Do You Want to Live Forever?

Recently, I completed a project for my biology class and learned some super interesting information that I wanted to share. Below is the entire transcript I wrote before realizing it was way beyond the project's required time limit (I edited a little bit). If you want a shortened version (it's basically the first half of the article), there is also a video down below.

What if you could live forever? Would you do it? Living forever has its advantages and disadvantages that are still being argued to this day. Nevertheless, scientists have been studying the aging process and its effects on a living organism for a long time in hopes of finding the key to immortality.

An organism’s life span, according to scientists, is a combination of two opposing forces: the buildup of genetic damage and the response to that damage. The damage is aging and the response is longevity, which is expecting to live a long life. In other words, our bodies are constantly fighting aging, but in the end, we lose. This genetic damage is anything from loss of DNA (genetic material) to mutations in the DNA. One theory suggests that oxygen-containing molecules created by metabolism produce damage (called oxidative damage or oxidative stress) over a long period of time; we will see some appearances of this theory later in the article.

However, the most supported research is about telomeres (shown above), which are sections of unnecessary DNA located at the end of chromosomes (the form DNA takes when it undergoes replication). When DNA replication occurs, it skips over a bit of DNA at the end of each chromosome. This is where telomeres come in. As cells divide, the telomeres become shorter each time until they’re completely gone. At this point, the cells are in “cellular senescence,” which is when a cell no longer divides. In other words, the cells have reached their replication limit. Human cells reach cellular senescence after approximately 50 divides. If cells didn’t have a limit, the organism would be more prone to cancer because the cells wouldn’t stop dividing. So, in a way, this aspect of aging protects us from cancer.

Over the years, scientists have developed ways to combat aging but not fully stop it. Most of these experiments were achieved through animal testing. Cloning is a relatively new concept, Dolly the sheep being the first-ever clone in 1996. A recent study shows that the cloning of cattle actually seems to reset its telomere length. This means that the telomere would probably never disappear, therefore protecting the important DNA. However, since the study is so recent, scientists will not know whether it affects aging until a few years down the road.

Another option is cell transplantation. A common example of this is stem cells. Stem cells are "general" cells that can turn into a particular type of cell if needed. For instance, if there was a lack of liver cells, a stem cell can turn into a liver cell. Stem cells have been a hot topic in the medical field in recent years because scientists can use stem cells from the lab to help cure diseases by replacing damaged cells. When there is a defective gene, it can be simply replaced by a healthy version of it; the body would accept it and would regenerate normally. Tests have been performed on immunodeficient (when the immune system is too weak to fight off infections and diseases) mice with isolated cow and human adrenal gland cells. The results were functional adrenal tissue that was similar to the normal version. Theoretically, we could replace every part of our body if needed.

As mentioned before, oxidative stress is thought to be a cause of aging. Despite not having enough evidence to completely prove this theory yet, scientists have created a drug containing enzymes that reduce oxidative stress. This drug has been shown to increase the average lifespan of nematodes, which are a type of worm, by roughly 50% and reverse premature aging due to high oxidative damage. The evidence indicates that oxidative stress is a likely cause of aging in nematodes.

Fun Fact: Nematodes are parasites that come in a variety of sizes; the largest of them inhabit whales and can grow up to 7 meters in length!

The most promising data points to caloric restriction (CR for short), or in layman’s terms, a diet. By decreasing the number of calories an organism consumes, its average and maximum lifespan increase; this change was linked with changes in metabolism. These results have been demonstrated with rodents, yeast, nematodes, and fruit flies. Tests have also shown that the risk of cancer and other diseases is reduced in rodents. According to the National Institute of Aging, CR also seems to boost the function of genes that mend or counter cell damage. In short, CR can extend an organism’s lifespan and reduce the risk of age-related diseases.

Humans often look towards nature for answers, and in this case, there are quite a few organisms who seem to be “biologically immortal.” Scientists don’t like the term “biologically immortal” because these species can still die. However, aging does not seem to be a cause of death for these organisms.

The bristlecone pine, for example, can live over 5000 years—and counting! Nobody knows what its secret to survival is yet, but scientists believe that it has something to do with the fact that the cells of this tree divide more slowly than other organisms. Therefore, DNA damage and loss occurs at a much slower rate. According to scientists, the tissue of the tree functions the same no matter how old the tree is, indicating that it doesn't age.

Another creature that doesn’t seem to age is the hydra. Generally, small organisms tend to have shorter lifespans, so living 4 years is a long time for a tiny creature like the hydra. Scientists don’t know exactly how long a hydra can live because they succumb to diseases easily. It has special stem cells that are crucial for reproduction since hydras literally form clones of themselves. However, scientists are more interested in a unique protein that these stem cells have called FoxO. This protein is thought to be an anti-aging protein. If this protein was taken away, the hydra would age. Humans that live past 100 years also tend to have more of this protein.

Fun Fact: The hydra gets its name from its ability to regrow large portions of its body—just like the Greek myth!

The oldest known organism in the animal kingdom is Ming the ocean quahog, a type of clam. Ming lived for 507 years. Unfortunately, when scientists pulled Ming out of the water to study it, it died shortly after. However, from the research they obtained, scientists believe its long life was primarily due to its resistance to oxidative stress.

Lobsters are known for being able to regrow their limbs, but the key to their long life, which can last up to 140 years, is that they can regenerate their telomeres. They have enzymes called telomerase that add onto their telomeres so that they never disappear completely during DNA replication. However, eventually, lobsters grow out of their shells faster than they can molt and grow a new one, which causes them to die, so their immortality is theoretical.

One organism that is particularly fascinating in regards to biological immortality is the immortal jellyfish. Unlike butterflies and frogs, it has a seemingly endless life cycle. In response to environmental stress such as starvation or injury, an adult immortal jellyfish can change back into an immature polyp and restart its life cycle from that stage.

Aging has been a mystery to scientists for a long time, but recently, there have been some breakthroughs. Although we are nowhere near immortality, we are discovering the secrets of aging and are becoming closer. Perhaps one day, we can live forever.

Shortened Video Version (~ 5 min): https://drive.google.com/file/d/153YeQ3I2s89fM3sn4MCglBC7jGh6iin7/view?usp=sharing

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Barras, Colin. “The Animals and Plants That Can Live Forever.” BBC, 19 June 2015, www.bbc.com/earth/story/20150622-can-anything-live-forever.

Berthold, Emma. “The Animals That Can Live Forever.” Australian Academy of Science, 9 June 2018, www.science.org.au/curious/earth-environment/animals-can-live-forever.

“Biology of Aging.” National Institute on Aging, www.nia.nih.gov/about/budget/biology-aging-3.

Fridovich-Keil, Judith L. “Dolly.” Encyclopædia Britannica, 27 May 2020, https://www.britannica.com/topic/Dolly-cloned-sheep.

Johnson, F. Brad, et al. “Molecular Biology of Aging.” Cell, vol. 96, no. 2, 1999, www.cell.com/cell/fulltext/S0092-8674(00)80567-X.

Moffit, Mitchell, and Gregory Brown. “The Science of Aging.” YouTube, uploaded by AsapSCIENCE, 7 Mar. 2013, www.youtube.com/watch?v=BkcXbx5rSzw.