Study: Pacific Islanders Appear To Have Most Ancient Human DNA On Earth

I don’t think I understand this. Did humans evolve more than once? Do we not all come from a single human origin? How can one group have older human DNA than another?

They have a lot of DNA inherited from pre-human ancestors (more closely related to the Neadnerthals, we call them “Denisovans” because we have one sample from a cave in Denisova, Siberia). This inheritance happened after the big Out-of-Africa migration. We can infer parts of the genome that are probably inherited from similar ancestors (including Neanderthals), and some groups have more than others. In particular, Pacific Islanders have more “Denisovan or similar” ancestral DNA sequences. (This probably indicates that Denisovans and others were mostly interacting with humans in the East Asia/Southeast Asia area).

Article says DNA stems from Denisovan-like groups and that some DNA may still be active in immune-response areas. I wonder to what extent DNA affects physical traits influencing outward appearance of the different evolutionary and migratory groups, outside of regional and environmental influences on the development of physical appearances. Oceania always seems so distinctive.