New research has brought the first evidence of non-random mutation in human genes. It has challenged a core assumption at the heart of evolutionary theory. It showed a long-term directional mutational response to environmental pressure. Scientists have used a novel method. University of Haifa scientists showed that the rate of generation of the HbS mutation is higher in people from Africa than in people from Europe. The HbS mutation protects against malaria. In Africa malaria is endemic.
This mutation-specific response to a specific environmental pressure cannot be explained by traditional theories. We know that life arose by evolution. Previously scientists believed that mutations occur by accident to the genome. Natural selection or the survival of the fittest, favours beneficial accidents. The accumulation of these presumed genetic accidents leads in turn to adaptations.
This view always left open fundamental questions like the problem of complexity. The only alternative at the fundamental level conceived of up until now consisted of variants of Lamarckism. The organisms can somehow respond directly to their immediate environments with beneficial genetic change. Lamarckism has not worked in general. So, notion of random mutation remained the prevailing view.
Scientists wanted to distinguish between the random mutation and natural selection explanation. They developed a new method for detecting de novo mutations. This means, mutations that arise “out of the blue” in offspring without being inherited from either parent. This method allowed something not previously possible. Scientists counted de novo mutations for particular points of interest in the genome.
Scientists applied their method to examine the de novo emergence of the human hemoglobin S mutation. This is the most well-known point mutation in biology and evolution. HbS provides protection against malaria for people with one copy. But it causes sickle-cell anemia in those with two. Malaria is a vector-borne blood disease.
It has been the strongest selection pressure acting on humans in the last 10,000 years. It caused more than a million deaths per year in Africa in the recent past. HbS is also used as a central example of random mutation and natural selection in evolution.
It assumed to have arisen accidentally in an individual in sub-Saharan Africa. It then spread inside Africa via natural selection. It spread until its malaria-protective benefits were balanced out by its sickle-cell anemia costs. Scientists examined the de novo origination of HbS.
They disentangled for the first time if the malaria-protective mutation arises randomly. Or it originated de novo more frequently in sub-Saharan Africans. This is a group that has been subject to intense malarial selection pressure for many generations. It should be equally likely to emerge in both geographical groups, if the mutation is random. It would actually emerge more frequently in Africans, if mutation is non-random.
