Most modern humans outside of Africa have between 1 and 4% Neanderthal DNA, with this DNA having considerable effects on physical and psychological traits today. Physical signs of carrying Neanderthal DNA include light skin and hair, baldness, lack of back hair, obesity, elongated skull shape, and height.

Neanderthal DNA affects the composition of fat throughout the body and how much of it is stored, and may help break down fat to use as energy faster. While being bald and easily sunburnt may be negative traits inherited from Neanderthals, the same gene that causes this also makes it more likely for skin and hair to be lighter in color, which helped absorb vitamin D in cloudy regions.

The shape of one's skull is a good physical marker for Neanderthal DNA, with less globular and more elongated skulls being a sign of Neanderthal ancestry. Height may also be influenced by a gene that decreases the risk of schizophrenia and is highly influenced by Neanderthal heritage. DNA tests can also show the amount of Neanderthal DNA one has and provide information about one's genetic code, paternal and maternal haplogroups, health, pharmacological, and nutritional information unique to one's DNA.