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In the world of biology it is generally understood that if you trace life back far enough, it will all converge at a single point. This point is known as the Last Universal Common Ancestor, or LUCA.
Whether you are tracing the biological genealogy of humans, cows, birds, trees, or bacteria, it all goes back to this single point when you look at the genetics.
But what happened before that point? While all life here today is descendant from LUCA, was that really the very first moment of life on Earth? No.
It has long been accepted that while LUCA is the earliest known point in genetics that life today comes from, it is also known that there was other life before it that just didn’t survive genetically to today.
For a long time, it was thought that this type of pre-LUCA life was essentially lost to us forever and could never be studied, but that may not be the case. In a paper published in Cell Genomics, researchers claim that it is possible to look ‘deep’ within the genes of modern life and learn about what life prior to LUCA may have been.
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In a statement about the study, Professor Aaron Goldman of Oberlin College, said:
“While the last universal common ancestor is the most ancient organism we can study with evolutionary methods, some of the genes in its genome were much older.”
Looking at the genome, it indicates that LUCA was a fairly complex organism (for its time). This was not the simplest form of life possible, so it is almost certain that it did not spontaneously form out of the inorganic material in its surroundings.
Goldman and his colleagues say that they are able to discover some of what came before LUCA by reconstructing its genes. This is possible because every lifeform has multiple different versions of essential genes in a family. this is called a paralog, and it is very important since having multiple copies of essential genes helps to prevent problems.
In humans, for example, about 70% of our genes are actually part of paralogs.
MIT’s Dr. Greg Fournier commented in the statement:
“The history of these universal paralogs is the only information we will ever have about these earliest cellular lineages, and so we need to carefully extract as much knowledge as we can from them.”
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According to the study, there are just seven universal paralogs that are present in all life today, meaning they go all thew ay back to LUCA and beyond. All of them are for genes that are responsible for controlling the way that proteins are produced or else for how molecules can cross cell membranes. These are obviously two very important aspects of life.
By looking at these ancient paralogs, researchers can determine not just which ones were present within LUCA, but also, perhaps, how much further back they went. This will give a glimpse into just how long ago life really emerged and what it may have been like.
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