“Man’s Size in Terms of Fundamental Constants”, William H. Press1980 (science)⁠:

Why are we the size we are, instead of some very different size? Simple physical scaling laws and 3 “requirements” dictate that our size be of order (h/²/m_ee²)(e²/Gm_p²)^1/4. They also “predict” the mass and radius of the Earth.

The three requirements are: (1) We are made of complicated molecules; (2) we breathe an evolved planetary atmosphere; (3) we are about as big as we can be without breaking.