Thanos really did eradicate half of all life.
At the end of Avengers: Infinity War it seemed as if all hope was lost. Despite the combined efforts of all the Avengers and the Guardians of the Galaxy, Thanos was able to get his hands on all the Infinity Stones. With a simple snap of his fingers, Thanos ended half of all life in the universe. The Mad Titan had grown up on a planet that became overpopulated, and his people died out because of it. Seeking to stop that occurrence from ever happening again, Thanos planned on "mercifully" killing off half of life in a painless way so that all others could thrive.
After the snap, all of the original members of the Avengers were left unaffected. That lead many fans to believe in the "Theory of the Six," an internet idea that states the original members will have to sacrifice themselves for the future of the universe. Marvel Studios head Kevin Feige recently sat down with Birth. Movies. Death. and revealed that the snap affected more than just the humans (and humanoid aliens) in the universe. When asked if Thanos' homicidal plans extended to the animals in the galaxy as well, Feige answered with a resounding "Yes!" He continued on to confirm, "Yes. All life." Damn Thanos... even the puppies?