Multigene families include two or more nearly identical genes or genes sharing nearly identical sequences. A classical ex is the set of genes for globin molecules, including genes on human chromosomes 11 and 16.

In comparing the genomes of humans and those of other higher primates, it is seen that humans have a large metacentric pair we call chromosome #2 among our 46 chromosomes, while the other primates of this group have 48 chromosomes and any pair like the human #2 pair is not present; instead the primate groups each have two pairs of midsize acrocentric chromosomes. What is the most likely explanation?

A. The ancestral organism had 48 chromosomes and at some point a centric fusion event occurred and provided some selective advantage.

b. Chromosome breakage results in additional centromeres being made in order for meiosis to proceed successfully.

c. At some point in evolution, human ancestors and primate ancestors were able to mate and produce fertile offspring, making a new species.

d. The ancestral organism had 46 chromosomes, but primates evolved when one of the pairs broke in half.

e. Transposable elements transferred significantly large segments of the chromosomes to new locations.