Eye color for a plausible argument stating that some eyes can or do change, based on chemical reactions and hormonal changes within the body. Studies on Caucasian twins, both fraternal and identical, have shown that eye color over time can be subject to change, and major demelanization of the iris may also be genetically determined. Most eye-color changes have been observed or reported in the Caucasian population with hazel and amber eyes. Carleton Coon created a chart by the original Martin scale. The numbering is reversed on the scale below in the (later) Martin–Schultz scale, which is (still) used in physical anthropology.
Ecological anthropology a shift towards applied ecological anthropology, political ecology and environmental anthropology. Ecological anthropology Ecological anthropology is a sub-field of anthropology and is defined as the "study of cultural adaptations to environments". The sub-field is also defined as, "the study of relationships between a population of humans and their biophysical environment". The focus of its research concerns "how cultural beliefs and practices helped human populations adapt to their environments, and how people used elements of their culture to maintain their ecosystems". Ecological anthropology developed from the approach of cultural ecology, and it provided a conceptual framework more suitable for scientific inquiry