The Avatar bodies were designed in order for humans to fit in with the indigenous Na'vi of Pandora, so they needed to look like them and share specific characteristics. For this, genetically modified human DNA was mixed with Na'vi genetic material and then grown into a fully-formed body.
Using their capability of advanced genetic engineering, humans develop "Avatar" hybrid bodies from genetically distinct modified human DNA and Na'vi alien genetic material. Through psionics, genetically matched humans are then mind-linked to these "Avatars" for remote control operation.
These Avatars are created using an embryo containing a mixture of Na'vi genes, and the human DNA of the person who will eventually sync and activate the body.
An avatar is a biological shell or clone of a Na'vi-human hybrid, crafted with the combined DNA of a Na'vi and specific human volunteer. Avatars are used to help humans explore Pandora (a moon in the Alpha Centauri star system) without breathing equipment, as the atmosphere on Pandora is toxic to humans.
The most obvious distinction between an avatar and a genuine Na'vi is the number of fingers and toes. A Na'vi only has four digits, while the avatar body has five due to the human DNA. At the end of Avatar, Jake decides to transfer his consciousness to his avatar body permanently.
Na'vi are monogamous creatures and the process of their reproduction is similar to Terran mammals, as they do possess genitalia; however, though they nurse their young and possess belly buttons where they were once connected to an umbilical cord, the Na'vi are non-placental, thus the details of their internal biology ...
Because Grace had an avatar body, Kiri possesses human-like traits such as her eyebrows and five fingers on her hands. She also lacks the elongated canines common amongst the Na'vi.
ATLA takes place on Earth, but it is not Earth as we know it. Instead of seven continents, the world is comprised of four nations: Water, Earth, Fire, and Air. The world is filled with humans, benders (people who can manipulate/use elements), chimera, and plants.
Pandora's air is unbreathable due to high levels of carbon dioxide and trace amounts of hydrogen sulfide, posing a threat to humans. Humans use exopacks and avatar bodies to survive and explore Pandora's toxic atmosphere, but these solutions have limitations and challenges.
Pandora, a potato-shaped moon, is coated in a fine (dust-sized) icy material. Even the craters on Pandora are coated in debris, a stark contrast to the crisply-defined craters of other moons, such as Hyperion. Curious grooves and ridges also appear to cross the surface of the small moon.
Comics later reveal that without an outside force such as war acting against them, Avatars tend to live about 150 years. Ultimately, Aang's short life allowed some of the original characters to make appearances in The Legend of Korra, since her time as the Avatar could not start until after his death.
How do humans become Na'vi? Pandora's atmosphere is inhospitable to humans, so Earth scientists combined human and Na'vi DNA to create Na'vi clones. Humans can then remotely pilot those clones, which are called avatars.
How long do Na'vi live? Landau: The Na'vi age slower than humans, so they have a longer life span. In the burial scene in the film, that woman would be older than the equivalent-looking human.
Shortly after the events of the Avatar, Jake has the Na'vi give his human body a traditional burial and moves the Omaticaya Clan near Hell's Gate to be close to the human allies who were allowed to stay on Pandora.
Aided by a few sympathetic (human) scientists, Jake successfully leads the Na'vi in battle by driving out the predatory humans. In the film's closing scene, the Na'vi transfer Jake into the avatar body permanently, eradicating his disability and neatly delivering him from his original role as a white colonizer.
Because it's set so far in the future, humans have improved their ability to space travel, which is fortunate, because Pandora is a reported 4.37 light years away, as the film depicts it being in the Alpha Centauri A system.
They briefly touch on this in the movie but I wish they elaborated a bit more on it. Humans can last 10 seconds breathing na'vi air, but na'vi can breathe human air for much longer than that but they still at some point need a mask to help them breathe regular human air.
Earth is divided to various nation-states and regions of the planet belonging to ever-shrinking forests and national parks. Earth was once fertile but by the 22nd century production consisted of protein farms.
The fully grown avatar is much closer in appearance to the long-limbed Na'vi than to a human. Typical adult size ranges from nine to ten feet (2.75 to 3.0m) tall with blue skin, bioluminescent markings and large eyes with golden irises.
Its diameter is three-quarters of Earth's, and its mass about half", whereas p. 6 of An Activist Survival Guide gives the diameter as 11447 km (about 89.7% of Earth's equatorial diameter of 12756 km) and its mass as 72% that of Earth.
Avatar was written and directed by James Cameron, The cast includes Sam Worthington, Zoë Saldaña, Sigourney Weaver, Michelle Rodriguez, Stephen Lang, Joel David Moore, Giovanni Ribisi, CCH Pounder, Dileep Rao, Matt Gerald, Laz Alonso, and Wes Studi, and was set in the year 2154.
Unless that theory is true, Grace was impregnated by someone. Kiri's brothers joke that the scientist Norm could be her father. The movie does not reveal much information about the birth of Kiri. It is unclear whether Kiri was conceived before Grace died and her avatar carried her to term.
Kiri is the inquisitive and intelligent adopted daughter of Jake Sully and Neytiri. Not long after Grace Augustine's death, her dormant avatar was discovered to be pregnant, and Jake and Neytiri adopted the child when she was born.
Augustine's colleague Norm Spellman (Joel David Moore) was the father and Grace conceived Kiri before the end of Avatar before somehow giving birth in her Avatar body. However, the more interesting theory is that Kiri is literally the child of Eywa due to some sort of immaculate conception.
