A big, powerful male gorilla is much more likely than a smaller, weaker gorilla to become the population's silverback, the pack's leader who mates
far more than the other males of the group. The pack leader will, therefore,
father more offspring, who share half of his genes, and are thus likely to also
grow bigger and stronger like their father. Over time, the genes for bigger
size will increase in frequency in the population, and the population will, as a
result, grow larger on average.
Determine the Mechanism of Evolution observed in the Scenario: