A–C Representative longitudinal sections and μCT images (insets) of control and FGF2 treated digits 21 days post treatment (DPT). A Control BSA treated digits do not display a regenerative response and are truncated. B The majority of FGF2 treated digits are truncated without displaying a regenerative response. C A minority of FGF2 treated digits produce an ectopic skeletal element distal to the amputation that articulates with the stump bone.
Although the Discovery Institute and its Fellows who advocate for Intelligent Design are usually careful not to identify their putative “intelligent designer” explicitly with the God of the Christian Bible, the dog-whistle signals they use leave their target audience in little doubt. The designer is understood to be the Christian god, merely relabelled for legal and tactical convenience. That being so, and if that god were actively interfering in the design and evolution of living systems — with humans as the supposed pinnacle of creation and occupying a special place in it — we might reasonably expect humans to have been given the best design available.
Instead, nature looks exactly as an unplanned evolutionary process would lead us to expect: a patchwork of compromises, contingencies and inherited limitations. As I describe in my book, The Malevolent Designer: Why Nature's God is not Good, humans are remarkable in some respects, particularly in our relatively large brains and consequent cognitive abilities, but in most other respects we are not especially impressive. We are not the strongest animals, nor the fastest. Birds of prey have far better eyesight; barn owls and dogs have far better hearing in relevant ranges; dogs have a vastly superior sense of smell; elephants and some other long-lived animals have evolved impressive cancer-resistance mechanisms; and the immune systems of many bats are tuned in ways that make our own look distinctly ordinary.
But perhaps the most striking contrast is in the ability of some animals to regenerate lost or damaged body parts. Several species can regenerate structures that humans simply cannot replace. Salamanders can regrow limbs; fish can replace fins and repair tissues that would leave mammals permanently damaged; and some invertebrates can regenerate astonishing portions of the body. Yet, noticeably, all the prayers, incantations and appeals to divine mercy have never once been shown to regrow an amputated human limb, replace a lost eye, repair a severed spinal cord, or restore dead heart muscle after an infarction. Nor do we see cancerous sections of colon removed by surgery obligingly regrowing as healthy tissue in answer to prayer. These are not impossible biological feats in principle; they are just things our lineage cannot normally do.
Now researchers from Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS) have found something that should be even more disturbing for Intelligent Design creationists. In a paper recently published in Nature Communications, they report that non-regenerating mouse digit wounds can be induced to move part-way towards regeneration. In other words, the relevant mammalian cells may not be entirely incapable of regeneration; their capacity appears to be suppressed or obscured by the normal wound-healing response. Creationists who reject the evolutionary explanation now need to explain why an intelligent, omnibenevolent designer would leave mammals, including humans, with a latent capacity for regeneration, while allowing that capacity to be overridden by scarring.
The researchers’ explanation makes perfect sense as the outcome of a utilitarian, unplanned evolutionary process. In mammals, rapid wound closure by scar-forming fibroblasts can be life-saving. A quick patch reduces blood loss, closes a route for infection and gives the injured animal a better chance of surviving long enough to reproduce. Regeneration, by contrast, is slower and more complex. Evolution has no foresight and no obligation to produce perfection; it merely preserves what works well enough under the circumstances. The injury is patched up with a near-enough-is-good-enough solution, and the animal lives to pass on its genes.
That, of course, should not have been beyond the wit of an intelligent designer to improve upon. A competent designer could have given us both abilities: rapid wound closure to prevent fatal bleeding and infection, followed by orderly regeneration of the missing structures. Instead, we have the familiar evolutionary compromise: survival first, elegance later — and often not at all.
The problem centres on fibroblast cells, which can follow different developmental routes. In ordinary mammalian wound-healing, they rapidly close the wound and form scar tissue. In strongly regenerative animals, similar cells can organise into a blastema — a temporary structure that seals the wound while also providing the cellular basis for rebuilding missing tissues. The Texas A&M team showed that, after the wound had first closed, applying fibroblast growth factor 2 (FGF2), followed later by bone morphogenetic protein 2 (BMP2), could redirect the response. The result was imperfect regeneration, but it included bone, tendon, ligament and joint-like structures.
The conclusion is not that humans are about to start regrowing limbs, nor that a mouse digit is the same as a human arm or leg. It is more interesting than that. The potential for regeneration in mammals may not have vanished completely. It may still be there, hidden beneath the faster, rougher, scar-forming response that natural selection has favoured. For creationists, that raises the awkward question of why their supposed designer would equip other animals with regenerative abilities, leave traces of the same capacity in mammals, and then arrange matters so that, when humans most need it, the system normally fails.
