Cancer – An Example of Evolution by Natural Selection
Cancer is a group of diseases that begins when cells, the building blocks of our body, start growing out of control and crowding out normal cells. The disease can lead to many different kinds of tumors, each with its own specific features.
When a cancer is diagnosed, medical professionals use tests to find out what kind of cancer it is and how far the cancer has spread. Most of these tests are designed to help prevent and treat the disease by finding it early, when it is often smaller and easier to treat. That is why it is important to get regular screening tests such as mammograms, colonoscopies, and prostate exams.
Most cancers are caused by DNA changes, or mutations, that allow abnormal cells to grow and divide without being controlled. Some of these gene changes are passed down from parents (inherited mutations) and others can happen during life. These genetic changes can happen because of things such as:
Cells are the basic units that make up all living organisms, from single-celled bacteria to multicellular organisms like plants and animals. They are the fundamental building blocks of our bodies and all tissues and organs in them. In most of our bodies, cells only grow and die as they need to, replacing old or damaged cells. But sometimes, the growth process goes wrong and new cells keep forming when they aren’t needed and old cells don’t die when they should. The result is a mass of abnormal cells that can grow, spread, and even invade other parts of the body. This is cancer.
The earliest descriptions of cancer referred to a large tissue mass, or tumor, that seemed to take up space in the body and to be growing fast and spreading throughout the tissues of the body. These early descriptions were consistent with the evolutionary sense of cancer going back millennia.
As we learned more about how cancer develops, we began to understand that it was a group of diseases with many different kinds of tumors. Earlier descriptions of the disease were inconsistent with the biological understanding of cancer, which was that it was an example of evolution by natural selection.
Natural selection is the process by which the environment selects for traits that improve a living thing’s chance of survival and reproduction, including resistance to disease or ability to compete for resources or withstand environmental hazards. Cancers are a perfect example of this: genetic changes that give them advantageous characteristics, such as ability to resist apoptosis or to evade the immune system, are selected for in the tumor microenvironment.
These genetic changes and selective pressures lead to the formation of a cancer population that eventually evolves to a lethal phenotype. This evolutionary perspective takes the mystery out of how and why cumulative mutations accumulate to form a cancer. It also helps us see how, in a predictable and orderly fashion, cancers can be treated with drugs that slow or stop the evolution of the cancer cells into lethal phenotypes.
Cancer is a group of diseases that begins when cells, the building blocks of our body, start growing out of control and crowding out normal cells. The disease can lead to many different kinds of tumors, each with its own specific features. When a cancer is diagnosed, medical professionals use tests to find out what kind of cancer it is and how far the cancer has spread. Most of these tests are designed to help prevent and treat the disease by finding it early, when it is often smaller and easier to treat. That is why it is important to get regular screening tests such as mammograms, colonoscopies, and prostate exams. Most cancers are caused by DNA changes, or mutations, that allow abnormal cells to grow and divide without being controlled. Some of these gene changes are passed down from parents (inherited mutations) and others can happen during life. These genetic changes can happen because of things such as: Cells are the basic units that make up all living organisms, from single-celled bacteria to multicellular organisms like plants and animals. They are the fundamental building blocks of our bodies and all tissues and organs in them. In most of our bodies, cells only grow and die as they need to, replacing old or damaged cells. But sometimes, the growth process goes wrong and new cells keep forming when they aren’t needed and old cells don’t die when they should. The result is a mass of abnormal cells that can grow, spread, and even invade other parts of the body. This is cancer. The earliest descriptions of cancer referred to a large tissue mass, or tumor, that seemed to take up space in the body and to be growing fast and spreading throughout the tissues of the body. These early descriptions were consistent with the evolutionary sense of cancer going back millennia. As we learned more about how cancer develops, we began to understand that it was a group of diseases with many different kinds of tumors. Earlier descriptions of the disease were inconsistent with the biological understanding of cancer, which was that it was an example of evolution by natural selection. Natural selection is the process by which the environment selects for traits that improve a living thing’s chance of survival and reproduction, including resistance to disease or ability to compete for resources or withstand environmental hazards. Cancers are a perfect example of this: genetic changes that give them advantageous characteristics, such as ability to resist apoptosis or to evade the immune system, are selected for in the tumor microenvironment. These genetic changes and selective pressures lead to the formation of a cancer population that eventually evolves to a lethal phenotype. This evolutionary perspective takes the mystery out of how and why cumulative mutations accumulate to form a cancer. It also helps us see how, in a predictable and orderly fashion, cancers can be treated with drugs that slow or stop the evolution of the cancer cells into lethal phenotypes.