Earth Is In Our Blood

In "The Chapter Ends" by Poul Anderson, Earth is being evacuated but a peasant refuses to leave, claiming that Earth is:

"'...in [man's] blood and bones and soul; he will carry Earth with him forever.'"
-Poul Anderson, "The Chapter Ends" IN Anderson, Starship (New York, 1982), pp. 253-281 AT p. 254.

In "Nor Iron Bars" by James Blish, the planetary explorer, Daryon Hammersmith, explains that:

the Sun is a variable star;
one of its subordinate cycles lasts 212 days and is reflected in the human pulse rate.

Second officer Oestreicher deduces:

"'...this means that we can never be lost! Not so long as the Sun is detectable at all, whether we can identify it or not! We're carrying the only beacon we need right in our blood!'"
-James Blish, "Nor Iron Bars" IN Blish, Galactic Cluster (London, 1963), pp. 61-92 AT 4, p. 90.

So Anderson's peasant is right about that but not about the need to stay on Earth forever.