Distinctions that are socially meaningful tend to be reflected in grammar. The huge importance accorded to age differences is hard-wired into lexical distinctions in many West African languages. In Bamanan (Bambara), siblings are differentiated primarily regarding age, and only secondarily according to gender: older siblings are designated kɔrɔ, younger ones dɔgɔ. The modifiers muso `woman’ and kɛ added to these words specify whether female or male siblings are referred to, but are not compulsory.
Wolof makes the same distinction: the term for elder sibling is mag, the one for younger sibling rakh. My personal favourite language Baïnounk Gujaher confirms the pattern: wanc is the word for older sibling, and udóón the one for younger sibling, without referring to the sex of these kin relations.
These terms do testify of a great sensitivity to age motivated by the link between age and superior social status. Being aware of age is important because the veneration of people of greater age, respect for their life experience and deference to them is common throughout the entire continent. It is therefore important to be aware of one’s age in relation to anybody one interacts with; and lexicalising this difference helps keeping track of where an ego is positioned with respect to others.