Our brains might have more in common with an octopus than we’d like to believe, suggesting that famed evolutionary biologist Richard Dawkins’ new paradigm is correct

Almost everyone knows that an octopus is much smarter than we would expect for a boneless creature that lives in the ocean, but next to no one expected they would achieve their intelligence using some of the same genes and chemical processes we do.

Octopi and their cephalopod cousins have long been regarded as unusually intelligent for invertebrates, exhibiting complex behaviors more often found in mammals, if not our closest cousins, the primates.  They appear to use tools, building dens and positioning stones as doors or shields to protect their homes, even decorating them with shells and rocks, leading to the Beatles’ famous song “Octopus’s Garden.”  They can also manipulate objects, opening sealed jars, moving barriers out of their way, even collecting and cleaning discarded coconut shells and using them as shelter.  They seem to be able to recognize people and other animals, including taking a liking to them – or not. For example, Scientific American reported on a story from the University of Otego in New Zealand, where an octopus in captivity would apparently grow angry when a certain staff member passed by, shooting a jet of water at her.  At the Seattle Aquarium, they compared an octopus’ behavior between those who fed them and those who touched them with a bristly stick, and the cephalopod in question reacted differently around the person in question regardless of whether it was feeding time and even though they wore the same uniform.  They can also learn the details of simple mazes, and exhibit complex hunting behaviors that demonstrate a robust internal map of their surroundings.  To some extent, this isn’t surprising: Octopi and other cephalopods have a much larger brain compared to body size (technically nine of them, one in the head and one in each tentacle) than any other invertebrate, boasting about as many neurons as a dog.  At the same time, why this would be the case for about 800 species of invertebrate out of at least 1.25 million known species, and somewhere between 5.3 million and 30 million unknown species including insects, arachnids, and more, has remained an evolutionary mystery.  How did this relatively minor branch, accounting for barely .001% of a major animal kingdom at a low end estimate, acquire such unusual intelligence above and beyond all others?  Scientists have never been able to say for sure, but a recent study led by Nikolaus Rajewsky at the Max Delbrück Centre for Molecular Medicine suggests how their intelligence is achieved on a genetic and chemical level, providing at least some confirmation to a radical new approach to evolution proposed by the legendary biologist Richard Dawkins and perhaps points the way forward to solving the mystery once and for all.

As incredible as it sounds, the last common ancestor shared between humans and cephalopods is believed to have lived 518 million years, long before the dinosaurs walked the Earth, but both wildly divergent species appear to build their big brains using the same underlying chemistry in a rather radical case of convergent evolution.  The chemistry in question is known as microRNAs, a series of small regulatory molecules that help regulate the expression of other genes.  Unlike traditional messenger RNA sequences, which transcribe information from DNA and then assemble proteins in the cell’s cytoplasm based on those instructions, microRNAs do not code directly for proteins.  Instead, they bind themselves to messenger RNA sequences already in flight from the nucleus and either accelerate or impede them, creating either more or less of a certain protein.  While microRNAs are used broadly across both development and ongoing bodily maintenance, in recent years scientists have discovered that they have a large impact on the building of the brain in particular. Based on studies in mice, microRNA genes were found to have impacted everything from the development of new neurons, the migration of neurons to their optimal location in the brain, and the differentiation into specific types of neurons.  From there, they also impact the branching of both axons and dendrites, and the axons that connect them, essentially wiring the entire brain from start to finish.  In addition to studies in mice, various neuro-degenerative diseases are believed to be caused by issues with microRNA function including dementia and glioblastoma.  Though the specific processes underlying their operation in anything as complex as the brain remains unclear and the subject of further study, the brain appears to express the highest number of unique microRNAS in the entire body, followed only by the rest of the nervous system, suggesting a crucial relationship between big, highly functional brains and their activity.  Previously, the expanded role of microRNAs in brain development and ultimately cognition was believed to be unique to humans and our mammalian cousins, but the team at the Max Delbrück Centre found analogous genes and processes at work in octopi and cephalopods.  As part of their research, scientists extracted neuronal and non-neuronal tissue from an octopus to identify genes related to microRNA production and the relative presence of microRNA in the respective tissues.  This included tissues from the vertical lobe, the frontal lobe, the olfactory nerve, and other parts of the brain proper, plus the nerve cords in the arms.  The non-neuronal tissues included everything from salivary glands to the heart and intensities, representing a broad cross section of organs with 18 samples in total.  The samples were then processed with three different methods and computational analyses to determine the presence of microRNA and the associated genes. As they described the findings, “We show that the major RNA innovation of soft-bodied cephalopods is a massive expansion of the miRNA gene repertoire,” and because these genes must’ve arisen long after the split between human and cephalopod lineage, they must’ve evolved independently, making them an incredible example of convergent evolution – and perhaps something more.

