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ld manuscripts from different cultures that have a long history behind them have taught us that we are not immortal, but our ancestors once had a life span of hundreds of years. Until 1961 we thought based on our knowledge that cells within an organic body are immortal when it comes to the aging process. We as humans age, but our cells have the same abilities.

Until 1961 we turned to different religions, cultures, and other historical sources to gain some understanding as to why we age. Science did not quite understand it, therefore it wasn’t able to give a reason behind the natural aging process. That was until 1961 when a biomedical expert made a discovery that changed the medical world forever.

Life of Leonard Hayflick

Hayflick was born in Philadelphia, Pennsylvania on the 20th of May, 1928. His parents, Edna Hayflick and Nathan Hayflick were working in the medical field which is a factor in Hayflick’s attraction to science and also biomedicine. What really pushed him forward to becoming a scientist in the medical field was at his birthday when he was turning nine. His uncle brought him a chemistry set as a birthday present.

Later on, in his teenage years, his parents built him a small biology and chemistry laboratory in the basement of their house. Once he started going to John Bartram High School in Philadelphia, Hayflick was so knowledgeable that he was the one correcting his chemistry teacher.

Hayflick was supposed to start studying at the University of Pennsylvania in 1946, but he had postponed his studies for military service. After his military service from 1946 to 1948, he returned to continue his studies. After graduating in 1951, he was hired as a research assistant in bacteriology. Although the job was good, he loved the environment within the University of Pennsylvania, which is why he returned to do a Master’s degree. Once he graduated, he won a fellowship to a Ph.D. program in medical microbiology and chemistry. He received his Doctorate in 1956.

An accidental discovery?

Hayflick in the lab in 1960 (Source: University of Pennsylvania Archives)

At the Wistar Institute in 1958, Hayflick began to study whether or not viruses could cause cancers in humans. That is why he would extract the viruses said to cause cancer and place them into normal healthy human cells to see if this was the case. In order to make the study unbiased, he had to use multiple samples, this meant growing more cells. Working on the culture of cells, he noticed something out of the ordinary, an older group of cells stopped dividing and he didn’t understand why.

The cells were not dead as they kept metabolizing, but they would not divide anymore. After looking at other cell cultures, he noticed that most of them would stop dividing about 50 cell population doublings.

In order to understand why this is quite unusual, here is a quick science lesson. Within our life, all our cells divide, this is a process that cannot be stopped. With each division, the telomeres that can be found at the end of each Chromosome get shorter and shorter to the point where they become very short. At that point, the cells stop dividing.

A representation of a cell dividing and with each division the telomeres get shorter (Source:CleanPNG)

Up to that point, scientists believed that the natural aging process was linked to the source of life, something that even to this day we are not able to understand or comprehend. Upon discovering this about the cells, Hayflick stopped his research of cancerous cells and focused on what today is known as gerontology (the study of the aging process).

In 2 years of research, he discovered that cellular aging was linked to the age of our human body and it is the reason why we only live around 125 years. His paper was published in 1961 entitled “The serial cultivation of human diploid cell strains.” In another study conducted, he looked at cells collected from different parts of the body as well as compared the cells collected from adults and fetuses.

All of the cells were dividing about 40 to a maximum of 60 times before stopping. Once they have stopped they would degenerate and die. The same applies to humans once they reach senior age, and this is what is the cause of natural death. The body degenerates and therefore it dies. The theory is very well described in his paper, as he mentions that the length of telomeres presented in different cells can take more or less time to shorten to the point where the cell division stops.

The Science behind it

Some cells divide only 40 times before they stop because due to the length of the telomers, also proving that every DNA is quite Unique. What this means is prof to why some people age quicker than others, it all comes down to genes. At around 60 divisions (if taken in correlation with the age of a person), the age of that person should be around 125 years old, and due to good genes containing longer telomeres, they manage to reach such an age.

A cell could complete mitosis, or cellular duplication and division, only forty to sixty times before undergoing apoptosis and subsequent death. As our bodies are made up only of cells, this would explain why death from old age is a thing. Also, the paper shows that with every cellular duplication and division, the cell itself becomes more fragile, sort of weaker, and less efficient at the mitosis process.

Presenting the lifecycle of cells that are in the subcultivation process (duplicating and dividing) from Heyflick’s study in 1961. (Source: ScienceDirect)

Above we can see the study conducted by Heyflick in 1961 where he tried to see how many times can a cell duplicate and divide within a cellular culture. When the 50th mitosis is complete, the cell stops and quickly begins the apoptosis process where the cell dies.

This is a perfect representation of the human aging process. With time as we become older, our bodies weaken, so do all the senses such as sight or hearing and most importantly, the healing process of any wound is slowed down due to cells taking longer to regenerate. As the cells are shown in the study and as in the cell of every organism, everything becomes slower and more difficult. Now when you hear old people complaining about pain and life becoming harder and harder you will understand why.

If it weren’t for Heyflick, we would still probably not understand the process of aging. Of course, there are much newer studies out there that give a better-defined explanation of the aging process. Isn’t it interesting how the most important discoveries within the medical field happened by accident? In this case, it was not really an accident, but a small detail within another study that could have been simply overseen.

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