In the late 1600s, following René Descartes' claims that animals could be understood as purely physical machines, there was increasing interest in the question of whether a machine could be designed that, like an animal, could generate offspring (a self-replicating machine).[8] After the climax of the British Industrial Revolution in the early 1800s, and the publication of Charles Darwin's On The Origin of Species in 1859, various writers in the late 1800s explored the idea that it might be possible to build machines that could not only self-reproduce, but also evolve and become increasingly intelligent.[8]