Grades and Clades
Much of the confusion in textual criticism in recent years comes from a failure to distinguish genetic similarity from mere coincidence of reading. Similar readings often imply kinship, to be sure -- but in a particular case, it may be the result of accidental levelling. Instances where this can happen especially easily include haplograpic errors, assimilation of parallels, and expansion of Christological titles.
The biological sciences have been aware of this problem for decades, and have evolved terminology to deal with it. The term for a set of things (species, manuscripts) with a similar set of characteristics is a grade; the term for a set of things which evolved from each other is a clade.
To illustrate how this works in biology, consider this family tree of the reptiles and their descendents (as best I understand it, with some attempt to translate this into clearer jargon than the books I've read):
proto-reptile
|
----------------------------------------------------------
| | |
non-turtle-like turtle-like |
reptiles reptiles |
| | pelycosaurs
----------------------- | |
| | | |
dinosaur-like lizard-like | |
reptiles reptiles | |
| | | therapsids
------------ ----------------------- | |
| | | | | | |
crocodiles dinosaurs snakes lizards tuataras turtles |
| |
birds mammals
In viewing this, the key point is to realize that all living reptiles are descended from that first proto-reptile, and no amphibians, fish, non-vertebrates, plants, or unicellular orgamisms are descended from it. That proto-reptile is the ancestor only of living reptiles, mammals, and birds.
Note that, when we speak of reptiles today, we mean only a subset of the creatures shown above:
proto-reptile
|
----------------------------------------------------------
| | |
non-turtle-like turtle-like |
reptiles reptiles |
| | pelycosaurs
----------------------- | |
| | | |
dinosaur-like lizard-like | |
reptiles reptiles | |
| | | therapsids
------------ ----------------------- | |
| | | | | | |
| |
| | | | | |
crocodiles dinosaurs snakes lizards tuataras turtles
|
| |
|
|
|
| |
birds mammals | |
This is based on a definition of reptiles as cold-blooded creatures which breathe air during their entire lives, do not secrete milk, do not have hair or feathers, and lay shelled eggs. Note that this is a definition based solely on characteristics.
Note also something rather absurd: If this genealogy is correct, modern birds are more closely related to crocodiles, and indeed to snakes and lizards and tuataras, than they are to turtles and tortoises. And yet, turtles are "reptiles" and birds are not; they're listed as birds.
The word "reptile," then, is grade terminology. It is based on characteristics only, with no genetic or genealogical component. The word "amphibian" is also a grade; descendents of the first amphibians include not only frogs and salamanders and such (which we call amphibians) but also reptiles and mammals and birds (which we do not call amphibians).
A "clade" is entirely different: It consists of all creatures descended from a common ancestor, no matter how similar or dissimilar they are. (The other technical term for this is monophyletic, but since it seems to refer to phyla -- sort of the biological equivalent of text-types -- it's probably clearer to avoid the term.)
If we wish to look at clades in the reptile diagram, the version below shows several (not all, of course)
proto-reptile
|
------------------------------------------------------------
| |||
|
non-turtle-like
reptiles
|
-----------------------
| |
turtle-like
reptiles
|
|
| |
pelycosaurs
|
|
|
| |
|
|
dinosaur-like
reptiles
|
------------
| |
crocodiles dinosaurs
|
birds
| |
|
lizard-like
reptiles
|
-----------------------
| | |
snakes lizards tuataras
| |
|
|
|
|
|
|
turtles
| |
|
|
|
|
therapsids
|
|
mammals |
Note that the leftmost clade shown, from dinosaur-like reptiles to birds, involves creatures we call reptiles and creatures we call birds, and it involves both living and extinct species -- but all are descended from the ancestor of the group. By contrast, though snakes and crocodiles (say) are both reptiles, they are not descended from the ancestor of croodiles and dinosaurs and birds, so they are not part of this clade.
There actually are clade names for a lot of the groupings above. All creatures descended from that first proto-reptile are "amniotes" -- so named because the eggs of reptiles contain an amniotic membrane to allow them to retain moisture when laid outside water. The group of all amniotes which are not mammals (that is, the turtles, birds, and what we now call "reptiles") are "sauropsids". The lizard-like reptiles are "lepidosaurs." The non-turtle-like reptiles, plus birds, are "diapsids." The group I've called "dinosaur-like reptiles" (crocodiles, dinosaurs, birds) are the "archosaurs." And the dinosaurs and birds, without crocodiles, are "ornithodires." But when have you ever heard any of those names used?