In his latest book, The Genetic Book of the Dead, famed evolutionary biologist Richard Dawkins proposed a radical new paradigm with which to view evolution.  DNA, as it is usually conceived, encodes information about how to make the various proteins that make cells and ultimately how to combine those cells into more complex organisms like ourselves or the trees outside our windows.  In addition to this more practical function, Mr. Dawkins suggested that DNA should also be seen as a model for the environment the organism inhabited, or more properly the environment the organism’s ancestors inhabited, as they place a live or die bet that the future will be mostly like the past.  From this perspective, the hypothetical DNA of an early eukaryote is an algorithm for surviving and reproducing in a primordial landscape, a set of instructions designed to cope with a set of conditions and because they are passed down from generation to generation, containing detailed information about the environment and the ancestral history.  Mr. Dawkins chose an obvious example to begin exploring this concept, a lizard that  lives in the desert.  Even at a glance, the most uninformed observer can see that the lizard’s skin almost perfectly matches the desert sands, helping to hide the creature from predators.  Given that the skin grows and is patterned according to proteins and processes encoded in DNA, the DNA itself must contain a model of the environment, one passed down by its ancestors, who survived long enough to reproduce, the same way a photograph stored on a computer can be said to contain a model of the subject.  Of course, the world isn’t entirely a desert, and as Mr. Dawkins put it, if you were to place that same lizard on a golf green, the model would completely fail.  Therefore, organisms that live in different environments encode different models, from the pattern of a tiger’s stripes or using a slightly different strategy, an insect that looks almost exactly like a leaf.  Nor are inanimate objects and plants the only aspect of an environment an organism needs to cope with, thus some animal DNA contains models of other animals – a fly that looks like a wasp, or the pattern on a butterfly’s wings that looks strikingly like a set of evil eyes to scare off predators.  Further, Mr. Dawkins argues that this beauty is far more than skin deep.  As visual creatures, we can easily understand and appreciate the outward show, but if it’s true for the leopard’s spots, it’s also true of the leopard’s insides, all of which has been finely attuned to pouncing on prey in a jungle, which necessarily means its DNA must model key aspects of this jungle including the plants and animals the leopard will encounter, the food it must consume and where it must find it, the fellow leopards it must mate with, and more.

As a means to validate this perspective, Mr. Dawkins claimed that wildly divergent animals – such as humans and octopi – are likely to evolve the same genes to serve the same function.  While this is normally termed convergent evolution, he was referring to something even deeper than the usual usage, identical genes rather than merely analogous structures such as the similarities between the wings of a bird and the wings of a bat.  In the book itself, he cited different types of animals that rely on sonar instead of regular vision as an example.  Bats, dolphins, whales, and some other animals have all developed a form of sonar, known as echolocation, that uses sound waves to “visualize” the environment rather than light waves like we do.  The ability isn’t shared equally across all species in the same family, however, meaning it didn’t originate with a single common ancestor and instead arose as a result of convergent evolution further down each animal’s unique ancestral history.  Therefore, only some bats, some dolphins, and some whales have it, acquiring the trait later in their lineage than their most recent common ancestors, but rather surprisingly, they seem to have done so by “discovering” the gene for the same protein, prestin.  Prestin is closely connected to hearing in mammals, present in cochlea in the inner ear.  If you map the echolocating animals entire genome and compare it to their closest relatives, you find the distribution of genes one would expect descended from a common lineage, but if you focus on the prestin genes alone, the disparate echolocating animals are clustered together, appearing much more closely related on this set of genes than on their entire set.  To Mr. Dawkins, this suggested a more general rule, that instances of convergence among animal lifestyles and environments should result in different clusters of genes, bringing animals from different lineages closer together in key adaptations than they are generally speaking.  At least on the surface, the Max Delbrück Centre study appears to be another, perhaps even deeper example, uniting humans with invertebrates, which from the point of view of our bodies are almost completely alien species, at a fundamental level and suggesting that if your goal is big brains for whatever evolutionary reason, miRNA is the preferred solution.