Final answer:
The condition of small brain size in modern humans is called microcephaly, where there's a significant reduction in head and brain size, often leading to developmental issues. The encephalization quotient is used to measure brain size relative to body size in evolutionary studies. Island dwarfism is an evolutionary process that can result in smaller brain size in isolated environments.
Step-by-step explanation:
The pathological condition characterized by abnormally small brain size in modern humans is known as microcephaly. This condition is typified by a significantly smaller head and brain size than is typical for an individual's age and sex. Microcephaly can arise from a variety of genetic and environmental factors and is often associated with developmental delays and neurological complications.
Another related term is the encephalization quotient (EQ), which is a measure of brain size relative to body size, often used in studies of human evolution. The increase in EQ over time is known as encephalization, and it denotes the evolutionary trend of increased brain size in the genus Homo. This contrasts with conditions like microcephaly, where brain growth is impeded.
When examining fossil records, paleoanthropologists may use endocranial casts to infer brain size and shape in hominids and other primates. Additionally, island dwarfism is an evolutionary process that may lead to smaller body and brain size in isolated environments, such as islands, due to different ecological pressures such as limited resources and lack of predators.