Is Devolution Possible?

Is devolution (biology) possible?

Check out this answer from Consensus:

The possibility of devolution in biology is supported by various lines of evidence from cancer biology, cognitive anthropology, evo-devo, and metaevolution. While traditional evolutionary theory views evolution as a unidirectional process, these studies suggest that under certain conditions, organisms can revert to previous states. Therefore, devolution, or reverse evolution, is not only possible but also an integral part of the complex and dynamic process of evolution.

The concept of devolution in biology, often referred to as “reverse evolution,” suggests that organisms can revert to a previous state in their evolutionary history. This idea has sparked considerable debate among scientists, as it challenges the traditional view of evolution as a unidirectional process. In this article, we will explore the possibility of devolution by examining various research studies and theoretical perspectives.

Phylogenetic Reconstruction and Devolution

One of the key areas where the concept of devolution is explored is in the phylogenetic reconstruction of cancer cell populations. The DEVOLUTION algorithm, for instance, is designed to deconvolve clones based on copy number aberration analyses of multiple tumor biopsies. This method allows for the reconstruction of the evolutionary history of cancer cells, providing insights into how these cells may revert to previous states under certain conditions1 2. This suggests that, at least in the context of cancer biology, devolution is a plausible phenomenon.

Knowledge Devolution in Human Societies

Another perspective on devolution comes from anthropological and cognitive studies. Research indicates that while biological science has advanced significantly, practical knowledge of nature among the general populace has diminished. This phenomenon, termed “knowledge devolution,” highlights how cultural and cognitive factors can lead to a regression in understanding and interacting with the natural world3. This form of devolution is not biological but rather a socio-cognitive process, demonstrating that devolution can occur in different contexts.

Evo-Devo and Speciation

Evolutionary developmental biology (evo-devo) provides another lens through which to examine devolution. Evo-devo research has shown that developmental mechanisms can give rise to key innovations that promote speciation. However, these same mechanisms can also lead to the re-emergence of ancestral traits under certain conditions, suggesting a form of devolution at the microevolutionary scale4. This indicates that devolution, in the sense of reverting to ancestral traits, is possible within the framework of evo-devo.

Metaevolution and Devolution

The concept of metaevolution, which refers to the evolution of the potentiality of evolution, also touches upon the idea of devolution. Metaevolutionary processes, such as crossing over, alternative splicing, and epigenetic modifications, enable the rearrangement of metabolic processes and anatomical characteristics. These processes can lead to the re-emergence of ancestral traits, supporting the notion that devolution is a component of the broader evolutionary process5.

Is devolution possible?

Kathryn Hall has answered Near Certain

An expert from Queensland Museum in Biology

My answer to this question is a qualified “yes”, the qualification being that I don’t support the idea of “devolution” as such, but I certainly have observed numerous instances of the loss of complex characters within a related group of species (a genus or family).

With my colleagues, I described two new species of marine sponges (full article) (and reassigned another species) which belong within a group (Family Theonellidae) that is characterised by having very large, complex and beautiful interlocking spicules (called desmas). These new species, though, entirely lack these complex spicules, and have comparatively very simple internal structures. It seems that, independently of each other, these species have lost their desmas. The reasons for the loss of the desmas is not clear, but what we do know is that without desmas, these sponges are able to live in the gaps between the rubble on the sea-floor, and that the ecological role they play, because of this gap-filling habit, is to aggregate the sea-floor providing a platform for other animals to colonise.

It does seem odd at first to consider that a very complex characteristic, that took millions of years to evolve, and which is so beautifully intricate, can be turned off and disappear entirely from the animal, but…that is evolution… Not having the complex character no doubt conserves energy and has enabled these sponges to enter into new ecological spaces (niches) that were otherwise unoccupied, meaning that there in the rubble of the sea-floor, these sponges have a unique job – cementing the rubble together, helping to stabilise the substrate and make new foundations for damaged reefs. Every ecological “gap” ends up being filled in the end – as they say, nature abhors a vacuum – and if the only way to access otherwise unexploited niches is to “devolve” so to speak, then, yes, that is certainly possible, and does happen in natural systems.

Is devolution possible?

Mark N Puttick has answered Near Certain

An expert from University of Bath in Biology, Palaeobiology

Yes, organisms can evolve to become more ‘simple’ over time. However, the concept is misleading. The idea of devolution is rooted in the assumption that evolution has a purpose and is trying to attain some goal of perfection. The only certain aim in evolution is to survive long enough to maximise reproductive output. It is irrelevant if organisms reach this goal by being more or less complex than previous generations. Additionally, complexity is a concept with no firm definition in evolutionary biology. Researchers have measured complexity in many ways, but there is no suggestion being complex is ‘better’ than being simple in evolution.

Evolution is rooted in the present and is blind to the future and the past. Natural selection acts on forms that are suited to the environment at that time with no future goals of progress in mind. Evolution does not conceive of long-term plans but acts to the select the best features today, even if this is costly for future generations. It may be costly to an organism’s ability to survive and reproduce to maintain or develop more evolutionary features. In this case, evolution will act to make organisms simpler over time as long as it continues to live long enough to pass its genes to the next generation.

There are potential examples throughout the tree of life. Placozoa are early animals with a simple body plan compared to their close relatives. For example, they do not possess organs or nerves (more discussion here: https://www.cell.com/current-biology/pdf/S0960-9822(17)31524-5.pdf). These Placozoa are not representative of the ‘first animal’ as evolutionary relationships show them to be related to more complex animals – jellyfish and corals. In this example, Placozoa have ‘devolved’ compared to the features possessed by the common ancestor they shared with corals and jellyfish, but this is irrelevant from an evolutionary viewpoint as Placozoa continue to survive and reproduce today. Within this view they are successful as every other organism on Earth from the simplest to the most complex.

Is devolution possible?

Donald McKnight has answered Near Certain

An expert from James Cook University in Ecology, Biology, Zoology

The short answer is “yes,” but that needs to be explained, because the concept of “devolution” is very misleading and makes assumptions about evolution that simply aren’t true (it’s not a term that I would recommend using).

 The concept of “devolution” is built on the notion that evolution has a direction (thus, devolution occurs when evolution goes “backwards”), but evolution does not have a direction. Natural selection simply adapts organisms to their current environment, and what is beneficial may change as the environment changes. Evolution is not going in a predetermined direction.

 Let me use penguins to illustrate. You could try to argue that penguins are an example of “devolution” because birds evolved the ability to fly, which penguins subsequently lost. The problem is that describing that as “devolution” inherently assumes that flight is an endpoint that evolution is working towards, which is incorrect. For penguins’ early ancestors (i.e., the first birds), flight was beneficial and allowed them to maximize their reproductive fitness, so it was selected for. In contrast, in penguins, flight was not advantageous, and it was better to be fat, so selection acted against flight, and features for living in cold environments evolved. Thus, penguins didn’t “devolve,” they simply adapted to their new environment, and in that particular case, that meant losing a feature that had previously been beneficial.

So yes, complex features can be lost, but I wouldn’t describe that as “devolution.” It’s just evolution doing its thing.