"Ten years ago most biologists would have agreed that all organisms evolved from a single ancestral cell that lived 3.5 billion or more years ago. More recent results, however, indicate that this family tree of life is far more complicated than was believed and may not have had a single root at all."
A recent article in the periodical journal Scientific American has shed extremely important new light on the faults of our simplified "tree of life:" the phylogenetic tree depicting the evolution of all life as we know it. Molecular phylogeny, the brainchild of California Institute of Technology students Emile Zuckerkandl and the now-legendary Linus Pauling, gave rise to an almost revolutionary blooming of new data on evolution. Eventually, it bred the three-domain system we use today (as proposed by Carl Woese of the University of Illinois in the late 1960s. SSU rRNA comparisons have allowed the formulation of new and credible phylogenetic trees of life.
However, the modern scientific community is still far from finding an ultimate resting place for the myriad theories on how today's diversity of life arose. Indeed, the endosymbiotic hypothesis key to the evolution of Eukarya was published in Scientific American only as recently as 1996! Indeed, the vast majority of cohesive evidence supports the dominant thesis in the community today-that Bacteria and Archaea diverged from a common ancestor, and the Archaean lineage gave rise to the Eukaryotes.
However, new evidence suggests, dealing a veritable blow to many feelings of omnisciency among experts, that the genomes of organisms in the three domains are far from such a simple solution. Rather, lateral gene transfer-the passing of genetic material not from a parent to daughter cell but across species lines-seems stunningly prevalent in our history. Eukaryotes have genes besides those involved in cellular respiration and photosynthesis (which could have come from the alphaproteobacterial symbionts that gave rise to the mitochondria and chloroplasts) that clearly spring from the Bacteria lineage. Even more shocking, Archaea do as well.
It is clear from the new data we have amassed that the tree of life as it stands today is far from perfect. It would seem that just as we felt at the pinnacle of success in delineating our evolutionary history, our parsimonious hypotheses were smashed. Yet we should be far from surprised. Since the proliferation of Darwinian evolutionary biology, scientists have sought a coherent explanation from the evolution of life. Now another monkey wrench has been tossed in the machinery, and our precious theories must be revised once more.
Will mankind ever find a certain solution to the mystery of life? Highly improbable, if even possible. Yet with each new piece in the jigsaw puzzle, a significant one being the discovery of lateral gene transfer, we come closer and closer to the ideal model. Perhaps most importantly, our sketches and diagrams seem to sprout new and increasingly complex branches with each revelation. It is this concept in itself that may prove the paramount lesson in our quest: the phylogenetic events that gave rise to the biotic bounty we know today are far too complex to be classified in a mere diagram or paragraph.