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LUCA: Last Universal Common Ancestor

Who and what is LUCA?

All organisms now living have common descent with LUCA. But LUCA is not the origin of life. It’s a common misconception to think that LUCA is the origin of life. But the origin of life existed long before LUCA.

It’s believed the origin of life happened 3.5 to 4.1 billion years ago. Whereas the last universal common ancestor is thought to have lived 3.5 to 2.5 billion years ago.

During the 500 million years that separate LUCA and the origin of life, DNA had to evolve into a somewhat functional system.

For example, DNA included replication enzymes, transfer RNA, and ribosomes at this time. This is because all living things share these same functions meaning they must have been present in LUCA.

LUCA Timeline

An intuition for the last universal common ancestor


All living things originated from a common ancestor called the last universal common ancestor (LUCA). Let’s put this in perspective from our human evolution history:

  • NEANDERTHALS: Suppose you took your DNA and compared it to a Neanderthal. You’d find that both your DNA is 99.7% identical.
  • CHIMPANZEES: Next, if you compare your DNA to a chimpanzee, you’ll see more differences. In fact, there’s about a 98.5% overlap.
  • CHICKENS: For a chicken, it’s 60% overlap with your DNA.

As you keep comparing, it never reaches a point where you don’t share any DNA. Simply, we share commonalities in our genetic composition and DNA with all organisms on Earth.

“LUCA is the common ancestor that unites us all. By comparing the genomes of simple bacteria with eukaryotes, LUCA has the most universal genes in all life.”

LUCA thrived in underwater hydrothermal vents


If you look back at Earth’s early atmosphere, it didn’t contain oxygen. So, this means LUCA likely was an obligate anaerobic organism.

LUCA also didn’t rely on other organisms. This is simply because there weren’t a lot around at this point in geologic time.

So, LUCA likely thrived in an iron-sulfur-rich lifestyle in underwater hydrothermal vents. This was the type of environment that could provide water rich in hydrogen, carbon dioxide, and other minerals for it to develop.

LUCA: Last Universal Common Ancestor

The Last Universal Common Ancestor (LUCA) is the hypothetical organism from which all life on Earth is believed to have descended.

LUCA is thought to be a single-celled, ancient microorganism that existed billions of years ago, serving as the common genetic ancestor to all forms of life on our planet today.

Do you have any questions about the origins of life? We do too! Please let us know your questions and comments below.

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  1. Who developed the LUCA theory?

    What evidence exists that support this theory?

    How much of the evidence can an “ordinary” person understand?

  2. Luca was a single celled organism. In the story of Life, multicellular life was most likely the result of 2 seperate single celled lifeform’s combining ( by one of them “consuming” the other” but maintaining both as 2 separate living organisms at first. This “event” was thought to have happened as a lethal poison killed many of the existing Lifeform’s at the time. The poison was a gas called Oxygen and yet it became the required fuel for more complex and higher functioned Life which meant what was first considered (and it was) a highly toxic & corrosive chemical …contained the necessary energy and other advantages that all higher order animals require to exist and it became instrumental in becoming the means to advance life beyond and above what existed before Oxygen became the choice for Most life that exists in profound variety & vigour today.

    The actual event that created the first multicellular lifeforms was and remains the most important step that Life ever took and made possible the variety, size ,variation and direction it has taken ever since it happened. ONCE.

    To underscore just how important and unlikely multicellular life is, over the course of the 4 billion years since life first began, multicellularity happened just the once…in fact most experts believe life will be found in our solar system and even exist in 3 or possibly 4 different places…most are almost certain it will be single celled Life.

    Such is the sheer luck that is Earth’s to claim and our good fortune to have had to happen.

  3. Were there other life forms different from Luca that existed at the same time as Luca and was Luca a singe cell or a combination of many organisms?

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