New York, Feb 26 (IANS) Although the last Neanderthal died tens of thousands years ago, their DNA sequences still influence how genes are turned on or off in modern humans, and their effects can contribute to traits such as height and susceptibility to schizophrenia or lupus, says a study.

Experts know that after leaving Africa, our ancestors -- the homo sapiens -- mated with Neanderthals thousands of years ago, and today Neanderthal DNA makes up one to four per cent of the genomes of modern non-African people. 

"Even 50,000 years after the last human-Neanderthal mating, we can still see measurable impacts on gene expression," said study co-author Joshua Akey from the University of Washington School of Medicine in Seattle.

"And those variations in gene expression contribute to human phenotypic variation and disease susceptibility," Akey added.

Previous studies have found correlations between Neanderthal genes and traits such as fat metabolism, depression, and lupus risk.

In this study, published in the journal Cell, researchers analysed RNA sequences in a dataset called the Genotype-Tissue Expression (GTEx) Project, looking for people who carried both Neanderthal and modern human versions of any given gene -- one version from each parent. 

For each such gene, the investigators then compared expression of the two alleles head-to-head in 52 different tissues.

"We find that for about 25 per cent of all those sites that we tested, we can detect a difference in expression between the Neanderthal allele and the modern human allele," added Rajiv McCoy, post-doctoral researcher at the University of Washington.

One example uncovered by this study is a Neanderthal allele of a gene called ADAMTSL3 that decreases risk of schizophrenia, while also influencing height.

"Hybridisation between modern humans and Neanderthals increased genomic complexity," Akey explained.

"Hybridisation wasn't just something that happened 50,000 years ago that we don't have to worry about anymore. Those little bits and pieces, our Neanderthal relics, are influencing gene expression in pervasive and important ways," Akey said.