Although it is unclear when the AMY1 gene copy number began to increase, it is known and confirmed that the AMY1 gene existed in early primates. Chimpanzees , the closest evolutionary relatives to humans, were found to have 2 diploid copies of the AMY1 gene that is identical in length to the human AMY1 gene,  which is significantly less than that of humans. On the other hand, bonobos , also a close relative of modern humans, was found to have more than 2 diploid copies of the AMY1 gene.  Nonetheless, the bonobo AMY1 genes were sequenced and analyzed, and it was found that the coding sequences of the AMY1 genes were disrupting, which may lead to the production of dysfunctional salivary amylase.  It can be inferred from the results that the increase in bonobo AMY1 copy number is likely not correlated to the amount of starch in their diet. It was further hypothesized that the increase in copy number began recently during early hominin evolution as none of the great apes had more than two copies of the AMY1 gene that produced functional protein.  In addition, it was speculated that the increase in the AMY1 copy number began around 20,000 years ago when humans shifted from a hunter-gatherer lifestyle to agricultural societies, which was also when humans relied heavily on root vegetables high in starch.  This hypothesis, although logical, lacks experimental evidence due to the difficulties in gathering information on the shift of human diets, especially on root vegetables that are high in starch as they cannot be directly observed or tested. Recent breakthroughs in DNA sequencing has allowed researchers to sequence older DNA such as that of Neanderthals to a certain degree of accuracy. Perhaps sequencing Neanderthal DNA can provide a time marker as to when the AMY1 gene copy number increased and offer insight into human diet and gene evolution.
2. Have any been selected against?
3. Given enough generations, would you expect one of these alleles to completely disappear from the population?
Why or why not?
4. Would this be different if you started with a larger population? Smaller?
5. After hundreds or even thousands of generations both alleles are still common in those of African ancestry.
How would you explain this?
6. The worldwide distribution of sickle gene matches very closely to the worldwide distribution of malaria (Figure 7). What is the significance of this?