*pops knuckles* I knew being a Transformers geek would come in handy eventually.
Okay, first, as Thundermuffin's said, continuity is a tricky thing in Transformers. You can divide G1 by itself into cartoon, comics, UK comics, Dreamwave comics, iDW comics, Japanese cartoon, and Japanese manga sub-continuities.
Then there's G2 which is a seperate continuity loosely based on prior G1, and Beast Wars which is set in the future of G1, based on a mish-mash of elements from all the G1 sub-continuities.
But anyway, the beginning of TF life tends to be pretty simple.
Animated G1 Continuity:
The Quintessons, an ancient biomechanical race of merchant traders, built two lines of mass produced machines. The Slaves and the Gladiators. The Slaves were intended for manual labor, and built as such, to maintain machinery and other civilian tasks. The Gladiators were military hardware, and built with conquest, destruction, and battle in mind. The Quintessons sold these machines from their planet sized factory world of Cybertron, spreading them far and wide. They also created massive drones called the Guardians to protect themselves. However, thanks to time travel, the present day Autobots enabled the Slave mech A3 to utilize a device that paralyzed the Guardians and allowed the Slaves and Gladiators to rise up against the cruel Quintessons and kick them off the planet. Thus began Cybertron's Golden Age.
This answers several of your questions
- Advanced robotic life didn't evolve. It was developed as products to sell by the Quintessons.
- They all look vaguely humanoid because the Quintessons are canny merchandisers and produced units that their customers would identify with(pretty much every alien in the TF universe BESIDES the Quintessons are humanoid)
- They transform into things because that was a useful feature for the Quintessons to include. The vast variety of vehicle modes were probably to give them the ability of faster travel as well as great strength in robot mode.
Anyway, now we move onto....
Comics G1 Continuity
In the beginning of the universe, two primordial gods, Unicron(the embodiment of destruction and chaos) and Primus(the embodiment of creation and order) fought one another in the newly born universe. Primus sought to protect the universe from Unicron's consuming rampages, but in the process of fighting him on the astral plane, not only was Primus weaker, but their battles destroyed the very creation Primus was trying to save. Primus thus decided to trick Unicron, returning to the physical plane. Unicron followed without thinking, and both wound up imprisoned within massive asteroids. Unicron, enraged by his imprisonment, focused his power on changing his prison into a massive new body for himself, that could transform from a planet sized vessel into a mimicry of his original astral form. Primus, however, took a different tactic, and began to create life upon his prison, reforming it into Cybertron and populating it with sentient mechanoids, the Children of Primus, who would help him to battle and perhaps destroy Unicron. Seeing what Unicron had done with his prison, he bestowed the ability of transformation on his children as well, to better prepare them for the final conflict. And then, as Cybertron entered a Golden Age, he fell into a deep sleep, exhausted by his efforts.
Here, most of your questions are answered as well.
- They didn't evolve. They were created specifically by Primus as sentient beings.
- They are humanoid because Primus created them in his image, and he was a humanoid form before he became the core of Cybertron.
- They transform because Primus gave them that gift after seeing Unicron use it in his mammoth new physical form, to better prepare them for the coming conflict.
Anyway, G2 was an entirely different continuity but generally didn't involve the creation myth, and Beast Wars/Machines actually tried to merge all THREE together into one big backstory(given the inherent contradictions this would cause, it's assumed that it sort of has another alternate G1 as its past, which features an entirely unique history). And then there's the various Japanese series, which if they have seperate creation myths for the TFs, I haven't heard of them.
Now, if you'll excuse me, I'm going to go watch some football while eating pork rinds or something suitably "manly" so I can try to pretend I'm not a COLLOSSAL geek for not needing to look any of that up.
)
Yep; I'm familiar with Marvel's Ultimate books; I've followed Ultimates, Ultimate X-Men, and Ultimate Spider-Man fairly closely for the past several years.