Anyone that has studied genomics at school will remember the basic principles, which describe how gene frequency with a population is directly proportional to the environmental advantage that it may express phenotypically. Consequently, as environments change, then so do the frequencies of those genes throughout the population. This process is the precursor to evolutionary diversity as, when two genetically identical populations become isolated, the environmental conditions on either side of the divide will vary, causing differences in the gene frequency. Given enough separation time the two species will diverge enough to become separate, genetically isolated organisms. As speciation continues to produce varying forms of life then some types will outcompete others for similar biological niches.
The principles properly describe what is observed in the natural world, and this has been demonstrated through many lines of reasoning, fossil records, genetics, phylogenetics, embryology and so on… but leaves each species at the mercy of their adaptive capability through mutational rates, genetically. Or does it?
Some members of this phylum can actually edit their genetic code!
A paper published in 2017 in the Journal Cell, by Liscovitch-Brauer et al, has looked at genomic evolution in the Cephalopods and found that some members of this phylum can actually edit their genetic code! The work showed that the individuals were enriching a large selection of genetic sites which related to their nervous system whilst preserving tens of thousands of segments within the code. This seems to offer these species a massive selective advantage as they can quickly respond to pronounced environmental changes.
Not only that, but this ability actually helps Cephalopods reduce the frequency of detrimental natural mutations within their genetic code and gives them a level of control that human society is only just debating the ethics of. Importantly, it adds a new method to environmental adaptations which no longer require DNA mutations, the method that humans are bound by.
“For us, generally when we have a gene, the coding can be improved through mutation. That’s the general picture of evolution, where a mutation comes along to adapt the protein to the needs of the organism,” co-author Eisenberg says. “But when you change the DNA, it’s hardwired. You change it, and that’s that”. This method allows them to quickly diversify the proteins available within the genetic pool, making them highly adaptable.
According to Joshua Rosenthal, lead author from the Marine Biological Laboratory at Woods Hole, USA, “When do they turn it on, and under what environmental influences? It could be something as simple as temperature changes or as complicated as experience, a form of memory”.
Cephalopods are all Molluscs, snails, slugs and such. However, it is the Coleoids, subclass – squid, cuttlefish and octopi that display a high degree of intellectual capacity. One of the implications of the study is that Coleoids have ‘engineered’ their brains through repeated optimisations of their nervous system.
Coleoids have ‘engineered’ their brains through repeated optimisations of their nervous system.
“You might edit the RNA in one tissue, say, the brain, and not in another, like the muscle,” Eisenberg explains. “You can have the old protein produced under normal conditions, and a new one when you’re under stress. You can edit it or not to varying levels; you can have the edited and unedited version in the same cell, working together”.
So why can humans not perform the same trick? To all intents and purposes, we do, but the events are highly infrequent. In performing this trick, the implications are that it may come at the expense their genomic evolution. The types of mutations which allow humans to adapt and survive through countless generations would simultaneously prevent Cephalopods from editing their genome due to the genetic structures not being in place.
It seems that once again mother nature has developed multiple ways for organisms to adapt and evolve by using such diametrically opposed processes. This could have much wider implications with respect to climate changes. By understanding new strategies in which organisms evolve, we might garner a better appreciation as to the impacts environmental changes are having on different species. Perhaps species which employ genomic editing are far more resilient to changes than even we can be? It is certainly an enticing thought.
A follow-on thought is: how many other species may have convergently evolved a similar mechanism that we have yet to discover? The paper suggests that it is a relatively recent development for the Coleoids, but surely its presence suggests that other clades might well make use of such a strategy. There certainly seems scope for such a hypothesis.
It also demonstrates that however much we think we understand about organisms; our planet can still offer us special surprises. Cephalopods continue to mesmerise us with their out-of-the-box answers for camouflage, communication, locomotion, intelligence, and now evolutionary mechanisms. It is hardly surprising that they are so frequently referred to as organisms from another planet.