Hooke’s interest in fossils began as a boy, when he clambered around the limestone shores of the Isle of Wight collecting interesting specimens. Even today, after the enthusiastic depredations of Victorian and 20th century fossil hunters, the island is noted for its abundant fossil record.
In Hooke’s day there was plenty of controversy over what exactly fossils were. Some said they were formed by a seed in the stone itself, some believed that they were of divine origin, others that they were shooting stars that had fallen to earth. The extinction of species and development of new species was not an idea that had come into circulation, so these strange, animal-like figures in stone, which looked so unlike the organisms people saw around them, were problematic. Even into the eighteenth century, well after Hooke’s death, scientists, most notoriously Johann Beringer, were still arguing over the origins of fossils.
In Micrographia, Hooke noticed the similarity in the microscopic structure of charcoal and coal, which prompted him to assert that coal was some form of petrified wood, and that mineral-rich water had deposited minerals in the organisms, which gradually hardened into stone.
In later writings, he referred back to his Isle of Wight outings and his observations of fossil-like objects on the shore, which were still soft but hardened further out to sea, again suggesting that fossils were organisms that had gradually hardened.
If fossils were traces of animals and plants, how could Hooke explain fossils of organisms that were not around at the time? In writings published posthumously, he suggested the possibility of extinction – and also, in a precursor of evolution, that new species might also appear:
‘There have been many other Species of Creatures in former Ages, of which we can find none at present; and that ’tis not unlikely also but that there may be divers new kinds now, which have not been from the beginning.’