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.
This question requires you to model the human body so that you can analyse the static loads, (comparing the pilates position and the abdominal sit-up position, figure above)
Using the body mass ‘M’ of 94 kg and a body height ‘h’ of 1.73 metres, establish which exercise requires the most effort...
Homework Statement
A 45 kg woman jumps from a height of 2.5 meters to a solid
floor. In an attempt to minimize the likelihood of injury, she lands on the ball
of her feet (the pads just behind her toes) with her knees bent. What
average force is needed on her feet to stop her fall if her...
In a very good book, Chabay and Sherwood explain that when an initially uncharged person touches a negatively charged metal object, free electrons from the metal neutralize some Na+ ions in the salty layer on the person's skin. The person then becomes negatively charged and the neutral Na atoms...
or Why War is a losing proposition for all involved.
http://www.npr.org/2011/08/11/138823855/the-human-toll-of-the-war-to-end-all-wars
It is a profound discussion.
Hi guys/gals,
I had a couple random questions on leverage and the human body. I am an active individual that enjoys lifting weights and working out. At the gym today, I got to thinking about the "mechanical advantages" that certain body types have doing particular lifts.
First question...
Folks,
I read an article in the Sunday Times as attached. How does this compare against the outcome of the autopsy performed on Einsteins brain?
The article seems to be implying intelligence depends on only the miniaturisation of cells and the density of connections. Surely the evolution...
Homework Statement
Problem 1
The emissivity of the human skin is 97.0 percent. Use 35.0 °C for the skin temperature and approximate the human body by a rectangular block with a height of 1.97 m, a width of 41.0 cm and a length of 34.5 cm.
a) Calculate the power emitted by the human body...
I am wondering if millions of years from now if the Earth and Moon became a true double planetary system, where one side of each body continually face each other, if it could have affects on the height of humans. If people living on the "lunar side" would be taller on average than people on the...
What's the percentage of sub-species of homo sapiens sapiens producing fertile offspring (excluding prolonged selective-breeding with the same genes)?
What circumstances make the percentage less than 100%??
in most mammals, the spine is usually horizontal
in monkeys swinging from branch to branch, the spine has evolved to operate vertically under tension
in humans (and other animals that walk on two legs), the spine is in compression when vertical
did humans evolve from swinging monkeys...
I recently read an article in Scientific American,it was given that the laws of physics will prevent the human brain from becoming an even more powerful thinking machine,i would like to know how do the researchers predict about the human brain's evolutionary limit when we are one of the most...
A human can develop an infinety strategies to solve apuzzle by his brain such as Rubik's cube ,and there is no limitation for the human hand motion rather than the limited movements to a robot , Can a robot be used to improve upon such limitations?
I am interested in making a Rubik's cube...
Hmmm. I hope you will understand my slight nervousness at posting on the philosophy forum with all of its tight rules and circling, predatory mentors. My hope is that by following your instructions closely I’ll avoid the awful finality of those thread closing talons.
So, moved from the...
Scenario:
If a human body is fully charged with positive electrons (protons/lack of electrons) and comes in contact with a pool of positive electrons such as a charged plate, the charge stays the same in the human body and the plate. Now if the human comes in contact with a source of negative...
Hello, Chitose wonder chick here again.
It's might be weird and I don't know where else to ask,
but I want to know about when human have to fight against dog.
... A Military Attack dog that is...
I try looking in internet and I found only how to handle when people get attack by...
Since the old topic is locked, I had to post a new one about this
(old topic here: https://www.physicsforums.com/archive/index.php/t-231156.html" )
People were talking about resonant frequencies for body parts and/or the entire body and someone was looking for a chart, not sure if this is...
Small accomplishment but hopefully it'll lead to greater things, here's the video:
http://ca.news.yahoo.com/video/tech-22186835/calif-students-build-musical-robots-then-jam-25217074.html
I am from Shanghai,China and I am not a native English speaker so there might be some mistakes in my words and I am sorry for it.
Back to the topic.
I have read some papers that some researchers believe with the development of technology, our evolution will come to a halt.
What is your...
Just been revising radiation for an upcoming exam, and was wondering which form of radiation, \alpha, \beta or \gamma is the worst to be exposed to?
Ionising power decreases from alpha to gamma, but penetrating power increases from alpha to gamma. Which is more important when considering how...
Please be gentle, I'm not a physicist, I'm a podiatrist trying to find the answer to a problem that has been confusing me! I hope you can help.
In podiatry we often use foot orthoses in an attempt to alter the magnitude, location and timing of reaction forces at the foot's interface. A...
