Between 15m-25m Humans and Eldar must have co-existed. Why did the Eldar let this happen?

Question

So, humans once lived on millions of planets and to me, seemed like they were pretty much running away with our galaxy.

Its my understanding however that Eldar ruled this Galaxy a long time before humans came about and that it was the birth of Slaanesh that stopped the warp storms that meant the humans could once again travel between human planets.

Meaning that the humans had around 10 thousand years before the fall of the Eldar to get rather powerful.

So why, with Farseers, did the Eldar race let humans get as powerful as they did?

Answer 1

They didn't care.

The Eldar mastered the galaxy before humans managed to spread out into the stars in any significant way and our original forays into the galaxy didn't trouble them at all.

Humans took forever to crawl out of their Solar system:

Millenium 1-15 Age of Terra Humanity dominates Earth. Civilisations come and go. The Solar system is colonised. Mankind lives on Mars and the moons of Jupiter, Saturn and Neptune.

Millenium 15-18 Age of Technology Mankind begins to colonise the stars using sub-light spacecraft. At first, only nearby systems can be reached and the colonies established on them must survive as independent states since they are separated from Earth by up to ten generations of travel

- Timeline, Galaxy in Flames, by Ben Counter

From M26 - M31, Warp storms separated human colonies and reduced us to independent systems and worlds, breaking any threat we might have posed to the Eldar.

Where as the Eldar were a bit more about their business:

c.M15-20 AN EMPIRE ASCENDANT
The Eldar are unparalleled masters of the galaxy. Those lesser races that dare oppose them present little challenge. Worlds live and die at their behest, for the supremacy of their great empire is beyond dispute.

- Page 20, Codex Eldar, 6th ed

Initially, they were so supreme we just weren't a threat:

There were, of course, many wars. Even when the galaxy was young there were upstart races seeking to gouge out petty empires of their own, [...]. Most of these conflicts, though, were so short-lived that the ease of their victory left the Eldar more sure of their ascendancy.

- Page 7, Codex Eldar, 6th ed

The reason they didn't care about humanity later is that they were too busy with their own pleasures and problems to pay any attention.

cM18-30 A SICKNESS OF THE SPIRIT
The luxurious paradise of the Eldar civilisation gives rise to a dangerous combination of curiosity and complacency. Throughout the empire, a profound degradation in moral discipline sets in. Over the millennia there is a gradual slide into sensual excess.

- Page 20, Codex Eldar, 6th ed

Answer 2

I don't have citations to support this, but since no-one else has answered:

The pre-Fall Eldar had become decadent and arrogant. They viewed other races as little better thn animals and it was inconceivable to them that humans would ever become a threat. Indeed, humans weren't a threat pre-Fall, and aren't that big a threat even post-Fall. The Fall was entirely self inflicted.

Answer 3

The reason the eldar let humans become so powerful despite having farseers is that farseers have limited capacity to predict the future, and the eldar are, ironically, horrifically short sighted in their actions because of this. All their actions are taken based on farseeing, completely ignoring obvious extrapolation on what will happen afterwards.

Typically, after a number of years, Seers pass to some other life as part of their quest to explore the rich possibilities of the Eldar Path. However, some amongst their number can end this journey by adopting the mantle of the Farseer which leads them being trapped on the Witch Path and thus unable to change their future role. Thus, these individual Eldar focus their remaining years on learning and exploring their psychic powers. Much of their time is spent casting Seer Runes whilst making endless calculations and prognostications where they attempt to guide the fortunes of their Craftworld. This sees them attempting to discern and anticipate the future by watching out for difficulties that lie ahead in coming events. As their calculations are based on predicted events that can be hundreds of years into the future, their immediate effect can be hard to determine. Despite this being the case, Farseers are seen as a vital part of a Craftworld who base all their political decisions around their predictions.

– Warhammer 40,000: Compilation, pg. 53

As you can see from the above, farseers are limited to "hundreds of years". As others have already pointed out, the time scales involved were actually in thousands of years. By the time the eldar figured out humans are going to be a problem, there was nothing they could do.

