If you have paid attention to the headlines during the last twenty years, you are probably aware of stem cells. A popular understanding of stem cells, at least, what I have understood, is that these early embryonic cells hold the potential to transform into every different type of cell an organism will possess.
However, as these cells divide and the embryo grows, stem cells begin to become specified as a particular type of cell. As this transformation occurs they lose the ability to become alternative cell types. Eventually, they fill a particular niche wonderfully, but have lost the ability to become a radically different type of cell.
Stem cells can serve as a metaphor illustrating a powerful idea regarding Darwin’s proposed mechanisms for evolution. Research reveals that random mutations and natural selection do transform species, however, at a surprising cost.
Before exploring what research is revealing about Darwin’s proposed mechanisms for evolution, a word or two about metaphors in general and my stem cell illustration in particular. A metaphor’s purpose should function to illustrate an idea, not prove it. Additionally, most metaphors can be pressed into extraneous details where they no longer accurately relate to what they are supposed to be illustrating.
Accordingly, my use of stem cells does not take into account what current research may have revealed about them, nor any other type of cell. Rather, my only desire is to tap into a commonly shared idea regarding stem cells and use that understanding to communicate an idea regarding random mutation and natural selection.
Earlier in 2019 a biochemist professor published a book documenting and expounding upon various research projects. He also contributed his own research findings and observations. What might catch us by surprise is that his conclusions can be paradigm shifting.
Citing various studies from finches to bacteria, he affirms that Darwin’s proposed mechanisms have been documented in enabling species to adapt to specific environments, even creating new species. What is enlightening, however, is that the research reveals this adaptation comes at the cost of degrading genes, not creating new viable DNA capable of manufacturing new functioning proteins.
In other words, think of what happens with stem cells (my illustration, not his). Although stem cells start with great potentiality, as they repeatedly divide and progress toward becoming a specific cell type, they lose the ability to be transformed into other cell types. If you will, stem cells are transformed into functioning exquisitely in a dead end, a particular type of cell. Hence, nerve cells have no capacity to become skin cells.
What this book suggests is that the research reveals the process of evolution entails a similar narrowing of options. Bears, birds, fish, wolves and so forth can evolve into adapting to specific environments. Polar bears are adapted to an icy environment and are capable of consuming a fatty seal diet. Finches have adapted to harsh environments or to a particular type of food source. The jaws of some cichlid fish change depending on their food source. Bacteria can gain the ability to reproduce much faster. And of course, we are all familiar with the great diversity of dogs whose canine origin can be traced back to some type of wolf.
What makes this adaptation possible at the biochemical level is that random mutations are predominately breaking functioning genes, while natural selection will favor these broken genes when such brokenness conveys an advantage. How could breaking genes give an organism an advantage? More about this in a second. The result is organisms experience evolutionary drift into becoming more adapted to their environmental niches at the cost of losing previously functioning genes.
It would seem life is not evolving upward. It survives by devolving to its environment.
Such evolution can lead to new species which are better suited to a specific environment than the parent species. However, such evolution predominately comes at the cost of damaging functioning genes.
For example, it appears that a polar bear’s white fur coat and ability to eat a fatty seal diet, which would normally cause heart disease and high cholesterol, result from genetic damage to the LYST and APOB genes. In other words, a bear with faulty LYST and APOB genes would be favored for survival in the arctic more than a brown bear possessing fully functioning LYST and APOB genes.
Polar bears are not on a path to becoming a different type of animal with new genetic information. Rather they are becoming bears trapped in the icy cold.
Among the professor’s various observations, another resonated with me particularly strong. He repeatedly points to our human imagination as empowering our acceptance of the Darwinian story.
Years ago I expressed a similar thought in an article, “The Naturalistic Imagination”:
Our ignorance fuels our ability to imagine the impossible and the absurd. … If life did not arise by naturalistic impulses, today’s naturalistic imagination of how life arose or how new kinds of animals came to be will always seem feasible given our current level of ignorance.”
In my viewpoint, to acknowledge our ignorance is a wonderful characteristic of humility that promotes learning and discovery. Furthermore, avoiding a speculative imagination would seem to be helpful, not only in evolutionary biology, but also in theology. How many well intentioned, but erroneous ideas have begun with, “I feel that …” or “I can imagine that …”
Not going beyond the evidence. Priceless.