Two main evolutionary hypotheses to explain repetitive, non-coding DNA:

1. It is functional, even though it does not actually encode proteins. It may be needed for some regulatory or structural reason, perhaps to keep the genes apart or correctly configured in the DNA molecule's three-dimensional shape.

2. The repetitive DNA may be selfish DNA: either neutral 'junk' DNA, or parasitic. This interesting new evolutionary concept is widely accepted as the explanation for much of the repetitive non-coding DNA.

The geneticist Linda Partridge discusses the concept of non-coding DNA.