" Haeckel had stirred such interest in embryology that he sowed the seeds for his own downfall. Eager to find evolutionary history in embryos, scientists studied embryonic development in diverse species. For the most part, von Baer’s idea of a similarity among embryos of different species held up, albeit with some exceptions. But the new data didn’t support Haeckel’s recapitulation theory; in fact, it did quite the opposite. At no stage of embryonic development could an ancestor be seen. "

― Neil Shubin , Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA