Evolution: Biology

Basic Ideas: Similarities in Morphology and Anatomy

Content

Similarities between living beings are of significant importance for evolution theory. Not only do they count as essential evidence of macroevolution, they also form the most important basis of the reconstruction of phylogenetic trees. The following article will show that the “evidence of similarity” for evolution is not substantive and that a lot of similarity findings are difficult to interpret by means of evolution theory.

Introduction

Convergence

Modular system

Conclusions

Quotations

Recommendations for further reading

Introduction

Living beings show far-reaching similarities among each other, by which they can be arranged hierarchically (see pic. 44). Common features (e.g. between man and chimpanzee) then count as indication of common ancestors. The more similarities between two species, the closer related they should be. This argument is based on a so called “analogy conclusion” which means a deduction from an observable field to an unobservable one. What is valid in the one (observable) case should be valid in a similar (unobservable) case, as well.

Applied to the argument of similarity this means: It is noticeable that descendants resemble their immediate ancestors. This observation can only be made within species or basic types – not beyond them. If it is concluded from the similarity between e.g. man and chimpanzee that both descended from common ancestors, a purely theoretical extension of reasoning has occurred: What is valid within crossbreeding kinds is claimed to also be valid where “similarity on account of descent” is no longer observable. This kind of conclusion is not compelling.

So the interpretation of the similarities as common origin is possible but not compelling because similarities are also to be expected on account of similar functions. Similar species often live in similar environment, take similar nourishment, breathe the same air, have to follow the same physical principles and so on. Therefore there must be similarities, however the species came into being.

Now the objection is raised that many similarities cannot be explained by the function of the compared organs but only by common origin, for instance similarities in the skeleton of vertebrate limbs (pic. 45).

It can hardly be proved, however, that certain similarities or differences are not caused by function. Moreover there are good functional reasons for the remarkable similarity between the limb skeletons, so the assumption of a common origin is not necessary.

Additionally similarities can always be explained by the “handwriting” of the same creator. Like there are “trademarks” in technology or art that point to the same author (see pic. 46), this can as well apply to living beings (see article “Similarities and vestigial organs”).

We can now state that similarities by themselves give no certain information about their origin.

Convergence

Within the theory of evolution not every similarity counts as evidence of common origin, though, but only – simplistically spoken – similarities with the same bodyplan of construction. Biologists call this kind of similarity homology and consider it to be an indicator for common origin. Some similarities however are thought to have evolved independently on different branches of the phylogenetic tree: convergence. Therefore convergences do not count as evidence for common origin. In many cases, though, a differentiation between homology and convergence is not objectively possible, a fact that is conceded by systematists without hesitation. An example is given in pic. 47.

Different complexes of characteristic features support contradicting constructions of phylogenetic trees.

Often ideas of evolution theory are needed in advance to be able to differentiate homologous similarities from convergences. Therefore it is circular reasoning to draw a conclusion from homologous similarities to common origin. This is another reason for our observation: Similarities cannot count as certain evidence of common origin.

Modular system

In many groups of animals and plants convergences are widespread (see expert article for examples). The features are spread so unsystematically in these cases that they appear assembled as separately available building blocks within the particular species or higher systematic unit. This kind of modular system is not easy to explain by means of evolution theories (attempt at explanation: „gene tinkering“ „genetic piracy“). One of the exceedingly numerous examples shall illustrate the building block-like spreading of features: Everybody knows the dandelion clock which is the infructescence of the dandelion. Each fruit is equipped with an umbrella (pic. 48) – a construction that is not only found within the family of the composites (that include the dandelion) but also within species that, according to the evolutionary theory, are not closely related to the composites, like for instance the valerian plants (pic. 49). This means that from an evolutionary point of view the umbrella is considered to have evolved independently . This again means that the similarities of the umbrellas have nothing to do with common origin. Pic. 50 illustrates the problem for the evolution theory.

Within the scope of a creation model the block-like arrangement of features is comprehensible („Mosaic forms as basic types and modular systems“).

Conclusions

It is observable only within crossbreeding species that similarity is caused by origin: The offspring resemble the parents. This observation however cannot be made concerning similarities between different basic types. Here one would have to deduce from an observable field to an unobservable one. This kind of conclusion never is compelling. This is all the more so because there are other reasons than common origin that may lead to similarity. As many examples in technology or art show, similarity can be attributed to the same author. This interpretation is possible for living beings as well (see article in „Similarities and vestigial organs“). The argument that similarity points to evolution is furthermore weakened by the frequent occurrence of convergences. That means: There is no compelling conclusion from the existence of biological homologies to common origin, for these cases evolutionary guidelines would have to be presupposed, by which the similarities can then be interpreted as caused by origin. But whenever evolution is to be assumed, there cannot be an independent proof of evolution. The “evidence of similarity” for evolution does not exist.

So the situation presents itself as follows: The observable data (the findings of similarity) are retrospectively included to in the already given concept of evolution. The data themselves do not “produce” or force a certain pattern of interpretation, on the contrary – it has to be presupposed. Whatever concept of origin is taken as a basis, only the result of emergence can be analyzed – not how it took place (see fig. 51).

The appearance of convergences can be made understandable by the creation model, because free combination of the features in the sense of a modular system can be expected. -„Mosaic forms as basic types and modular systems“

Quotations

The following quotations of evolution theorists may serve to illustrate some statements of this passage.

Günther Osche, zoologist, concedes that the common source of information for similarities does not necessarily have to be searched for in a common ancestor: “As storage of information

[Ed.: He means the cause for similarity.] a “creator” can be assumed, after whose “plan” the compared structures are drawn up.”

(G. Osche: Das Homologisieren als eine grundlegende Methode der Phylogenetik. Aufsätze und Reden der Senckenbergischen naturforschenden Gesellschaft 24 (1973), S. 155-165.)

Dieter Stefan Peters, ornithologist, expresses it like this: The phenomenon of the graduated, hierarchically arranged similarity of living beings “is exceptionally compatible with the idea of evolution. But it is at least as compatible with the idea of a scala rerum or a static typologically arranged world. That is without additional assumption the mere similarity of organisms does not force one to believe in evolution.”

(D. S. Peters: Evolutionstheorie – Zwangsläufigkeit und Grenzen. In: P. Kaiser & D.S. Peters (Hg.) Evolutionstheorie und Schöpfungsverständnis. Regensburg 1984, S. 193-218.)

Wolf-Rüdiger Arendholz, botanist: “The differently distinguished species might as well be thought genetically independent next to each other and were indeed thought so beyond the evolutionism.”

(W.-R. Arendholz: Die Evolution ein Faktum? Zum Selbstverständnis der Synthetischen Theorie. Ethik und Sozialwissenschaften 5 (1994), S. 209-211)

Recommendations for further reading

R. Junker & S. Scherer: Evolution - ein kritisches Lehrbuch. Gießen 2001, Kap. V.9 und VII.17.4.

R. Junker: Ähnlichkeiten, Rudimente, Atavismen. Design-Fehler oder Design-Signale? Studium Integrale. Holzgerlingen, 2002. (This book offers e.g. a detailed analysis of the similarity argument of evolutional theory.)

Translator: Sarah Aziz, 30.04.2008

Author: Reinhard Junker

 
© 2008