Called by human names, we always existed
So we are looking for the human names for something that has existed before humans.
We are like sinful dwarves, or wonders that glisten.
There were seven dwarves in the tale of Snow White (I figured this out) and @AHKieran has figured out that the line also mentions sins (of which there are said to be 7), and wonders (7 wonders of the world). Also there are 7 further lines after this one. So the answers are things that belong to a set of 7.
They could be:
The 7 classical planets ("planets" of our solar system which can be seen with the naked eye, including our two luminaries the sun and moon)
One of us is there to listen. JUPITER (known for its eerie sounds)
One of us is there to cook. MERCURY (the element Mercury is used in thermometers, which in turn can used in cooking)
Another, at night, is there to look. MOON (the nighttime luminary, some say it has a face)
One is the leader to show the way. VENUS (appears in the night sky usually before the stars do)
One does what is done by day. SUN (the daytime luminary)
One is there to look into life. MARS (scientists have searched for life on Mars)
Another carefully cuts like a knife. SATURN (the only one left - has blade-like rings)
Alternatively:
other things I rejected that come in a group of 7 and existed before humans named them:
- days of the week
- continents
- seas
- colours of the spectrum