The Last Universal Common Ancestor

Scientists believe that life on Earth began many eons ago.  Simple organisms developed into more complex organisms.  Mutations branched off into different species, resulting in the diversity of life that exists today: plants, fish, animals, and of course humans.

If this is true, then – at some point in our prehistoric past – there was a single living organism from which all of this biodiversity originated.  It would not have been the first living organism.  Instead, it would have been the most recent organism from which all current life can be traced – the “root” of Earth’s family tree, so to speak.

The concept of a “last universal common ancestor” – more affectionately nicknamed “LUCA” – was first proposed by naturalist Charles Darwin in his 1859 book “On the Origin of Species”:

“Probably all the organic beings which have ever lived on this earth have descended from some one primordial form.”

Since then, scientists have tried to pinpoint LUCA, what it looked like and when it inhabited the Earth. In recent years, advances in genomics and analytical instrumentation have helped evolutionary biologists to isolate and identify protein-coding genes and their characteristics.  Agilent solutions used in the search for LUCA include an LC/MS, UV-Vis spectrophotometer and E. coli cells.

In a recent study, German researchers sorted through 6 million genes and 2,000 genomes that have been assembled in DNA databanks over the past two decades.  Looking for commonalities, they identified 355 genes they believe were carried by LUCA.

According to this genetic profile, LUCA was a single-celled, bacterium-like organism.  It lived about four billion years ago, when the Earth was a mere 560 million years old.  It likely survived without oxygen, instead pulling energy from carbon dioxide and hydrogen in an extremely hot hydrothermal vent at the bottom of the ocean.

That’s something to think about, the next time you’re working on your ancestral family tree…


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