One of my serious concerns about much of the anti-evolution writing is that it contains numerous
severe errors, omissions or distortions, and often these will not be readily apparent to the reader
who doesn’t have a background in evolutionary biology. Consequently, when the authors use this
erroneous information to reach conclusions, those conclusions are invalid, but the unenlightened
reader will not know it, and be misled. One example of this phenomenon is the treatment of the
age of humanity
by Geisler & Bocchino.
On pages 185-187 of Unshakable Foundations, Geisler & Bocchino present a severely distorted
and incorrect summary of estimates of the age of humanity
, in which they attempt to demonstrate
that mainstream science has presented wildly divergent estimates of the age of humanity
, ranging
from 5 to 15 million years
in the late 1950s, to 43,000 years in the mid 1990s. This short
section of their book illustrates a number of ways that these authors apparently do not understand
their source material. Furthermore, they base this range on four articles -- three from the popular
press, and one from a scientific journal. Their choice of sources reveals the first two of numerous
flaws in their attempt to discredit mainstream science. First, their choice of sources is similar
to that found throughout their book, in which the overwhelming majority of sources cited are popular
press articles or creationist publications, and a minority are from the accepted, peer-reviewed
scientific literature. Second, their choice of sources is exceedingly biased in an attempt to
accomplish their objective; the one article from a mainstream science journal was clearly chosen
to present the youngest date possible. The article they cite (Whitfield et al. 1995) presents an
age (37,000 - 49, 000 years ago) that reinforces their goal of discrediting mainstream science, but
Geisler & Bocchino conveniently ignore a similar article only 2 pages earlier in the same issue of
Nature, which presents a different age (~188,000 years ago) that does not support their goals.
This is a clear example of “cherry-picking” scientific findings to present a biased and therefore
inaccurate picture.
The first of the major distortions in this section is that the authors either do not understand, or
have decided not to reveal to their readers, that the cited articles do NOT present the above times
(e.g. 5-15 million years, or 5-7 million years) as the “age of humanity” or age of the human race.
Clearly Geisler & Bocchino equate “age of humanity” with the appearance of Homo sapiens (see upper half
of page 186). However, the age range of 5-15 million years discussed in the first two sources (Tierney
et al. 1988, Shreeve 1990) is most emphatically NOT the time of appearance of Homo sapiens, but the
estimate of time of appearance of the first hominids. Thus Geisler & Bocchino are presenting the two
“oldest” age estimates as the “age of humanity”, when in truth these numbers represent the time of
appearance of far more primitive species, which may have been human ancestors. This distortion allows
the authors to compare 10 million years (the average of 5 and 15 million) to the youngest estimate (43,000
years) and then tell the reader that mainstream science cannot decide and exhibits a 99.57% margin of error.
It is unfortunate that most readers will not realize that both of the older estimates are NOT for the time
of appearance of Homo sapiens, but for a different and more primitive creature; therefore their “99.57%
margin of error” is grossly distorted at the upper end.
A second major distortion of Geisler & Bocchino’s “age of humanity” section is that the lower end of the
age estimates (43,000 years) is also wrong. This estimate draws from a 1995 paper in the journal Nature
(Whitfield et al. 1995) which reports on studies of living human Y-chromosomes, and concludes from rates
of mutation that all living human males can trace their lineage to a male between 37,000 and 49,000 years
ago (average of 43,000 years ago). This type of study parallels earlier research that proposed a
“mitochondrial Eve” that was the maternal ancestor of all living humans, who lived in Africa roughly 200,000
years ago. However, neither the Whitfield et al. study, nor the “mitochondrial Eve” study, suggested that
the proposed dates were the time of first appearance of Homo sapiens -- indeed, neither study concludes
from their data anything at all about the origin of any hominid species. In fact, the Whitfield et al.
study makes an effort to explain that their findings could be prone to any of several types of errors, and
that the age range they propose is likely to be the result of a selective sweep of advantageous Y-chromosomes,
and not the formation of a new species. A variety of sources of evidence currently suggest that modern humans
arose in Africa around 100,000 to 200,000 years ago, and migrated out of Africa later, perhaps 40-60,000 years
ago. During this latter time, there is genetic evidence of a population bottleneck that reduced modern humans
to a relatively limited number of breeding individuals (Stringer 2001, Stringer & Andrews 2005, Willoughby 2007),
which would make it much more feasible for a selective sweep to occur. Nevertheless, the dates presented in
the Whitfield et al. article have nothing to do with the formation of the modern species of Homo sapiens, so
Geisler & Bocchino are again incorrect in presenting 43,000 as a lower limit to the age of humanity
.
Finally, in a shocking display of pure speculation (page 186), Geisler & Bocchino follow the presentation of
the Y-chromosome age of humanity
as 37,000-49,000 years old, with the completely baseless assertion that
It is possible that this date can be reduced even more to between 10,000 and 20,000 years ago or less.
The
authors provide no basis for the statement, and contemporary scientific literature has no such claims.
Consequently, it appears that the authors have literally made it up.
Unfortunately, most readers will not be aware of these egregious erros on the part of Geisler & Bocchino,
and therefore will be misled by the graph on the lower part of page 186, which shows a rapidly-descending
“estimated age of the human race”, which starts at 10 million years in the late 1950s, and decreases to 43,000
in the mid 1990s. They calculate the meaningless “margin of error” of 99.57%, and claim It is clear that
this macroevolutionary dating game operates at an incredibly high margin of error -- nearly 100% on the human
level.
They then use this calculation to conclude that there is no basis to the charge that the biblical
age of humanity conflicts with modern science.
This sad conclusion is based entirely on the authors gross
distortion of the science, and is itself therefore misleading and profoundly incorrect.
Literature Cited
Stringer, C. 2001. The evolution of modern humans: where are we now? General Anthropology 7: 1-5.
Stringer, C., and P. Andrews. 2005. The Complete World of Human Evolution. Thames & Hudson, London.
Willoughby, P.R. 2007. The Evolution of Modern Humans in Africa. Altamira Press, Lenham, MD.