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Introduction

For years, PumpkinPerson (PP) has been pushing an argument which states that “if you’re the first branch, and you don’t do anymore branching, then you’re less evolved than higher branches.” This is the concept of “more evolved” or the concept of evolutionary progress. Over the years I have written a few articles on the confused nature of this thinking. PP seems to like the argument since Rushton deployed a version of it for his r/K selection (Differential K) theory, which stated that “Mongoloids” are more “K evolved” than “Caucasians” who are more “K evolved” than “Negroids”, to use Rushton’s (1992) language. Rushton posited that this ordering occurred due to the cold winters that the ancestors of “Mongoloids” and “Caucasoids” underwent, and he theorized that this led to evolutionary progress, which would mean that certain populations are more advanced than others (Rushton, 1992; see here for response). It is in this context that PP’s statement above needs to be carefully considered and analyzed to determine its implications and relevance to Rushton’s argument. It commits the affirming the consequent fallacy, and assuming the statement is true leads to many logical inconsistenties like there being a “most evolved” species,

Why this evolutionary progress argument is fallacious

if you’re the first branch, and you don’t do anymore branching, then you’re less evolved than higher branches.

This is one of the most confused statements I have ever read on the subject of phylogenies. This misconception, though, is so widespread that there have been quite a few papers that talk about this and talk about how to steer students away from this kind of thinking about evolutionary trees (Crisp and Cook, 2004; Baum, Smith, and Donovan, 2005; Gregory, 2008; Omland, Cook, and Crisp, 2008). This argument is invalid since the concept of “evolved” in evolutionary trees doesn’t refer to a hierarchical scale, where higher branches are “more evolved” than lower branches (which are “less evolved”). What evolutionary trees do is show historical relationships between different species, which shows common ancestry and divergence over time. So each branch represents a lineage and all living organisms have been evolving foe the same amount of time since the last common ancestor (LCA). Thus, the position of a branch on the tree doesn’t determine a species’ level of evolution.

The argument is invalid since it incorrectly assumes that the position of the branch on a phylogeny determines the evolution or the “evolutionary advancement” of a species. Here’s how I formulate this argument:

(P1) If you’re the first branch on the evolutionary tree and you don’t do any more branching, then you’re less evolved than higher branches.
(P2) (Assumption) Evolutionary advancement is solely determined by the position on the tree and the number of branches.
(C) So species represented by higher branches on the evolutionary tree are more evolved than species represented by lower branches.

There is a contradiction in P2, since as I explained above, each branch represents a new lineage and every species on the tree is equally evolved. PP’s assumption seems to be that newer branches have different traits than the species that preceded it, implying that there is an advancement occurring. Nevertheless, I can use a reductio to refute the argument.

Let’s consider a hypothetical scenario in which this statement is true: “If you’re the first branch and you don’t do any more branching, then you’re less evolved than higher branches.” This suggests that the position of a species on a phylogeny determines its level of evolution. So according to this concept, if a species occupies a higher branch, it should be “more evolved” than a species on a lower branch. So following this line of reasoning, a species that has undergone extensive branching and diversification should be classified as “more evolved” compared to a species that has fewer branching points.

Now imagine that in this hypothetical scenario, we have species A and species B in a phylogeny. Suppose that species A is the first branch and that it hasn’t undergone any branching. Conversely, species B, which is represented on a higher branch, has experienced extensive branching and diversification, which adheres to the criteria for a species to be considered “more evolved.” But there are logical implications for the concept concerning the positions of species A and species B on the phylogeny.

So according to the concept of linear progression which is implied in the original statement, if species B is “more evolved” than species A due to its higher branch position, it logically follows that species B should continue to further evolve and diversify. This progression should lead to new branching points, as each subsequent stage would be considered “more evolved” than the last. Thus, applying the line of reasoning in the original statement, it suggests that there should always be a species represented on an even higher branch than species B, and this should continue ad infinitim, with no endpoint.

The logical consequence of the statement is that an infinite progression of increasingly evolved species, each species being represented by a higher branch than the one before, without any final of ultimate endpoint for a “most evolved” species. This result leads to an absurdity, since it contradicts our understanding of evolution as an ongoing and continuous process. The idea of a linear and hierarchical progression of a species in an evolutionary tree culminating in a “most evolved” species isn’t supported by our scientific understanding and it leads to an absurd outcome.

