Flaws emerge in RNA method to build tree of life

>For example, in the case of the turtle study, Peterson’s team had searched for microRNAs in RNA extracted from cells, rather than by sifting through the turtle genome — which was not available when they did the study. The discrepancy likely results from the fact that some pieces of RNA are only expressed at particular moments in an animal’s lifetime, whereas genes in the genome are steady.

Ouch. If micro-RNA is expressed differently at times, that seems like a rather fatal flaw in using them for similarity measurements.

Maybe it's just hindsight, but it seems fairly obvious that RNA-that-controls-gene-expression would vary through a lifetime, and therefore make it a problematic source for measuring similarity. Unless they can detect and ignore ones that come and go...?