Every cell in your body has ancestors

Every cell in your body has ancestors. And every cell in your body can trace its lineage back, eventually, to the bodies of your parents. And the future of every lineage in your body is a dead end, with the sole exception of the one that will go on to live in your children. This ongoing line of cells are called germ cells, and the dead-end lines are called somatic cells.

These germ cells are still fairly well adapted to the conditions they evolved in a billion years ago before the innovation of multicellularity, the ancient warm, nutritious, briny, and well-oxygenated seas of the late Precambrian. It is no coincidence that this is the same habitat your somatic cells provide them with.

Periodically, this lineage will shed its habitat and form a new one, and has existed in countless other bodies through the eons.

You are a single celled organism living in a spacesuit made of the bodies of its kin.

And you are, in a very real sense, your ancestors' living hands in the world.