The essence and origins of life. What is it? Yes, we can define characteristics that differentiated the living from the non-living. The building blocks of life are still not the same as a simple virus. Do you think new forms of life "become living" these days?. Do you think that the conditions to form new life simply do not exist anymore? Evolution can not even begin until something (still yet unknown to us) happens first. Do you think we will ever discover the recipe?
Actually, once one gets to the point of toolmaking, that is about the end of development, isn't it? After that, it's just making better and better tools, physical and intellectual. I think an advanced race would have to recognize us as on the same path as them, even if they are far ahead of us. I don't think we can assume their ethics to be similar to ours, though.
I can imagine an alien population of intersellar shaman, making stops at sacred water planets. Where their tools are advanced, but they attempt to repair planets to support/maintain life. They would be driven by a vision of the sacred/practical that might not be ours. Their tools being used for some perceived higher purpose. Such a group might see us as an infection, needing eradication, or education.
Given the vast distances, if we ever receive a radio signal from a highly evolved alien species, they have probably died off by the time their signal reaches us.
We may have received such a radio signal already. The 'WOW!' signal has withstood exhaustive attempts since 1977 to assign it a possible terrestrial origin. It didn't come from a satellite, passing aircraft, radio tower, equipment malfunction, or any number of other possible sources.
The WOW signal apparently originated from deep space. It was 30 times stronger than natural radio background noise, lasted for 72 seconds, and was broadcast on a frequency that corresponds to the electromagnetic resonance of hydrogen, the most common element in the universe.
Occam's Razor not withstanding, none of this proves a thing of course. But it's still pretty interesting to contemplate. Here's a bit about it from Stephen Hawking's Universe.
I picked up this signal last night.
Maybe if we offered them some cough drops they wouldn't be so cranky.
Warf? Is that you?
They send us WOW, we send them Chuck Berry.
Here's one possibility:
Alien poop hypothesis! Given enough space junk surface, radiation, and non-attion from the orbital sanitation crew, who knows what could come down...;p)
Alien spacecraft of vast proportions visits earth to pump its bilge and dump its organic waste in our oceans.
I really could just be a few pints!