Modern humans and Neanderthals lived alongside one another and interbred tens of thousands of years ago. As a result, many people retain a small proportion of DNA of Neanderthal origin: around 2% on average in European and Asian populations, and considerably less in African populations.
Some of these variants have been linked to traits such as pigmentation and immune response, and research into their role in health continues. To calculate your percentage, we compare your DNA with variants identified in sequenced Neanderthal genomes.
Your Neanderthal DNA percentage is included in Starter, Advanced and Ultra, and in paid Raw Data plans. You can find it in your account under Results → Ancestry → Neanderthal.