One important illusion, sometimes called the illusion of “misplaced concreteness,” is that a scientific study deals directly with facts, and that scientific arguments appealing to the facts can prove statements about reality. For example, one might suppose that an argument involving facts in the form of fossil bones can prove that anatomically modern humans really did arise in Africa 100,000 years ago. Thinking this, one might strongly argue, on the basis of certain facts, that the statement “anatomically modern humans arose in Africa 100,000 years ago” represents the truth. If the facts are part of reality, and the arguments are sound, then surely the conclusion must be true. Or, at least, granting our human fallibility, we can be reasonably confident that it is true.
The problem here is that in the field of paleoanthropology the facts being considered are not directly part of reality. Indeed, if a “fact” is examined closely it is found to resolve into (1) arguments based on further “facts,” or (2) claims that someone has witnessed something at a particular time and place. Thus “facts” turn out to be networks of arguments and observational claims.
To some extent, this is true of the facts discussed in any field of science. But the facts of paleoanthropology have certain key limitations that should be pointed out. First, the observations that go into paleoanthropological facts tend to involve rare discoveries that cannot be duplicated at will. For example, some scientists in this field have built great reputations on the basis of a few famous discoveries, and others, the vast majority, have spent their whole careers without making a single significant find.
Second, once a discovery is made, key elements of the evidence are destroyed, and knowledge of these elements depends solely on the testimony of the discoverers. For example, one of the most important aspects of a fossil is its stratigraphic position. However, once the fossil is removed from the earth, the direct evidence indicating its position is destroyed, and we simply have to depend on the excavator’s testimony as to where he or she found it. Of course, one may argue that chemical or other features of the fossil may indicate its place of origin. This is true in some cases but not in others. And in making such judgements, we also have to depend on reports concerning the chemical and other physical properties of the strata in which the fossil was allegedly found.
Persons making important discoveries sometimes cannot find their way back to the sites of those discoveries. After a few years, the sites are almost inevitably destroyed, perhaps by erosion, by complete paleoanthropological excavation, or by commercial developments (involving quarrying, building construction, and so forth). Even modern excavations involving meticulous recording of details destroy the very evidence they are recording, and leave one with nothing but written testimony to back up many key assertions. And many important discoveries, even today, involve very scanty recording of key details.
Thus a person desiring to verify paleoanthropological reports will find it very difficult to gain access to the “real facts,” even if he or she is able to travel to the site of a discovery. And, of course, limitations of time and money make it impossible to personally examine more than a small percentage of the totality of important paleoanthropological sites.
A third problem is that the facts of paleoanthropology are seldom (if ever) simple. A scientist may testify that “the fossils were clearly weathering out of a certain Early Pleistocene layer.” But this apparently simple statement may depend on many observations and arguments involving geological faulting, the possibility of slumping, the presence or absence of a layer of hillwash, the presence of a refilled gully, and so on. If one consults the testimony of another person present at the site, one may find that he or she discusses many important details not mentioned by the first witness.
Different observers sometimes contradict one another, and their senses and memories are imperfect. Thus, an observer at a given site may see certain things, but miss other important things. Some of these things might be seen by other observers, but this could turn out to be impossible because the site has become inaccessible.
Then there is the problem of cheating. This can occur on the level of systematic fraud, as in the Piltdown case. As we shall see, to get to the bottom of this kind of cheating one requires the investigative abilities of a super Sherlock Holmes plus all the facilities of a modern forensic laboratory. Unfortunately, there are always strong motives for deliberate or unconscious fraud, since fame and glory await the person who succeeds in finding a human ancestor.