Science is a body of knowledge that is grounded in a method which allows investigators to establish—frequently with a high degree of certainty—specific conclusions about the natural world. There is broad agreement regarding the steps which comprise the scientific method: Observations are made; an explanatory hypothesis is developed; ‘if-true’ predictions are put forward; finally, those predictions are then tested to see if they are actually borne out. If they aren’t, the hypothesis is discarded; if they are, the hypothesis remains viable. As more predictions are tested, if the results remain consistent with the hypothesis, scientists become increasingly confident in the likelihood that the hypothesis approximates reality.
Frequently, there is a collective body of hypotheses on related matters which have been tested and confirmed in this way; if so, the collection comes to make up a generalized framework called a theory. One such theory is that humankind was created through the evolutionary process. It is part of a larger overall theory that all living organisms have been created through the evolutionary process, but in this essay, I will concentrate on the creation of the human species.
Since space is limited, I will restrict this essay to three observations, put forward a hypothesis to explain each, explore its predictions and examine results from testing those predictions.
The body features of a chimpanzee and a human are very similar.
Hypothesis: Chimpanzees and humans descend from a common ancestral species.
Prediction: Fossils will be found which document a progressive change in body form from ape to human which is correlated with the age of the fossils.
Test: Examine progression of fossils, detail their characteristics to see if they become more humanlike in a manner that correlates with their age.
Nowhere is the progressive timing of the transitions better documented than in the Great Rift Valley of northeastern Africa. One of the oldest (4.4 million years of age) was found in November 1994, when a single hand bone was found peeking out of some sedimentary rock. Careful excavation of the site resulted in the recovery of forty-five percent of the skeletal remains from one individual, a female of the species Ardipithecus ramidus. She had features that pointed to a lifestyle adapted to both trees and ground. Like today’s great apes, she had a splayed big toe sticking out sideways that would have served well in tree climbing. She had hands and arms that were well suited for life in the trees as well. However, she was not a knuckle walker and was clearly bi-pedal.
Beginning with fossils about 3.7 million years of age, the finds are different. Ardipithecus is no longer present, instead species like Australopithecus afarensis are found. The face of this species was apelike with a flattened nose and strongly protruding lower jaw and the brain was about one third the size of ours. The shoulder blade was not humanlike; it resembled that of a gorilla. But unlike Ardipithecus other features like the foot, the hands and the ankles are strongly humanlike. Beginning at about 2 million years of age, fossils that share an increased number of our characteristics our found. These individuals had a large brain case and a narrower, less stocky body shape with shorter arms and longer legs. Observations of this sort continue throughout the fossil record with species increasingly resembling our own until about 100,000 to 200,000 years ago when a body form virtually indistinguishable from our own emerges. The ages are determined by various techniques including but not restricted to isotopic analysis; they can sometimes by double checked by independent methods; and the results are broadly consistent with a progression through time that is increasingly humanlike.
Conclusion: Results are thoroughly in agreement with the hypothesis; it is difficult to explain them in any other way.
The DNA code of the chimpanzee and the human are extremely similar—differing by only about 1.5% to 3% (depending upon how one defines ‘difference’).
Hypothesis: Chimpanzees and humans are created from a common ancestral species; the basis of their DNA difference is that mutations have been accumulating in each lineage since that common ancestral species lived.
Prediction: Since we can measure how many DNA changes (i.e. mutations) occur in one generation in living humans, we can predict the number of mutations over 350,000 generations, the approximate number of expected generations [based on fossil data] since humans and chimpanzees had a common ancestor.
Test: Determine the number of mutations per generation (about 70) and then calculate the expected number of differences if mutations were the cause of those differences.
When that calculation is done it turns out that the number of expected mutations corresponds within a factor of two to the actual number of coding differences between the two species. To be that close to the predicted value after about 6-7 million years of passing the slowly-mutating DNA from parents to offspring is highly confirmatory. However, the confirmation goes one step further: we know that at particular sites in the DNA of living persons there is a particular type of mutation which occurs 18 times more frequently. When one compares the code between humans and chimpanzees, the number of differences at such locations is approximately 18-fold higher.
Conclusion: Results are thoroughly consistent with the hypothesis; it is difficult to explain them any other way.
We have scars on our body as a result of old injuries; they stay on our skin even though the skin cells have been renewed hundreds of times since the old injury. DNA has scars too and they are the result of the DNA molecule having been damaged in particular ways at particular times. Just like a scar of well-defined shape might memorialize an old injury to (for example) your chin, so humans and chimpanzees each have well-defined DNA ‘scars’ at very precise positions and of a well-defined character.
Hypothesis: Humans and chimpanzees have a common ancestor. DNA is injured in an ancient ancestor of both humans and chimpanzees and that damage is faithfully passed on to each species from that common ancestor.
Prediction: Since DNA is replicated faithfully from generation to generation (just like scarred skin cells are replicated every 27 days on your body), one would predict that old DNA injuries (i.e. those which occurred more than 350,000 generations ago) will be present in exactly the same place in the DNA code of humans as it is in chimpanzees.
Test: Determine the location and specific nature of damage of a set of DNA ‘scars’ in both chimpanzees and humans.
There are many examples of such scars which are present in exactly the same place, shaped in exactly the same way, and are exactly the same size in both humans and chimpanzees. This is consistent with the hypothesis that the damage occurred in a common ancestral species and has been faithfully passed on ever since.
Conclusion: Results are thoroughly consistent with the hypothesis and it is difficult to explain them any other way.
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The three examples I’ve discussed are a sub-set of the many observations and confirmed predictions. Many whole books have been written, three of which are referenced here, which elaborate on that which—because of space—I have discussed only briefly here. Like all scientific theories, we must humbly emphasize that science does not establish absolute certainty. All that the science enables us to say is that this theory—the creation of humans through the evolutionary process—is highly consistent with a broad swathe of data and that it is highly likely to be true.
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 See Darrel Falk, ‘Human Origins: The Scientific Story’. Evolution and the Fall, William T. Cavanaugh and James K. A. Smith (eds.) (William B Eermans, 2017), pp3-22.
 For a thorough review see Ian Tattersall, Masters of the Planet: The Search for our Human Origins (St. Martin’s Press, 2012).
 Mark Jobling, E. Hollox, M. Hurles, T. Kivisild, C. Tyler-Smith, Human Evolutionary Genetics (Garland Science, 2014), p54.
 See John Laing, Darrel Falk and Fuz Rana, ‘The Biological Evidence: Does Genetics Point to a Common Descent?’. Old Earth or Evolutionary Creation? Kenneth Keathly, J.B. Stump, and Joe Aguire, eds. (Inter Varsity Press, 2017), pp178-198. This reference provides an overview and more references.
 Graeme Finlay, Human Evolution: Genes, Genealogies, and Phylogenies (Cambridge University Press, 2013).
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