5.II: Hello, Modern Humans; Goodbye, Early Humans

Neanderthals, Cro-Magnon
Neanderthals as they might have appeared when first encountering modern humans.

A.  The Last Early Humans
B.  Introducing Homo Sapiens
C.  Out of Africa One Last Time
D.  Citations

A. The Last Early Humans

If you think that today’s humans are diverse, you should have seen them 300,000 years ago!  At the turn of this chapter, humans differed not only in hair and skin coloration but in skeletal form.  Although these forms are traditionally categorized as separate species, we don’t know if that’s completely accurate.  Which variants were ancestral to us, and which have gone extinct?  We will probably never know the full story of the transition, but one fact is undeniable.  By the end of this chapter, beings that we would call early humans no longer walked the earth.

1.  Erectus and heidelbergensis
2.  Neanderthals and Denisovans
3.  Hobbits and other exotic humans

1. Erectus and heidelbergensis

Homo erectus, the longest-lasting human form of all time, continued to live well into Chapter 5.  After 300 TYA, it was found only in southern and eastern Asia.  In a time when sea levels were lower, southeastern Asia was more interconnected by land than it is today, forming a peninsula called Sundaland that extended all the way to Bali. Eastern Asia offered one of the most open north-south corridors in the Old World.  Unrestricted by mountain ranges, deserts, or seas, erectus was able to freely migrate to different latitudes as climate and ecology changed.  This mobility could explain its lasting endurance. 1 Rising sea levels eventually stranded erectus on tropical islands. The youngest erectus fossils are found on Java with an age currently estimated at 50,000 years. 2

Sundaland, Sahul, Homo erectus, Wallace Line, Java Man
Pleistocene shorelines of Sundaland (Southeast Asia) and Sahul (Australia / New Guinea / Tasmania). Early humans expanded as far as the Wallace Line. 3

It is difficult to track the fate of Homo heidelbergensis, partly because it is seen as a transition between erectus and later forms.  Its fossil characteristics gradually blurred into Neanderthal features in Europe and modern human features in Africa.  The African version, then, is probably the predominant genetic contributor to Homo sapiens, our “parent species” if you like. A famous late specimen from Zimbabwe, once called Rhodesian Man, is dated to 125 – 300 TYA.  Some populations that lived in northern China 130 – 260 TYA are also possibly late Heidelbergs. 

2. Neanderthals and Denisovans

Neanderthals are mostly known from sites 30 – 100 TYO, ranging from western continental Europe to western Asia.  They were robust, muscular people with large noses and brains even bigger than our own.  Neanderthals were heavily carnivorous.  They fished and hunted mammals (their favorite was the ibex, a long-horned sheep) probably by stabbing them directly with wooden spears! 4

The entire Neanderthal genome has been sequenced.  Some Neanderthals had genes for pale skin like modern Europeans.  All Neanderthals shared one of our genes associated with speech.  There is a great deal of debate about their intellect and the “modernity” of their behavior.  We know that they buried their dead and created simple art such as rectangles and handprints. 5 However, there is no direct evidence of ritual or spirituality, and we can only speculate about what these activities meant to them.

Denisovans diverged from Neanderthals 200 – 500 TYA. 6 They roamed a broad territory from Siberia to Sundaland before vanishing less than 40 TYA.  The species is known from just a few teeth and knucklebones in Denisova Cave, Russia.  This is obviously not enough physical evidence to reconstruct the Denisovan anatomy (other than that they had large teeth and bones) but it has yielded a nearly complete genome. 7 The sampled individuals had dark skin and hair.  Artifacts from Denisova Cave include some of the world’s oldest jewelry and needles, though it must be kept in mind that modern humans used the same cave. 8  

3. Hobbits and other exotic humans

An early human officially called Homo floresiensis is named after its tiny home island of Flores, Indonesia.  It is nicknamed “Flo” or “the hobbit” because it was the size of a modern three-year-old child and had large feet.  Flo is more closely related to australopithecines than to modern humans, 9 raising the possibility that its ancestors left Africa even before Homo erectus.  Its fossils are dated to 60 – 100 TYA, 10 surprisingly recent for such a primitive species.  Flores, east of the Wallace Line, was never joined to Sundaland.  This raises the puzzling question of how Flo got there.  It is fun to speculate about hobbit boats, but, due to Flo’s Oldowan technology, small brain, and exclusion to one island, fortuitous island-hopping or tsunamis are more likely scenarios. 11

