> Perhaps you look like monkeys that you all believe that you evolved
> from them. What are the chances that evolution happened?
Observer
The ignorant have not read science the truly stupid will not.
What is Universal Common Descent?
Universal common descent is the hypothesis that all living,
terrestrial organisms are genealogically related. All existing species
originated gradually by biological, reproductive processes on a
geological timescale. Modern organisms are the genetic descendants of
one original species or communal gene pool. Genetical "gradualness", a
much misunderstood term, is a mode of biological change that is
dependent on population phenomena; it is not a statement about the
rate or tempo of evolution. Truly genetically gradual events are
changes within the range of biological variation expected between two
consecutive generations. Morphological change may appear fast,
geologically speaking, yet still be genetically gradual (Darwin 1872,
pp. 312-317; Dawkins 1996, p.241; Gould 2002, pp. 150-152; Mayr 1991,
pp. 42-47; Rhodes 1983). Though gradualness is not a mechanism of
evolutionary change, it imposes severe constraints on possible
macroevolutionary events. Likewise, the requirement of gradualness
necessarily restricts the possible mechanisms of common descent and
adaptation, briefly discussed below.
Common Descent Can Be Tested Independently of Mechanistic Theories
In this essay, universal common descent alone is specifically
considered and weighed against the scientific evidence. In general,
separate "microevolutionary" theories are left unaddressed.
Microevolutionary theories are gradualistic explanatory mechanisms
that biologists use to account for the origin and evolution of
macroevolutionary adaptations and variation. These mechanisms include
such concepts as natural selection, genetic drift, sexual selection,
neutral evolution, and theories of speciation. The fundamentals of
genetics, developmental biology, molecular biology, biochemistry, and
geology are assumed to be fundamentally correct—especially those that
do not directly purport to explain adaptation. However, whether
microevolutionary theories are sufficient to account for
macroevolutionary adaptations is a question that is left open.
Therefore, the evidence for common descent discussed here is
independent of specific gradualistic explanatory mechanisms. None of
the dozens of predictions directly address how macroevolution has
occurred, how fins were able to develop into limbs, how the leopard
got its spots, or how the vertebrate eye evolved. None of the evidence
recounted here assumes that natural selection is valid. None of the
evidence assumes that natural selection is sufficient for generating
adaptations or the differences between species and other taxa. Because
of this evidentiary independence, the validity of the
macroevolutionary conclusion does not depend on whether natural
selection, or the inheritance of acquired characaters, or a force
vitale, or something else is the true mechanism of adaptive
evolutionary change. The scientific case for common descent stands,
regardless.
Furthermore, because it is not part of evolutionary theory,
abiogenesis also is not considered in this discussion of
macroevolution: abiogenesis is an independent hypothesis. In
evolutionary theory it is taken as axiomatic that an original self-
replicating life form existed in the distant past, regardless of its
origin. All scientific theories have their respective, specific
explanatory domains; no scientific theory proposes to explain
everything. Quantum mechanics does not explain the ultimate origin of
particles and energy, even though nothing in that theory could work
without particles and energy. Neither Newton's theory of universal
gravitation nor the general theory of relativity attempt to explain
the origin of matter or gravity, even though both theories would be
meaningless without the a priori existence of gravity and matter.
Similarly, universal common descent is restricted to the biological
patterns found in the Earth's biota; it does not attempt to explain
the ultimate origin of life.
What is Meant by "Scientific Evidence" for Common Descent?
Scientific theories are validated by empirical testing against
physical observations. Theories are not judged simply by their logical
compatibility with the available data. Independent empirical
testability is the hallmark of science—in science, an explanation must
not only be compatible with the observed data, it must also be
testable. By "testable" we mean that the hypothesis makes predictions
about what observable evidence would be consistent and what would be
incompatible with the hypothesis. Simple compatibility, in itself, is
insufficient as scientific evidence, because all physical observations
are consistent with an infinite number of unscientific conjectures.
Furthermore, a scientific explanation must make risky predictions— the
predictions should be necessary if the theory is correct, and few
other theories should make the same necessary predictions.
As a clear example of an untestable, unscientific, hypothesis that is
perfectly consistent with empirical observations, consider solipsism.
The so-called hypothesis of solipsism holds that all of reality is the
product of your mind. What experiments could be performed, what
observations could be made, that could demonstrate that solipsism is
wrong? Even though it is logically consistent with the data, solipsism
cannot be tested by independent researchers. Any and all evidence is
consistent with solipsism. Solipsism is unscientific precisely because
no possible evidence could stand in contradiction to its predictions.
For those interested, a brief explication of the scientific method and
scientific philosophy has been included, such as what is meant by
"scientific evidence", "falsification", and "testability".
In the following list of evidences, 30 major predictions of the
hypothesis of common descent are enumerated and discussed. Under each
point is a demonstration of how the prediction fares against actual
biological testing. Each point lists a few examples of evolutionary
confirmations followed by potential falsifications. Since one
fundamental concept generates all of these predictions, most of them
are interrelated. So that the logic will be easy to follow, related
predictions are grouped into five separate subdivisions. Each
subdivision has a paragraph or two introducing the main idea that
unites the various predictions in that section. There are many in-text
references given for each point. As will be seen, universal common
descent makes many specific predictions about what should and what
should not be observed in the biological world, and it has fared very
well against empirically-obtained observations from the past 140+
years of intense scientific investigation.
It must be stressed that this approach to demonstrating the scientific
support for macroevolution is not a circular argument: the truth of
macroevolution is not assumed a priori in this discussion. Simply put,
the theory of universal common descent, combined with modern
biological knowledge, is used to deduce predictions. These predictions
are then compared to the real world in order see how the theory fares
in light of the observable evidence. In every example, it is quite
possible that the predictions could be contradicted by the empirical
evidence. In fact, if universal common descent were not accurrate, it
is highly probable that these predictions would fail. These
empirically validated predictions present such strong evidence for
common descent for precisely this reason. The few examples given for
each prediction are meant to represent general trends. By no means do
I purport to state all predictions or potential falsifications; there
are many more out there for the inquiring soul to uncover.
Are There Other Scientifically Valid Explanations?
The worldwide scientific research community from over the past 140
years has discovered that no known hypothesis other than universal
common descent can account scientifically for the unity, diversity,
and patterns of terrestrial life. This hypothesis has been verified
and corroborated so extensively that it is currently accepted as fact
by the overwhelming majority of professional researchers in the
biological and geological sciences (AAAS 1990; NAS 2003; NCSE 2003;
Working Group 2001). No alternate explanations compete scientifically
with common descent, primarily for four main reasons: (1) so many of
the predictions of common descent have been confirmed from independent
areas of science, (2) no significant contradictory evidence has yet
been found, (3) competing possibilities have been contradicted by
enormous amounts of scientific data, and (4) many other explanations
are untestable, though they may be trivially consistent with
biological data.
When evaluating the scientific evidence provided in the following
pages, please consider alternate explanations. Most importantly, for
each piece of evidence, critically consider what potential
observations, if found, would be incompatible with a given alternate
explanation. If none exist, that alternate explanation is not
scientific. As explained above, a hypothesis that is simply compatible
with certain empirical observations cannot use those observations as
supporting scientific evidence.
Regards
Psychonomist