Homunculus
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Side view of sensory homunculus
Image courtesy Wikimedia CommonsI thought homunuculus was just a name for a fictional tiny humanoid, but discovered there’s a little more to it. In medieval times it was believed that a homunculus could be created through alchemy, but from the late 18th to the late 19th century, scientists believed in preformationism.
This theory held that a perfectly formed miniature person existed in a sperm or an egg and simply developed into a full-sized human being.
Nicolaas Hartsoeker, (1656-1725) was a Dutch polymath who was interested in embryology. He invented the screw-barrel simple microscope in about 1694 and claimed to be the first person to study sperm cells under a microscope. It is said that he believed that a tiny person was present in a sperm cell, although he never claimed to have seen one.
He sketched his theory, which neatly explained how a human baby was conceived in a woman. Conception was ill understood! They knew the means but not the fine detail.
Image courtesy Wikimedia Commons
The cortical homunculus is a visualisation to represent how much of the brain is dedicated to different body parts. The size of each body part indicates ‘the degree of sensory or motor control it requires.’ A homunculus is shown with a huge face and tongue, for example, because they have a greater range of fine motor movement and a greater density of neurons. Legs and trunk are disproportionately small because they assume less space on the cortical map.
Goodness. It was the sort of word that made me think you were going to write about something from a Harry Potter story. I do vaguely recall memory of having encountered the word and read about the beliefs you describe, but I guess it's the kind of info we chuckle about now and then forget we read it. Imagine alchemists hoping to create a perfectly formed small human! Mind you they are still trying - they call themselves genetic engineers these days.
ReplyDeleteI've heard the word before but thought it was one of the many evolutionary stages man went through. In a way I suppose it is, from egg and sperm to fully formed human. There were some strange ideas along the way about how it all happened.
ReplyDeleteAnd there was me imagining a gardening post from that title.
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