Friday, January 7, 2005

Fossils and Human Evolution

Derek at Weapons of Mass Distraction links us to an article in the Telegraph on fossils and human evolution. The article mentions that in the past "fossil-hunters" were quick to place new fossil finds into different species so that today,

"The number of human species claimed by fossil-hunters now stands at around 10, while the total number of human-like species exceeds 50. Such claims have long been based on supposedly significant differences in sizes and shapes of fossil bones. Now they have all been thrown into doubt by research showing that the differences lie within the range expected for just a single species."

In other words, all those charts we saw in high school showing man evolving through several progressive stages until finally arriving at his present exalted state as Homo sapiens are now lining canary cages.

Prof Henneberg found that the fossils show clear evidence of evolution, with substantial increases in both skull sizes and body-weight. However, he also found that the fossils show no evidence of being anything other than a single species which had grown bigger and smarter over time. According to Prof Henneberg, the much-vaunted differences in fossil size used to identify "new" species all lie within the normal range expected for one species.

Notice here the subtle bit of professional CYA the good professor is indulging in. He claims on the one hand that all the fossils of early hominids are really H. sapiens, but not wanting to give succor to the creationists who have been saying precisely this for the last fifty years he notes that they nevertheless show "clear evidence of evolution." He uses the word evolution here to mean simple variability (microevolution), but the general reader will perhaps assume that he means that the fossils show clear evidence of having evolved from one basic form of life into a radically different form (macroevolution). By this locution he manages to undo a century and a half of Darwinian orthodoxy without exposing himself to the charge of heresy.

Henneberg's findings suggest that disputes among scientists as to the evolutionary relationships among the various types of fossil hominids are meaningless, as they ignore the possibility of huge differences within the same species.

In discussing the relationship of Neanderthals and humans, for instance, he states that "What evidence there consistent with Neanderthals being from the same species as modern humans."

It's impossible to say how many of his colleagues agree with him although evidently some do:

Other authorities hailed Prof Henneberg's findings as a much-needed reality check. "Clearly there is a need to be more aware of the possibility of variation - but that is not the inclination today," said Geoffrey Harrison, emeritus professor of biological anthropology at the University of Oxford. "It has been a problem because the discoverers [of the fossils] have usually put so much effort into finding the evidence, so they want it to be important".

Skeptics, of course, have long thought the evidence for numerous hominid species was tenuous. It was, after all, based upon purely structural differences. If the bones of various breeds of dogs were pried from different rock strata they'd doubtless be classified as different species based on morphological considerations, but, in fact, every dog from Great Danes to Daschunds are members of the same species. The problem is that the concept of species is slippery. Scientists define it as a reproductively isolated population of organisms, which means that if two members of a population can produce fertile offspring then they are members of the same species. There is, however, no way to tell by looking at a few bones whether or not members of the populations from which the bones came were capable of producing fertile offspring.

Perhaps one reason why scientists were so confident that the bones they had unearthed over the years were from different species of hominids is that they were absolutely convinced that man has evolved from an ape-like ancestor. If there is no question that species evolve over time, then bones taken from rock strata separated by millions of years just must be from different species. In other words, the reproductive isolation of the hominids was assumed, based on the theory of human evolution, and then the assumption that the hominids were different species was employed as evidence to reinforce the theory that humans have evolved from ape-like ancestors.

It's a nice, tight little circle.

Bad News For Iraqi Terrorists

Strategy Page has an interesting fact about the Iraqi police:

Since November 10th, anti-government forces made twelve attacks on police stations, and were defeated every time. Earlier in November, nine police stations were overrun and no attacks were defeated.

If you read the whole post you'll come away with a much different picture of the Iraqi military and national guard than what you get from watching the evening news. As the above quote suggests, they are growing in strength and competence. The process is slow, and there are problems finding good leadership, but there is good reason for cautious optimism.

This is especially important inasmuch as our own military is being stretched. The more troops the Iraqis can field to provide for their own security, the more pressure it will take off the United States to come up with adequate manpower to keep the peace.