Mendel observed that organisms develop from a given genotype, a specific set of ``instructions'' encoded as genes, to present a variety of phenotypes, such as whether the skin of a pea is wrinkled or smooth, or the eyes of a fly are white or red. For certain traits, the phenotype produced may depend upon the genotype and the specific environment in which the organism lives.
The introduction of a mutation, a change in the organism's genome, leads to a change in genotype that may result in a change in phenotype. In certain instances, a change in phenotype may change the organism's ``fitness'' or its ability to survive and breed. The concept that an individual organism can change, and that the survival of that organism may depend on how those changes effect their fitness, is central to the theory of natural selection, one theory that has been proposed to explain the great diversity of life on Earth.
The ``rust heads'' can also be appreciated through this evolutionary lens. Each rust head has a specific genotype, created by the artist as a pattern of iron filings on fabric, the arrangement of the fabric, and the placement of the salt. That particular ``genotype,'' in combination with the environment of flowing wind and water, leads to a resulting ``phenotype'' that we observe as the image transferred to the concrete, the rust head of the scientist.
Variations in the environment may cause the same genotype, the particular arrangement of filings, fabric and salt, to produce a variety of phenotypic variations. These variations are visible in a series of images that are ``identical twins'' at the level of filings, fabric and salt, but unique as the images have evolved in varying environments. The artist may also introduce variations in the genotype, by altering the arrangement of filings in creating the image of a particular scientist. And in the mind of the artist, the resulting images may show varying levels of aesthetic appeal or fitness, influencing the future generations of heads through a process of natural selection and evolution in art.
