Who affirmed the unity of all life?

That would be Charles Darwin.

Saint Francis. And he was centuries before Darwin.

St Francis would probably say Christ.

Was it ever confirmed?

I’m not sure it is confirmable in the first place. Darwin looked at things from the biological point of view. I think there’s more to it than that.

I don’t buy into the Christological point of view that @zenvelo suggests. There are plenty of us in the world who don’t accept Catholic dogma who still see that there is some degree of unity between species. Ascribing that to a catholic theologian seems, well, simplistic.

Disney (The Circle of Life)

“Any man’s death diminishes me, because I am involved in Mankind.”

-John Donne

Mitochondrial DNA seems to be a pretty good unifier. There are some outlers however. Some of the species found near high temperature and pressure sea vents and volcanic hot springs. Although, even these have ribosomal RNA analyzed in 1977 by Carl Woese and George E. Fox

I’m guessing Science and movies. Three words. “Carbon based lifeforms.”

@mazingerz88: I’m talking about the interconnectedness of everything, that everything has life, including objects.

See link especially Edward Taylor…
The idea of animism was developed by the anthropologist Sir Edward Taylor in his 1871 book Primitive Culture
Source:
https://en.wikipedia.org/wiki/Animism

Animism (from Latin anima, “breath, spirit, life”)[1][2] is the religious belief that objects, places and creatures all possess a distinct spiritual essence.[3][4][5][6] Potentially, animism perceives all things—animals, plants, rocks, rivers, weather systems, human handiwork and perhaps even words—as animated and alive.