Bipedalism is the basic adaption of the hominin line, and it is considered the main cause behind a suite of skeletal changes shared by all bipedal hominins. Over the years, science fiction communicated scientific ideas, imagined a wide range of possibilities, and influenced public interest in and perspectives of extraterrestrial life. Increasingly, however, an understanding of brain functions is being included in psychological theory and practice, particularly in areas such as artificial intelligence , neuropsychology , and cognitive neuroscience. Sex is related to the very purposes of human existence: In most societies kinship places mutual responsibilities and expectations of solidarity on the individuals that are so related, and those who recognize each other as kinsmen come to form networks through which other social institutions can be regulated. There are two points of contention with the above account of rights. Chewing does aid digestion, however, by reducing food to small particles and mixing it with the saliva secreted by the salivary glands.
Utilization of food by the body
The science of extraterrestrial life in all its forms is known as exobiology. Since the midth century, there has been an ongoing search for signs of extraterrestrial life. This encompasses a search for current and historic extraterrestrial life, and a narrower search for extraterrestrial intelligent life. Depending on the category of search, methods range from the analysis of telescope and specimen data  to radios used to detect and send communication signals.
The concept of extraterrestrial life, and particularly extraterrestrial intelligence, has had a major cultural impact, chiefly in works of science fiction.
Over the years, science fiction communicated scientific ideas, imagined a wide range of possibilities, and influenced public interest in and perspectives of extraterrestrial life. One shared space is the debate over the wisdom of attempting communication with extraterrestrial intelligence. Some encourage aggressive methods to try for contact with intelligent extraterrestrial life.
Others—citing the tendency of technologically advanced human societies to enslave or wipe out less advanced societies—argue that it may be dangerous to actively call attention to Earth. Alien life, such as microorganisms , has been hypothesized to exist in the Solar System and throughout the universe. This hypothesis relies on the vast size and consistent physical laws of the observable universe. According to this argument, made by scientists such as Carl Sagan and Stephen Hawking ,  as well as well-regarded thinkers such as Winston Churchill ,   it would be improbable for life not to exist somewhere other than Earth.
Alternatively, life may have formed less frequently, then spread—by meteoroids , for example—between habitable planets in a process called panspermia. Since the s, scientists have proposed that " habitable zones " around stars are the most likely places to find life. Numerous discoveries in such zones since have generated numerical estimates of Earth-like planets —in terms of composition—of many billions.
A study published in suggests that due to how complexity evolved in species on Earth, the level of predictability for alien evolution elsewhere would make them look similar to life on our planet. One of the study authors, Sam Levin, notes "Like humans, we predict that they are made-up of a hierarchy of entities, which all cooperate to produce an alien.
At each level of the organism there will be mechanisms in place to eliminate conflict, maintain cooperation, and keep the organism functioning. We can even offer some examples of what these mechanisms will be. It has been suggested that this capacity arises with the number of potential niches a planet contains, and that the complexity of life itself is reflected in the information density of planetary environments, which in turn can be computed from its niches. Life on Earth requires water as a solvent in which biochemical reactions take place.
Sufficient quantities of carbon and other elements, along with water, might enable the formation of living organisms on terrestrial planets with a chemical make-up and temperature range similar to that of Earth.
It is also conceivable that there are forms of life whose solvent is a liquid hydrocarbon , such as methane , ethane or propane. About 29 chemical elements play an active positive role in living organisms on Earth. These six elements form the basic building blocks of virtually all life on Earth, whereas most of the remaining elements are found only in trace amounts.
The carbon atom has the unique ability to make four strong chemical bonds with other atoms, including other carbon atoms. These covalent bonds have a direction in space, so that carbon atoms can form the skeletons of complex 3-dimensional structures with definite architectures such as nucleic acids and proteins. Carbon forms more compounds than all other elements combined.
