The characters' responses to their discoveries drive the plot of the series and influence its fictional history, particularly by encouraging humanity to progress with technological development.

However, the evolutionary development projects they began would by their nature require very long time spans to complete, far longer than the lives of their creators.

When they encountered a living world that had features in favour of the evolution of intelligent life, they left behind the Monoliths as remote observers that were also capable of taking a variety of actions according to their creators' wishes.

TMA-1 was dug up during the lunar night but, after sunrise and its exposure to direct sunlight, TMA-1 emits a single powerful burst of energy, interpreted as radio waves – aimed at Iapetus (a moon of Saturn) in the novel or Jupiter in the motion picture.

In the novel, some scientists speculate that its magnetic field came from large electric currents, circulating in a system of superconductors for millions of years as an energy-storage mechanism.

In 2061: Odyssey Three, it is implied that TMA-2 is the monolith found resting on its side on Europa because it has the same size (2 kilometers long) and contains the digitized minds of Dave Bowman and HAL; however, no character refers to it as TMA-2 or Big Brother, instead christening it "The Great Wall".

In any case, HAL and Bowman infect that monolith with a computer virus after it is learned that its superiors are sending an order to destroy humanity.

In the year 2513, the first Monolith to be encountered by humankind's prehistoric evolutionary predecessors (the ones featured in the first novel) was found in Olduvai Gorge, buried in ancient rock, and retroactively dubbed "TMA-0".

In the second, in 3001: The Final Odyssey, millions of monoliths are generated to block both the Earth and human-settled Ganymede from their primary star in an attempt to destroy the humans.

(Arthur C. Clarke admitted to changing some concepts each time he wrote another sequel novel so it is not possible to fully reconcile TMA-2 and The Great Wall.)

In the 3001 novel, it is realized that back in the early 22nd century, TMA-2 broadcast a status report message to a point 450 light years away and is just now receiving instructions in return.

The Monoliths are extremely long-lived and reliable machines, able to survive for millions of years buried in the ground or resisting meteorite impacts and radiation in space with no apparent damage.

The two Monoliths recovered and examined by humans are virtually indestructible and impenetrable, resisting all attempts to analyze their composition or internal structure right up to the end of the series.

Dr. Heywood Floyd proposes they have some sort of force shield, an impression he gets from touching it; this hypothesis is later accepted as probable because the Monoliths resist destructive testing beyond the theoretical limits of material strength.

However, they are not completely indestructible: The Great Wall Monolith (perhaps the same as TMA-2) was knocked on its side and suffered from damage caused by a giant meteorite of solid diamond that collided with Europa in 2061: Odyssey Three.

TMA-2 replicates itself by a form of symmetrical binary fission and exponential growth to create thousands or millions of identical Monoliths in just a matter of days.

Their assessment seems to prove true, as subsequently Frank Poole and the other humans land on Europa and attempt to start peaceful relations with the primitive native Europs.

When TMA-2 transformed Jupiter into the new star "Lucifer", it warmed Europa to nearly the average temperature of Earth, melting the ice sheets which once covered the moon - and giving an evolutionary boost to indigenous life-forms which had existed in the oceans hidden beneath.

Due to the branching storylines of each book, the third novel ends with a flash-forward 20,000 years into the future, with the Europs developing a basic civilization without outside contact from humanity.

The fourth and final novel, 3001, altered this to end with the revived Frank Poole making first contact with the Europs and attempting to begin peaceful relations.

In response, the Europs gradually evolved to build basic shelters for themselves on the ocean floor - comparable to Earth cephalopods using shells as "tools" in the form of protection.

The Monolith's warming of the moon spurred the Europs to become amphibious, migrating on land where they construct basic ice-igloos, as an advance over their underwater hovels.

One area of pre-sapient activity observed among the Europs by 3001 is that they are fascinated by metal artefacts from crashed human spaceships and probes - as they have no counterpart in their raw state under the oceans.

Whenever the Europs find abandoned human machinery (or the crashed ship Tsien) they strip all the metal from them, and pile it in heaps, frequently rearranging the pieces.

Frank Poole speculatively compares this to the "Cargo cult" phenomenon on Earth in the twentieth century, and cites it as a spark of curiosity that shows an advance from pure animal instinct.

At the end of the final novel, when Frank Poole approaches the Europs for first contact, he carries a large, shiny copper wire as a peace offering to them.

Kubrick approved, but was disappointed with the glassy appearance of the prop on set, leading art director Anthony Masters to suggest making the monolith black.