Gene variants or alleles that don’t themselves directly affect the inherited characteristics of an organism but increase random distribution of characteristics may be a significant force in evolution, driving the development of the wide variety of traits — from height to skin tone to disease risk — seen in modern populations, Johns Hopkins scientists suggest.

In standard Darwinian theory, characteristics that affect an organism’s ability to adapt and survive in times of environmental change have been thought to arise by chance through random mutations in an organism’s DNA, or more recently, thought to be caused by epigenetic* factors.

However, this view could not explain how such mutations, which arise only rarely, help organisms of every size and variety adapt quickly enough through time. Nor could it explain how diseases that lead to a dramatic loss of survival — such as diabetes, heart disease, autism, and schizophrenia — persist in populations.

*Heritable traits (over rounds of cell division and sometimes transgenerationally) that do not involve changes to the underlying DNA sequence.