A new research has suggested that humans should thank their Neanderthal ancestors not only for giving the disease-fighting genes but also for their allergies.

According to two new studies published on January 7 in the American Journal of Human Genetics, genetic variants present in modern humans that originally belonged to Neanderthals could predispose the immune system in human body to overreact to environmental allergens.

However, these Neanderthal loaner genes could have had a silver lining as the study have also discovered that interbreeding with Neanderthals could have helped ancient humans, belonging to Africa, in getting a head start in settling down in Europe.

In a statement, Janet Kelso of Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, said, “Neanderthals, for example, had lived in Europe and western Asia for around 200,000 years before arrival of modern humans. They were likely well-adapted to local climate, foods and pathogens. By [Neanderthals] interbreeding with these archaic humans, we modern humans gained these advantageous adaptations”.

Nearly 50,000 years back, Neanderthals interbred with humans when humans emerged from Africa into Europe for the first time. According to studies the last Neanderthal-human mating has had possible occurred as recently as 37,000 years back.

Genetic studies suggested that as a result of this interbreeding, around 2.5% of the DNA of present day's Europeans came from Neanderthals, whereas as per another research up to 6% of modern DNA has originated with ancient hominins. The group contains both Neanderthals and a strange set of human ancestors that belonged to Siberia, known as Denisovans.

Previous study has suggested that a number of the genes that modern humans inherited from Neanderthals play a part in the modern human immune system, though the exact roles aren’t clear so far.