Ernst Haeckel: Biography, Facts & Theory

Instructor: Christopher Sailus

Chris has an M.A. in history and taught university and high school history.

In this lesson, we explore the life and work of Ernst Haeckel. A German biologist, zoologist, and proponent of evolution, Haeckel made great contributions to science and, unfortunately, the rise of Nazism.

Ernst Haeckel

Have you ever had something blow up in your face? Perhaps you made your roommate breakfast, only to have made him something to which he is allergic. Or maybe you spent two years developing a really cool technology, only to have it appropriated by bomb-makers.

Life is full of unintended consequences. Such was the case for the work of Ernst Haeckel. Though he worked most of his life on biology, embryology, and evolutionary medicine, a generation after his death his views would be partially appropriated by Nazis trying to justify ethnic cleansing.

In this lesson, we will investigate the life and theories of Haeckel which were so ill-used in the 1940s.


Haeckel was born in 1834 in Potsdam in what was then part of Prussia. The son of a government official, Haeckel grew up in Merseburg where he graduated high school in 1852. He went on to Berlin where he studied medicine according to his father's wishes.

He graduated in 1857 and began practicing medicine. However, Haeckel was soon attracted back to the fields of biology and zoology, an interest originally sparked by research trips to the North Sea during his time at the university. In fact, on a trip to Italy, Haeckel conducted a serious study of single-celled organisms called Radiolarians.

The publication of Darwin's On the Origin of Species by Means of Natural Selection in 1859 was the last piece that hooked Haeckel on the subject of evolutionary biology. He soon began a secondary education in his passion, completing his dissertation at the University of Jena in 1861. The following year he was granted a position as a junior professor of zoology, beginning his tenure by publishing the work on Radiolarians that he completed in Italy a few years before.

Haeckel focused his work and his lectures on building upon the theory of natural selection first proposed by Darwin in the book which caused Haeckel to change his career path. Haeckel's ideas were as controversial as Darwin's in his time, and some still are considered unproven or radical by biologists today.

Haeckel received a full professorship at Jena in 1865. He continued his work from there for the rest of life until his death in 1919 at age 85.

Theories & Ideas

Haeckel's work focused often on the genesis and evolution of life and on the embryology of humans. Haeckel was fond of drawing linear and symmetrical trees of evolution, tracing humanity's ancestry back to life's earliest forms, especially the protozoa he had published on at the beginning of his career. One of his more revolutionary claims was that life was created by chance in the deep sea through random combinations of basic elements like carbon, oxygen, and sulfur. He termed these early organisms Monera, and Haeckel continued to believe in their existence long after scientific experiments proved this to be impossible.

Perhaps his most famous idea came in the development of recapitulation theory. According to this theory devised by Haeckel, the embryos of each organism, during the early stages of development, go through stages resembling forms once taken by their earliest evolutionary ancestors. This idea he summed up quaintly as 'ontogeny recapitulates phylogeny,' giving the aforementioned theory its name.

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