humans are omnivorous, capable of consuming a wide variety of plant and animal material, and have used fire to prepare and cook food since the time of H. erectus. They can survive for up to eight weeks without food, and three or four days without water. Humans are generally diurnal, sleeping on average seven to nine hours per day. Childbirth is dangerous, with a high risk of complications and death. Both the mother and the father provide care for human offspring who are helpless at birth.
Humans have a large and highly developed prefrontal cortex, the region of the brain associated with higher cognition. They are intelligent beings, capable of episodic memory, flexible facial expressions, self-awareness and a theory of mind. The human mind is capable of introspection, private thought, imagination, volition and forming views on existence. This has allowed great technological advancements and complex tool development possible through reason and the transmission of knowledge to future generations. Language, art and trade are defining characteristics of humans. Long-distance trade routes might have led to cultural explosions and resource distribution that gave humans an advantage over other similar species.

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  1. G

    Human evolution - From sperm to ape

    The reason I'm writing this is because I would like to share my thoughts about this interesting thing I was thinking about. So we all know how animals and all other living organisms share a common microbial ancestor that dates back billions of years. Well, I just find it fascinating how when...
  2. Rainie Metis

    Comparing Crushing Forces: Human vs. Fly

    Homework Statement Hello All, I might be at best HS level physics understanding but I’m quick study and need guidance. I am in a debate with someone who thinks a body can be crushed to the point of dust. I’d like to know if a comparison can be made, basic ratio: Human crushed by a building at...
  3. ISamson

    Salt vs Sugar: Which is More Harmful to the Human Body?

    During these days, I have asked my mother: What is better/worse for the human body: salt or sugar? Both of these substances are quite dangerous in high amounts, but which one is worse? Salt was used in food preservation, with its abilities (Which abilities? I have never understood this...) and...
  4. B

    Distance from the equator and human evolution

    I was pondering human evolution on different continents recently and some thoughts occurred to me: 1# the distance a region is from the equator determines the temperature of a climate all over the Earth 2# humans have probably been in regions of varying distances from the Equator long enough for...
  5. B

    How the human MRCA possibly have lived just 3,000 years ago?

    https://en.wikipedia.org/wiki/Most_recent_common_ancestor I was reading about the human most recent common ancestor (MRCA) at the above link at Wikipedia. According to this article at Wikipedia, there have been common human ancestors to all humans alive today. This sounds far-fetched to me...
  6. ErenJaeger2

    B What is the True Dimension of Human Perception?

    I have read things saying humans see 2d and also things saying its more like "two and a half d" but that humans don't actually see in three dimension. But when you explain the spatial dimension, you start with the first which can be explained by a line. So anything living in 1d would only be...
  7. BuCDr3H4

    Energy of beamed EM field that can heat human tissue

    I only have a background in mathematics, and I lack knowledge on this matter. I want to get quantitive value about that problem. What would be the kind of wave or EM field that could heat human tissu of 1°C in (say a body part like the thigh), say in one hour, at a distance of 2m ? We could...
  8. Zeynel

    What would make the human eye see more details?

    First let me tell you the context: There was this recently discovered tiny sealstone depicting warriors in battle measuring only 1.4 inches across. This piece contains incredible detail that modern human eye cannot discern without a mechanical aid. Read more at...
  9. L

    Human Haplogroups rule out humans descending from....

    I am not a professional in this field so please bear with my ignorance. I try to be science literate where ever I can.My question is: Do genetics broadly and haplogroups more specifically rule out humans descending from more than one gene pool of common ancestors?To put it another way: Could it...
  10. S

    No sublimation for human body in vacuum? [Thermodynamics]

    In my Thermodynamics course, we recently learned about the saturation pressure and saturation temperature of different substances -mainly water. As you know, the saturation temperature at which a substance begins to boil is specific to a fixed saturation pressure. Water only boils at 100...
  11. F

    Biomechanics, center of mass of human body and balance

    Hello everyone, I know that the any object, human body included, when the vertical line from its center of mass to the floor falls outside the base of support, topples under the influence of gravity: the force of gravity produces a nonzero torque that rotates the body. Is the human body able to...
  12. L

    What types of light can safely pass through the human body?

    What types of light are able to pass through the human body without causing damage to tissue or individual cells? Are there any truly safe alternatives to x-rays that could allow doctors to see internal body parts but not cause damage from extended exposure?
  13. N

    Medical What Causes the Human Brain to Believe in Fictional Phenomena?

    What is it in the human brain that causes a person to believe completely something that is fictional such as astral projection or that theyve talked to God so to speak. How can said person believe fully that they have experienced such a thing whilst knowing it is impossible. Basically I am...
  14. P

    Can human traits be formalized?

