At Reasons.org: Bear Species Hybridization Shows God’s Providence

Fazale Rana writes:

Adaptability—the capacity to manage change is an invaluable trait in today’s ever-changing work environment. Adaptable workers are resilient, curious, and resourceful. They are willing to experiment and to risk failure. Most importantly, they understand the big picture, always keeping it at the forefront of everything they do. Some people are innately adaptable; others aren’t. Still, those who aren’t adaptable by nature can develop the qualities that help them to thrive on the job. 

Adaptability is also a valuable quality in biology. In fact, many biologists believe that adaptability is one of the universally descriptive features of life. Organisms are exquisitely suited for their environments. Yet the environment changes. And like adaptable employees who can navigate workplace changes, organisms have the means to adapt to a shifting landscape. Those organisms that respond to change will persist; those that can’t will disappear. 

Biologists have discovered a variety of mechanisms that operate at a population level that enable species to adapt to: (1) changes in the environment, (2) predatory pressure, and (3) fluctuating resources. The mechanism list includes: (1) natural selection, (2) sexual selection, and (3) genetic drift. 

Recently, a large team of collaborators, headed by researchers from the University of California, Santa Cruz, highlighted another mechanism that they think contributes to organisms’ ability to adapt: introgression—the introduction of genetic material into the gene pool of another species through interbreeding or hybridization.¹ Insights like this one are often viewed as prima facia evidence for life’s evolutionary history. But this discovery can also be viewed legitimately from a creation model standpoint, where adaptability reflects God’s providential care for his creation. In other words, God has designed the world so that populations of organisms have the innate capacity to adapt and ensure that they will survive and thrive. 

Polar Bear and Brown Bear Introgression
More evidence for the connection between introgression and adaptability became available when the UC Santa Cruz-led team examined the genome of a polar bear fossil specimen that age-dates between 70 and 110 thousand years ago. This specimen consists of a jawbone recovered from the beach near the Beaufort Sea by Port McLeod in Arctic Alaska. 

From the ancient DNA extracted from one of the polar bear’s fossilized teeth, the team reconstructed high-quality sequences for the nuclear and mitochondrial genomes. The sequence data indicates that this specimen was indeed a polar bear but its genetic fingerprint falls outside the genetic diversity range for extant polar bears. 

Comparison of this ancient polar bear genome with the genomes of extant brown bears indicates that the population to which the polar bear belonged interbred with a group of brown bears, around 100,000 years ago. As it turns out, these ancient recipients of the polar bear genetic material became ancestral to all brown bears living today. In fact, about 10% of the contemporary brown bear genome comes from this ancient introgression. 

Introgression and Adaptation 
One of Charles Darwin’s most important scientific accomplishments was to identify a mechanism to account for the origin of species. In the process, he demonstrated that species aren’t fixed entities but can change through natural and sexual selection. 

These two mechanisms, along with genetic drift, allow populations of organisms to adapt. This adaptation can occur in one of two ways: (1) through changes in standing genetic variation in the population with the frequency of the alleles in the population changing in the response to environmental changes, or (2) through mutations that introduce new alleles altogether. The former mechanism leads to rapid response to environmental changes; the latter mechanism requires much more time to effect change. 

Based on the recent work by the UC Santa Cruz-led investigators (along with other studies), introgression can be added to the list of mechanisms that serve as drivers for adaptive change.² Adaptive introgression can rapidly introduce a large amount of new genetic information into a population across multiple genetic loci. The result is a response to environmental changes that’s more rapid than mutations afford and a more comprehensive response to environmental changes than is offered by changes in the frequency of already existing alleles.

Evolutionary Adaptation and God’s Providence
From a creation model perspective, the adaptability of organisms is understood as part of the design God ordained in the biological realm. In line with Christian theology, the RTB model maintains that God not only created the world, but he also actively and continually preserves and governs all that he has made. God’s governance of the creation includes the natural processes he instituted when he brought the universe into existence. It is through these processes that he sustains the universe and everything in it. 

Evolutionary Adaptation Is Not Evidence for the Evolutionary Paradigm
On the other hand, just because one embraces organisms’ ability to adapt through evolutionary processes, it doesn’t mean they are obligated to accept the totality of the evolutionary paradigm. I don’t. 

While abundant evidence exists for microevolution and adaptation (driven by natural and sexual selection, genetic drift, and, now, introgression), it isn’t clear that merely extrapolating these mechanisms over vast time periods can explain large-scale evolutionary change (macroevolution). To put it another way, it isn’t clear if natural and sexual selection, genetic drift, and even adaptive introgression can account for biological novelty and innovation—particularly when life transitions from one regime of complexity to another. 

These issues also mean that life scientists cannot legitimately enlist the sound and well-evidenced explanations for microevolution and adaptation in support of macroevolution. They also justify the skepticism that some ID proponents and creationists express about the capacity of evolutionary mechanisms to fully account for the origin, design, and history of life.

I wonder if modern-day biology will be adaptable enough to make a place at the table for ID and creation models—particularly in the face of the shortcomings of current evolutionary theory.

Endnotes

1. Ming-Shan Wang et al. “A Polar Bear Paleogenome Reveals Extensive Ancient Gene Flow from Polar Bears into Brown Bears,” Nature Ecology and Evolution 6 (June 16, 2022): 936–944, doi:10.1038/s41559-022-01753-8.
2. For example, see Philip W. Hedrick, “Adaptive Introgression in Animals: Examples and Comparison to New Mutation and Standing Variation as a Source of Adaptive Variation,” Molecular Ecology 22, no. 18 (September 2013): 4606–4618, doi:10.1111/mec.12415.
3. News Staff, “Scientists Sequence Genome of 100,000-Year-Old Polar Bear,” Sci News, June 17, 2022, http://www.sci-news.com/genetics/polar-bear-paleogenome-10914.html.
4. Douglas H. Erwin and James W. Valentine, The Cambrian Explosion: The Construction of Animal Biodiversity (Greenwood Village, CO: Roberts and Company, 2013), 10–11.
5. Gerd B. Müller, “Why an Extended Evolutionary Synthesis Is Necessary,” Interface Focus 7 (August 18, 2017): 20170015, doi:10.1098/rsfs.2017.0015.