Harvard astrophysicist Abraham Loeb has claimed that humans may be the last to evolve in universe.
Loeb told Space.com that when the universe was 15 million years old, the temperature of the cosmic microwave background (CMB) was like that of a warm summer day on Earth.
He said that if rocky planets existed at that epoch, then the CMB may have kept their surface warm even if they did not reside in the habitable zone around their parent star, CNET reported.
Loeb said that there might have been huge stars exploding and emitting the heavy elements.
He asserted that any planets that may have resulted from these explosions would have enjoyed the warmth of cosmic microwave background radiation. Therefore, water may have been present and life forms may have existed.
He suggests that planets with atmospheric bio-signatures around low-metallicity stars in the Milky Way galaxy or its dwarf galaxy satellites may once have been analogous to the very earliest of planets.