Floresiensis was not the only barely-human species to survive so long.  Dinaledi Cave, South Africa, is filled with the bones of Homo naledi.  This 200 – 300 TYO human still had the hips, shoulders, and curved fingers of an arboreal ape.  Its skull was modern in shape but archaic in size, and its body was midway in size between Lucy and erectus. 12 While its unexpected physique is perplexing enough, naledi’s location has really thrown paleontologists for a loop.  The only known specimens are all crammed into two small, pitch-dark, nearly inaccessible cave chambers.  Its discoverers believe that the only way those remains could have gotten there is if naledis deliberately buried their dead. 13  This is a bold claim, because naledi lived long before Neanderthals or modern humans practiced burial. For now, other scientists are reserving judgment. 14

B. Introducing Homo sapiens

At long last, the moment we’ve been waiting for!  After patiently waiting 100,000 years 100,000 times over, this universe finally produced Homo sapiensAnthropologists also refer to sapiens as “modern humans” to distinguish us from earlier variations of the Homo genus

When we pick up a natural history book, we crave easy answers to simple questions like, “Where and when did the first modern humans live?”  The answers to these questions depend just as much on our own arbitrary categories as on the facts of the past.  If we are to understand the origins of the “modern human”, we must now wrestle with its definition.  Brace yourself; it’s complicated.  In fact, there are at least four ways to define human modernity:  cladistic, anatomical, genetic, and behavioral.  These characteristics all emerged gradually (and not necessarily together) over a considerable span of time. 

The modern human clade is the family tree of our ancestors shared by no other species, living or extinct.  Depending on our definition of “species” and the history of inter-human crossbreeding, this clade could have originated anywhere between 30,000 and 2,000,000 years ago!  There is no definitive line where early humans end or sapiens begins.

Of course, the pre-sapiens humans did not quite resemble us.  It took some time for the skeletal features that define anatomically modern humans (AMH) to appear.  The earliest known arguably AMH fossils are 100 – 300 TYO, all from Africa. 15 This is the timeframe in which paleontologists feel it is appropriate to start using the label Homo sapiens.  Not surprisingly, we also find evidence that important segments of the modern human gene pool coalesced around that same time and place. 16 Modern mentality and sapient (literally “wise”) behavior also began to appear in the Middle Stone Age but were not universal until the Upper Paleolithic

C. Out of Africa One Last Time

1.  Modern humans in Africa
2.  Modern humans in Eurasia, or “When Africans conquered Europe”

1. Modern Humans in Africa

The discovery that Africa gestated and gave relatively recent birth to a fully modern Homo sapiens is usually described as “Out of Africa” theory.  That phrase is a little confusing, because we know that early humans and possibly even some pre-human ape ancestors had already been venturing out of Africa for millions of years.  The phrase “recent African evolution of modern humans” is less poetic but more accurate.  Maybe we could compromise and call the intercontinental conquest of modern humans “Out of Africa one last time”. 

Although our ancestors of the past two million years were probably spread throughout the Old World, the roots and trunk of the family tree remained in Africa.  Eurasian early humans lived in small scattered patches. 1718 African populations were larger and denser. When these populations mixed, then, the African features became dominant. 

Transitional Africans suffered periodic population losses and fragmentation too.  The southern continent endured a series of “megadroughts”, when even tropical Africa had deserts. 19 Middle Stone Age technology is strangely sporadic.  Sometimes innovative new forms of tools or behavior show up in the archaeological record only to vanish for tens of thousands of years before resurging.  This might indicate that these cultural forms were sometimes confined to shrinking isolated communities. 20 At other times, African populations were more robust and interconnected, allowing Homo sapiens to evolve multiregionally on an African scale.  That is, some modern features first appeared in northern Africa and others in southern or eastern Africa, and over time they blended together into the modern human composite. 21

Although the Sahara Desert is virtually uninhabitable now, it has gone through numerous wet and dry cycles 22 that may have served as a “pump” for mass migration.  There is evidence that southeastern Africans were drawn to northern Africa in interglacial “green Sahara” phases and were then forced to evacuate the Sahara when it was desiccated again during ice ages. 23 Some of them migrated into southwestern Asia, the first Homo sapiens to step out of Africa.

