TALES FROM THE COSMIC SEA: We all share a common ancestor,” but this elusive common ancestor has not been found yet, and it may be because the primordial beginnings of our beings came not from one ancestor, but two! The commonly accepted theory or origin has been bacteria– cosmic bacteria carried in on an asteroid, introduced to a happy earth, and welcomed to the world at large. Since the days of Darwin’s finches, the scientific view of the origins of life on earth has been this: living species on earth spiraled down through space-time from a point of origin – a common ancestor. It was considered that the last universal common ancestor (LUCA –dubbed in 1996) had to be bacterial, archaic, or eukaryotic, anything but viral! However, with the recent discovery of Mimi it seems the tables may have turned. It’s seemingly possible now that the common ancestor we share with fish and trees may be viral (or a combination of viral-bacterial) in nature.

The discovery of Mimi– an oversized, genetically packed specimen of what appears to be a hybrid of ancient viral origin – was for scientists, like finding an alien grandmother you never knew you had. The specimen poses big questions about the origins of life and the role viruses have played in the shaping of our complex organisms. For decades scientists have viewed viruses as evolution’s evil little offspring; freaks by all accounts, and unclassifiable in the ways of living organisms. And yet…they do and always have had a life of their own. This anomaly has perplexed scientists who aren’t quite content to label viruses as “living” or “non-living,” probably because the word “life” itself is like a cloud of human metaphor which everyone can see, but no one can define.

The Mimivirus (named for mimicking bacterium) is shockingly co

mplex; it contains more than a thousand genes, weighs in at 1.2 million genome letter, is ten times larger than every other known virus, and comes complete with some DNA repair enzymes, protein synthesis and translation. Comparative DNA analysis revealed something even more amazing: Mimi belongs to her own unique and “extremely ancient lineage of large DNA”. It’s so genetically complex, and unlike anything seen before, that scientists now face remodeling the tree of life to account for this large hidden branch. Mimi’s DNA does not fit into any of the three groups for living organisms (eukaryotes, bacteria, and archaea), it is just as old (perhaps even older) than all three, and Mimi has signature genes which have been maintained in the virus genomes we know now.

Evidence supports that Mimi underwent reductive evolution very early in the timeline of life, trading much of its complexity baggage for a more simplistic, but still smartly dressed self. As Siebert so delicately puts it in his article, “The implications of that finding are truly radical: that Mimi, or a Mimi-like ancestor, emerged prior to the three other domains and played a key role in inventing the very cells of which human and all complex cellular life-forms are made.

Symbiogenesis

Darwin postulated that the evolution, variation and adaptation of living organisms were determined by 4 forces of Evolution: Genetic drift, random mutation, gene flow or migration, and natural selection (some also consider a fifth force which is non-random sexual selection). Lynn Margulis – a biology professor at Boston University and former wife of the late Carl Sagan, was not satisfied with the explanation for new inherited variations. She argued that random mutation and genetic drift alone are non-sufficient for producing new variations in organisms. Darwin, she said, emphasized the facility of competition but neglected one of nature’s favorite mechanisms: cooperation. After many of years of research she published her Endosymbiosis or Symbiogenesis theory in 1967.

Symbiogenisis proposes that symbiotic relationships are the effective agglutinating force of evolution. Through cooperation and mutual interactions, living systems (“vivisystems”) organize themselves into increasingly more complex vivisystems. Thus the creation of organelles, cells, organs, species, etc. etc. is brought on by necessity, and executed by organismal interaction. To support her theory, Margulis focused on the evolution of prokaryotic and eukaryotic cells, and their organelles. She looked at mitochondria and chloroplasts (the power plants for animal and plant cells), fossil records. Margulis purported that the organelles of cells (the mitochondria and chloroplasts) were the result of endocytosis between photosynthetic bacteria, aerobic bacteria, and larger anaerobic bacteria, during the days of anaerobic atmosphere. The anaerobic bacteria consumed or ingested the smaller photosynthetic and aerobic bacterium, and the two became life-long friends, both mutually benefiting from the other’s presence: the smaller providing energy for the cell without exposing the cell to toxic oxygen, and the larger cell providing permanent protection for the smaller structure. Margulis predicted that because they were originally separate organisms, they would have their own DNA different from the cells. This was actually proven in the 1980’s, and her theories are now widely accepted.

And the moral of the story is…

4 billion years ago, interaction between primordial bacteria and viruses culminated inthe ‘parent cell’, the common ancestor of all life on Earth.

Are viral ancestors the equal opposites for the ancient bacteria that Lynn Margulis describes in her theory of Symbiogenisis? Would that make ancient bacteria our father, the first component to the reproduction of living things; and an ancient virus, our mother, the progenitor of an ever-evolving transformation, growing and cultivated in the Tree of Life? I find this concept rather appealing and realistic especially in consideration of the innumerable dualities found intrinsically in the physical universe.

Even if these discoveries and deductions are falsified by future generations, the poetic value of such revelations will always remain, contained in their sweet moments as just another chapter, just one more Tale from the Cosmic Sea.

Much Love,

Liz Mathews.