The life you see around you has all come down from just one source with a cute-sounding name---Luca, an acronym for 'Last Universal Common Ancestor'. Meet the microbe that existed four billion years ago. It developed adaptations for living in "mineral-rich, oxygen-free and warm environments", very much like hot springs today. The earlier microbes survived on nitrogen, carbon dioxide and hydrogen gases that were emerging from their warm, liquid habitats.
Luca was the "last common ancestor" of humans today, or the "last universal common ancestor", to locate which experts examined 6.1 million genes situated in single-celled organisms today. It was the "bacterium-like single-cell organism" that existed when the earth was just 560 million years old.
The research, led by William Martin at Heinrich Heine University in Germany, used the genetic information to reconstruct the microbe's lifestyle. The microbe must have received hydrogen living in hydrothermal vents, as it was the only source of hydrogen gas on Earth. "I was flabbergasted at the result, I couldn't believe it," he said.
Experts discovered 355 protein groups that had been, with most probability, retained from the ancestor microbe, from which archaea and bacteria also split about four billion years ago. Understanding parts of the primitive microbe's genetic structure also provided clues to its habitat. This was because the genomes were usually well-adapted to their environment.
The 355 genes indicated that the organism survived "deep sea vents, the gassy, metal-laden, intensely hot plumes caused by seawater interacting with magma erupting through the ocean floor."
Around that time, says a biologist at the University of Manchester in the UK, James McInerney, the collisions warmed up the earth's oceans, so that they vaporised regularly. Just those organisms that could survive in very hot water lived through it.
The German genetic study was published in the journal Nature Microbiology and was conducted at the University of Düsseldorf.
