Final answer:
The loss of genetic diversity in maize can be attributed to a genetic bottleneck, artificial selection, and genetic drift, which led to a reduction in allelic variation and a change in genetic structure from the original maize populations.
Step-by-step explanation:
The loss of genetic diversity in maize observed 4400 years ago can be explained by multiple factors that include a genetic bottleneck, artificial selection, and genetic drift. A genetic bottleneck occurs when a population's size is significantly reduced due to random events, such as natural disasters, which in turn can cause a drastic loss in genetic variation. This random reduction in population size and the resultant genetic effects can significantly alter the genetic structure of the surviving population.
Artificial selection, on the other hand, is a process where humans select for desirable traits in organisms, which can lead to a reduction in genetic variation as specific alleles are favored over others. In the case of maize, this strong selection likely meant that certain alleles advantageous for agricultural purposes were chosen, while others were discarded or ignored.
Lastly, genetic drift can cause allele frequencies to change by chance in small populations. This may occur alongside bottleneck events or in isolated populations where the chance events could substantially shift the genetic makeup over time. Both artificial selection and genetic drift represent mechanisms of evolutionary change that can lead to reduced genetic diversity within cultivated crops like maize.