Thus, the logical implications of the statement “If you’re the first branch and you don’t do any more branching, then you’re less evolved than higher branches” leads to an absurd and contradictory result and so it must be false. The concept of the position of a species on an evolutionary tree isn’t supported by scientific evidence and understanding. Phylogenies represent historical relationships and divergence events over time.

(1) Assume the original claim is true: If you’re the first branch and you don’t do any more branching, then you’re less evolved than higher branches.

(2) Suppose species A is the first branch and undergoes no further branching.

(3) Now take species B which is in a higher branch which has undergone extensive diversification and branching, making it “more evolved”, according to the statement in (1).

(4) But based on the concept of linear progression implied in (1), species B should continue to evolved and diversity even further, leading to new branches and increased evolution.

(5) Following the logic in (1), there should always be a species represented on an even higher branch than species B, which is even more evolved.

(6) This process should continue ad infinitim with species continually branching and becoming “more evolved” without an endpoint.

(7) This leads to an absurd result, since it suggests that there is no species that could be considered “more evolved” or reach a final stage of evolution, contradicting our understanding of evolution as a continuous, ongoing process, with no ultimate endpoint.

(8) So since the assumption in (1) leads to an absurd result, then it must be false.

So the original statement is false, and a species’ position on a phylogeny doesn’t determine the level of evolution and the superiority of a species. The concept of a linear and hierarchical progression of advancement in a phylogeny is not supported by scientific evidence and assuming the statement in (1) is true leads to a logically absurd outcome. Each species evolves in its unique ecological context, without reaching a final state of evolution or hierarchical scale of superiority. This reductio ad absurdum argument therefore reveals the fallacy in the original statement.

Also, think about the claim that there are species that are “more evolved” than other species. This implies that there are “less evolved” species. Thus, a logical consequence of the claim is that there could be a “most evolved” species.

So if a species is “most evolved”, it would mean that that species has surpassed all others in evolutionary advancement and there are no other species more advanced than it. Following this line of reasoning, there should be no further branching or diversification of this species since it has already achieved the highest level of evolution. But evolution is an ongoing process. Organisms continously adapt to and change their surroundings (the organism-environment system), and change in response to this. But if the “most evolved” species is static, this contradicts what we know about evolution, mainly that it is continuous, ongoing change—it is dynamic. Further, as the environment changes, the “most evolved” species could become less suited to the environment’s conditions over time, leading to a decline in its numbers or even it’s extinction. This would then imply that there would have been other species that are “more evolved.” (It merely shows the response of the organism to its environment and how it develops differently.) Finally, the idea of a “most evolved” species implies an endpoint of evolution, which contradicts our knowledge of evolution and the diversification of life one earth. Therefore, the assumption that there is a “most evolved” species leads to a logical contradiction and an absurdity based on what we know about evolution and life on earth.

The statement possesses scala naturae thinking, which is also known as the great chain of being. This is something Rushton (2004) sought to bring back to evolutionary biology. However, the assumptions that need to hold for this to be true—that is, the assumptions that need to hold for this kind of tree reading to even be within the realm of possibility is false. This is wonderfully noted by Gregory (2008) who states that “The order of terminal noses is meaningless.” Crisp and Cook (2004) also state how such tree-reading is intuitive and this intuition of course is false:

Intuitive interpretation of ancestry from trees is likely to lead to errors, especially the common fallacy that a species-poor lineage is more ‘ancestral’ or ‘diverges earlier’ than does its species-rich sister group. Errors occur when trees are read in a one-sided way, which is more commonly done when trees branch asymmetrically.

There are several logical implications of that statement. I’ve already covered the claim that there is a kind of progression and advancement in evolution—a linear and hierarchical ranking—and the fixed endpoint (“most evolved”). Further, in my view, this leads to value judgments, that some species are “better” or “superior” to others. It also seems to ignore that the branching signifies not which species has undergone more evolution, but the evolutionary relationships between species. Finally, evolution occurs independently in each lineage and is based on their specific histories and interactions between developmental resources, it’s not valid to compare species as “more evolved” than others based on the relationships between species on evolutionary trees, so it’s based on an arbitrary comparison between species.

