Climate change primarily related to methanogenesis by human endosymbiotic and colonic archaea can lead to endosymbiotic archaeal growth and neanderthalisation of the homo sapien species. The exposure to the low level of EMF fields consequent to widespread use of the internet, radiosatellites and radar equipments leads to increased endosymbiotic archaeal growth. The colonic and endosymbiotic archaea also generates RNA viroids which are converted to DNA viroids by colonic epithelial HERV reverse transcriptase and gets integrated into the colonic genome. The RNA and DNA viroids and gut bacteria can also hybridise with human genomic sequences for immunity, metabolic regulation, growth factors, cell growth, cell death, neurotransmitters and HERV sequences. The hybridization of archaeal RNA viroids with human genomic HERV and other sequences can generate retroviruses, SARS, COVID 19 and MERS. Endosymbiotic archaea can help human species withstand global warming by modulating metabolism producing ammonia oxidation and carbon dioxide fixation.