![the story of the human body: evolution, health, and disease. mismatch the story of the human body: evolution, health, and disease. mismatch](http://pressbooks-dev.oer.hawaii.edu/explorationsbioanth/wp-content/uploads/sites/139/2020/07/image14-1-1.png)
![the story of the human body: evolution, health, and disease. mismatch the story of the human body: evolution, health, and disease. mismatch](https://miro.medium.com/max/1400/1*9UVdOrQoT2L1D65ZQWx06w.jpeg)
![the story of the human body: evolution, health, and disease. mismatch the story of the human body: evolution, health, and disease. mismatch](https://images-na.ssl-images-amazon.com/images/I/71hsrpkyWhL._AC_UL115_.jpg)
The final and most important point about adaptation is really a crucial caveat: no organism is primarily adapted to be healthy, long-lived, happy, or to achieve many other goals for which people strive. Your body is a jumble of adaptations that accrued over millions of years. Perfection may be unattainable, but bodies function remarkably well under a wide range of circumstances because of the way evolution accumulates adaptations in bodies much like the way you probably keep accumulating new kitchen utensils, books, or items of clothing. Natural selection rarely, if ever, achieves perfection because environments are always changing. Stated formally, natural selection occurs whenever individuals with heritable variations differ in the number of surviving offspring they have compared to other individuals in the population (in other words, they differ in their relative fitness). Like it or not, natural selection just happens.
![the story of the human body: evolution, health, and disease. mismatch the story of the human body: evolution, health, and disease. mismatch](https://images-na.ssl-images-amazon.com/images/I/41oZy7BlFpL._SL500_PIsitb-sticker-arrow-big,TopRight,35,-73_OU01_AA130_.jpg)
If you agree that variation, heritability, and differential reproductive success occur, then you must accept that natural selection occurs, because the inevitable outcome of these combined phenomena is natural selection. Often, differences in reproductive success seem small and inconsequential (my brother has one more child than I do), but these differences can be dramatic and significant when individuals have to struggle or compete to survive and reproduce. The third and final phenomenon is differential reproductive success: all organisms, including humans, differ in how many offspring they produce who, themselves, survive to reproduce. Your height is much more heritable than your personality, and which language you speak has no genetically heritable basis at all. The second phenomenon is genetic heritability: some of the variations present in every population are inherited because parents pass their genes on to their offspring. Your family, your neighbors, and other humans vary widely in weight, leg length, nose shape, personality, and so on. The first is variation: every organism differs from other members of its species. Natural selection is a remarkably simple process that is essentially the outcome of three common phenomena. Even die-hard creationists recognize that the earth and its species have not always been the same. Yet, despite much controversy and passionate ignorance, the idea that evolution occurs should not be contentious. Other mismatch diseases arise from the modern lifestyle:.Many of today’s most common diseases are “mismatch diseases” that originated with the development of agriculture:.Highly efficient sweat glands to increase endurance beyond most mammals.Shift of diet away from fruits and to meat and grains.Key biological adaptation among early humans include:.The domain of disease and resistance to disease is one of the most important changes.The human body has undergone significant genetic change.The common assumption that humans stopped evolving biologically since the advent of civilization is false.If you would like to learn more about how biology has affected human history, read my book From Poverty to Progress: How Humans Invented Progress, and How We Can Keep It Going. Liebermann explores the genetic history of the human body, and how genetics still plays a role in human history. If you enjoy this summary, please support the author by buying the book. Title: The Story of the Human Body: Evolution, Health and Disease