Immortality seems to be brimming on the edge of everyone’s horizon. At least for those who dream we can turn science fiction into pure science. For instance, the immortal jellyfish who can infinitely go through transdifferentation, Turritopsis. It has a unique way of escaping death. Instead of having offspring and growing old to die, it has offspring and the grows into a polyp again. If humans could learn the secret behind this behavior immortality would be ours. At least in theory, but there are usually tradeoffs in nature.
The Turritopsis is a one of a kind Jelly fish. It is only about 5mm in size, once full grown. The males shoot their sperm into the water stream, and impregnate the females who carry eggs in their bellies. Once this is done the eggs mature in just a few days and then come out. After that they anchor themselves to rocks or other stationary surfaces where they feed on plankton. It can take several years for them to grow into adults. During this time they go from being one single polyp to making many more which are all connected through feeding tubules. After a signal for growth occurs they begin forming tubes down the sides. Soon the ridge like tubes form the body of the umbrella and then their tentacles form. They are now full grown jellies and ready to move on to the next stage. What is shocking is that there seems to be no limit on the number of times they can do this.
They have even spread all over the ocean, due to the ships which navigate from port to port. The jellies have found a solid object where they can be stationary. Now scientists are finding them all around the globe. Since they create so many polyps and offspring there is no limit to the amount of these which can exist in nature. They are however prey for larger animals. Being only 5mm makes it easy for larger predators to consume them as part of their diet. Forgoing this the jellies are immortal.
With humans the process could get a lot more complex. Since the Turritopsis has to actually reabsorb the tentacles and then revert into a polyp, it would be hard to define a point that would be safe for humans to commit the same acts. Something in this process has suited the jelly in evolution may not suit us at all. The problem is that transdifferentiation would require all of our organs to revert to some stage in the past. Being as we are multi celled organisms with complex digestive systems, and differentiated cells by the thousands it could get challenging. The signals which differentiate cells in the human body are currently under study. If we could utilize the methodology of the jelly it would be possible to revert all of our cells. However; the problem would arise in the terminal stage of this transdifferentiation. Since we begin as nothing more than gametes the potential to revert to this stage exists. If it was a controlled situation here we would transdifferentiate to a previous stage such as a baby, then it is likely that we humans would lose all memory of our previous selves. It could get more complex. Seeing as how organs would also have to transdifferentiate we would be facing the potential of dying while undergoing the process. Since this is not a natural event for humans we would have to know the amount of signals to give, the length and degree to which we wanted reverted, and hope that the body can accept the signals. Our DNA would have to undergo extensive repair, and basically we would need to reabsorb as many aged cells as possible. It would be a highly energy consuming and possibly painful situation. Since we have bones and an extensive nervous system the cells from the bones would have to be reabsorbed in a fast process which could cause instability, and pain in movement. The nervous system breaking down might send signals randomly since it would have to also be reabsorbed.
The ability of this jelly to transdifferentiate is a process which needs a lot of study. For us to understand what it the transition of cells from one type of mature somatic cell to another without a intermediate or pluripotent and progenitor stage is unique in this jelly. Humans have cells which do undergo those stages. For us the reversion of mature somatic cells to any other cell would need to include the intermediate process. If it could be eliminated then we would have mature somatic cells which would have differentiated, but to what extent is only a guess. During the embryonic stage a human fetus has three layers of tissue. The endoderm, mesoderm, and ectoderm. It is the invaginations of the ectoderm which forms the nervous tissue. Such changes mean pluripotent cell changes. Our stem cells have to commit to change, which is the pluripotent stage. Once it has reached this point the cell is not yet committed but is ready. After this a signal is given and the cell goes on to become another type of cell and then matures. The problem with humans transdifferentating would be in this area.
While it would be an interesting phenomenon to see humans revert to childhood and live indefinitely there is always an evolutionary cost. The price of that may be in suffering during the changes, something that may be forgotten later. But the duration of the change and the need for stationary existence might mean extreme danger. During this vital time of transdifferentiation humans may not be able to intake vital nutrients which could also hinder the process. It would be a tremendous expense of cells and energy. There would be some evolutionary cost to us. Perhaps in how we procreate, or worse, with the cycle beginning at intervals we are not aware of.
So while this makes for great speculation and even interesting fiction, for now that is simply all it is. We can be jealous of the immortal jelly who will seem to escape death even long after we are gone, but the cost to him is still unknown.While dreams of mortality and the way to induce it are still in the forefront of our minds, the reality seems to be a heavy chore. Perhaps the key to it is in the simplicity of the organism. Since jellies are not highly complex creatures and they lack the appendages and structure of our system they are unable to become highly complex. Part of their immortality may be in the slow growth and stationary period of their lives. In fact it may be why they are only 5mm. Since there is a price to be paid for everything. For now we can dream of living life as this immortal jelly, and envy his evolutionary trail, but while we do entropy and decay seem to belong to the best of us. The future may unlock all the doors, but having the key does not eliminate the price you pay for having it.