5/21/2009

NO ANCESTRAL CHAIN IMPLIED

Here's a much-publicized event: the discovery of a 47-million-year-old primate fossil. It's a gorgeous specimen that provides significant new information about the history of primates, and there's going to be a documentary airing on The History Channel which, based upon their recent efforts, will probably be entertaining and informative. I know I'll be watching. Google has commemorated the event with one of their banner tributes:






All well and good. But in the middle of this media blitz, there is more than a bit of hype. There's the usual breathless prose claiming that this specimen is 'a missing link' that 'changes everything' about what we know about the origins of mankind. Well, let me be blunt: this is crap, and one of the sure signs of lousy science journalism is when you see the term 'missing link'. At best, this term is speculative and of little use to working scientists. At worst, it's a deeply misleading and unrealistic trope about the fossil record.

Look, people: all of those hominid fossils, all of them? With a few possible exceptions of older females with well-preserved pelvic regions, we have no clue as to whether there is any likelihood any of the individual organisms of which we have specimens had any offspring, ever! Most of them probably didn't, frankly . . . and there is no guarantee that any of those that did that would have any living ancestors today, because there is no way to know if any of their offspring lived to reproduce. In the near future, the emerging Neanderthal genome may allow us to identify many genes that are strongly conserved between the former and our own genus, but that tells us nothing about whether any of the specimens are ancestral to anyone.

NO ANCESTRAL CHAIN IS IMPLIED! EVER.

Rather, what we see is a pattern of change between different specimens that have 'transitional features', and paleontologists prefer to speak of 'transitional features', rather than the special case of 'transitional forms', and they almost entirely eschew the expression 'missing link' The latter implies common descent between the specimen in question and other species, and this is not justified from the data. Even the case of 'transitional forms' is tricky, because true transitions within a lineage are not documented except in those rare cases where we see continual deposition in the same environment for extended periods of time.

It is an interesting fact that Gould studied snail populations that fit this case, and that the populations he studied by and large showed stasis, a predictable consequence of evolutionary theory. "Punctuated equilibria" was simply Gould's term for the pattern often observed when there is high resolution in the fossil record: long periods of stabilizing selection, interrupted by bursts of evolution when environmental conditions change. Creationists routinely misread this as somehow constituting 'proof' that there is something fundamentally wrong about Darwin's theory, and their clumsy attempts to shoehorn their misconceptions into the literature are aided and abetted when journalists (even well-meaning ones) use the unfortunate term 'missing link.'
QUIZ

No comments: