Examples of posthuman level entities: Dr Manhattan.

Here is an example of an individual from fiction who has elevated them self to become a so called post-human.

Jonathan Osterman was born in Germany sometime during the year 1929. His Father was noted watch maker whom Jon planned to follow in his footsteps. One of Osterman's earliest memories came in 1938 when his Father presented him with a complicated clock to teach him about weight and power.

At the beginning of the second world war Jon's family decided to flee Germany before the Nazi's could take Jon's Jewish mother. Jon was hidden inside a box for market goods until they reached a ship destined for America, unfortunately the carriage they were in was stopped by Nazi's. Jon's mother ran away in an attempt to distract the guards from searching the wagon resulting in her death. Jon's father killed the Nazi soldiers then escaped with Jon to Brooklyn where he could continue his profession as a watch maker.

When the U.S dropped the bomb's on Hiroshima and Nagasaki, Jon was 16 and eager to understand Nuclear physics. The day after the bombs dropped Jon was studying the pocket-watch his father had gave him until his Father confronted him about the undeniable benefits of Relativity theory to Modern science, Jon's Father threw the clocks out of the window then urged Jon to take a career as a Nuclear physicist.

Jon attended Princeton university from 1948-1958 during this time he heard a lecture from Albert Einstein which interested him some what since Einstein was one of the reasons he wanted to become a physicist. His life at university wasn't particularly interesting since he didn't interact well with other people due to him always working day in and day out.

In 1959 his body was disintegrated by an intrinsic filed removable resulting in him becoming a disembodied consciousness. When his body finally reappeared it look like the picture above a blue glowing man of pure energy with the symbol of the hydrogen atom imprinted on his forehead.

So what makes Doctor Manhattan a post-human?

His abilities of course.

His powers are immense to the point of being almost god-like. He can regenerate from any damage in infinitesimal fractions of time, he can even regenerate from a single subatomic particle such as a proton , he can control atomic and sub-atomic particles to such a degree that he can create life and reverse entropy. He is immune to all diseases, does not need to eat , sleep , drink , is effectively immortal , his quantum senses allow him to see the past , present and future all at the same time , he can create multiple copies of himself , teleport over huge distances , move planet sized objects with his mind , project devastating energy blasts , phase through objects , walk on stars as easily as one might walk on a planet , grow to become giant sized , shrink to become sub-atomic , disintegrate people by removing their intrinsic field and much more.

Take into account that Manhattan is still pretty primitive when it comes to post-humans since he still has many notable weaknesses, such as his inability to accurately see into the future.