One might think that, as science progressed, it would crush the Russian-doll theory through its lucid biological lens. But that’s not precisely what occurred – instead, when the microscope finally enabled researchers to see not just eggs but sperm, the preformation theory morphed into a new, even more patriarchal political conceit: now, held philosophers and some students of reproduction, the egg was merely a passive receptacle waiting for vigorous sperm to arrive to trigger development. And sperm? The head of each contained a tiny preformed human being – a homunculus, to be exact. The Dutch mathematician and physicist Nicolaas Hartsoeker, inventor of the screw-barrel microscope, drew his image of the homunculus when sperm became visible for the first time in 1695. He did not actually see a homunculus in the sperm head, Hartsoeker conceded at the time, but he convinced himself that it was there.
More powerful microscopes eventually relegated the homunculus to the dustbin of history – but in some ways not much has changed. Most notably, the legacy of the homunculus survives in the stubbornly persistent notion of the egg as a passive participant in fertilisation, awaiting the active sperm to swim through a hailstorm of challenges to perpetuate life. It’s understandable – though unfortunate – that a lay public might adopt these erroneous, sexist paradigms and metaphors. But biologists and physicians are guilty as well.