Final answer:
The smaller linkage disequilibrium blocks in African populations are most likely due to the fact that these populations have been evolving longer since the African population is the most ancient human lineage, which has allowed for more recombination and more mutations over time.
Step-by-step explanation:
The likely explanation for the smaller size of the linkage disequilibrium (LD) blocks in African populations compared to non-African populations is C) More generations since the African population was founded. The human populations in Africa have the oldest genetic lineage, which suggests that they have been evolving for a longer period. This longer period has allowed more recombination events to break up LD blocks, leading to smaller blocks compared to non-African populations, which have gone through a population bottleneck during their migration out of Africa. This bottleneck reduced genetic diversity and, consequently, resulted in larger LD blocks due to fewer recombination events.
When humans migrated out of Africa, the founder effect and the population bottleneck played a significant role in determining the genetic makeup of the human populations that settled in other parts of the world. Moreover, genetic drift has a more pronounced effect on smaller populations, leading to a less diverse genetic structure.
Populations in Africa have had more opportunities for mutation and adaptation over a longer time frame than populations that left Africa. This is evidenced by the wider genetic variation in African populations.