The hunt for the Last Universal Common Ancestor, or LUCA, has been going on for centuries. Ever since 1859 when Darwin closed the paper “On the Origin of Species” by mentioning LUCA, “…that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed,” scientists have been searching for the Last Universal Common Ancestor. Finding LUCA would lead to great leaps in understanding evolution and life as we know it today.
Further proof that LUCA existed can be found in the patterns in genomic sequences and similarities in phenotypes and molecules across a diverse range of species. These patterns have kept scientists intrigued with LUCA, as according to these likenesses we can conclude that all evolved from the same ancestor. Genomic and proteomic data collected from the Tree of Life has led to scientists being able to draw conclusions about the characteristics of the genome and proteome of LUCA, so through this study, we have more information regarding LUCA.
Many studies have been done to try to find LUCA, with each study adding to the pool of knowledge that previous research has built. From this research, we know that LUCA had between 30-100 proteins for ribosomes and translation. Additionally, LUCA must have had an early immune system and been a prokaryote-grade anaerobic acetogen. This can be backed up by the theory that the first lineages of the archaea and bacteria were H2-dependent autotrophs which grew from life forming at hydrothermal vents. These vents came from movement in the Earth’s crust caused by interactions between rock and water. Additionally, studies have suggested that evolution is a thermodynamic process, which would add to the theory that LUCA is anaerobic and comes from hydrothermal vents.
Unfortunately, LUCA existed over 3.5 billion years ago. Given that evolution has occurred since the time of LUCA, gene families may have disappeared. This will make tracking LUCA nearly impossible, as we will have to fill in the gaps in the genetic code of the past. Additionally, LUCA would remain incomplete without knowing which genetic families have become extinct. Given that the LUCA could not have been a simple replicator and would have to have been a relatively complex cellular organism, LUCA would not have been around at the origin of life. A considerable amount of evolution must have occurred between the first sign of life and LUCA. Through horizontal gene transfer between heterogeneous lineages, LUCA evolved, but, contrary to previous research, LUCA was also the only survivor of multiple contemporaneous lineages.
More studies are currently in the works for being able to fill in potential genetic gaps that LUCA could be influenced by, as well as more research is occurring around trying to track LUCA. With the technology that we have today, it is highly unlikely to be able to find LUCA, yet as artificial intelligence evolves and the equipment that researchers have grows with the breadth of study, there may be a time when LUCA is found. If LUCA does get found, secrets about our evolution and our interconnectedness with other species would be revealed. So the search for the Last Universal Common Ancestor continues.
- Mabel Carroll
Sources:
- https://www.mdpi.com/2073-4425/3/1/81
- https://deeshee.wordpress.com/wp-content/uploads/2019/09/weiss2016.pdf
- https://www.nature.com/articles/s41559-024-02461-1
- https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.8930
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