Krypto, and Kandor and introduced another newly discovered survivor, Karsta Wor-Ul. Kryptonian civilization's reported level of technological advancement has also varied. Some works, such as Kevin J. Anderson's novel The Last Days of Krypton, describe it as a few centuries ahead of Earth, while others, such as the Superman film series and Man of Steel, describe it as thousands or even hundreds of thousands of years more advanced. Versions of Krypton Krypton in the Golden Age of Comic Books History In its first appearance, Krypton was only depicted at the moment of its destruction. Soon, beginning in the Superman comic strip, Krypton was shown to have been a planet similar to Earth, only older by eons and possessed of all the beneficial progress that implied (though the downside was the hint that Krypton exploded due mainly to old age). The debut of the Superman newspaper comic strip in 1939 delved into further details about Krypton, introducing the idea that all Kryptonians possessed a level of heightened physical abilities, including super-strength and super-speed. In the early comics' version of Krypton, Superman's parents were named "Jor-L" and "Lora" (changed to the more familiar "Jor-El" and "Lara" by the end of the 1940s). The Golden Age Krypton would be revised into another form almost as soon as it was defined, and very few stories were initially written about it. However, after the introduction of DC's multiverse in the 1960s, this version of Krypton was declared to be the Krypton of the Earth-Two universe (the native dimension of DC's Golden Age characters) and its Superman. After the emergence of Earth-Two as a differentiated alternate universe within the DC Multiverse, Power Girl (Kara Zor-L) was introduced as Krypton-Two's alternate Supergirl in 1976. Kal-L and Kara Zor-L were the only known survivors of Krypton-Two, unlike the Silver Age analogue. Earth-Two's universe lacked its own Brainiac, so its Kandor was never abducted from Krypton Two before its destruction, nor did Kal-L have his own version of Krypto as an infant and toddler on this world. In the Golden Age, Superman was unaware initially of his true origins; in Superman #61, Superman discovered the existence of Krypton for the first time and learned of his Kryptonian heritage. He later encountered other survivors prior to Kara's arrival in the form of three criminals, U-Ban, Kizo, and Mala, who were exiled by Superman's father before Krypton's destruction. Krypton in transition