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Bottom-Up Bottoms Out


In any other scientific arena, the amount of failure we’re about to see would send scientists out the door of the science building in disgrace to look for a new job. When it comes to evolutionary biology, however — since no alternatives are allowed — the advocates of scientific materialism are allowed to completely ignore logical alternatives and to fail with impunity, even after well over a century of trying.

Let’s introduce Jordi van Gestel and Corina E. Tarnita. Their paper in the Proceedings of the National Academy of Sciences, “On the origin of biological construction, with a focus on multicellularity,” is made to order for a debate. But don’t hold your breath. These evolutionists from the University of Zurich and from Princeton, respectively, address the topic, “Resolved: Bottom-up approaches are superior to top-down approaches for explaining the origin of hierarchical biological organization.” Stephen Meyer in his book Darwin’s Doubt wrote extensively on this question. Gestel and Tarnita, on the other hand, tell us:

Biology is marked by a hierarchical organization: all life consists of cells; in some cases, these cells assemble into groups, such as endosymbionts or multicellular organisms; in turn, multicellular organisms sometimes assemble into yet other groups, such as primate societies or ant colonies. The construction of new organizational layers results from hierarchical evolutionary transitions, in which biological units (e.g., cells) form groups that evolve into new units of biological organization (e.g., multicellular organisms). Despite considerable advances, there is no bottom-up, dynamical account of how, starting from the solitary ancestor, the first groups originate and subsequently evolve the organizing principles that qualify them as new units. [Emphasis added.]

This admission of failure is not a good way to end a scientific paper, so they try something new:

Guided by six central questions, we propose an integrative bottom-up approach for studying the dynamics underlying hierarchical evolutionary transitions, which builds on and synthesizes existing knowledge. This approach highlights the crucial role of the ecology and development of the solitary ancestor in the emergence and subsequent evolution of groups, and it stresses the paramount importance of the life cycle: only by evaluating groups in the context of their life cycle can we unravel the evolutionary trajectory of hierarchical transitions. These insights also provide a starting point for understanding the types of subsequent organizational complexity. The central research questions outlined here naturally link existing research programs on biological construction (e.g., on cooperation, multilevel selection, self-organization, and development) and thereby help integrate knowledge stemming from diverse fields of biology.

Everything evolutionists have tried before is a failure, but take heart: we have a new series of questions, they basically say. The only approaches allowed will be unguided and purposeless, with natural selection and self-organization being two relentless contenders. To Gestel and Tarnita, these contenders don’t have to win anything. Just showing up is enough to win applause from the audience.

It will sound more scientific to throw in some recondite jargon. They announce a new made-up acronym, “HET” for “hierarchical evolutionary transition.” Presumably, this includes the Cambrian explosion, though they don’t mention it.

From a primordial soup of elements to the emergence of protocells, from single cells to multicellular organisms, and from multicellular organisms to animal groups, evolution has been punctuated by hierarchical evolutionary transitions (HET), whereby simple units assembled into groups that themselves became new units of biological organization. The popularization of these HET [also known as transitions in individuality] as part of the “major transitions in evolution by Maynard Smith and Szathmáry, resulted in extensive research efforts — both empirical and theoretical — to understand how new units of biological organization can evolve. However, this endeavor has proved challenging, not least because a unique definition for what constitutes a unit of biological organization has eluded the field; instead, the literature abounds with definitions that differ in the minimal criteria for a group to be considered a unit of biological organization.

Surely some transitions are clear-cut: e.g., the twenty or so new body plans that “emerged” at the onset of the Cambrian. Or the onset of sexual reproduction. Or the “emergence” of consciousness. Or the origin of life itself from said “primordial soup.” Contenders to face this challenge must subscribe to Darwin’s blind mechanism, natural selection:

There seem to be only two points of general agreement: (i) a necessary criterion, common to all definitions, for a group to be a unit of biological organization is that the group must be a unit of selection (i.e., it can undergo evolutionary change by natural selection) (SI Appendix, Text S1); and (ii) there are certain entities that are unambiguously units of biological organization (e.g., animals, plants, eusocial colonies). This has engendered a “top-down” approach for the study of HET that starts with such paradigmatic examples of biological units, identifies their properties (e.g., high level of cooperation, reduced conflict, differentiated types, metabolic specialization) (SI Appendix, Text S1), and explores how a group could have evolved each of these properties. While this approach has revealed a wealth of valuable insights, we argue that it is insufficient to understand the origin and evolution of HET.

They mention “top-down” approaches, but none of them include intelligent causes as Meyer and other ID advocates would propose. What they mean are evolutionary approaches taken by biologists who already assume things evolved without guidance, who then look for just-so stories to tell about how they evolved (i.e., “explores how a group could have evolved each of these properties”). Yet even these two criticize evolutionary top-down approaches, saying they fail to recognize the ancestor, the mechanisms involved in the transition, and the “the evolutionary trajectory from the solitary ancestor to a new unit of biological organization.”

Second, in addition to ignoring the ancestral properties, by fixating on certain properties common to the known paradigmatic examples of HET, the top-down approach fails to explore the full potential of evolutionary trajectories and transitions, not only the paradigmatic but also the peripheral, and not only the actual (i.e., realized) but also the possible. This likely paints an incomplete picture of HET and precludes a valuable comparison across potential evolutionary transitions: only by comparing their full spectrum can we determine the causal factors that explain why certain trajectories did result in new units of biological organization and others did not.

