A new study is out here. They were studying epigenetic effects in planaria flatworms. Same planaria, three different “species”-level “heads” were regenerated.
Of course, everything must have an “evoltuion-did-it” explanation; so, for the record, here it is:
The ease with which a particular shape could be coaxed from a G. dorotocephala worm was proportional to the proximity of the target worm on the evolutionary timeline. The closer the two species were related, the easier it was to effect the change. This observation strengthens the connection to evolutionary history, suggesting that modulation of physiological circuits may be one more tool exploited by evolution to alter animal body plans.
However, there is more to mull over:
Working with Girardia dorotocephala – free-living planarian flatworms, which have remarkable regenerative capacity – researchers were able to induce the development of different species-specific head shapes by interrupting gap junctions, which are protein channels that enable cells to communicate with each other by passing electrical signals back and forth. The changes were more than skin deep; they included not only the overall shape of the head but also the shape of the brain and the distribution of the worm’s adult stem cells.
Further:
The finding that head shape is not hard-wired by the genome but can be overridden by manipulating electrical synapses in the body suggests that differences in species could be determined in part by the activity of bioelectrical networks.
The difference here between “species” is not due to “changing allele frequencies” brought about by some kind of genetic isolation, as per “neutral genetic drift,” which suggests that “alleles” are “lost” (or gained?) in the process of “speciation”.
Something completely different is going on. Something is really amiss here in evolutionary understanding.
From the pdf file:
Based on these results, we conclude that discrete, species-specific head shapes can be achieved by manipulating the connectivity of physiological networks in the planarian flatworm during head regeneration.
Something is rotten in the state of population genetics.