Posted on 02/13/2015 12:32:32 PM PST by SunkenCiv
Thanks to natural climate cycles, there's been a pulse of ingress into neighboring areas from Central Asia, followed by a population crash, ingress into Central Asia as the world warmed back up, a population spike, then mass exit when the temperature crashes again. The various cultures managed to carve out new realms in China, India, the Middle East, Anatolia, and Europe.
Then in 2016, a true ghost emerged from the genomes of 44 individuals who lived in the Middle East between 14,000 and 3400 years ago. Their DNA held genetic markers indicative of a distinct group of ancient H. sapiens based in the region more than 45,000 years ago. The members of this population are now known as Basal Eurasians, and they present a conundrum. Their DNA, which is still found in modern Europeans, shows none of the telltale signs of interbreeding with Neanderthals. This came as a surprise because ancestral humans mated with Neanderthals very soon after leaving Africa 60,000 years ago in the migration that was to give rise to all people of non-African heritage alive today... the genomes of modern Africans who belong to groups with deep ancestral roots, including the Baka hunter-gatherers from Cameroon, and the Hadza and Sandawe from Tanzania. Within these genomes, they have found stretches of DNA that appear to come from another hominin species. Because this DNA is found only in the descendants of African people - not in any Eurasians - the ghost species must have interbred with H. sapiens after the out-of-Africa migration 60,000 years ago. In fact, by the team's calculations, this probably happened within the past 30,000 years. If true, this is huge. It means that until very recently, there was at least one other species of hominin living alongside us in Africa. According to Akey, soon-to-be published evidence suggests there might have been more than one... It now transpires that Denisovans had their own ghosts. People living in Oceania and East and South-East Asia today have inherited about 5 per cent of their DNA from Denisovans. By taking a closer look at these genetic sequences, Akey's team found that they don't all relate to the original finger-bone genome in the same way. In fact, the group found signs of two evolutionarily distinct Denisovan populations. "That was really unexpected," he says. "There's actually another, ghost, Denisovan lineage."
Traces of mystery ancient humans found lurking in our genomes | October 10, 2018 | Catherine Brahic | New Scientist
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