On the shores of the west coast of Australia lies a window to our past: the stromatolites and microbial mats of Gathaagudu (Shark Bay).

To the untrained eye they look like a collection of rocks and slime – but they are in fact teeming with microbial life. And these stromatolites are living “relics” of ancient ecosystems that thrived on Earth billions of years ago.

If you wade past, it feels like you’re walking back through time. In fact, the first bubbles of oxygen that filled the atmosphere on early Earth likely came from ancient stromatolites. You could say we owe our very existence to these piles of rocks.

So, what other secrets of our past could these ecosystems tell us? Through decades of research, we know how early life has woven its path through these “living rocks”. But most recently our team embarked on the greatest genealogy search of them all: searching for our great microbial ancestors, the Asgard archaea.

And in a new paper, published today in the journal Current Biology, we report how this search led to the discovery of a key clue that could help explain how complex life evolved on Earth.

The cells that comprise complex life

Asgard archaea were originally named after Norse gods. This fascinating group........

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