Final answer:
Smaller inversions are likely to produce viable gametes because they involve only a minor part of the chromosome and maintain the gene functionality. They generally do not cause significant genetic imbalances and can contribute to increased genetic variation and the evolution of new species.
Step-by-step explanation:
Smaller chromosome inversions, such as the pericentric inversion in chromosome 18 related to human evolution, are more likely to produce viable gametes because they involve only a small portion of the chromosome and therefore have a minor impact on the overall arrangement of genetic material. As opposed to larger inversions which can disrupt many genes and regulatory regions, small inversions might preserve the integrity of most genes, thus allowing them to still function normally. During meiosis, homologous chromosomes with small rearrangements can often align and pair effectively, reducing the likelihood of creating gametes with significant genetic imbalances. Additionally, small inversions can sometimes lead to increased genetic variation and even foster the evolution of new species, as seen with humans and our genetic differences from chimpanzees.