The great versatility of the carbon atom makes it the element most likely to provide the bases—even exotic ones—for the chemical composition of life on other planets. Some bodies in the Solar System have the potential for an environment in which extraterrestrial life can exist, particularly those with possible subsurface oceans. According to NASA's Astrobiology Strategy, "Life on other worlds is most likely to include microbes, and any complex living system elsewhere is likely to have arisen from and be founded upon microbial life.
Important insights on the limits of microbial life can be gleaned from studies of microbes on modern Earth, as well as their ubiquity and ancestral characteristics. Mars may have niche subsurface environments where microbial life might exist. The panspermia hypothesis proposes that life elsewhere in the Solar System may have a common origin. If extraterrestrial life was found on another body in the Solar System , it could have originated from Earth just as life on Earth could have been seeded from elsewhere exogenesis.
The first known mention of the term 'panspermia' was in the writings of the 5th century BC Greek philosopher Anaxagoras. Directed panspermia concerns the deliberate transport of microorganisms in space, sent to Earth to start life here, or sent from Earth to seed new stellar systems with life.
The Nobel prize winner Francis Crick , along with Leslie Orgel proposed that seeds of life may have been purposely spread by an advanced extraterrestrial civilization,  but considering an early " RNA world " Crick noted later that life may have originated on Earth. In the early 20th century, Venus was often thought to be similar to Earth in terms of habitability, but observations since the beginning of the Space Age have revealed that Venus's surface is inhospitable to Earth-like life.
However, between an altitude of 50 and 65 kilometers, the pressure and temperature are Earth-like, and it has been speculated that thermoacidophilic extremophile microorganisms might exist in the acidic upper layers of the Venusian atmosphere.
Life on Mars has been long speculated. Liquid water is widely thought to have existed on Mars in the past, and now can occasionally be found as low-volume liquid brines in shallow Martian soil.
There is evidence that Mars had a warmer and wetter past: Nevertheless, present conditions on Mars' subsurface may support life. Ceres , the only dwarf planet in the asteroid belt , has a thin water-vapor atmosphere.
Carl Sagan and others in the s and s computed conditions for hypothetical microorganisms living in the atmosphere of Jupiter. Scientists have indications that heated subsurface oceans of liquid water may exist deep under the crusts of the three outer Galilean moons —Europa,    Ganymede ,      and Callisto.
Jupiter's moon Europa has been subject to speculation about the existence of life due to the strong possibility of a liquid water ocean beneath its ice surface. The case for life on Europa was greatly enhanced in when it was discovered that vast lakes exist within Europa's thick, icy shell.
Scientists found that ice shelves surrounding the lakes appear to be collapsing into them, thereby providing a mechanism through which life-forming chemicals created in sunlit areas on Europa's surface could be transferred to its interior. On 11 December , NASA reported the detection of " clay-like minerals " specifically, phyllosilicates , often associated with organic materials , on the icy crust of Europa.
Enceladus , a moon of Saturn, has some of the conditions for life, including geothermal activity and water vapor, as well as possible under-ice oceans heated by tidal effects. The temperature and density of the plumes indicate a warmer, watery source beneath the surface.
Titan , the largest moon of Saturn , is the only known moon in the Solar System with a significant atmosphere. Data from the Cassini—Huygens mission refuted the hypothesis of a global hydrocarbon ocean, but later demonstrated the existence of liquid hydrocarbon lakes in the polar regions—the first stable bodies of surface liquid discovered outside Earth. Small Solar System bodies have also been speculated to host habitats for extremophiles.
Fred Hoyle and Chandra Wickramasinghe have proposed that microbial life might exist on comets and asteroids. This is in contrast with the oceans that may be inside larger icy satellites like Ganymede, Callisto, or Titan, where layers of high-pressure phases of ice are thought to underlie the liquid water layer.
Hydrogen sulfide has been proposed as a hypothetical solvent for life and is quite plentiful on Jupiter's moon Io , and may be in liquid form a short distance below the surface. The scientific search for extraterrestrial life is being carried out both directly and indirectly.