2. Modern Humans in Eurasia, or “When Africans Conquered Europe”

Modern humans established an initial limited presence in western Asia almost 200,000 years ago. 24 Some modern human fossils as far away as China are 70 – 120 TYO according to some studies. 25 Those pioneering populations did not expand northward for tens of thousands of years, perhaps due to challenges with diseases. 26

Once out of Africa, modern humans slowly but surely proceeded to encroach upon the domains of early humans.  We know that sapiens prevailed mightily while the older species faded away.  Our imagination is tantalized; we can’t help but wonder if Homo sapiens stormed into this world in a bloody genocidal campaign.  Fortunately, there’s not much evidence of violent confrontation.  There are other factors that are less dramatic but more likely to be relevant, like competition and assimilation.  Homo sapiens’ greater populations gave them advantages in both regards.   

Sapiens’ most significant interactions were with Neanderthals and Denisovans, and these interactions involved mating.  Neanderthals occupied the Levant when modern humans first entered that region.  Sapiens and Neanderthals coexisted near the Sinai gateway for millennia, and this was probably their mating nexus. 27 Neanderthal DNA is present in almost all modern human populations, most abundantly outside of sub-Saharan Africa. 28 This suggests that sapiens mated with Neanderthals early in their expansion into the Old World, before scattering in different directions. 

Anthropologists cite several survival advantages that Homo sapiens may have had over Neanderthals.  Technology was the best-known advantage.  Modern humans were throwing spears with sharp stone / bone points while Neanderthals were still stabbing their prey with sharpened sticks.  Modern humans sewed tailored clothes.  We don’t know if Neanderthals wore anything at all, but if they did it wasn’t very sophisticated.  They lacked needles and made limited use of animals traditionally used for fur trim. 29 Neanderthals wore down their teeth using them as tools.  Biologically, H. sapiens had a more diversified omnivorous diet, while Neanderthals were overly reliant on meat. 30 There is mixed evidence that Neanderthals grew up faster than modern humans. 3132 If so, they may have missed out on some important social and educational development that comes with our extended childhood.

Mysteriously, sapiens paused at the Levant for perhaps 10,000 years before entering Europe, where they are known as Cro-Magnon Man.  This delay is only partly explainable by ice age climate.  Some experts speculate that competition with Neanderthals slowed down Cro-Magnon expansion as well. 33 As the harsh MIS 2 ice age took hold, Neanderthals retreated to southern Europe and Cro-Magnons filled the void further to the north.  They probably shared Europe briefly around 40 TYA. 34 The last known Neanderthal refuge is at the Rock of Gibraltar, where the cliffs of Spain look out across the Mediterranean to Africa. 

Denisovan DNA survives most predominantly in Melanesia, at the far reaches of the Pacific Islands.  We can be sure that Denisovans never made it that far, so eastbound modern humans must have mated with them en route, probably in southeast Asia.  Another wave of migrants that ended up in China and Japan picked up a smaller trace of Denisovan DNA. 35 One of the genes important for survival at high altitudes was passed from Denisovans to modern Tibetans. 36

Less than 5% of modern DNA is derived from early humans.  Assuming that Neanderthal and Denisovan populations were only a small percentage of sapiens’, then the interbreeding seems to have assimilated them into the gene pool while retaining only slight traces of their physical appearance.  It’s striking, though, that the Neanderthals and Denisovans who did not mate with sapiens have indeed died off.  A major advantage that modern humans had was sheer numbers.   In times of crisis, sapiens could absorb more losses. 

There is little to no evidence of direct AMH contact with the other surviving early human species, though their habitats probably did overlap.  The general presumption is that the ancient forms such as Homo erectus simply couldn’t keep up.  By 30,000 years ago, they were all gone.  It was Homo sapiens’ world now. 

