A friend of mine by the name of
Gary Onn sent me this link on the origin of life two days ago via WhatsApp
chat.
Just in case you cannot open the
above link, here’s the text:
Scientists have rewritten the
history of life on Earth with a new estimate for the age of LUCA, or the Last
Universal Common Ancestor, who is generally acknowledged as the common ancestor
of all living things, thanks to a ground-breaking study.
The study, which was published
in Nature
Ecology & Evolution, indicates that LUCA lived approximately 4.2
billion years ago, which is significantly closer to Earth's origin than
previously thought.
LUCA, a common ancestor to all
organisms and not the first life form, has been a controversial topic among
scientists for centuries. Life fossil evidence goes back as far as 3.4 billion
years, yet this study proposes that LUCA might be close to being the same age
as the Earth. The genetic code and DNA replication, which are two of the vital
biological processes, might have developed almost immediately after the planet
was formed.
The research team performed
analysis of 700 genomes of bacteria, archaea, and fungi and constructed LUCA's
genome, excluding eukaryotes such as plants and animals that evolved later.
They have found 57 gene families responsible for the evolutionary relationships
of those organisms in their study.
Their results depict LUCA as a very
intricate organism, a kind of modern bacteria or archaea that does not possess
the capability of photosynthesis. The study proposed a new way of finding
LUCA's age using paralogous genes and fossil data to solve the problem of so
little direct fossil evidence of the early days of Earth.
This LUCA reconstruction represents
a significant advancement in understanding the evolution of living organisms on
Earth. Nevertheless, the research work has made sure that their deductions are
not the last ones. With new organisms being discovered and technology
developing, it is very likely that our interpretation of LUCA will develop,
furthermore to the point of giving our knowledge more depth at the ancient
beginnings of life.
Here's my view on the above
article:
The above article sent to me
discusses fascinating research on LUCA, the Last Universal Common Ancestor,
which is considered the shared ancestor of all life on Earth. The study
highlights a new estimate for LUCA's age, suggesting it lived around 4.2 billion
years ago, much earlier than previous estimates. This timing would place LUCA
closer to the formation of Earth itself, which is about 4.5 billion years old.
The study seems to make significant
contributions to our understanding of early life by analyzing 700 genomes from
bacteria, archaea, and fungi, and reconstructing LUCA's genome. The exclusion
of eukaryotes, which evolved later, helps focus on the very earliest branches
of life. The identification of 57 gene families that are key to evolutionary
relationships in these organisms is crucial for piecing together LUCA's
characteristics.
One of the most striking findings
is that LUCA is depicted as a complex organism, more like modern bacteria or
archaea, but without the ability to perform photosynthesis. This challenges the
notion that early life forms were extremely simple.
The methodology used—combining
genomic analysis with fossil data and paralogous genes—provides a novel
approach to dating LUCA and may offer insights into the origin of key
biological processes like DNA replication and the genetic code.
While the research marks a
significant step forward, it's important to note, as the article does, that
this is not the final word on LUCA. As new technologies emerge and more
organisms are discovered, our understanding of early life will continue to evolve.
The findings underline the complexity of life's origins and suggest that life's
foundational processes might have developed more quickly after Earth's
formation than previously thought.
This research is exciting because
it opens up new avenues for exploring how life began and evolved on Earth,
offering a deeper understanding of our planet's ancient past.
However, according to an
independent source, and other papers I read that were presented at the Cold
Spring Harbor Symposia on Quantitative Biology Volume LXXIV on “Evolution: The
Molecular Landscape” - that was also part of my forum presentation and dissertation
on Evolution, a postdoctoral course I read at the University of Cambridge in
2019, we believe the last universal common ancestor (LUCA) is the
hypothesized common ancestral cell from which the three domains of life, the
Bacteria, the Archaea, and the Eukarya originated. The cell had a lipid
bilayer; it possessed the genetic code and ribosomes which translated from DNA
or RNA to proteins. The LUCA probably existed at latest 3.6 billion years ago,
and possibly as early as 4.3 billion years ago or earlier. The nature of this
point or stage of divergence remains a topic of research.
Phylogenetic tree linking all major
groups of living organisms, namely the Bacteria, Archaea, and Eukarya, as
proposed by Woese et al in 1990, with the last universal common ancestor (LUCA)
was shown at the root
All earlier forms of life preceding
this divergence, and all extant organisms are generally thought to share common
ancestry. On the basis of a formal statistical test, this theory of a universal
common ancestry (UCA) is supported versus competing multiple-ancestry
hypotheses. The first universal common ancestor (FUCA) is a hypothetical
non-cellular ancestor to LUCA and other now-extinct sister lineages.
Whether the genesis of viruses
falls before or after the LUCA–as well as the diversity of extant viruses and
their hosts–remains a subject of investigation.
While no fossil evidence of the
LUCA exists (except chemical footprints of nucleotides
and nucleic acids of possibly early
life found in primordial oceans), the detailed biochemical similarity of all
current life (divided into the three domains) makes its existence widely
accepted by biochemists and biological evolutionists.
Its characteristics can be inferred
from shared features of modern genomes
I think I can confidently summarize
that LUCA and its significance in the evolutionary history of life is spot on.
I think we have captured the essence of the concept and its complexities.
LUCA is indeed the hypothesized
common ancestor from which the three domains of life—Bacteria, Archaea, and
Eukarya—descended. The features I mentioned, like the lipid bilayer, genetic
code, and ribosomes, are all fundamental characteristics that would have been
necessary for the basic functioning of a cell, making LUCA a highly
sophisticated organism rather than a primitive one.
I have also mentioned the
Phylogenetic tree proposed by Woese et al. in 1990. This is important because
it was a groundbreaking work that reshaped our understanding of life's
evolution by establishing the three-domain system. This tree places LUCA at the
root, emphasizing that all life, despite its immense diversity, shares a common
origin.
The distinction between LUCA and
FUCA (First Universal Common Ancestor) adds another layer of complexity. While
LUCA is considered cellular and more advanced, FUCA is a hypothetical ancestor
that may have existed before cellular life, possibly as a non-cellular or
proto-cellular entity. This reflects the ongoing research and debate in the
field, as scientists like us who have studied evolutionary biology try to
reconstruct the earliest stages of life.
The genesis of viruses in relation
to LUCA is indeed a hot topic. Some hypotheses suggest that viruses may have
evolved before LUCA, perhaps even playing a role in the development of early
cellular life, while others propose that viruses originated later. The
diversity of viruses and their hosts, along with their complex interactions,
make this a challenging question to answer definitively.
Finally, as we rightly pointed out,
despite the lack of direct fossil evidence for LUCA, the biochemical
similarities across all current life forms strongly support its existence.
These shared features in modern genomes allow scientists to infer many characteristics
of LUCA, even in the absence of physical fossils.
Overall, our source presents a
thorough and accurate view of LUCA and its role in the history of life,
reflecting both the current consensus and the ongoing debates in evolutionary
biology.
What do my gentle readers here think? Do you think you agree or disagree with me? If not, why? Give me your concrete, technical and scientifically logical reasons if you disagree. But it has to be well-qualified reasons preferably at research and doctorate (PhD) levels.
Thank you for reading and sharing
ju-boo lim
No comments:
Post a Comment