LIFE

The Oldest Reef, Built by Microbes

~3.43 billion years ago

Archean · Paleoarchean

In Western Australia, a carbonate platform kilometres across preserves mounds, cones and wavy sheets raised by microbial mats as they trapped passing sediment. Seven distinct shapes recur across the platform, each in its own zone, arranged along the ancient shoreline exactly as living mats arrange themselves by water depth. It is a reef, and nothing but microbes built it.

Why it matters

What survives here is not a single cell but a whole ecosystem, mapped across its landscape: the earliest picture we have of life already in business rather than just beginning.

Dating & uncertainty

Layered mounds can also be built by chemistry alone, which is why every claim this old is contested. Here the argument rests on scale: seven distinct shapes distributed across a kilometres-wide platform exactly as living microbial mats distribute themselves with water depth.

Sources

1. Allwood et al. (2006), Nature · Stromatolite reef from the Early Archaean era of Australia
2. Allwood et al. (2007), Precambrian Research · 3.43 billion-year-old stromatolite reef from the Pilbara Craton of Western Australia
3. Allwood et al. (2009), PNAS · Controls on development and diversity of Early Archean stromatolites

Earth history as one day

05:52:0418 h 8 min before midnight

if Earth’s 4.54 billion years were compressed into a single day