And Had Great Successnew study further confirms this. lineage-specific structures are the antithesis of evolution and its expected common descent pattern. Instead, structures appear in a few species, or even in just a single species, and are nowhere else to be found. Biology, as John Ray found three centuries ago, is full of unique solutions.
The new study found that imposing the common descent pattern, where microRNAs must be conserved across species, is hampering the search:
These results highlight the limitations that can result from imposing the requirement that miRNAs be conserved across organisms. Such requirements will in turn result in our missing bona fide organism-specific miRNAs and could perhaps explain why many of these novel miRNAs have not been previously identified.
Evolutionary theory has been limiting the science. Indeed, while the common descent pattern has been the guide since the initial microRNA studies, these researchers liberated themselves from that constraint, and it appears this will lead to good scientific progress:
In the early days of the miRNA field, there was an emphasis on identifying miRNAs that are conserved across organisms … Nonetheless, species-specific miRNAs have also been described and characterized as have been miRNAs that are present only in one or a few species of the same genus. Therefore, enforcing an organism-conservation requirement during miRNA searches is bound to limit the number of potential miRNAs that can be discovered, leaving organism- and lineage-specific miRNAs undiscovered. In our effort to further characterize the human miRNA repertoire, we liberated ourselves from the conservation requirement: not surprisingly then, 56.7% of our newly discovered miRNAs are human-specific whereas 94.4% are primate- specific. Considering that many miRNA studies to date have focused on seeking and analyzing conserved miRNAs, it is not surprising that, of the human miRNAs in miRBase, we found a larger fraction to be conserved in rodents and invertebrates. These findings strongly suggest the possibility of a wide-ranging species-specific miRNA-ome that has yet to be characterized. Indeed, it is reasonable to expect that at least some of these novel primate-specific miRNAs participate in unexplored aspects of regulatory processes that cannot be captured by the currently available mouse disease models. Thus, not only could these newly discovered miRNAs provide new molecular insights but they could also help us define novel biomarkers for tissue or disease states.
The evolutionary assumption is needed for evolutionary studies, but not elsewhere.