According to the market response model, it is increasing prices that drive providers to search for new sources, innovators to substitute, consumers to conserve, and alternatives to emerge. Taxing certain goods or services, and so increasing prices, should result in either decreased use of these resources or creative innovation of new sources or options. The money raised through the tax can be used directly by the government either to supply services or to search for alternatives. Many examples of such "green taxes" exist.Facing landfill costs, labor expenses, and related costs in the provision of garbage disposal, for example, some cities have required households to dispose of all waste in special trash bags, purchased by consumers themselves, and often costing a dollar or more each.The results have been greatly increased recycling and more careful attention by consumers to packaging and waste. By internalizing the costs of trash to consumers, there has been an observed decrease in the flow of garbage from households.

Scientists today are able to accurately date fossils, the rock-bound remains of organisms from past geologic ages. When fossils are arranged along a timeline, scientists can see gradual changes from simple to more complex life forms. In some cases, evolution through various intermediate forms over millions of years can be detected and compared to the present state of an organism. For example, the earliest known species of horse lived some 60 million years ago and, according to the fossil record, was shorter than 20 inches (50 centimeters) high at the shoulders. Successive rock layers yield fossils of increasingly larger horse species, culminating in the horses of today. As size changed, so did other aspects of the horses' anatomy: teeth became adapted to eating grass, the bones of the lower leg fused, and multiple toes evolved into a single toe surrounded by a hoof.