Final answer:
The secular trend in physical growth and development is primarily influenced by cultural and environmental factors.
Step-by-step explanation:
The changes in the patterns of physical growth and development that are known as the secular trend are most likely caused by cultural factors. Cultural factors, such as regional standards for attractiveness, have influenced physical characteristics like skin tone, height, and body morphology. Additionally, environmental factors, such as nutrition and exposure to stressors, can impact biological development in individuals.
Developmental biology also highlights how environmental factors, like maternal nutrition or exposure to infections, can affect fetal development and lead to different physical outcomes. Furthermore, epigenetics, the change in gene expression due to environmental exposure and mutations, can result in heritable changes in DNA that impact physical traits.
In summary, the secular trend in physical growth and development is primarily influenced by cultural and environmental factors, which can shape biological development in individuals over time.