(CNN) Genes inherited from Neanderthal ancestors may be involved in some cases of severe Covid-19 disease, researchers in Germany reported Wednesday. A team of experts on Neanderthal genetics examined a strand of DNA that has been associated with some of the more serious cases of Covid-19 and compared it to sequences known to have been passed down to living Europeans and Asians from Neanderthal ancestors. The DNA strand is found on chromosome 3, and a team of researchers in Europe has linked certain variations in this sequence with the risk of being more severely ill with Covid-19.