Reasons To Believe : Science News Flash: Has the Last Universal Common Ancestor Been Identified?


Have these researchers provided us with a key insight into LUCA’s identity? Have they identified the locale for the origin of life? Not necessarily. Here are some points to consider: If life originated under high temperatures, the genetic code should reflect life’s hot heritage, yet the genetic code shows no indication that it is suited for a high-temperature environment. From an evolutionary perspective, the genetic code must have arisen under moderate, mesophilic conditions. Based on this result, it’s reasonable to conclude that life also arose under mild conditions as well. The guanine-cytosine (GC) content of rRNAs for the hypothetical LUCA would have been too low to support a thermophilic lifestyle.  Organisms that live in a high temperature environment characteristically employ higher amounts of GC in DNA and RNA molecules. Life’s building blocks and RNAs’ three-dimensional structures are highly unstable under hydrothermal vent conditions. Again, this makes it unreasonable to think that life originated at these ocean vents. This work also highlights the complexity of the first life-forms on Earth. This complexity is too great to be accounted for by evolutionary origin-of-life scenarios.

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