One might think of clades as "vertical" relationships, from an ancestor to descentents. Grades are "horizontal" -- all the children in a school class, perhaps. They're all the same age, but they aren't from the same family.
There are several ways in which this distinction can be applied to manuscripts and the history of the text. Manuscripts of, say, the ninth century are a grade but not a clade; there is very little genetic relationship between, say, 33 and 461, but they are the "ninth century" grade. On the other hand, Dp, Dabs1, and Dabs2, while not of the same century, are clearly related; since the latter two are copied from the first, they are unquestionably a clade.
Now consider a genealogy of the Versions of the New Testament. (Please note that this is much simplified and very theoretical; not everyone agrees with this. Indeed, I don't agree with it myself. But we have to do something for demonstration purposes.)
Greek Text
|
-----------------------------------------------------------
| | | | | |
Old Latin Vulgate Old Syriac Coptic Gothic OC Slavonic
| | |
--------------- | --------------------
| | | | | |
Anglo-Saxon Old French Armenian Bulgarian Russian Serbian
|
|
|
Georgian
Now let's divide this into grades:
Greek Text
|
-----------------------------------------------------------
|
| | | | | | PRIMARY
Old Latin Vulgate Old Syriac Coptic Gothic OC Slavonic VERSIONS
| | |
|
--------------- | --------------------
| | | | | | SECONDARY
Anglo-Saxon Old French Armenian Bulgarian Russian Serbian VERSIONS
|
|
|
| TERTIARY
Georgian VERSIONS |
(In this context, I am using the terms primary version, secondary version, tertiary version not in terms of the importance of the version but in terms of their relationship with the Greek text: A primary version is taken directly from the Greek, a secondary is taken from a primary version rather than the Greek, and a tertiary is taken from a secondary version rather than from the Greek or a primary version.)
There can be, in some cases, some real use to this grade classification -- for instance, if you are dealing with grammatical questions about the original text, a primary version is much more likely to carry useful information than a secondary or tertiary, simply because such distinctions will become progressively more blurred with each language the text is translated through. So the distinction between primary and secondary versions is quite important for, say, the Hebrew Bible, where the versions are almost the only sources independent of the MT. But we don't need such help very much in connection with the Greek New Testament, where we have so many independent witnesses.
Which means that grades of versions aren't much use in NT textual criticism. The Old Church Slavonic may be a primary version in terms of its origin -- but it is translated from the Byzantine text. Even if you are a believer in Byzantine priority, it's pretty useless, because there are older and better Byzantine sources in Greek. On the other hand, the Armenian may be a secondary version (this is of course much disputed), but it is a secondary version from an interesting and early source. Thus the Armenian version, though of an inferior grade, is of a superior clade.
If that is all that knowledge of grades and clades told us, it would be just a bit of minor terminology that we could all ignore. The true importance, however, lies in what we can learn from the biologists. The essential point is that clades are much more useful than grades. Especially if you want to know something about earlier ancestors. In an evolutionary context (which the progressive change of manuscripts clearly is), grades are meaningful only if all change is in the same direction. The chart above, for reptiles, shows this. The grade "reptile" is meaningful if you think evolution had a goal, to get from amphibians to reptiles to mammals. But it is demonstrable that this was not the goal; this is demonstrated by the fact that many thousands of unevolved reptile species still exist, and the reptiles also evolved into birds. Reptiles were not some sort of way station from amphibians to something "higher"; they are simply a stage. To treat them as if they are something to progress past is equivalent to saying that, because you drive through Baltimore on your way from Washington, D.C. to Philadelphia, that Baltimore isn't a city and no one goes there!
And this matters because of -- text-types. (You probably knew all along that I'd get to this eventually.) Or, rather, attempts to define text-types.
In recent years, I have been, frankly, disgusted by attempts to discuss text-types based on things like the Aland Categories and the Colwell-Tune Definition. Reading about grades and clades finally made me realize what the problem is: All these definitions are grade definitions! Colwell has a 70% agreement rule. The Aland categories are basically categories of Byzantine-ness: Category I has almost no Byzantine influence, Category II is perhaps 50% conformed to the Byzantine text, Category III up to 75% Byzantine, uncategorized manuscripts are less than 90% Byzantine, and Category V are more than 90% Byzantine.
The results thus produced are as useful as anything based on grades can be. And it is much easier to determine membership in a grade than membership in a clade. But they are just grades; they are not clades. This means that the results of these these classification schemes cannot be used genealogically. Of course, many these days do not use genealogical methods. But it is important to realize that these classifications simply aren't capable of being so used.
For more information on how biologists seek to find clades, see the article
on Cladistics.