Well, that’s a novel suggestion: “potential” evolutionary transitions. Anything is possible. If a trilobite had wings, it could fly. Why didn’t they follow that trajectory? What “causal factors” led them to scour the seafloor for food instead? This sounds like an attempt to use imagination instead of dealing with the real world. But since top-down approaches (evolutionary ones, that is) leave so many questions, top-down is out in their opinion, and bottom-up must take its place.

Their work is cut out for them. They already recognize that animals and plants represent “entities that are unambiguously units of biological organization.” We can envision Meyer showing a slide of trilobites, worms, vertebrate fish, and other Cambrian biota to help them illustrate what they mean. For example, look at the fossil trilobite at the top of the post, via PLOS ONE, that shows clearly what it had for lunch. The caption says, “New research on 514-million-year-old trilobite fossils from this area reveals that trilobite digestion was sophisticated from early on in their evolution.” So will Gestel and Tarnita be able to identify any “causal factors” — some vera causa — necessary and sufficient to account for the rise of new hierarchies of functional information at this level? No! The gut of the paper is all questions:

Here we identify six questions, Q1–Q6, that, regardless of the definition for what constitutes a new unit of biological organization, need to be addressed in a bottom-up approach to the study of HET:

Q1: When/how does a group originate that has the potential to undergo a HET?

Q2: What emergent properties do these groups have? (For example, in the case of multicellular groups: group size, composition, shape, and the interactions of cells inside the group, including cooperative interactions.)

Q3: How does selection act on these properties?

Q4: How does this affect the ancestral developmental program(s) and change group properties? Selection is only effective when group properties emerge from a heritable developmental program. In the case of newly formed groups, the developmental program is that of the solitary ancestor(s) that make up the group. Selection will therefore exert its effect by affecting the ancestral developmental program(s).

Q5: When/how does this lead to novel organizing/developmental principles within the new unit? (For example, in the case of multicellular groups: differential adhesion, pattern formation and cell signaling.)

Q6: What kinds of organizing complexity can evolve?

To address these questions from the bottom up, they draw on the complete arsenal of evolutionary tools, both research-based (natural selection, phylogeny, experimental evolution, developmental evolution, sociobiology, etc.) and theoretical (multilevel-selection, cooperation, self-organization, etc.). Then they look at one of the simplest transitions, to multicellularity, as a case study for asking their six questions.

Following John T. Bonner’s ideas from the 1960s and 1970s, they view the “life cycle” as the unit of biology and the thing most likely to evolve by natural selection. Maybe at various times in a life cycle, organisms will be more prone to form groups, they say. When they do, natural selection can act.

Therefore, according to this definition, one cannot establish a group’s potential to undergo a HET by examining its properties at a given moment in time; instead, one has to trace the group and its descendants over time to determine the reproducibility of group formation. Furthermore, we do not require the group to be formed in every successive instantiation of the life cycle (henceforth generation), only that it is formed sufficiently frequently for selection to potentially act on the group stage.

We don’t need to wade through the rest of their jargon, because it’s all “scenarios” about what might happen — very unscientific. One can imagine anything. Maybe an ecological change could “lead to” overexpression of a protein that causes more adhesion between cells. Maybe a mutation could weaken a cell wall, resulting in clumping. Isn’t a scientific paper supposed to connect with reality somewhere? And what does clumping have to do with new levels of hierarchical information, as seen in the Cambrian animals? What case of “emergence” by sheer dumb luck is likely to produce a gut, or an eye, or articulated limbs? That’s what the debate should be about.

Yet, even with their simplest case of the origin of multicellularity, they are left with nothing but questions:

Even though we focus in our bottom-up approach largely on questions underlying the very origin of HET (Q1–Q4), we believe that this approach nevertheless can provide a valuable starting point toward understanding the kinds of organizational complexity that can emerge subsequently, which constitutes an important research challenge (Q5 and Q6). We are surrounded by an incredible diversity of multicellular organization, from filamentous algae to metazoan development, but it remains unclear what determines the organizational outcomes of these HET. Even though we have some intuitive understanding (e.g., filamentous organisms might be unlikely to evolve 3D structures), there are no theoretical or empirical studies yet that systematically approach this question. This is problematic, because intuition often fails.

Have they identified any causes of hierarchical transitions? No. Have they demonstrated any examples (of HET that don’t assume evolution)? No. After eliminating examples that beg the question of evolution (social amoebas, wasps, green algae, and a few others), all they have are promissory notes.

A systematic, bottom-up approach to the study of HET could reveal what is possible, not only what seems intuitively probable. And by understanding how the earliest organizing principles came about, we could identify questions that help us understand the evolution of more advanced ones.

In other words, don’t expect answers; they haven’t even found the questions yet!

We argue that only by starting with the solitary ancestor and its life cycle, and studying these six questions, can we derive an understanding of the causal factors underlying HET. Then, by comparing different instantiations of the same transition (e.g., the multiple origins and transitions to multicellularity), we can determine whether the same causal factors underlie different transitions and which causal factors explain the different organizational outcomes of those transitions.

Translation: If we knew the causes of transitions, we could apply them to other transitions.

As we said at the start, bottom-up has bottomed out. After 157 years of Darwin supremacy, evolutionists are still at square one. It’s long past time for a Revolution.

Photo credit: Fossil trilobite shows what it had for lunch, © 2017 Hopkins et al.