Answer 4

Eldar were not warlike. Also they wouldnt care for the humans pre-fall as they STILL think of humans as a bit more than monkeys.

After the fall Eldar see the humans as the first line of the defence against Chaos or as a species that will bring the downfall sooner. Depending on witch Farseer you speak to.

It is all in the books but I won't bother you with a "wall of text" when i think that this answer is sufficient.

Answer 5

Dark Age of Technology humanity did have at least one war with the Eldar. It is stated that during the war, humanity moved the entire Sol system through the warp and placed it right on the doorstep of the Eldar Empire as a threat. The Eldar immediately backed off and retreated to their core worlds (the ones now in the Eye of Terror). That is canon fluff. The Eldar viewed themselves as masters of the galaxy but only occupied a tiny corner of it. When humanity rose to power, it spread throughout the galaxy as a whole and crushed anything that attacked it.

The Eldar "co-exist" with no one. Besides, before the Fall, there were no Farseers. The ones who became the first Farseers were those few who foresaw the Fall and convinced others to follow them and to construct the Craftworlds. After the Fall, Asuyan trained the first Aspect Warriors.

After the Fall, the Eldar were amongst the first to raid human worlds. Admittedly, this was out of desperation. Currently, the Eldar seem to be in a state of "blissful" ignorance. They honestly believe they are dominant and that everyone else are squatters. Would you want to be friends with someone like that?

Furthermore, the Eldar never actually advanced at all. They are explicitly stated to be using technology and sorcery/magic/psychics/whatever that were given to them by the Old Ones. This bit them in the butt after the Fall because they never had scientist or philosophers or intellectuals. Everything they wanted was given to them by the technology the Old Ones had given them. They never even evolved, having been created by the Old Ones, given their technology and sorcery, and unleashed upon the Necrons during the War in Heaven. They never even discovered fire. Kinda sad, really. They will never be able to have pride in any sort of achievements or advancements or discoveries because they will never have made any.

In comparison, by the height of human advancement, humanity had (canonically) all but matched the Eldar through sheer technological might. Though Eldar technology was said to be more sophisticated. That is like the difference between an iPhone and a Droid smartphone. Where the Old Ones tech the Eldar used (probably a lesser version than the originals, for fear of rebellion or something) often combined science with magic to create an unbelievably advanced piece of technology, humanity achieved about the same result through scientific knowledge alone. Then, just before the Fall, the first human psykers (excluding the Emperor) appeared and began developing and studying their powers. Human psykers are said in the lore to be more powerful than their Eldar counterparts. All Eldar are psykers, but the most that the vast majority can do is mild telepathy and empathy. The weakest human psyker is fully capable of ripping your mind apart or your soul out of your body. I would imagine that Eldar hubris would have eventually lead to another war to determine who was "superior" or some other pointless thing if the Fall had not happened.

As it is, in one of the Eldar novels (though if you take it for canon or not is up to you), an Eldar Farseer of Alaitoc is shocked to discover (the hard way) that Imperial ships have void shields. She was one of her Craftworld's leaders and was so removed from reality that she didn't even know her Craftworld's primary enemy had shields. That shows a distinct refusal to accept reality on her part and, given her station in Alaitoc, likely the entire Craftworld. Possibly her whole species.

Basically, the Eldar "let" humanity become so powerful pre-Fall because they rejected the fact that someone could be as strong as them. Then got their rears handed to them by a new species and went to party it off, got too high, gave birth to an eldritch abomination that thinks it's a god, got eaten by said abomination, and then they had no power to stop the storm they had unleashed upon the galaxy (not that they would if they could).

The Eldar would never have expected a species to advance so quickly. To them, they glanced away for a moment to do something else and when they look back, we've gone from stone age to overwhelming. From one world to everywhere the Eldar look. All on our own merits. Unfortunately, this is also what grabbed Chaos's attention and focused it on us. That didn't end well. Then we were the only species devastated by Chaos that managed to crawl back to the top. That had the unfortunate effect of keeping Chaos's attention on us.