Null-i

In previous musings, I questioned the hegemonic notion that all life on Earth has a common ancestor. I expressed this notion as thus: "If conditions on Earth supported one biological genesis, then these conditions were such that a genesis could have been supported on multiple occasions." For whatever independently arriving at this conjecture is worth, I later found this notion to be referred to as the Shadow Life Hypothesis. The ramifications vary based upon how stringent one's claims are therein, yet the foundation of the hypothesis is simply more than one origin of life. However, published in the latest edition of Nature, life's origins were analyzed.

Douglas Theobald, a biochemist at Brandeis University, began his study by selecting 23 proteins ubiquitous across the taxonomic spectrum. Each species represents these proteins via a structure that is particular to that given species. Theobald then ran the gamut of statistical analyses in order to yield the likelihood of any model to derive these protein structures. His computational simulations indicated that the universal common ancestor hypothesis is 10^2,860 times more probable than any concatenation of multiple ancestors. In spite of the fact that many microbiologists may note that microorganisms of disparate species may swap genetic material, the computations accounted for this and still found a single ancestor to be the most efficacious solution.








*Blue dotted line represents swapped genetic material

Theobald qualifies that his study does not in any way suggest the number of times life on Earth emerged. Nonetheless, it does suggests that only one strain would ultimately reign supreme. In any case, while we may concede that this statistical analysis is perfectly cogent, it may be begging the question with regard to our taxonomic categorization. Further, Theobald's statistical analysis as a formal study is questionable; our notion of nature as a pinnacle manifestation of logical eloquence does not always prevail. Considering what we know of the human genome (and genomics writ large), the retention of archaic sequences from genetic ancestors that no longer code for active traits serves as a case in point where the precedent of logical eloquence and simplicity in nature breaks down in biology. (**EDIT** - in light of my critique, I just happened upon this article.)