A political-economic pact for collective colonial security, the Alliance is the central galactic institution of human society. The Alliance gained associate membership of the Citadel Council in 2165 and full membership in 2183, with Ambassador David Anderson representing humanity.
Human political-economic relationships vary between combative and lucrative. The turians who'd fought humans during the 2157 First Contact War have become valuable trade partners, despite residual social hostility.
Other relationships are even more complicated. The rapid rise of human political influence on the Council - achieving in decades what others waited for are still waiting centuries to acquire -- has galvanized suspicion and resentment against humanity. That negativity is vastly outweighed by the respect and trust humanity earned by saving the Council during the 2183 attack on the Citadel, at the cost of Alliance cruisers Cairo, Cape Town, Emden, Jakarta, Madrid, Seoul, Shenyang, and Warsaw and their 2400 crew.