From Myth to Science: The Pioneering Regeneration Discoveries of Abraham Trembley

The concept of regeneration has its roots in Greek mythology, with notable examples including the punishment of Prometheus for stealing fire and Hercules' Twelve Labors, particularly the slaying of the Lernaean hydra, where severed heads were replaced with two new ones. More subtle accounts of regenerating lizard tails can also be found in the works of ancient Greek scientists, including Aristotle.

Up until the eighteenth century, the field of biology primarily revolved around observing and documenting the natural world. One of the pioneers in experimental biology was the Swiss naturalist Abraham Trembley. While he was a tutor for a prominent Dutch family, Trembley stumbled upon polyps (Chlorohydra viridissima) in a freshwater pond. What fascinated him was the varying number of arms on individual polyps. Upon cutting a polyp in half, he observed it regenerating into two complete organisms. Further experiments showed that when the polyp was divided into multiple pieces, multiple organisms would emerge. He even managed to create a seven-headed polyp, which he named a hydra, inspired by the Greek mythological creature. In other experiments, grafting two polyps together resulted in a fused, single individual. Trembley meticulously documented these experiments and their outcomes in a book published in 1744. Initially, he believed polyps were plants, but their movement led him to revise this classification. At the time, Trembley was unaware that Antonie van Leeuwenhoek had previously described these creatures in 1702–1703 as one of his "animalculum."

While Trembley's discoveries were celebrated by much of the scientific community, not everyone readily accepted them. The ability of dissected hydras to regenerate into complete replicas of the original organisms challenged the prevailing belief in preformation, which held that embryos developed from pre-existing parts. One of the early skeptics was Trembley's cousin, Charles Bonnet, also a Swiss naturalist. However, Bonnet changed his mind in 1745 when he witnessed similar regeneration in worms. 

 

The hydra, known for its legendary regenerative abilities, is featured in the painting "Hercules and the Hydra" created by the Italian artist and sculptor Antonio del Pollaiolo (c. 1429–1498) around 1475.