In an earlier essay, I argued that the process(es) by which symbionts become organelles constitute macroevolutionary change. While this was discussed largely in the context of a fascinating long-term experiment begun by K. W. Jeon and colleagues in the 1960’s, it is also relevant to the origins of more identifiable organelles such as mitochondria and chloroplasts. Which brings me to another matter, a line of experimentation that shows yet another case whereby macroevolutionary change can be studied by direct experimentation, almost in real time.
The progression from symbiont to organelle involves many steps or processes. Among these is a migration of genes from the symbiont genome to the host genome. The end results of such migrations may be seen in the genomes of modern eukaryotes; thus, nuclear genomes are “littered” with genes that are derived from prokaryotic ancestors, but are expressed as eukaryotic genes and whose protein products end up in the organelle. Attendant with such migrations have been a number a number of changes, modifications that would permit the new nuclear gene to be expressed, and its protein product to be transported from the cytoplasm into the organelle.
Until recently, studies of these migrations have been matters of sequence comparisons and analyses. These approaches are very informative, and have told us about the ancestry of the relevant genes. However, for the most part, matters of mechanism have been harder nuts to crack, largely because it had been assumed that migratory events occur on an evolutionary time scale, and thus that they would be unlikely to be caught “in the act”. Recent studies reveal that this is not the case. Briefly, it is now known that gene migration from organelle to nucleus can be observed and studied in real time, and that questions pertaining to the “activation” of organellar genes after migration to the nucleus can be asked (and answered). In other words, this sort of macroevolutionary change can be studied as it occurs.
There is more to this story, some of which may be found here, where comments may also be left. (As a further teaser, I would note that this phenomenon impacts the field of biotechnology and GMOs.) The bottom line is simple, though - macroevolutionary changes involving gene migration can be studied in real time, once again putting the lie to the ID/antievolutionist assertion that macroevolution cannot be addressed experimentally.