Hello there,
My name is Rick and a couple of my friends are having a discussion at a local rock climbing gym about the weight of a person and whether or not a person who is heavier, works harder than someone who is lighter.
Neither one of us are gurus when it comes to physics but would love an...
The moral corruption of the UN reached a new level of stink when the Security Council was unable to agree upon issuing a condemnation of the Assad regime's cold-blooded murders of their own citizens (how many condemnations, with much less evidence behind them, have been issued against Israel?)...
I have think I might have a feeble grasp on the idea that simultaneity of events at different points of space depends on the reference frame. However I was having a conversation with my friend and we were trying to figure out if there would be a reference frame where our whole life happened...
I've always had an interest in physical sciences. As my username implies, I have a degree (two, actually) in Electrical Engineering. Several years ago, I browsed some of the threads here, but haven't been back, until encountering PF again today. I've had a girlfriend for the past 18 1/2...
Me and a friend were talking in the pub the other day about evolution, and how some people hold the view that, because of modern engineering and medicine, human evolution by the process of natural selection has stopped.
What do you think? Has evolution stopped? If not, how are "good" or "bad"...
Bill is farsighted and has a near point located 116 cm from his eyes. Anne is also farsighted, but her near point is 74.0 cm from her eyes. Both have glasses that correct their vision to a normal near point (25.0 cm from the eyes), and both wear glasses 2.0 cm from the eyes. Relative to the...
Somewhere between one third and one half of all human deaths all deaths of children under 5 are caused, either directly or indirectly, by malnutrition.
Human starvation is an issue which is surely on all our minds a great deal of the time. It is often discussed, and there is a mountain of...
I have kept the title of this thread quite general because, depending on how it goes, there are a few different points that I’d like to discuss, and that’s really the general theme, as it were. I know the format preferred on this website is for those of us with less expertise to ask questions of...
Hello all,
Im no expert on the subject, but it has always seemed to me that for nuclear power to be safe, they should simply set up power plants far away from human populations.
This seems very simplistic, so I am just curious to know what problems there are with this idea.
Say for...
Ok, I know that the human eye lens adjusts its focal length depending on the object distance to obtain a sharp image on the retina because the image distance has to remain constant. What I am not able to understand is how do the ciliary muscles and the suspensory ligaments contract in order...
Given two people of different complexion, one short and chubby and the other one tall and thin, but same weight (180 lbs each):
a> Do they have the same number of atoms in their bodies
b> If not, will the percent difference be significant?
c>Is there a way to know an estimate of this...
Human body is mass having energy. thanks to Joule it is proved.
Newton explained First, Second and Third laws.
Now,
1. Two equal amount of forces in opposite direction at a given time may not move the OBJECT as per third law of Newton. This is horizontal pull like Tug-of-War. Here 'x'...
Hello everyone,
I was lately thinking about how exactly do these two main electrical measures - current intensity and voltage - differ in describing the effects of electricity on human tissue (skin/muscle/brain etc). For example, I know that most of the time there are warnings of high voltages...
For the Math and Science Learning Materials Forum
Excellent Speaker, Robert Sapolsky, from Stanford University:
http://www.youtube.com/view_play_list?p=848F2368C90DDC3D
Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%.
From Wikipedia, Earth's Atmosphere
Is possible for a human to breathe in an...
Hello, Chitose here
this is first time I post 'talk' instead of 'question'
.......
well, you know that world weather these day is gone haywire.
so... most of people know what the cause (Global worming, El Niño, bla bla bla)
but what the main root of all this problem?
Here's what...
Is access to the Internet a universal human right that should be recognized by the United Nations? *This*question,*buzzing around the world this week, is certainly one that I hadn’t thought of at length until now, so I posed it to …...
I was reading about current electricity and some how I came across the idea that a circuit of no earthed point will not cause any electric shock.
I wonder if it is right cause if it is, why do we need an Earth wire in our appliance.
I am also suspicious because if the circuit is not earthed...
Hello, Chitose wonder chick here again.
As topic says, why human like us don't have mating season like other animal?
what make us special ... or rather different? are our revolution deviate form nature some how?
and other thing, Are there any other animal that don't have mating season...
Does anyone know what is normal voltage for a young, physically healthy human male?
If you take a usual voltmeter and will ground the negative end how many millivolts do you suppose to read by touching dry human skin with the positive end?
Is there suppose to be some difference between skin on...
Hello,
I don't even know if this two are related in the way I think, but this is what i would like to know.
for example
If we traveled far away from the planet Earth and looked back at it (no telescopes), we would see a blue marble but would not be able to see for example our familly...