Up to Chapter 5

Back to Section 5.I:  Introduction And Timelines

Continue to Section 5.III:  Anatomically And Genetically Modern Humans

D. Citations

  1. Clive Finlayson, The Humans Who Went Extinct, Oxford University Press (Kindle eBook edition, 2009) p. 109.
  2. Yuji Yokoyama et al., “Gamma-ray spectrometric dating of late Homo erectus skulls from Ngandong and Sambungmacan, Central Java, Indonesia”, J. Hum. Evol. 55(2):274-7 (August, 2008), https://www.sciencedirect.com/science/article/pii/S004724840800047X (accessed and saved 12/14/19).
  3. Sundaland map By Maximilian Dörrbecker (Chumwa), CC BY-SA 3.0  (https://creativecommons.org/licenses/by-sa/3.0), via Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Map_of_Sunda_and_Sahul.png (accessed and saved 8/04/18).
  4. Steven E. Churchill, “Of Assegais and Bayonets: Reconstructing Prehistoric Spear Use”, Evol. Anthropol. 11(2002): 185-6, https://onlinelibrary.wiley.com/doi/abs/10.1002/evan.10027 (accessed and saved 8/11/18).
  5. D.L. Hoffmann et al., “U-Th dating of carbonate crusts reveals Neandertal origin of Iberian cave art”, Science 359(6378):912-915 (2/23/2018), http://science.sciencemag.org/content/359/6378/912 (accessed and saved 8/11/18).
  6. Kay Prüfer et al., “The complete genome sequence of a Neanderthal from the Altai Mountains”, Nature 505:43-49 + extended data (1/02/2014), https://www.nature.com/articles/nature12886 (accessed and saved 8/12/18).
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  8. “World’s oldest needle found in Siberian cave that stitches together human history”, The Siberian Times, 8/23/2016, https://siberiantimes.com/science/casestudy/news/n0711-worlds-oldest-needle-found-in-siberian-cave-that-stitches-together-human-history/ (accessed and saved 8/12/18, archived 12/14/19).  I take this article with a grain of salt.  A related article in DailyMail.com mentioned a 2017 meeting with international scientists to corroborate that the artifacts were Denisovan-made.  If there ever was such a meeting, I cannot find its report.
  9. Debbie Argue et al., “The affinities of Homo floresiensis based on phylogenetic analyses of cranial, dental, and postcranial characters”, Journal of Human Evolution 107:107-133 (June, 2017). https://www.sciencedirect.com/science/article/pii/S0047248417300866 (Accessed and saved 12/14/19).
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  11. Chris Stringer as interviewed by Robin McKie in “How a hobbit is rewriting the history of the human race”, The Guardian (2/20/2010), https://www.theguardian.com/science/2010/feb/21/hobbit-rewriting-history-human-race (accessed and saved 8/12/18, archived 12/14/19).
  12. Jamie Shreeve, “This Face Changes the Human Story.  But How?” National Geographic (9/10/2015), https://news.nationalgeographic.com/2015/09/150910-human-evolution-change/ (9/10/2015, accessed and saved 8/13/18, archived 12/14/19).
  13. Paul H.G.M. Dirks et al., “Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa”, eLife 2015;4:e09561 (9/10/2015), https://elifesciences.org/articles/09561 (accessed and saved 8/12/18).
  14. Aurore Val, “Deliberate body disposal by hominins in the Dinaledi Chamber, Cradle of Humankind, South Africa?” Journal of Human Evolution, vol. 96, pp. 145-148 (July, 2016), https://www.sciencedirect.com/science/article/pii/S0047248416000282 (accessed and saved 8/12/18).
  15. Daniel Richter et al., “The age of the hominin fossils from Jebel Irhoud, Morocco, and the origins of the Middle Stone Age”, Nature 546, 293-296 (6/08/2017), https://www.nature.com/articles/nature22335 (accessed and saved 8/19/18).
  16. J.H. Relethford, “Genetic evidence and the modern human origins debate”, Heredity 100(6):555-63 (June, 2008), https://www.ncbi.nlm.nih.gov/pubmed/18322457 (accessed and saved 8/19/18).
  17. Alan R. Rogers et al., “Early history of Neanderthals and Denisovans”, PNAS 114(37):9859-63 (9/12/2017), http://www.pnas.org/content/114/37/9859 (accessed and saved 9/01/18).
  18. Chad D. Huff et al., “Mobile elements reveal small population size in the ancient ancestors of Homo sapiens”, PNAS 107(5):2147-2152 (2/02/2010), http://www.pnas.org/content/107/5/2147 (accessed and saved 9/01/18).
