Seal a glass vessel, bury it in fermenting horse manure for forty days, then feed it human blood for forty weeks, and a tiny transparent artificial human is supposed to emerge. This deep dive unpacks the homunculus, the little person of Paracelsus's 1537 De Natura Rerum, and follows the idea from Zosimos of Panopolis and the Jabirian takwin tradition through French mandrake rituals and the golem to Carl Jung's reading of it as a symbol of spiritual rebirth.

We then track its transformation into accepted science: the spermist preformationists who claimed to see tiny folded humans through blurry single-lens microscopes, the infinite-regress problem they embraced because it explained original sin, and why medieval paintings show the infant Jesus as a small middle-aged man. Finally we meet its modern descendants: the cortical sensory and motor  ...