Humans May Have Lost Beneficial Traits

Imagine if you could regrow teeth all your life. Have we lost some capabilities during human history?

Aside from the occasional aches and pains, our bodies are pretty amazing. Cuts can heal, hearts can beat for decades non-stop, and brains can conceive profound abstractions. The versatility of human motion is astonishing, as any Olympic Games broadcast shows. Still, we can see other animals with traits that would be nice to have. On second thought, maybe our ancestors did have them.

Jaws envy. Sharks can regenerate teeth throughout their lives. Why can’t we? Science Daily describes the genetics behind tooth regeneration in sharks, then says,

Humans also possess this set of cells, which facilitate the production of replacement teeth, but only two sets are formed — baby and adult teeth — before this set of specialised cells is lost.

The Sheffield-led team show that these tooth-making genes found in sharks are conserved through 450 million years of evolution, and probably made the first vertebrate teeth. These ‘tooth’ genes, therefore make all vertebrate teeth from sharks to mammals, however in mammals like humans, the tooth regeneration ability, that utilises these genes, has been highly reduced over time.

Why would evolution keep a trait for so long, only to reduce it in the most advanced organisms?

Partial regeneration hints at better times past. Liver tissue can regenerate. Skin and bone can heal. Stem cell research shows that our bodies carry around raw materials for rebuilding tissues and organs. Why can’t we regrow arms like amphibians? Why do some people go bald? Is the partial regenerative ability of the human body merely a leftover of a full repair kit that would enable much longer life? Here are some headlines that suggest innate regenerative potential in the body.

1. Aging diminishes spinal cord regeneration after injury (Medical Xpress). Why does this ability decline over time?
2. Researchers link absence of protein to liver tissue regeneration (Science Daily). A healthy liver can regrow 70% of its tissue after injury. Why don’t other organs do that?
3. Specific gene network found that promotes nervous system repair (Science Daily). UCLA scientists found “an existing drug that mimics that gene network has been repurposed to promote nerve regeneration in the CNS [central nervous system].” Has that ability been lost?
4. Mechanism to regenerate heart tissue identified (Science Daily). If drugs can “help the body grow muscles and remove scar tissue,” what if the body could have done this without external help?
5. New research shows young muscle stem cells can improve adult muscle regeneration (Medical Xpress). If the muscles are there and work in the unborn child, why do they lose capacity later in life?
6. Complex learning dismantles barriers in the brain (Medical Xpress). The brain has astonishing ability to rewire itself and re-learn things after injury. Why, then, do some brain disorders fail this repair process?
7. Induced pluripotent stem cells (iPSC) shown to form multiple types of functional lymphocytes in vivo (Medical Xpress). What if this capability did not have to be induced but happened naturally as the need arose?
8. Stem cells used to successfully regenerate damage in corticospinal injury (Medical Xpress). A team finds that neural stem cells support regeneration.
9. 3-D ‘mini-retinas’ grown from mouse and human stem cells (Science Daily). Cambridge biologists are trying to “harness the flexibility” of stem cells to regenerate parts.
10. Bioengineering a 3D integumentary organ system from iPS cells using an in vivo transplantation model (Science Magazine). Their experiments can regrow skin, complete with hair. A cure for baldness coming? See the picture and description in the BBC News; the sample even sprouted hair and glands.

‘Game changing’ stem cell repair system (Science Daily). This headline screams for attention in the stem cell world. Scientists publishing in PNAS announced a promising new method for tissue regeneration. Using a new way to reprogram body cells into “induced multipotent stem cells” (iMS), scientists can extract fat cells and dope them with AZA, a compound known to induce cell plasticity. “When the stem cells are inserted into the damaged tissue site,” Science Daily says, “they multiply, promoting growth and healing.” The new cells take on the characteristics of the tissue into which they are inserted. This new method overcomes ethical problems with embryonic stem cells, and doesn’t require viral vectors to reprogram the cells. Look what they compare it to:

Stem cell therapies capable of regenerating any human tissue damaged by injury, disease or ageing could be available within a few years, following landmark research led by UNSW Australia researchers.

