THE
MYSTERY OF CHILDHOOD LEUKEMIA: AN EVOLUTIONARY APPROACHTHE
MYSTERY OF CHILDHOOD LEUKEMIA: AN EVOLUTIONARY APPROACHThis website was created by Shannon McGlauflin, Jolene Munger, and Rebecca Nelson as a class project for ANTP 347: “Humans, Disease, and Death,” a class focusing on evolutionary medicine. This approach applies the principles of biological evolution to the diseases and conditions that affect people today, viewing them as the products of natural selection. Each disease has a proximate explanation, which explains why a particular person as opposed to others has come down with it, as well as an evolutionary explanation, which explains why the human population is subject to this disease at all. Evolutionary medicine seeks to understand why diseases are still present in the human population, why natural selection has not eliminated them. This approach is theoretical, and although its explanations often lead to new therapies, these must be rigorously tested in clinical trials before they are used to help patients.
Leukemia
Leukemia, also known as leukaemia, is the most prevalent cancer among children in industrialized nations. It is a cancer of the bone marrow and blood, which occurs when bone marrow creates excess, malformed white blood cells. Leukemic cells circulate through the body with the blood, replacing normal cells and blocking their production. Leukemia is divided into acute and chronic forms based on the rate of disease progression.
The chronic forms of the disease are less severe, and the prognosis for patients with chronic leukemia is better than for those with acute leukemia. Leukemia is also classified according to the type of cell affected: lymphoid, comprised of lymphocytes (the body's immune system T- and B- cells), or myeloid, including granulocytes, which destroy bacteria, and monocytes, which produce macrophages. Thus, there are four basic types of leukemia:
Acute Lymphocytic Leukemia (ALL)
Acute Myelogenous Leukemia (AML)
Chronic Lymphocytic Leukemia (CLL)
Chronic Myelogenous Leukemia (CML)
Why has natural selection not eliminated leukemia from the human population? Evolutionary biologists term cancer a “disease of civilization,” because in general cancer only becomes a major disease when people live long enough to express the disease, and lead lifestyles that are different from how people used to live. Three of the major types of leukemia-- AML, CLL, and CML-- tend to strike people over the age of 45, and for most of human history the average life expectancy has been far shorter than that. This may explain why adult-onset leukemias have not been a selection factor over time, but what about the leukemias like ALL that affect young children before they reach a reproductive age? This website will postulate an evolutionary explanation for childhood leukemia.
Created by Shannon McGlauflin, Jolene Munger, and Rebecca Nelson, 2005