the battle of the ages: biology vs. physics
Perhaps the most powerful force in the universe is entropy. According to modern cosmology, in the beginning of time and space, the cosmos was incredibly organized and as it began to age, increasing entropy allowed a whole host of phenomena responsible for stars, planets, galaxies, black holes and us. But according to Sean Carroll, a theoretical physicist working to explain time, entropy also plays a significant role in aging. After all, if our bodies accumulate damage and will quite literally wear out after a century or so, doesn’t it make sense to think of aging as another manifestation of the disorder we see in the universe at large? Not so fast says Jerry Coyne in his post about aging and biology. Sure, entropy has a role to play but genetics and selection have a much bigger and more important role to play, so much so that they could postpone and even prevent aging.
As we’ve discussed in a post about DARPA’s endeavors in creating immortal life forms in the lab, there are creatures that seem to achieve something similar to physical immortality and postpone senescence in large scale structures like tissues and organs. That, Coyne argues, provides very compelling evidence that entropy doesn’t have much to do with aging as far as organisms are concerned. Not only that, but immortality isn’t an impossibility in the biological world and we can take creatures which can repair damage done by radiation, or salamanders able to re-grow their limbs as an example of potential adaptations that may lead to full blown immortality. Their abilities wouldn’t violate the second law of thermodynamics because they’ll exist in an open system while the universe’s overall entropy is actually increasing. The problem with immortal organisms in normal environments, however, would be their susceptibility to extinction and limits to the resources they need to survive. If you have organisms living for thousands of years, they’ll consume a lot more than ones living for just a few decades. Their population would have to be small to account for the limits of the food supply, and if a volcanic eruption, an outbreak of a fatal disease, or a predator struck, they could be facing the possibility of extinction in the blink of an eye thanks to their small numbers.
On top of this, organisms with limitless lifespans would evolve very slowly since the evolutionary process has to depend on large populations and new generations. The more individuals and the more offspring, the faster the rate of evolution. This is why humans are evolving at a breakneck pace. There are a lot of us and we’re in ecological niches all over the world, consuming all sorts of different diets. It’s simply more efficient for species to keep death around. Of course we need to remember that there is no on/off switch or gene in organisms so the entire aging process and the subsequent end of life depend on a confluence of environmental and genetic factors to weaken the organism enough to be killed off by something, anything. This is why life extension isn’t an impossible dream. If we find how to keep our bodies thinking that we’re young and need repairs, updates, replacements and continuing maintenance without running the risk of triggering cancers, there’s absolutely no reason why we couldn’t live well past several centuries, if not more. After all, some organisms found ways to live for a very long time and at least one creature known to science is practically immortal, as we mentioned already. Yes, this is far, far easier said than done and the biology of aging is very complex, but it shows that an entropic Grim Reaper isn’t out to get us when our time is officially up according to a physical law.