Neanderthal-human Hybrids

Mason and Short propose a solution to the apparent paradox of human-neandertal hybridization: that is, that human mtDNA shows no trace of neandertal lineage and there are few Y-linked neandertal genes in the human genome, yet autosomal DNA shows clear evidence of interbreeding. They suggest that only male neandertals were able to mate with female humans, perhaps due to the larger size and dominance of male neandertals over the human females which would not have existed for female neandertals over male humans. They add that Haldane's Law tells us that heterogametic offspring are often sterile, if even viable, and therefore XY offspring of any interbreeding would not contribute further to the human gene pool. Left would be females with human mtDNA but autosomal components from their paternal neandertal lines.