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In order to understand where hearts came from, we have to go back to the earliest common ancestor of everything that has a heart. It took hundreds of millions of years, and countless different iterations of the same basic structure to lead to the heart that you have today.

Thanks as always to Nobu Tamura for allowing us to use his wonderful paleoart: http://spinops.blogspot.com/

Thanks to Ceri Thomas for the Ichthyostega reconstruction. Check out more of Ceri's paleoart at   / alphynix   and http://nixillustration.com

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