Haeckel fudged his embryo drawings — and textbooks copied them for a century

In 1868, Ernst Haeckel — a prominent German zoologist and professor at the University of Jena — published a famous series of embryo drawings. Arranged in a comparative grid, they appeared to prove his theory that 'ontogeny recapitulates phylogeny': that each creature replays its evolutionary past as it grows in the womb.

The evidence was fudged. As the biologist Matthew Cobb wrote in New Scientist in 2015, Haeckel 'placed the drawings into a comparative grid, highlighting similarities between species and blurring differences' — and 'the results are highly inaccurate.'

Critics were not fooled for long. From the 1870s, expert critics accused Haeckel of drawing the embryos more alike than they really are. German colleagues exposed the deception and pressured him into admitting it — he blamed his draftsman, and the admission was soon forgotten, with no proper retraction.

The images outlived the correction. Textbooks 'copied and recopied them through the 20th century' — including postwar textbooks in Britain and the United States and Scott F. Gilbert's developmental-biology textbook as late as 1985. In 1997, the British biologist Michael Richardson compared Haeckel's figures with real embryos and exposed them once more. A century after the fraud, it became the textbook case of scientific fraud.