Life on Earth is Old

Life on Earth began somewhere. Scientists think that there was one single ancestor, which they call LUCA (Last Universal Common Ancestor). This would have been a unicellular organism that eventually diverged to create every living thing we have today. And I mean everything, from tiny bacteria to blue whales. And LUCA began a long, long time ago.

About 530 million years ago, the Cambrian Explosion saw the major expansion of complex life. It’s been estimated that LUCA appeared 4 billion years ago, about 600 million years after Earth’s formation.

But one study pushes that arrival back to about 4.2 billion years ago. It also indicated fascinating details of what life for LUCA might have been like.

To find exactly when life appeared on Earth, scientists had to work backward. They first compared genes in species living today and counted the number of mutations that have occurred since the common ancestor. Using a genetic equation, they worked out that LUCA must have existed as early as 400 million years after the planet’s creation. That would put his organism in the middle of the Hadean Eon, which was a hellish geologic nightmare. During this time, Earth experienced frequent collisions, including the one that created the moon. The surface was unstable, with lava bubbling to the surface.

The evolutionary history of genes is complicated. Scientists had to use complex evolutionary models to reconcile the history of genes with the genealogy of species.

The team also retraced the physiological characteristics of living species to discover what LUCA must have been like. Surprisingly, even though it was a unicellular organism, it appears to have had an immune system. This would indicate LUCA was already fighting off primordial viruses, which makes one wonder if viruses are truly alive.

While LUCA was exploiting and changing its environment, it’s likely it didn’t live alone. Its waste would have been eaten by other microbes such as methanogens, which produce methane as a by-product of their metabolism. Such arrangements might have created a recycling ecosystem.

Although this is the oldest common ancestor known, scientists don’t understand how life evolved from its very origins to the early communities that LUCA was part of.

 

https://www.msn.com/en-us/news/technology/all-life-on-earth-comes-from-one-single-ancestor-and-it-s-so-much-older-than-we-thought/ar-AA1So3MH?ocid=hpmsn&cvid=694052ebf2b54b488c496cce3ccd1493&ei=107