A World With More Than One Human Species

our closest relatives share so much in common with us, I sometimes find it hard to imagine another human species.  In fact, sometimes I shudder to think what it would be like if we were sharing this planet with another human species.  Just think about all of the genocideracism and ethnocentrism that has occurred in the past and is still occurring within our species.  I find it only plausible to believe that the situation would be worse if we were actually sharing a planet with a different human species.  However, for most of our species history we did have to share this planet with more than one species.  So who were these other human species?  And did we get along with them?

Meet your (extinct) family

Modern humans came onto the scene in between 150,000 and 200,000 years ago in East Africa (around modern day Ethiopia).  They spread quickly throughout Africa and eventually began migrating into Eurasia, first down into the south of Asia (65 kya) and Australia (50-45 kya), and then later into northern Asia (40 kya) and Europe (35 kya).

However these humans were not exploring uninhabited landscapes.  Although it is unknown whether modern humans encountered different humans species in Africa, we do know that they encountered other human species in Asia and Europe.  Evolutionary anthropologists and archaeologists have known for a long time that one of those species was Homo neanderthalensis.  The neanderthals had quite an extensive range and lived in diverse environments throughout much of Eurasia (although most neanderthal research has focused on their existence in Europe).  When humans entered these environments, all evidence suggests that their populations were already in decline, however our presence may have been the nail in the coffin.  Neaderthals quickly underwent what can best be described as demographic collapse and soon they were pushed to the fringes of Iberia in western Europe either due to lack of resources, an inability to compete with modern humans or succumbing to human encroachment.

Although it is evident that modern humans and neanderthals did not co-exist peacefully, all encounters between the two species must not have been purely antagonistic.  This is because recent genetic evidence suggests that neanderthals have contributed in between 1-4% genetically to humans of non-African origin.  Admittedly, interbreeding between humans and neanderthals is not evidence for love, peace and camaraderie between the two species.  Interbreeding could have been the result of rape after human raiding (and knowing our species I’m more inclined to think that is how any interbreeding would have occurred).  However, if modern humans still possess some uniquely neanderthal genes, then there were hybrid offspring that survived, and went onto reproduce themselves.  This means that it is conceivable that some neanderthals and neanderthal-hybrids were subsumed within human society.  Were they treated equally?  Were they accepted as part of the human family?  Unfortunately, we may never know the answers to those questions.

It has also become obvious that the human landscape was even more complicated than that.  Two other species of human were living in Eurasia at the time of human expansion out of Africa.  One of these species was the Denisova hominin.  Although not much is currently known about Denisovans, we do know that they co-existed with both modern humans and neanderthals in Siberia.  On top of that, we do know that they interbred with both modern humans and neanderthals, although the timing, extent and nature of the interbreeding patterns is substantially different than that of humans and neanderthals.  It appears as though Denisovans contributed approximately 6% of their genetic information to some of the descendants of the first modern humans to migrate out of Africa.  Recent studies have shown that the ancestors of Aboriginal Australians, people from Papua New Guinea, and many Negrito populations throughout Southeast Asia interbred with Denisovans, but modern humans descended from later migrations share no genetic information with Denisovans.  This indicates that the Denisovans predominantly populated south and south-east Asia 50-60 kya but died out before later human populations inhabited these regions.

The third human species we shared this planet with for most of our history is Homo floresiensis.  Flores Man is somewhat controversial and still mysterious.  They had by far the smallest range of all the human species living during the Late Pleistocene eking out an existence on the tiny island of Flores.  They were also very small (approx. 3 feet, 6 inches), earning them the nickname ‘Hobbit’.  Unlike the neanderthals and denisovans, it is unlikely that modern humans ever encountered Flores Man and even more unlikely that we ever interbred with them.  Consequently, they were the longest lived of all the three other human species of the Late Pleistocene, becoming extinct only 13,000 years ago (possibly due to volcanic eruption).

Fortunate extinctions?

So am I right to shudder when I think about the modern world with Homo sapiensHomo neanderthalensis, Denisova hominins and Homo floresiensis?  Although it seems that modern humans interbred with other species wherever they migrated, it is also clear that extinction for other species was soon to follow human migration.  This is despite that fact that modern humans did not have the technology or infrastructure to systematically eradicate another species in the same way a modern industrial society could.  What would modern era war mongers like Napolean, Hitler, Stalin, Pol Pot, or Mao have thought of other species, when they could barely handle cultural, racial and ethnic diversity?  Although racism has been endemic and has led to the subjugation and enslavement of racial and ethnic minorities in the past, what would specism (I think I made up that word) have been like?  If different species of humans existed throughout modern humans recorded history I think there is no chance that we would have co-existed with them peacefully.  This might be a dark commentary on our nature, but I think our past has shown that when it comes to difference, we have the capacity for mind-numbing levels of cruelty.

 

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About Cadell Last
I am a science educator, freelance science writer, and founder of The Advanced Apes based in Toronto, Ontario. In the past my academic research focused on the evolution, ecology, and behaviour of non-human primates (i.e., chimpanzees, gorillas, ring-tailed lemurs). Currently, my official blog, The Ratchet, can be found via The Advanced Apes and Svbtle. I enjoy exploring recent research in human evolutionary sciences, as well as biology, ecology, astronomy, physics, and computer science. My work has been featured in Scientific American, American Humanist, Richard Dawkins Foundation for Reason and Science, and Jane Goodall Institute of Canada. I am also exploring science popularization in new mediums in collaboration with PBS Digital Studios with an animated YouTube channel. You can contact me on Twitter (@cadelllast) or via email: cadell.last@gmail.com

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