"There was...a family of high repute, for it was large and wealthier than most. ...The most inquisitive and curious-minded of that family was Smeagol. He was interested in roots and beginnings; he tunneled into green mounds; and he ceased to look up at the hill tops, or the leaves on trees, or the flowers opening in the air: his head and his eyes were downward." (A Shadow of the Past, Lord of the Rings, J.R.R. Tolkien).
This is the first mention of Gollum in the Lord of the Rings, and practically the only glimpse we have of his life before the Ring of power consumed him. Gollum was from a people very similar to hobbits, Gandalf told Frodo, and indeed, from a situation very similar to the Baggins' in nearly every way. Both he and Bilbo are from respectable, rich hobbit families, and both stumble upon the Ring by chance. However one is consumed by it to point of murder within the first few moments of seeing it, and the other gives it up freely after 61 years of ownership. Neither knew whether the Ring was good or evil, they did not make a conscious choice what to do with the Ring, their reaction simply came from the character they already had.
Bilbo was not necessarily a hobbit of great character, certainly not at the beginning of The Hobbit. He is not courageous or selfless, all he wants is to keep living the comfortable life he is living in his comfortable hole and smoke. But his contentedness with his life may be exactly what protects him from the power of the Ring. Bilbo is very rooted in the Shire, all throughout The Hobbit he longs to be back in his own hole, even after he gains courage and becomes the leader of the group of dwarves in Mirkwood after Gandalf leaves them. It is his satisfaction with his own life that allows him to refuse the treasure he is offered at the end of The Hobbit, and possibly it also helps him resist the lure of the Ring.
Gollum on the other hand is not rooted at all in his community. He sought knowledge, Gandalf tells us, and it caused him to turn away from seeing or appreciating the little things in life, such as trees and flowers. He was too focused on the causes to appreciate the effects. I could be wrong, but I think Tolkien may have been making a subtle critique of science here. The pursuit of knowledge can cut you off from normal life and make you more vulnerable to the corruption of power. Bilbo sought nothing and so did not fall prey to that which was offered him. Gollum was always seeking, and leaped at the first opportunity for more he could get.
Saruman and Gandalf could be an intriguing parallel to Gollum and Bilbo. Both Saruman and Gandalf are wizards, coming from similar backgrounds. Gandalf, though he wanders, is well-rooted in Middle Earth. Though we do not know much of his wanderings other than what he tells Frodo, we do know that he is good friends with Frodo, as he was with Bilbo before him. He and Aragorn were also friends and traveled together seeking Gollum after Bilbo's party and before Frodo left the Shire. Even Barley Butterbur, the innkeeper at the Prancing Pony seems to be on very familiar terms with Gandalf. Gandalf does not oversee the inhabitants of Middle Earth, he cares for them, he is rooted in them.
Saruman is very nearly opposite of Gandalf. While Gandalf delighted to study hobbits, Saruman focused his studies on darker topics. He did not wander like Gandalf did, but neither was he rooted in Middle Earth. He did not mingle with any of the people, rather he sat up in his tower and watched. Like Gollum, he pursued knowledge to destructive ends, through the Palantir instead of the Ring, although he also sought that. The Palantir allowed him to watch without becoming involved. While Gollum became isolated digging under hills, Saruman became isolated sitting atop his tower; both in pursuit of knowledge. And in their pursuit, both fell prey to evil and corruption. Gollum saw the people around him as threats, while Saruman saw them as objects. While it is possible Tolkien was critiquing science through Gollum, it is much more commonly believed that he was critiquing industry through Saruman. (An in-depth look here: http://www.councilofelrond.com/2004/05/lotr-and-industrialization/)
Tolkien did not believe knowledge was evil by any means, it is lamented often in the Lord of the Rings how much history has been forgotten. Tolkien himself was a very intelligent and well-educated man. He worked on the Oxford English Dictionary, did translations of great works, was a code-breaker during WWII, was a professor at several colleges/universities including Oxford, not to mention created several languages, histories/mytholiges, and complex back-stories to go along with the Lord of the Rings. Tolkien was very knowledgeable, but he realized the importance of also being grounded, otherwise the love of knowledge makes one vulnerable to isolation and therby corruption. While this is most noticeable in Saruman, it also pops up subtly, like in Gollum's history and with Denethor. Tolkien's emphasis on the importance of being rooted is found much more frequently, through Gandalf, Bilbo, and Sam particularly, but also with minor characters such as Tom Bombadil or Farmer Maggot. In fact, Tom Bombadil regarded Farmer Maggot highly for that very reason.
"There's earth under his old feet, and clay on his fingers, wisdom in his bones, both his eyes are open"
In the House of Tom Bombadil, The Lord of the Rings, J.R.R. Tolkien.
There is much more that could be said on this, but that would take much longer, and as neither of us have Entish patience it shall have to wait for another day. Feel free to leave any thoughts in the comments, as I certainly have left some things out.
