The same applies here.Sickle cell trait describes a condition in which a person has one abnormal allele of the hemoglobin beta gene (is heterozygous), but does not display the severe symptoms of sickle cell disease that occur in a person who has two copies of that allele (is homozygous). Those who are heterozygous for the sickle cell allele produce both normal and abnormal hemoglobin
Sickle cell disease is a blood disorder wherein there is a single amino acid substitution in the hemoglobin protein of the red blood cells, which causes these cells to assume a sickle shape, especially when under low oxygen tension. Sickling and sickle cell disease also confer some resistance to malaria parasitization of red blood cells, so that individuals with sickle-cell trait (heterozygotes) have a selective advantage in environments where malaria is present.
More simply, heterozygous individuals have some resistance to malaria and low incidence of Sickle Cell Disease. This is an advantageous position which promotes heterozygotes in the population. A large number of heterozygous individuals will result in consequent homozygous individuals who exhibit full-blown Sickle disease but nevertheless typically survive to reproduce, unlike children who die of malaria.
Malaria is most common in the African region which accounts for 93% of infections and 94% of deaths. In 2018 that would be 212M infected and 381K dead or a 0.18% death rate. This region also accounts for 70% of the world's children with SCA, with approx 310K births per year. The SCA childhood survival rate in Africa is 10% for children without access to treatment, and 50% with access to treatment. Of the remainder, 10% will be dead by 23 and the life expectance for the remaining males is 38, and female is 42.
So allow me to do the math for you. Without access to healthcare, which is the majority of the African region, 10 out of 100 will live to see their 12th birthday, of those ten, nine will live to see their 23rd birthday, who will then begin die off, not surpassing 38 -42. With access to healthcare which the majority cannot afford to pay for [remember there is no free healthcare] 50 out of 100 will live to see their 12th birthday, of those fifty, forty-five will then begin to die off, not surpassing 38-42. The life expectancy in Sub-Saharan Africa is 62 years.
The difference between you and me is that you believe sickle cell disease is beneficial. It is as beneficial as malaria or cancer. All diseases are bad. Similar to arguing that hemophilia is good because it drastically reduces the risk of forming blood clots, which bring about stokes, pulmonary embolism, deep vein thrombosis, heart attacks, etc
And this is not evidence of NS. At the most you have a mutation that brings about a terrible disease, that helps with another.