Characterization of Normal Mediolateral Angular Direction of Lower Eyelid Eyelashes in Different Age Groups.

Purpose: To characterize the normal eyelash mediolateral angular direction of the lower eyelid in different age groups.

Methods: Sixty patients were divided into 3 groups: G1 - 6 to 12 years; G2 - 20 to 35; and G3 - 60 to 85. Digital photographs were obtained and eyelids were divided in lateral, central, and medial portions.

The roots of multilevel selection: concepts of biological individuality in the early twentieth century.

As multilevel selection theory has gained greater acceptance over the past quarter-century, scientists and scholars have shown an increased interest in the theory's historical antecedents. Despite this interest, however, the early twentieth century remains largely unexplored. It is generally assumed that biologists thought "naively" about evolutionary dynamics during this era, and that their attempts to explain biological phenomena often lacked sophistication.