Understanding the Intricacies of LUCA

The ‘last universal common ancestor’ of all living organisms, LUCA, lived 4.32 to 4.52 billion years ago. This is supported by a study published in Nature Communications by NIOZ biologists Tara Mahendrarajah and senior author Anja Spang, together with collaborators from universities in Bristol, Hungary, and Tokyo. It is uncertain what LUCA looked like, but it had to be a cell with ribosomal proteins and an ATP synthase, among other things.

These proteins are shared by all bacteria, archaea, and eukaryotes such as plants and animals.”

Anja Spang, Study Senior Author and Biologist, Royal Netherlands Institute for Sea Research

The researchers were able to determine the exact times when LUCA split into bacteria and archaea and when eukaryotes first appeared by employing a novel molecular dating technique.

Dating the root

The new dating of the first living form does not significantly alter the earlier estimates.

Dating gets increasingly uncertain towards the root of the tree of life.”

Tom Williams, Associate Professor, Molecular Evolution, University of Bristol

Further up the tree of life, this research by Mahendrarajah and colleagues has one of the true surprises.

Spang added, “Archaea are often called ancient bacteria. hat would suggest that they stem from an ancestor that is older than the one of today's bacteria. But with this improved dating approach, we see that the ancestor of all current archaea lived between 3.37 and 3.95 billion years ago (Figure 1). This makes the last common ancestor of known archaea younger than the one of all bacteria, which lived between 4.05 and 4.49 billion years back (Figure 1). This suggests that earlier archaea either died out, or they live somewhere hidden on Earth where we have not found them yet.”

We are fusions

The last common ancestor of all eukaryotes, or cells with a nucleus, which includes all plants and animals, was between 1.84 and 1.93 billion years ago.

If you imagine all life on earth as a family tree, LUCA is at the base and at some point, the trunk splits into a bacterial and an archaeal branch. But eukaryotes are not a separate branch on this tree of life, but rather a fusion of two branches that came out of the bacterial and the archaeal branches. We have a bit of both in us.”

Tara Mahendrarajah, Biologist, University of Bristol

Understanding natural history

Our new estimates for the age of the archaeal and bacterial ancestors of eukaryotes will help to improve our models on eukaryotic origins. his new way of viewing the tree of life helps us track how cells have evolved over time on Earth. It also gives us a foundation to figure out what those early microbes did in their old environments and how their evolution is linked to natural history.”

Edmund Moody, Research Associate, University of Bristol

Spang concluded, “Insights into the role of both ancient and extant microbes in nutrient cycling can help to better understand and predict future biodiversification in a changing environment, including climate warming.”