    I've been wondering about modeling human traits that seem to have a universal aspect of nature. Though this is worthy of another topic, on a more fundamental level or serving as a good example, can 'masculinity' have a more objective measure of measuring it and formalizing it. In other words, is...
  15. F

    Atmospheric air pressure on the human body

    Hello, It is well known that the atmospheric air pressure is significantly strong but our body does not get crushed by it because and equal pressure pushes from the inside our body. That said, does it mean that air can exist and be diffused inside solid organs like the lungs, our heart, etc...
  16. D

    Human Cell Walls as Capacitors

    Homework Statement Some cell walls in the human body have a layer of negative charge on the inside surface. Suppose that the surface charge densities are ##±0.50 \times 10^{-3} C/m^2## , the cell wall is ##5.0 \times 10^{-9} m## thick, and the cell wall material has a dielectric constant of...
  17. Asmaa Mohammad

    Medical The power of the human eye's lens

    Hello, I read in my physiology book that when the ciliary muscle relaxes, the power of the eye lens decreases, hence we get the ability to see far objects. I am new to physiology, and when I googled "the power of the eye lens" I didn't find articles explain the sentence above simply. So I...
  18. F

    TV based education instead of Human teachers?

    I have thinking about this issue quite a lot recently; Imagine a class of students where students don't ask any questions to teacher; All of the communication is only from teacher to students. ( I myself have attended such classes when I was a student.) In such class why teacher can not be...
  19. M

    B Can Increasing Human Body Density Enable Breaking Rocks by Hand Compression?

    Hello, I've been watching too much anime. I know that isn't the best way to ask a question scientific in nature, but visualizing bizarre situations is one of the best ways to come up with interesting questions. Anyways, in order to break a rock by compressing it with your hands, you would need...
  20. J

    Practical Skills - Recording time with human error

    Homework Statement Please could someone help me with how raw data should be dealt with when using a human operated stop watch. I have attached the information we were given and it makes little sense to me. Homework Equations See attachement The Attempt at a Solution We are constantly reminded...
  21. Graeme M

    Resolution of the human visual system in physical terms

    I've often wondered at the "resolution" of the human visual system but it's not at all clear from what I've read whether this question even makes sense. As a sort of general position, many of the articles I've read suggest that the human eye, over the full field of vision, delivers around...
  22. Sophrosyne

    Medical Optical transparency of the human cornea and lens

    There are two optically transparent tissues in the human body: the cornea and the lens. But how they achieve this transparency is different, and both in turn appear to achieve this differently than in other optically clear materials like glass. The transmission of light through glass or other...
  23. Thinkaholic

    I'm Terrified of Human Extinction

    Hi, all. I'm nearly 14, and self-teaching physics and mathematics. One quote of Newton's really inspires me. It is the 'Shoulders of giants' quote, and even though it was just Newton taking a stab at Robert Hooke's short stature, it has meaning to me, and probably you guys, too. I want people to...
  24. S

    The human brain and integration

    What does this mean, and is it true?
  25. Buzz Bloom

    Bad society from human genetic manipulation

    In the thread https://www.physicsforums.com/threads/first-human-embryos-edited-in-u-s.921238/ the film Gattaca was discussed as an example of a very bad society brought about by the use of human genetic manipulation. In my opinion the Gattaca society is a very poor example of this in that is is...
  26. Zeynel

    Exploring Telomeres and Aging: A Layman's Guide

    I read that cells in human body are continuously oxidized. Can you explain in layman's term what this means? Is it possible to explain cell oxidation withot reference to "electron loss." Because I cannot imagine visually how a cell can lose an electron or what that means.
  27. Greg Bernhardt

    First Human Embryos Edited in U.S.

    Researchers have demonstrated they can efficiently improve the DNA of human embryos. https://www.technologyreview.com/s/608350/first-human-embryos-edited-in-us/
  28. R

    B How to track the center of mass of a human in a video

    So a few months or years ago I learned that most of the energy from swinging comes from raising the center of mass at the lowest point of a swing. I also recently found a method of swinging that maximizes this energy gain. You squat on the swing, and stand up every time it gets to the lowest...
  29. JAA

    An elementary question - Percussive waveform moving through human tissue

    I need a better understanding and explanation of how a percussion wave form can move through biological soft tissue. I know that human soft tissue functions microscopically in a fluid environment however I also understand that there are also obstructive forces in the way of a wave moving in a...
  30. I

    Desalination of water and its effect on the human body

    I have been thinking, looking for an answer. It is known to me that drinking pure H2O is bad for the body, reason is it saps all of the minerals from the body since it does not contain any. I have been thinking, if I take salt water from a certain sea, put it in a container and boil the water...
  31. davidge

    I Time: A Human Way of Measuring Change?

    First of all, it's not intended to be a philosophical question, but rather a physical one. So, what can we say about time? Maybe, it's a human way of measuring how things evolve in space? Suppose there are a room with objects within it, where nothing ever happens. There's no need to talk about...
  32. G

    What's the aspect ratio of human vision?

