As far as the laws of mathematics refer to reality, they are not certain, as far as they are certain, they do not refer to reality. - Albert Einstein.
The Homo Sapiens species, being cut off from the wider knowledge of the galactic community, has been long studied by an organization of semi-peaceful races who waited until the people of Earth would 'mail' themselves to a different star, by way of cryogenics. They had waited past what they thought was an appropriate length of time and some were getting impatient, as humans had one of the most fertile areas in the entire galaxy. Sending ships every once in awhile was a policy until a base upon another planetary body had been established by humans. After the Lunar Expeditionary Teams from the United Nations Space Agency set up a 5 kilometre base within a week, the Outsiders knew that it was time for observed development from afar, without sending in close range ships.
The humans progress was still slower than many species they had seen before, but the fusion reactors the humans built were comprehensive in their automation by AI-controlled quantum computer networks. With these, an energy crises had been averted and resource wars were only fought by paranoid nations. By the time the bases on Mars were developing an independent organization to colonize it's own moons, the asteroid mining outposts were in full swing and Pluto with the OSSETI (Outer Space Search for Extra-Terrestrial Intelligence] base was in its second orbital session.
But Humanity still had not discovered any signs other than the tourist memorabilia from the ISSETI (Inner Space Search for Extra-Terrestrial Intelligence). It was getting to seem hopeless, when one day, at 24:00 Midnight Central Time in North America, June 20th, 2105 AD, the Gatherers appeared. They had over 10,000 ships, all appearing from no space at all it seemed. Sending out an 'invitation', they hid between the orbits of Mercury and Venus, waiting for the first ships to arrive. Both Earth and Mars sent ships to investigate this opportunity. At August 23rd, the ships of the Human System approached the flagship of the alien and came into contact with the first undeniable signs of life out there.