Scientists search for biosignatures within the Solar System by studying planetary surfaces and examining meteorites.
It is designed to assess the past and present habitability on Mars using a variety of scientific instruments. The rover landed on Mars at Gale Crater in August The Gaia hypothesis stipulates that any planet with a robust population of life will have an atmosphere in chemical disequilibrium, which is relatively easy to determine from a distance by spectroscopy. However, significant advances in the ability to find and resolve light from smaller rocky worlds near their star are necessary before such spectroscopic methods can be used to analyze extrasolar planets.
To that effect, the Carl Sagan Institute was founded in and is dedicated to the atmospheric characterization of exoplanets in circumstellar habitable zones. In August , findings by NASA, based on studies of meteorites found on Earth, suggest DNA and RNA components adenine , guanine and related organic molecules , building blocks for life as we know it, may be formed extraterrestrially in outer space.
In August , and in a world first, astronomers at Copenhagen University reported the detection of a specific sugar molecule, glycolaldehyde , in a distant star system. The molecule was found around the protostellar binary IRAS , which is located light years from Earth. This finding suggests that complex organic molecules may form in stellar systems prior to the formation of planets, eventually arriving on young planets early in their formation.
Projects such as SETI are monitoring the galaxy for electromagnetic interstellar communications from civilizations on other worlds. The length of time required for a signal to travel across the vastness of space means that any signal detected would come from the distant past. Some astronomers search for extrasolar planets that may be conducive to life, narrowing the search to terrestrial planets within the habitable zone of their star.
There is at least one planet on average per star. The nearest known exoplanet is Proxima Centauri b , located 4. Almost all of the planets detected so far are within the Milky Way, but there have also been a few possible detections of extragalactic planets.
The study of planetary habitability also considers a wide range of other factors in determining the suitability of a planet for hosting life. One sign that a planet probably already contains life is the presence of an atmosphere with significant amounts of oxygen , since that gas is highly reactive and generally would not last long without constant replenishment. This replenishment occurs on Earth through photosynthetic organisms.
One way to analyze the atmosphere of an exoplanet is through spectrography when it transits its star, though this might only be feasible with dim stars like white dwarfs. The science of astrobiology considers life on Earth as well, and in the broader astronomical context.
In , "remains of biotic life " were found in 4. In , University of California, Santa Cruz , astronomer and astrophysicist Frank Drake devised the Drake equation as a way to stimulate scientific dialogue at a meeting on the search for extraterrestrial intelligence SETI.
The equation is best understood not as an equation in the strictly mathematical sense, but to summarize all the various concepts which scientists must contemplate when considering the question of life elsewhere.
Drake's proposed estimates are as follows, but numbers on the right side of the equation are agreed as speculative and open to substitution:. The Drake equation has proved controversial since several of its factors are uncertain and based on conjecture, not allowing conclusions to be made.
Based on observations from the Hubble Space Telescope , there are between and billion galaxies in the observable universe. Even if it is assumed that only one out of a billion of these stars has planets supporting life, there would be some 6. A study based on results from the Kepler spacecraft estimated that the Milky Way contains at least as many planets as it does stars, resulting in — billion exoplanets.
The apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for such civilizations is known as the Fermi paradox. Cosmic pluralism, the plurality of worlds, or simply pluralism, describes the philosophical belief in numerous "worlds" in addition to Earth, which might harbor extraterrestrial life.
Before the development of the heliocentric theory and a recognition that the Sun is just one of many stars,  the notion of pluralism was largely mythological and philosophical. With the scientific and Copernican revolutions , and later, during the Enlightenment , cosmic pluralism became a mainstream notion, supported by the likes of Bernard le Bovier de Fontenelle in his work Entretiens sur la pluralité des mondes.