    What's the average aspect ratio of human vision as we perceive it?
  33. Evo

    Mystery Species of Human Relative Discovered: Homo Naledi

    It will be interesting to see what comes of this. https://www.yahoo.com/news/homo-naledi-mystery-human-species-091635429.html
  34. Daniel Travis

    Artificial gravity -- consequences for the human body

    Hey all, *this is my first post on this forum* I've read a lot about the different ways of artificial gravity on this forum, and we've discussed everything from realistic ideas that can be accomplished with today's tech, all the way to fictitious situations in sci fi books. BASICALLY, I would...
  35. jim mcnamara

    Early human DNA in cave sediments

    http://science.sciencemag.org/lookup/doi/10.1126/science.aam9695']science.sciencemag.org/lookup/doi/10.1126/science.aam9695[/PLAIN] Researchers have found a way to extract DNA from cave floor sediment strata. Mixed in with a lot of other mammalian DNA is DNA from Neandertal and Denisovan...
  36. A

    Why was the curious ape grooming a human? Watch the beautiful video now!

    Beautiful video. Useful perhaps to educate people who are ashamed of our primate cousins? Richard Dawkins says he is proud to be an African ape.
  37. teacherman

    Medical When (and Why) Does a Human Baby's Vision "Flip"

    Greetings to all, I realize that there is another "dead thread" about this subject (with a lot of interesting comments) but I think I can add a "new dimension" to the conversation.:smile: I have also put this question out on a few other Science Forums... The human eye is much like the lens of a...
  38. teacherman

    Medical Why does a human baby's vision invert?

    Mentor note: Split the thread in two parts, the other part is here: When (and Why) Does a Human Baby's Vision "Flip". This thread discusses the inversion of human vision, "up/down", "left/right" and 180 degree rotations. Greetings to all, I realize that there is another "dead thread" about this...
  39. J

    I Farthest distance a human can travel from Earth in a life

    I've been stuck on this physics problem for several years now. I would be very grateful if someone could explain how to solve this problem. The farthest a human could travel from Earth in one lifetime theoretically is limited only by the acceleration a human can withstand, and the length of...
  40. Delta Force

    Physics of Human Caused Earthquakes?

    I'm not sure if this is the right area of the forum (it may be more Earth physics) or even the right site for this (it might be more of a geology question), but I'm wondering if someone more knowledgeable in physics could explain the physics of human caused earthquakes to me. Recently the United...
  41. Ygggdrasil

    Medical National Academies Recommendations on Human Gene Editing

    This week on, Feb 14, the US National Academy of Sciences and National Academy of Medicine released a report giving recommendations on how...
  42. Avatrin

    Physical properties of materials in the human body

    I am looking for resources on the physical properties of the various components that make up the human body. As an example of what I am looking for; If we look at the finger, we know it has bones, skins, nails, blood etc. What are the various physical properties of these different parts...
  43. D

    How can you measure frequencies in the human body?

    I read posts from a few years ago regarding measuring frequencies in the human body. I am wondering if there are any new developments. What devices can measure frequency? Thanks!
  44. L

    B Venus -- a more attractive target than Mars for human colonization?

    If Venus had an atmosphere similar to that of Mars, would Venus then be a more attractive target than Mars for human colonization?
  45. H

    Human marathon limit challenged by Nike

    Some claim not possible naturally, ie beat 2 hours. While not possible under race conditions Nike is trying to see if it is humanly possible; http://running.competitor.com/2016/12/news/nike-launches-program-break-2-hour-marathon-barrier-2017_160032
  46. S

    Frequencies -- what is the average frequency for the human body?

    Hi all, Would anyone be able to let me know what the average frequency is for the human body? Also, what is the average frequency of a home? What would be considered abnormal? According to the Ofcom UK Frequency Allocation Table it notes different frequency uses e.g. a frequency of 1,600...
  47. J

    B Does the human calculator stuff really work?

    I have seen books and videos that claim to teach you how to become a human calculator. does this stuff really work? if it does can you recommend a good book or video ?
  48. Stephanus

    Where Did People in Indonesia Originate From?

    Dear PF Forum, It's been a while that I've been wondering. Where did people from particular island in Indonesia come from? Here is the map As I understand it, homo sapiens came out of Africa 70 thousands years ago, and they went to Australia. Is that why that our brothers (and sisters) from...
  49. L

    Detailed list of all known human ancestors

    Hi everyone, In Carl Sagan's Cosmos there's a short animation video illustrating the shape of all human ancestors, starting from single cell organisms, morphing towards the modern humans. I've searched for a complete list of known human ancestors like that one, but I couldn't find anything like...
  50. M

    Magnetisation ratio in human body using gyromagnetic ratios

    Homework Statement The number density of 1H nuclei in the body is roughly 600 times greater than that of 13C nuclei. By what factor is the magnetisation M0 of 1H greater than 13C in the same external magnetic field? Homework Equations 3. The Attempt at a Solution [/B] Surely it can't be as...
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