The exact details of how life began remains a mystery, but scientists might have found some compelling evidence on what the common ancestor of all living things on Earth might have looked like.
Researchers from the University of Düsseldorf in Germany have determined the fundamental features for a Last Universal Common Ancestor (LUCA) – a fundamental concept for the study of evolution and the origin of life – by analyzing the evolutionary relationship of 6.1 million protein-encoding genes from single cell organisms.
The team found 355 protein groups that are likely to have originated from an ancient organism. These genetic elements suggest that LUCA didn’t require oxygen to live and all its metabolic function used carbon dioxide, hydrogen, and nitrogen. It also suggested how it might have thrived in (relatively) high-temperature environments, making hot springs a suitable location for a LUCA to evolve.
In the paper, published this week in Nature Microbiology, the authors also highlight how LUCA was dependent on transitional metals such as iron, or elements such as selenium. These characteristics are very interesting, indicating that LUCA seemed to be autotrophic, able to extract nutrients from the inert environment around it.
"These are the answers that the data delivers. They could have indicated photosynthesis, or glucose fermentation, or some kind of respiration. But they didn’t. They point to an ancestral kind of carbon metabolism that starts from CO2, but also energy harnessing of geochemically generated ion gradients," said senior author Bill Martin to IFLScience.
"Can we be sure? We can never be 100% certain about anything in evolution, there are always factors that come into play in our inferences from the data. But the data speak quite a clear language on this question, we were very excited".
There are some organisms today, such as the clostridia and the methanogens, which have similar lifestyles to LUCA, enjoying geothermically active environments. Sometimes you don’t change a winning design.
LUCA is believed to have lived between 3.5 and 3.8 billion years ago, not quite the first example of life on Earth, but close. The earliest paleontological discovery places the introduction of the first lifeforms at 4.1 billion years ago.
The environment back then was significantly different. Then, our planet had just come out of a cosmic pool match with the rest of the Solar System, known technically as the Late Heavy Bombardment, when asteroids and cometary impacts were a lot more common. There were a lot of volcanos, the Sun was dimmer, and there was no oxygen-rich atmosphere.
The first organisms had to battle the odds of this incredibly harsh planet, until LUCA appeared and took over, evolving into all the forms we see today. No matter what the universe throws at us, life on Earth seems surprisingly resilient.