As further inbreeding occurred through the generations, the gene pool grew smaller and smaller, to the point that people of one language family all had the same or similar features.
Uzao ulipoendelea zaidi katika vizazi, ule utofauti wa chembe chembe za damu ulipungua zaidi, hadi kiwango kwamba watu wa lugha ya familia moja wote walikuwa na tabia moja.