Since the early 1900s, scientists have been wondering how birds and mammals could have developed almost identical conduction systems independently of each other when their common ancestor was a cold-blooded reptile with a sponge-like inner heart that has virtually no conduction bundles.
The studies show that it is simply the spongy inner tissue in the foetal heart that gets stretched out to become a fine network of conductive tissue in adult birds and mammals. And this knowledge can be put to use in the future.
PLOS ONE