In previous articles, we observed that just a few thousand animals likely accompanied Noah on the Ark. From these creatures, a myriad of species arose.
In response to the question of how this might be possible, we took a cue from Darwin’s own work. We observed that the comparison of breeds to species indicated that species must have arisen recently—within thousands of years, not millions of years.
What Darwin didn’t know is that his indirect evidence would be spectacularly confirmed over 150 years later.
The century and a half wait was a consequence of a long-standing secret in the evolutionary community—the massive risk that Darwin took when he wrote On the Origin of Species. In arguing for a particular view of the origin of species, Darwin put his entire explanatory edifice in great danger. Since species are defined by traits and characteristics that are heritable, the origin of species is a fundamentally genetic question. In other words, we recognize zebra species because the information that specifies stripes is inherited consistently generation after generation. Elephants are an iconic species because their iconic feature—their long trunk—is present in each generation. In short, the concept of species exists because genetics exists.
When Darwin wrote his book in 1859, genetics wasn’t even a scientific field. The father of modern genetics, Gregor Mendel, hadn’t even published his foundational observations in pea plants. Mendel’s findings wouldn’t be announced until 1865, and then Mendel’s work would be lost for several decades. Only at the turn of the century, after genetics was connected to cellular structures termed chromosomes, was the term genetics coined.
While the chromosome link moved the field of genetics forward, it also sparked a new debate. Since chromosomes are composed of two major molecules (DNA and protein), geneticists would debate which molecule was the substance of heredity for another several decades. Finally in 1953, when Watson, Crick, and colleagues discovered the structure of DNA, scientists finally settled on DNA as the molecule possessing the heritable genetic information.
Like so many scientific discoveries, the elucidation of the structure of DNA concluded one scientific story and started another. With this newfound knowledge, the scientific community could now go about the business of finding out the sequence of the DNA code in each species. Again, this information was slow in coming. Only in the last few years has enough DNA sequence existed in the public databases whereby Darwin’s origin claims can be directly evaluated.1
To clarify, no other scientific field directly records a species’ ancestry. Fossils, geography, anatomy, and physiology are not inherited. DNA is the actual chemical that is passed on in sperm and egg. Hence, only the field of genetics acts as a direct record of species’ ancestry.
Conversely, by virtue of the manner in which DNA changes each generation, DNA also records the passage of time.
To understand how the DNA clock ticks, it’s helpful to understand the structure of the DNA molecule. DNA exists in the form of a twisted ladder. Each rung of the ladder represents a chemical letter, and the different colors of the rungs represent the different DNA letters.
Though only four different DNA letters exist in the DNA code, this small chemical alphabet of sorts can carry tremendous amounts of information. For example, in humans, a total of six billion DNA letters—rungs of the ladder—exist in each person.2 The arrangement of these letters—their order, their spatial relationship to other letters, and so on—carries the information for a species’ traits and characteristics.
When sperm and egg copy their DNA in preparation for fertilization, the copying process is imperfect. In terms of the diagram we just examined, copying errors change the color of one of the rungs to a different rung color. Over time, the number of color-changed rungs increases, acting like a clock that measures time since the DNA sequence first came to be.
By comparing the rungs of the DNA ladder in various 