  19. Andrew S. Cohen et al., “Ecological consequences of early Late Pleistocene megadroughts in tropical Africa”, PNAS 104(42):16422-7 (10/16/2007), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2034256/ (accessed and saved 8/26/18).
  20. Christopher Seddon, “The long African dawn”, Humans: from the beginning, Glanville Publications (Kindle revised ebook, 2015) Ch. 10.
  21. Eleanor M.L. Scerri et al., “Did Our Species Evolve in Subdivided Populations across Africa, and Why Does It Matter?”, Trends in Ecology & Evolution 33(8):582-594 (8/01/2018), https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(18)30117-4 (accessed and saved 8/26/18).
  22. Nick A. Drake et al., “Ancient watercourses and biogeography of the Sahara explain the peopling of the desert”, PNAS Early Edition (12/27/2010), http://www.pnas.org/content/early/2010/12/23/1012231108 (accessed and saved 8/19/18).
  23. Jessica E. Tierney, Peter B. deMenocal, and Paul D. Zander, “A climatic context for the out-of-Africa migration”, Geology 45(11):1023-1026 (10/02/2017), https://pubs.geoscienceworld.org/gsa/geology/article/516677/a-climatic-context-for-the-out-of-africa-migration (accessed and saved 8/26/18).
  24. Israel Hershkovitz et al., “The earliest modern humans outside Africa”, Science 359(6374):456-459 (1/26/2018), http://science.sciencemag.org/content/359/6374/456 (accessed and saved 9/01/18).
  25. Wu Liu et al., “The earliest unequivocally modern humans in southern China”, Nature 526:696-699 (10/29/2015), https://www.nature.com/articles/nature15696 (accessed and saved 12/14/19).
  26. Gili Greenbaum et al., “Disease transmission and introgression can explain the long-lasting contact zone of modern humans and Neanderthals”, Nature Communications 10:5003 (11/01/2019), https://www.nature.com/articles/s41467-019-12862-7 (accessed and saved 11/28/20).
  27. Sriram Sankararaman et al., “The Date of Interbreeding between Neandertals and Modern Humans”, PLOS Genetics 8(10): e1002947 (10/04/2012), https://doi.org/10.1371/journal.pgen.1002947 (accessed and saved 9/02/18).
  28. Sriram Sankararaman et al., “The Combined Landscape of Denisovan and Neanderthal Ancestry in Present-Day Humans”, Current Biology 26(9):, 1241-7 (5/09/2016), https://doi.org/10.1016/j.cub.2016.03.037 (accessed and saved 9/02/18).
  29. Mark Collard et al., “Faunal evidence for a difference in clothing use between Neanderthals and early modern humans in Europe”, Journal of Anthropological Archaeology Vol. 44 Part B, 235-246 (12/2016), https://www.sciencedirect.com/science/article/pii/S0278416516300757 (accessed and saved 12/15/19).
  30. Michael P. Richards et al., “Neanderthal diet at Vindija and Neanderthal predation: The evidence from stable isotopes”, PNAS 97(13), 7663-7666 (6/20/2000), http://www.pnas.org/content/97/13/7663 (accessed and saved 9/02/18).
  31. Tanya M. Smith et al., “Dental evidence for ontogenetic differences between modern humans and Neanderthals”, PNAS 107(49):20923-8 (12/07/2010), http://www.pnas.org/content/107/49/20923 (accessed and saved 9/02/18).
  32. Antonio Rosas, “The growth pattern of Neandertals, reconstructed from a juvenile skeleton from El Sidron (Spain)”, Science 357(6357):1282-1287 (9/22/2017), http://science.sciencemag.org/content/357/6357/1282 (accessed and saved 9/02/18).
  33. Anders Eriksson et al., “Late Pleistocene climate change and the global expansion of anatomically modern humans”, PNAS 109(40):16089-94 (10/02/2012), https://www.pnas.org/content/109/40/16089 (accessed and saved 2/02/20).
  34. Tom Higham et al., “The timing and spatiotemporal patterning of Neanderthal disappearance”, Nature 512:306-309 (8/21/2014), https://www.nature.com/articles/nature13621 (accessed and saved 9/02/18).
  35. Sharon R. Browning et al., “Analysis of Human Sequence Data Reveals Two Pulses of Archaic Denisovan Admixture”, Cell 173(1):53-61.E9 (3/22/2018), https://www.cell.com/cell/comments/S0092-8674(18)30175-2 (accessed and saved 9/02/18).
  36. Emilia Huerta-Sanchez et al., “Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA”, Nature 512(7513):194ff. (July, 2014), https://www.nature.com/articles/nature13408 (accessed and saved 12/15/19).
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