Sometimes referred to as Theia, something collided with the Earth 4.5B years ago, and after the collision, we got the Moon. Maybe the thing that hit the Earth had life on it, and all that survived the collision was the microbes, which we evolved from?
Theia (/ˈθiːə/) is a hypothesized ancient planet in the early Solar System that, according to the giant-impact hypothesis, collided with the early Earth around 4.5 billion years ago, with some of the resulting ejected debris gathering to form the Moon.[1][2] Such a collision, with the two planets' cores and mantles fusing, could explain why Earth's core is larger than expected for a body its size. Collision simulations support the idea that the large low-shear-velocity provinces in the lower mantle may be remnants of Theia.[3][4] Theia is hypothesized to have been about the size of Mars, and may have formed in the outer Solar System and provided much of Earth's water.
https://en.wikipedia.org/wiki/Theia_(planet)