Many of us carry Neanderthal genes, thanks to interbreeding 60,000 years ago and it could have an important impact on the way we absorb medicines, a new study has shown.
For a drug to be effective and not harmful it needs to be administered at the right dosage, but people with Neanderthal genes eliminate drugs such as the blood-thinner warfarin differently.
The gene variants could mean that a drug dose that would normally be effective is actually toxic instead, the researchers warn.
The gene variants are carried by 20% of present-day Europeans.
Neanderthals were a group of ancient humans that populated Europe and Asia before the arrival of modern humans.
When modern humans and Neanderthals met, they mixed - so people with roots outside Africa tend to carry one to two percent of their genome from Neanderthals.
The researchers say that certain enzymes in the body eliminate drugs, and the activity of these enzymes vary between individuals.
Researchers at the Max Planck Institute for Evolutionary Anthropology in Germany and Karolinska Institutet in Sweden studied enzymatic variants which eliminate drugs less efficiently and which are inherited from neanderthals.
Precision medicine aims to customise health care, with treatments tailored to each patient.
The hope is that patients are prescribed medications in the right dosage, appropriate to them, based on genetic and other factors.
It is well known that genetic variants in the genes encoding enzymes in the cytochrome P450 family affect how efficient these enzymes are.
In the study published in The Pharmacogenomics Journal, researchers that two of the most important genetic variants influencing the ability to eliminate drugs are inherited from neanderthals.
The study, led by, and Svante Pääbo, director at the Max Planck Institute for Evolutionary Anthropology, identified a DNA segment inherited from neanderthals, carrying two cytochrome P450 enzymes.
These enzymes eliminate several common drugs such as the blood thinner warfarin, the antiepileptic drugs phenytoin, the cholesterol lowering drugs statins and common painkillers such as ibuprofen.
The neanderthal variants of the enzymes are generally less efficient at eliminating drugs.
Researcher Hugo Zeberg, researcher at the Department of Neuroscience and Max Planck Institute for Evolutionary Anthropology, Karolinska Institutet, said, "This is one case where the admixture with neanderthals has a direct impact in the clinic. Otherwise therapeutic doses can be toxic for carriers of the Neanderthal gene variant.”
Watch: Discovery of child's tooth in cave 'puts human evolution back 10,000 years'