A German zoologist and evolutionist who was a strong successor of Darwinism and who introduced new notions of the evolutionary descent of human beings for his time, which were not originally received well by his peers. He was the first to confirm single celled organisms to be real, which changed the course of

Attempting to explain both inorganic and organic nature under the same physical laws, Haeckel portrayed the lowest creatures as mere protoplasm without nuclei; he speculated that they had arisen spontaneously through combinations of carbon, oxygen, nitrogen, hydrogen, and sulfur. In those days of great interest in protoplasm, it was believed for a while that certain deep-sea dredgings had brought up such structureless organisms; when scientists found this to be in error, Haeckel continued to insist, throughout the years, that “monera” existed. From them he traced one-celled forms with nuclei and three kingdoms—animal, vegetable, and the neutral, borderline “protista.” His artistic leanings toward ideal symmetries led him to outline numerous genealogical trees, sometimes to supply missing links or branches; and he reconstructed the human ancestral tree to demonstrate humankind’s descent from the lower animals.