Final answer:
Evolution has not eliminated malaria due to the adaptive nature of the malaria parasite, the evolution of drug-resistant strains, and the fact that certain genetic adaptations in humans, like the sickle-cell trait, persist due to their advantages in malaria-endemic environments. Despite global reduction efforts, including vaccines and insecticide-treated nets, malaria remains prevalent due to the rapid evolution of the parasites and challenges in creating long-term effective treatments.
Step-by-step explanation:
The reason evolution hasn't gotten rid of malaria is primarily due to the complex interaction between the evolving malaria parasite, human genetic adaptations, and environmental factors. The malaria-causing parasites, primarily Plasmodium falciparum and Plasmodium vivax, have evolved resistance to drugs intended to treat the disease. Additionally, the mosquitoes carrying the parasites have developed resistance to insecticides used to control their populations. Moreover, genetics play a role in the coexistence of humans and malaria. For example, individuals with sickle-cell trait (heterozygous AS) have a protective advantage against malaria, which keeps the gene present within the population, especially in malaria-endemic regions. Despite significant reduction efforts and the development of prevention measures such as insecticide-treated bed nets and research towards effective vaccines, malaria remains a major cause of death, particularly among children in Africa.
Organisms, including pathogens like Plasmodium, are constantly evolving in response to environmental selective pressures. An infection cycle can see the evolution of the parasite in response to the selective pressure of anti-malarial drugs. As the fight against malaria continues, researchers and health organizations make concerted efforts worldwide, yet the adaptation and survival of the parasite continue to pose significant challenges in eradicating the disease.