Final answer:
The boundary between the African and Eurasian plates is not clear due to Earth's spherical shape, curved and segmented boundaries, and the influence of geographical features on migrations and connections between regions.
Step-by-step explanation:
The boundary between the African and Eurasian plates isn't clear due to several factors. Firstly, Earth is a sphere, so the boundary between two tectonic plates doesn't always appear as a straight line. It can be curved or segmented. Additionally, the topography of the continents provides evidence of plate boundaries, but not all mountain belts formed at plate boundaries are straight lines. Lastly, geographical features like deserts and savannas can act as barriers or encourage migrations, which can influence cultural and historical connections between regions.