Humans and Neandertals

http://www.sciencemag.org/news/2016/02/humans-mated-neandertals-much-earlier-and-more-frequently-thought
http://www.bbc.com/news/science-environment-35595661
http://www.livescience.com/28036-neanderthals-facts-about-our-extinct-human-relatives.html
https://genographic.nationalgeographic.com/neanderthal/
http://www.nature.com/nature/journal/v530/n7591/full/nature16544.html
https://www.newscientist.com/article/dn26435-thoroughly-modern-humans-interbred-with-neanderthals/
https://www.mpg.de/9970936/gene-flow-modern-humans-neanderthals
http://news.discovery.com/human/genetics/humans-infected-neanderthals-with-diseases-160412.htm
http://www.mirror.co.uk/news/technology-science/science/one-earliest-skulls-found-galilee-5060002