Were Our Bodies Created for Self-Repair?
Studies of amphibians are suggesting that higher animals also had regenerative abilities that have been lost over time.
Imagine losing an arm and having it grow back. That trick happens with salamanders and some lower animals, like hydras and flatworms. How come we can’t do that? Why would evolution lose such a clever ability?
These questions come to light when pondering this headline on Science Daily, “Capacity to regenerate body parts may be the primitive state for all four-legged vertebrates.” (We may be two-legged vertebrates, but we are classified as tetrapods, so we should be included.) Evolutionists in Germany and New York are saying, “the extraordinary regenerative capacities of modern salamanders are likely an ancient feature of four-legged vertebrates that was subsequently lost in the course of evolution.” What does that mean? Are we like blind cave fish?
Salamanders are extraordinary among modern four-legged vertebrates in showing an astonishing capacity to regenerate limbs, tails, and internal organs that were injured or lost due to amputation repeatedly and throughout their entire lifespan. The mechanisms controlling this high regenerative capacity are the focus of a large field of research driven by the hope to some day apply the findings to human medicine.
And yet salamander limbs develop the same basic way as ours. One curious difference exists, though: “Salamanders on the contrary form their fingers in a reversed order compared to all other four-legged vertebrates, a phenomenon that has puzzled scientist [sic] for over a century,” one of the researchers pointed out. Nature Communications says this is due to an orphan gene. Interestingly, lizards can regrow their tails once or twice, but not their limbs. How does evolution explain these differences?
The new study suggests that regeneration was widespread in the Carboniferous and Permian. From fossils and from living representatives, the researchers conclude that it was the default back then. “Many lineages may have lost it,” the article states.
“The fossil record shows that the form of limb development of modern salamanders and the high regenerative capacities are not something salamander-specific, but instead were much more wide spread [sic] and may even represent the primitive condition for all four-legged vertebrates” says Nadia Fröbisch. “The high regenerative capacities were lost in the evolutionary history of the different tetrapod lineages, at least once, but likely multiple times independently, among them also the lineage leading to mammals.“
That is certainly a “surprising” finding for an evolutionist. Usually a beneficial trait is supposed to be maintained by natural selection, unless it is too energetically costly, as it would be with flightless birds and insects on windy islands and blind fish in caves. This leads to a corollary conclusion that the ability still exists in a latent form: “mechanisms that all land vertebrates carry within them due to their common evolutionary heritage.”
Charlotte Stephenson writes about this on The Conversation. She shows a fossil salamander that demonstrates regeneration in progress. “This pushes back our current understanding of limb regeneration in the animal kingdom to almost 300m years ago,” she says, failing to explain how it evolved in the first place (see “Poof Spoof” in the Darwin Dictionary).
If we look back into the fossil record, there’s also evidence for tail regeneration there. Fossils of the extinct microsaur amphibians Microbrachis and Hyloplesion clearly show where part of the tail has regrown and joined to the original tail bone. Just another incredible example of how nature has been able to evolve and adapt from the very dawn of life on Earth.
These discoveries have helped our understanding of the evolutionary and genetic processes behind the salamander’s incredible ability to regrow limbs.
Once again, though, it’s not clear why evolution would have lost this beneficial capability. Isn’t that what stem cells are for? Humans have the ability to regrow parts of the intestine that are removed during surgery. Tissues can heal. DNA can repair itself; that fact won this year’s Nobel Prize (Nature). Other scientists have found genes in the inner ear that might restore lost hearing and balance (Science Daily). Why not larger structures like limbs? If the genetic instructions are present, why would evolution switch off this capability? Wouldn’t it improve fitness?
Speaking of stem cells, Science Magazine just reported results of a new study that shows reprogrammed adult stem cells (induced pluripotent stem cells, or iPS) are just as good as embryonic stem cells.
Researchers who hope to use stem cells—the unspecialized cells that produce all of our tissues—to treat diseases face a dilemma. Stem cells from embryos (ES cells) could provide a wealth of new cells but spark ethical objections. Stem cells produced from adult cells (so-called induced pluripotent stem [iPS] cells) avoid the ethical difficulties, but some scientists have questioned whether they are as powerful as ES cells. A new study suggests that the two types of stem cells are equivalent and may help soothe worries about the capabilities of iPS cells.
This also should undercut the justification for experimenting with human embryos. If they “spark ethical objections” without providing any advantages, why use them at all? The new study proved that “ES cells and iPS cells were equally good at specializing into a variety of nervous system cells.” They ran other tests that proved the ES and iPS cells were “functionally indistinguishable” from each other. Yet for some reason, holdouts are still expressing “a little bit of reservation about how broad the conclusion can be.” Maybe they should focus their “little bit of reservation” toward the “ethical difficulties” of destroying human embryos.
What’s it going to take to stop the use of embryonic stem cells? Yamanaka’s Nobel-Prize-winning discovery of iPS cells was a godsend. Now, nine years later, almost every objection has been answered. They are functionally indistinguishable. That should be great news. It’s astonishing that some researchers still want to hold out hope that killing human embryos will be “better” somehow. These holdouts need to read the Ten Commandments.
It would be great news to figure out how salamanders regrow limbs and learn how we could do the same. From a creation standpoint, it’s reasonable to assume that God gave the first people and animals that capability. We are decrepit remnants of the original people who could live for almost a thousand years even after the Fall. Mutations have accumulated over the generations. We have probably lost many beneficial traits from the original “very good” creation. What’s amazing is that anyone can be as beautiful and healthy as they are this late in earth history. Much of that is due to medical science finding ways to fix or prevent the effects of mutational load. It’s certainly a worthwhile project to understand regeneration and see if it can be switched on again. Intelligent design—not evolution—is a more rational motivation for thinking so. (See Evolution News & Views about DNA repair as an intelligent design research program.)