Biological Understanding

I was outside yesterday playing tag while babysitting for three little girls of the ages 4, 6, and 10. The youngest girl ran across a feather lying on the ground and picked it up to show the rest of us. Immediately after telling her sisters about the amazing find she had just made, both girls began to scold her and warn her of the diseases the feather contains. The six year old repeated that birds are dirty while the ten year old shrieked that she would catch the "bird flu" from the feather. After struggling to aruge that she had touched feathers before and not gotten sick, the four year old finally dropped the feather and ran into the house crying that she didn't want the "bird disease." Each of these children displays a different level of understanding of the biological process and is at a different stage of her mental development.
According to the criteria for biological understanding outlined in the chapter, Conceptual Development, the ten year old displays a clear understanding that germs can be found on matter from other living creatures and can cause illness. This is a concept she states, "Mom said," implying that her knowledge of feathers causing diseases is a nurtured concept passed on from her mother. She does not connect it with being a disgusting object but simply something undesirable to touch in order to avoid the consequences. The six year old understands the concept of illness, but is still having trouble distinguishing between biological reactions and emotional reactions. She believes that the feather is "yucky" and is therefore going to make her sick. She is however able to distinguish between the yucky-ness of the feather and the yucky-ness of green beans. The feather is found outdoors and is from a living creature that may carry germs. Green beans are yucky because they taste bad but they will not give you a disease if you eat them. Finally, the four year old displays a fairly naive understanding of illness. First, she believes in the "all or none" scenario where if she has touched one feather and not gotten sick she can therefore touch all feathers without getting sick. Once her sisters are able to persuade her to think differently, she thinks she will become immediately sick and begins to cry. She has no conceptual knowledge of the slow development of illnesses and the process of how germs pass.
The biological cue that all three children and their mother misinterpreted is that most diseases cannot pass from birds to humans becuase of the genetic basis of disease. Just as dogs with illnesses do not generally get their owners sick, disease carried by birds generally cannot cause humans to become ill. Such knowledge is not widely known in the general public and often causes scares such as the "bird flu" paranoia that circulated several years ago. Such differences in the level of biological understanding cause me to think that the majority of this type of conceptual development is due to nurture. People are not predetermined to learn false information about biology. We learn the majority of our knowledge of how the world works through teaching and through direct experience with the world. We must observe and test our own theories in nature everyday so we continually nurture the concept of biological processes.