Squirrels, Eels, Algae and Ardi: A Clarification

The "First human ancestor", which the ABC reports looked "like a squirrel" is of course not to be mixed up with the "Human Family's Earliest ancestor", namely Ardipithecus ramidus or “Ardi”, which Smithsonian.com tells us is a "... a female who lived 4.4 million years ago”. Not that this is to be confused with the Telegraph’s 'earliest human ancestor', a “prehistoric eel-like creature discovered in a Canadian shale bed has been identified as the earliest known ancestor of man", or indeed the ABC's "Oldest Human ancestor", an "elusive, single-cell creature evolved about a billion years ago and did not fit in any of the known categories of living organisms - it was not an animal, plant, parasite, fungus or alga, they say."

I hope this clarifies who our first, oldest and earliest ancestors really were.

The Absence of Evolution (Homology)

We almost labeled the paper entitled Bringing Homologies Into Focus by Anastasia Thanukos as 'Paraphyly Watch'. Here is why.

The paper is part of a new journal called Evolution: Education and Outreach - aimed at science school teachers rather than academia in general. The paper is a rather typical guide to homology - for instance:

"Homologies are traits present in two or more organisms that were inherited from the common ancestor of those organisms. The human five-fingered hand and the five-toed foot of a lizard, for example, were both inherited from our common ancestor that lived more than 300 Mya" (p. 498).

Almost right. Homologies, as a concept, existed in the literature before 'ancestors' were accepted in an evolutionary context - so it would be technically incorrect to associate them with ancestors per se - in the same way Alexander von Humboldt wasn't a biogeographer (the concept may have existed but not as we understand it today; and the term was coined much later to refer to something else). Is this a case of whiggish history? Possibly. Homologies are the only evidence we have of a common history, that is evolution. We may be splitting hairs but explanations as to how things originate does rather detract from the meaning (as we will show later). A clearer definition is "Homologies are relationships and occur when the same structure exists in two organisms but as different manifestations (in this case forearm and wing)". What this implies (and how it got there) is another matter that detracts from the homologies themselves. And this is exactly what happens with the rest of the paper.

Why would a paper titled 'Bringing Homologies Into Focus' give more space to explaining analogies and homoplasies? Is the absence of homology really more interesting? If so, we would assume non-evolution is of greater interest. This is a typical trend in evolutionary biology - attempting to explain why evolution is not present by invoking other assumed 'evolutionary' mechanisms. This is contradictory and send out the wrong message. What is important is when evolution is present - namely homologies. When it is not present it should really be of little or no interest. Then why probe into the absence of evolution?

There is a misconception in science that everything needs to be explained. This is the underlying premise of paraphyly 'enthusiasts'. When a group turns out to be non-monophyletic, that is non-evolutionary, people insist that evolution has gone on anyway. Apart from flying in the face of empiricism, explaining the absence of evolution by using other explanatory 'evolution' mechanisms is meaningless. Convergent evolution is not evolutionary. It does not result in homologies, only in analogies, that is non-homologies. Why this is even taught as 'evolution' mystifies us. We wonder if this happens in other fields? When volcanic rocks are absent from an area, do geologists explain it through volcanism? They could, but it would be very silly indeed.

References
Anastasia Thanukos (2008). Bringing Homologies Into Focus. Evolution: Education and Outreach, 1 (4), 498-504 DOI: 10.1007/s12052-008-0080-5

Complexity, Pattern & Process

Species are biologically complex. The Merriam-Webster Online Dictionary define Complex as "a whole made up of complicated or interrelated parts", that is 'interrelated parts' that are "consisting of parts intricately combined". Species on the other hand are harder to define.

I will not define a species here. There are enough species concepts to go around and adding another one will not aid the growing problem of understanding species. The difficulty that many have with species is that they do not classify well. This presents us with a problem: if classification makes sense of complexity, then why can't we classify species? Why, for instance, do some claim species are never monophyletic? If species are presented by genealogical and therefore reticulated lineages that include ancestors and descendants, it will be impossible for us to classify them - to divided up related individuals into separate groups. The same argument can be made of genera and families too, but we are able to classify them. Why do species present us with this problem. The answer lies in what we mean by pattern and process.

A pattern is a repeating relationship. The character-states 0(11) for instance represent a relationship or homolog that relate the taxa A, B and C. If A = 0, B= 1 and C = 1, the relationship can be expressed as A(BC). If this taxic relationship occurs many times in different characters, it forms a pattern or homology. Process however is harder to define.

Returning to the Merriam-Webster dictionary we find the process means "a natural phenomenon marked by gradual changes that lead toward a particular result". For example, ontogeny is a process. What of the processes we are unable to see or measure? These processes can be discovered through patterns. The homology A(BC) is a discovery of evolution. That is a common and shared history. A 'hidden' process, such as the sexual behavioral traits of hadrosaurs is completely unknown to us (if they had any at all). We are able to model these traits based on assumptions, wild guesses or on the behavior of related living taxa such as birds. What ever result is generated (artificially produced) will never represent a discovery. We will never see such behavioral traits, so our models are merely speculations. The same is true for genealogical relationships. We only know who we are related to simply by observation, written documentation or by word-of-mouth. Through our DNA we are able to discover how similar we are to other people, either dead or alive, but we will never know if they are our direct descendants. Genealogy, as an unobserved process, is therefore often hypothesized. In order to make that process consistent we assign a rational hypothesis or explanatory mechanism. Genealogical relationships that move beyond our understanding (i.e., observation, recorded history etc.) rely on this hypothesized explanatory mechanism.

Explanatory mechanisms (unobserved processes) do not discover patterns. They generate artificial and ad hoc hypotheses. Observed processes however do. They provide a more robust explanation, but offer little in the way of a direct or trivial narrative (e.g., who begot whom).

Let us return to species. We assume that they are interbreeding classificatory 'units' real or otherwise. Species that are defined on an unobserved 'process' are mechanical. For some this helps conceptualize a species, for others it has little to do with classification.

Biological classification is based on patterns and the observed processes that help to uncover them. We may infer explanatory mechanism from patterns, but we will never be able to discover patterns from explanatory mechanisms. Species, as defined by explanatory mechanisms, have no place in classification. As arbitrary taxa (like genera or families), however, they make perfect sense.