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Genetics Unzipped – Fish, facts and fiction – from Haeckel’s embryos to Tiktaalik

Posted by , on 30 January 2020

ClownfishIn this episode exploring great ideas in genetics, we’re discovering our inner fish – finding out whether we really do go through a fishy phase in the womb, and looking at the legacy of Tiktaalik, the first fish to walk on land. 

Born in 1834, Ernst Haeckel was a German zoologist with a flair for illustration – and a knack for creating incredibly detailed and widely shared scientific images. But do his infamous embryo drawings really show the true picture of early development? 

Haeckel thought that we went through a ‘fish’ stage in the womb because our embryos appear to have gills during early development. Although his theory that ‘ontogeny recapitulates phylogeny’ has subsequently been shown to be incorrect, we now know there is a close connection between development and evolution, or ‘evo-devo’ as it’s sometimes known. 

In short, our evolutionary history is written in our developmental genes, and it’s a history that we can trace right the way back to the very first vertebrates. The best example of this is Tiktaalik – our oldest ‘fishapod’ ancestor that forms the missing link between fish and land-dwelling tetrapods.

Genetics Unzipped is the podcast from The Genetics Society. Listen now at, and find full show notes, transcript, music credits and references.

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