The repair system, similar to the method used by salamanders to regenerate limbs, could be used to repair everything from spinal discs to bone fractures, and has the potential to transform current treatment approaches to regenerative medicine.

Morally challenged descendents. Why are there psychopaths with no empathy for others? Why so much hate and anger in the human race? Maybe charity is the default, and lack of it represents a degradation. Some UCLA neuroscientists claim to have found “potentially groundbreaking” evidence that humans are “hard-wired for altruism,” Science Daily says:

It’s an age-old quandary: Are we born “noble savages” whose best intentions are corrupted by civilization, as the 18th century Swiss philosopher Jean-Jacques Rousseau contended? Or are we fundamentally selfish brutes who need civilization to rein in our base impulses, as the 17th century English philosopher Thomas Hobbes argued?

After exploring the areas of the brain that fuel our empathetic impulses — and temporarily disabling other regions that oppose those impulses — two UCLA neuroscientists are coming down on the optimistic side of human nature.

“Our altruism may be more hard-wired than previously thought,” said Leonardo Christov-Moore, a postdoctoral fellow at UCLA’s Semel Institute of Neuroscience and Human Behavior.

Evolutionary theory would have us believe that beneficial capabilities arose by chance, then were lost by chance. What if, instead, there has been a gradual decline in original capabilities due to the accumulation of mutations and genetic entropy?

Update 4/6/16: Another article in Science Daily appeared suggesting that humans lost regenerative abilities:

If you trace our evolutionary tree way back to its roots — long before the shedding of gills or the development of opposable thumbs — you will likely find a common ancestor with the amazing ability to regenerate lost body parts.

Lucky descendants of this creature, including today’s salamanders or zebrafish, can still perform the feat, but humans lost much of their regenerative power over millions of years of evolution.

But why would evolution lose an “amazing ability” that would surely seem to augment fitness? The system was already there. It’s just a matter of genes and proteins and stem cells. This is devolution, not evolution. Millions of years not required.

Christians believe the original creation was perfect, but that perfect state fell due to sin. Even so, the Bible says humans lived for hundreds of years before the Flood before succumbing to the judgment of death God had warned our parents of. If God’s “plan A” was eternal life, it makes sense He would have created with built-in capacities for repair and regeneration, along with an environment conducive to health (a stronger magnetic field and better atmosphere, perhaps, and unknown benefits from the Tree of Life). The fact that some of these regenerative mechanisms still exist suggests that they were stronger in the past, but have declined over the millennia due to mutational load and genetic entropy.

Even with today’s genetic burdens, there’s no reason humans couldn’t live much longer and healthier lives than most do. Medical science and healthful advice about diet and exercise can often improve longevity. It won’t cure death this side of the New Creation, of course, but there’s something charitable about reversing some of the effects of the curse. The Bible’s description of a future state (some consider this the Millennium) hints at much longer, healthier lives before a final judgment, then life everlasting for those who repent of their sin and trust Christ. There will be no bodily regeneration without spiritual regeneration first (Titus 2:11-14). But with bodies this amazing even in a fallen world, just imagine what resurrection bodies will be capable of in the absence of sin! (I Corinthians 15:42-49). Here’s a quote from C.S. Lewis:

To shrink back from all that can be called Nature into negative spirituality is as if we ran away from horses instead of learning to ride. There is in our present pilgrim condition plenty of room (more room than most of us like) for abstinence and renunciation and mortifying our natural desires. But behind all asceticism the thought should be, ‘Who will trust us with the true wealth if we cannot be trusted even with the wealth that perishes?’ Who will trust me with a spiritual body if I cannot control even an earthly body? These small and perishable bodies we now have were given to us as ponies are given to schoolboys. We must learn to manage: not that we may some day be free of horses altogether but that some day we may ride bare-back, confident and rejoicing, those greater mounts, those winged, shining and world- shaking horses which perhaps even now expect us with impatience, pawing and snorting in the King’s stables. Not that the gallop would be of any value unless it were a gallop with the King; but how else— since He has retained His own charger—should we accompany Him? — C.S. Lewis, Miracles

It makes sense that an all-wise Creator, who intends abundant life for His creatures, knows how to bring it about. It makes no sense to think that regenerative abilities arose by chance.