Scientists Discover Humans Share One Common Ancestor (And It’s Not Adam)

We all derive from a single-cell organism known as LUCA, with scientists suggesting that we share our DNA with a variety of organisms, from really small bacteria to larger animals. 

Scientists believe this is a tiny and essential organism that is the forefather of things varying in size, from very small bacteria to the blue whale.

However, the new research suggests that LUCA was on Earth around 400 million years earlier than previously thought. This means it was around during the Hadeon Eon. 

This era is when dust and gas that orbited the Sun would form into a molten mass. The Hadeon Eon lasted from 4.5 to 4 billion years ago.

This includes amino acids that are used to build proteins in cellular organisms, shared energy currency, cellular machinery such as ribosomes and cellular life using DNA to store information. 

This is because, throughout history, genes have either been lost, gained or swapped between branches. This meant a complicated model had to be created to be able to study them. 

As the time of separation from some species is only known from the fossil records, the scientists used a genetic equivalent of the familiar equation to calculate the speed in physics, which reached 4.2 billion years ago. 

The team said they had to “work backward” to “zero in on exactly when LUCA appeared on Earth.”

It was both anaerobic and autotrophic, meaning it didn’t breathe air and had to make its food from the environment around it, which was dark and metallic. Its ability to have a metabolism also depended on hydrogen, carbon dioxide and nitrogen, which would turn into compounds, such as ammonia. 

The technology needed to sequence genomes and build up genetic libraries has grown rapidly over the last two decades. This has enabled scientists to study genes in more detail than ever before.

The scientists were also able to discover that LUCA’s metabolism was likely able to provide a niche for other microbial community members and hydrogen by recycling atmospheric photochemistry that likely supported an early ecosystem.

Acetogenesis is a process of converting hydrogen and carbon dioxide into energy. The presence of an immune system in LUCA also establishes that this organism was able to withstand the harsh conditions of the Hadeon Eon.

Scientists thought life on Earth began after the Hadeon Eon (about 3.8 billion years ago). They believed life aligned with the Earth’s cooling phase because the oldest known fossil dates back to this period.

This is because the planet accumulated dust and gas, forming a boiling sphere devoid of stable landmasses or oceans. The surface was predominantly molten rock and often underwent intense meteorite bombardments. It is no surprise that scientists thought that this environment could not sustain any life.

“We did not expect LUCA to be so old, within just hundreds of millions of years of Earth formation,” said Dr. Sandra Álvarez-Carretero from the University of Bristol.

However, as LUCA evolved so early on and a lot quicker after the formation of Earth than previously thought, it proves that the process of evolution is a lot simpler than previously thought. 

LUCA was also able to exploit and change its environment, with scientists looking to gain further knowledge into how it did this. 

The new timeline shows how quickly life emerged when the Earth formed. The appearance of LUCA at 4.2 billion years ago suggests that life formed as soon as the planet became minimally hospitable.

“Our work draws together data and methods from multiple disciplines, revealing insight into the early Earth and life that could not be achieved by any one discipline alone,” said Professor Philip Donoghue from the University of Bristol. “It demonstrates just how quickly an ecosystem was established on early Earth.”

Rather than the simple forms of life that scientists imagined early forms of life would be, the opposite is true. LUCA’s immune system and other traits illustrate that life itself is inherently complex and always has been.

The fact that LUCA had an immune system highlights a similar evolutionary arms race between early life forms and the pathogens that would have harmed them. Evidence that LUCA fought against diseases has shaped the entire history of life on Earth.

With this conclusion comes the implication that other planets with similar conditions to the Hadeon Eon could also have early forms of life living on them.

It is believed that these biospheres are flourishing as a result of LUCA, but further research will be needed to see how much they are thriving, or if they are flourishing at all.

Spang said: “The findings and methods employed in this work will also inform future studies that look in more detail into the subsequent evolution of prokaryotes in light of Earth history.”