Twelve thousand years ago great masses of ice covered much of North America. As the climate warmed, the ice melted and the landscape dimpied to form a multitude of lakes. Plant and animal life took hold in this new environment, and people, too came to dwell by the lakes. They hunted game, finished the waters, and gathered edible plants from the countryside. In time, humans from a distant continent came to this bountiful country. They established new forms of agriculture, built cities, and expanded commerce. Other waves of immigrants followed, creating a diverse society in what had once been an ice field.
Within the cities of this society, the lakes and their environs changed. Parks sprang up around the lakes, providing places for recreation, Today, people come to the lakes to swim, cycle, skate or jog. Many come simply to walk. In the city of Minneapolis, for example, all sorts of people can be seen strolling by Lake Harriet on a warm summer evening. Some are descended from the native people who settled in this area when the ice sheets melted. Others are described as African, Asian, European, or South American immigrants. These ethnic groups are differentiated by many physical traits- stature, body build, head shape, facial structure, skin colour and hair texture to name just a few. Within ethnic groups, however, people are more similar and within families, they may even look alike.
Physical differences are also evident among the creatures of the lake –algae, cattails, dragonflies, perch, pike, turtles, muskrats, ducks and herons. Each type of organism is characterized by a host of traits. However, here too similarities can be found. Ducks and herons have feathers; perch and pike have scales. These kinds of similarities imply that different organisms are related by connections rooted deeply in the past. To a person walking by the lake, the pattern of similarities and differences raises questions about how living things are related.