The astronomer Camille Flammarion promoted the notion of cosmic pluralism in his book La pluralité des mondes habités. There was a dramatic shift in thinking initiated by the invention of the telescope and the Copernican assault on geocentric cosmology.
Once it became clear that Earth was merely one planet amongst countless bodies in the universe, the theory of extraterrestrial life started to become a topic in the scientific community. The best known early-modern proponent of such ideas was the Italian philosopher Giordano Bruno , who argued in the 16th century for an infinite universe in which every star is surrounded by its own planetary system.
Bruno wrote that other worlds "have no less virtue nor a nature different to that of our earth" and, like Earth, "contain animals and inhabitants".
In Baroque literature such as The Other World: The Societies and Governments of the Moon by Cyrano de Bergerac , extraterrestrial societies are presented as humoristic or ironic parodies of earthly society.
Fontanelle 's "Conversations on the Plurality of Worlds" translated into English in offered similar excursions on the possibility of extraterrestrial life, expanding, rather than denying, the creative sphere of a Maker. The possibility of extraterrestrials remained a widespread speculation as scientific discovery accelerated. William Herschel , the discoverer of Uranus , was one of many 18th—19th-century astronomers who believed that the Solar System is populated by alien life.
Other luminaries of the period who championed "cosmic pluralism" included Immanuel Kant and Benjamin Franklin. At the height of the Enlightenment , even the Sun and Moon were considered candidates for extraterrestrial inhabitants. Speculation about life on Mars increased in the late 19th century, following telescopic observation of apparent Martian canals —which soon, however, turned out to be optical illusions.
Wells to write the novel The War of the Worlds in , telling of an invasion by aliens from Mars who were fleeing the planet's desiccation. Spectroscopic analysis of Mars's atmosphere began in earnest in , when U. The science fiction genre, although not so named during the time, developed during the late 19th century.
Jules Verne 's Around the Moon features a discussion of the possibility of life on the Moon, but with the conclusion that it is barren. Stories involving extraterrestrials are found in e. Wells was published in which stands at the beginning of the popular idea of the "Martian invasion" of Earth prominent in 20th-century pop culture. Most unidentified flying objects or UFO sightings  can be readily explained as sightings of Earth-based aircraft, known astronomical objects , or as hoaxes.
The possibility of extraterrestrial life on the Moon was ruled out in the s, and during the s it became clear that most of the other bodies of the Solar System do not harbor highly developed life, although the question of primitive life on bodies in the Solar System remains open.
The failure so far of the SETI program to detect an intelligent radio signal after decades of effort has at least partially dimmed the prevailing optimism of the beginning of the space age.
Notwithstanding, belief in extraterrestrial beings continues to be voiced in pseudoscience , conspiracy theories, and in popular folklore , notably " Area 51 " and legends. It has become a pop culture trope given less-than-serious treatment in popular entertainment.
At the same time, the data returned by space probes, and giant strides in detection methods, have allowed science to begin delineating habitability criteria on other worlds, and to confirm that at least other planets are plentiful, though aliens remain a question mark.
In , geologist and paleontologist Peter Ward and astrobiologist Donald Brownlee published a book entitled Rare Earth: Why Complex Life is Uncommon in the Universe.
Ward and Brownlee are open to the idea of evolution on other planets that is not based on essential Earth-like characteristics such as DNA and carbon. Theoretical physicist Stephen Hawking in warned that humans should not try to contact alien life forms. He warned that aliens might pillage Earth for resources. In November , the White House released an official response to two petitions asking the U.
According to the response, "The U. In , the exoplanet Keplerf was discovered, along with Keplere and Keplerc. A related special issue of the journal Science , published earlier, described the discovery of the exoplanets. On 17 April , the discovery of the Earth-size exoplanet Keplerf , light-years from Earth , was publicly announced;  it is the first Earth-size planet to be discovered in the habitable zone and it has been hypothesized that there may be liquid water on its surface.