Finally, I can refute this using Gould’s full house argument.

P1: If evolution is a ladder of progress, with “more evolved” species on higher rungs, then the fossil record should demonstrate a steady increase in complexity over time.
P2: The fossils record does not shit a steady increase in complexity over time.
C: Therefore, evolution is not a ladder of progress and species cannot be ranked as “more evolved” based on complexity.

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P1: If the concept of “more evolved” is valid, then there would be a linear and hierarchical progression in the advancement of evolution, wjtcertsin species considered superior to others based on their perceived level of evolutionary change.
P2: If there a linear and hierarchical progression of advancement in evolution, then the fossil record should demonstrate a steady increase in complexity over time, with species progressively becoming more complex and “better” in a hierarchical sense.
P3: The fossils record does not show a steady increase in complexity over time; it instead shows a diverse and branching pattern of evolution.
C1: So the concept of “more evolved” isn’t valid, since there is an absence of a steady increase in complexity in the fossil record and this refutes the notion of a linear and hierarchical progression of advancement in evolution.
P4: If the concept of “more evolved” is not valid, then there is no objective hierarchy of superiority among species based in their positions on an evolutionary tree.
C2: Thus, there is no objective hierarchy of superiority among species based on their positions on an evolutionary tree.

There is one final fallacy contained in that statement: it affirms the consequent. This logical fallacy takes the form of: If P then Q, P is true so Q is true.” Even if the concept of “more evolved” were valid, just because a species doesn’t do any more branching doesn’t mean it’s less evolved. So this reasoning is as follows: If you’re the first branch and you don’t do anymore branching, then you’re less evolved than higher branches (If P and Q, then R). It affirms the consequent like this: You didn’t do anymore branching (Q), so this branch has to be less evolved than the higher branches (R). It incorrectly infers the consequent Q (not doing anymore branching) as a sufficient condition for the antecedent P (being the first branch), which leads to the flawed conclusion (R) that the species is less evolved than higher branches. Just because a species doesn’t do anymore branching doesn’t mean it’s less evolved than another species. There could be numerous reasons why branching didn’t occur and it doesn’t directly determine evolutionary status. The argument infers being less evolved from doing less branching, which affirms the consequent. If a species doesn’t do anymore branching then that branch is less evolved than a higher branch. So since the argument affirms the consequent, it is therefore invalid.

Conclusion

Reading phylogenies in such a manner—in a way that would make one infer the conclusion that evolution is progressive and that there are “more evolved” species—although intuitive is false. Misconceptions like this along with many others while reading evolutionary trees are so persistent that much thought has been put into educating the public on right and wrong ways to read evolutionary trees.

As I showed in my argument ad absurdums where I accepted the claim as true, it leads to logical inconsistenties and goes against everything we know about evolution. Evolution is not progressive, it’s merely local change. That a species changes over time from another species doesn’t imply anything about “how evolved” (“more or less”) it is in comparison to the other. Excising this thinking is tough, but it is doable by understanding how evolutionary trees are constructed and how to read them correctly. It further affirms the consequent, leading to a false conclusion.

All living species have spent the same amount of time evolving. Branching merely signifies a divergence, not a linear scale of advancement. Of course one would think that if evolution is happening and one species evolves into another and that this relationship is shown on a tree that this would indicate that the newer species is “better” in some way in comparison to the species it derived from. But it merely suggests that the species faced different challenges which influenced its evolution; each species adapted and survived in its own unique evolutionary ecology, leading to diversification and the formation of newer branches on the tree. Evolution does not follow a linear path of progress, and there is no inherent hierarchy of superiority among species based on their position on the evolutionary tree. While the tree visually represents relationships between species, it doesn’t imply judgments like “better” or “worse”, “more evolved” or “less evolved.” It merely highlights the complexity and diversity of all life on earth.

Evolution is quite obviously not progressive, and even if it were, we wouldn’t see evolutionary progression from reading evolutionary trees, since such evolutionary relationships between species can be ladderized or not, with many kinds of different branches that may not be intuitive to those who read evolutionary trees as showing “more evolved” species, they nevertheless show a valid evolutionary relationship.