If it hadn't been for a lack of concentration, Onesmo ole-MoiYoi's plans to be a cattle herder might have worked out. As a boy growing up in a Maasai village on the border of Tanzania and Kenya, he regularly took charge of the community's herd, often numbering some 800 cows. But his lack of concentration led to him being relieved of his cattle-caring tasks and sent to school - which set him on the path to becoming one of Africa's top scientists.