On 13 February , scientists including Geoffrey Marcy , Seth Shostak , Frank Drake and David Brin at a convention of the American Association for the Advancement of Science , discussed Active SETI and whether transmitting a message to possible intelligent extraterrestrials in the Cosmos was a good idea;   one result was a statement, signed by many, that a "worldwide scientific, political and humanitarian discussion must occur before any message is sent".
The group contracted the services of the meter Robert C. From Wikipedia, the free encyclopedia. For other uses, see Astrobiology. Some major international efforts to search for extraterrestrial life.
Clockwise from top left: The search for extrasolar planets image: Kepler telescope Listening for extraterrestrial signals indicating intelligence image: Allen array Robotic exploration of the Solar System image: Curiosity rover on Mars. Planetary habitability , Habitability of natural satellites , and Exobiology. List of planetary systems. Including red dwarfs would increase this to 40 billion. The New York Times. Retrieved 20 November Controversial pieces of evidence for extraterrestrial life".
Retrieved 18 February Retrieved 6 January Archived from the original on 24 October Retrieved 10 March Other Worlds, Other Universes. Art of Mentoring Series. Chemical Evolution and the Origin of Life. International Journal of Astrobiology. Retrieved 15 December Retrieved 3 December Astrobiology Science Conference Surviving Catastrophes and Extremes on Earth and Beyond.
Retrieved 30 March Retrieved 24 April University of Puerto Rico. Retrieved 29 April Retrieved 5 November Towards the qualitative assessment of biological potential on exoplanets". International Journal of Astrobiology: The National Academies Press.
In Shils, Maurice E. Modern Nutrition in Health and Disease 9th ed. Retrieved 8 August Much of it was for survival: We moved to gather food, escape predators and migrate to more forgiving land. Even as humans advanced, our bodies were in motion. Long days of farm work, trudging into town for school or supplies and other factors of everyday living meant there was little time for our ancestors to rest on their laurels. In the mid th century, however, technological advances, a rise in car culture and a shift from physically demanding work to office jobs began chipping away at our physical activity.
Today, at a time when we have more choices than ever in almost every aspect of our lives, most of us choose to be stationary. But how does not moving regularly take a toll on our health? The World Health Organization estimates that a lack of physical activity is associated with 3. Researchers found the highest level of frailty experienced the most severe impact. A study of more than 80, people found each hour they spent watching TV increased their risk of developing diabetes by 3.
Remaining stationary for too long slows blood circulation to the legs, which can lead to swollen ankles, blood clots , swelling and pain. At the scarier end is deep vein thrombosis , when a blood clot forms in your legs.
The clot can eventually break free and obstruct other parts of your body, including your lungs. Ironically, sitting down to work can actually lead to trouble concentrating. This slows down our cognitive functions and leads to brain fog. We need our bodies to maintain lean muscle tissue so we can perform our daily tasks without hurting or taxing our bodies.
With a sedentary lifestyle, that all changes. Ordinary events, like grocery shopping or picking things up, become much more difficult. This becomes especially important in older adults, who are already losing muscle mass and bone strength. The kicker with our sedentary lifestyles is that even if you exercise regularly, it might not be enough to combat all those hours you spend sitting at work or in the car.
Are you standing yet? The good news is that you can prevent the effects of a sedentary lifestyle, even if you do work in an office environment — and none of them include exercising more.
Use your smartphone for good, not evil. Keep your brain engaged and your legs moving by scheduling walking meetings with your team. Being up on your feet and not slumped in a chair can spark your creativity as your body sends blood to the brain. Plus, you can walk to lose weight at the same time! How many emails do you send to co-workers a day? From the sound of it, you might think leaky gut only affects the digestive system, but in reality it can affect more.
Click here to learn more about the webinar. Josh Axe is on a mission to provide you and your family with the highest quality nutrition tips and healthy recipes in the world Health Weight Loss Current: Why a Sedentary Lifestyle Stinks The human body was designed to move.