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 we took a time machine back 300,000 years and felt adventurous enough to scour the Old World, we would encounter several varieties (species?) of early humans.  We will probably never know the full story of their demise, but all were gone by the end of this chapter.

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

1. Erectus and heidelbergensis

Homo erectus, the longest-lasting human species 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 what is today the island of 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.

It is difficult to track the fate of Homo heidelbergensis, partly because it is seen as a transition between erectus and later species.  Its fossil characteristics gradually blurred into Neanderthal features in Europe and modern human features in Africa.  The African version, then, is the most likely candidate for our parent species.  The youngest fossils still described as Heidelberg (at least by some scientists) survived into the last few hundred thousand years.  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.  These Chinese lineages seem to have gone extinct. 3

2. Neanderthals and Denisovans

Neanderthals are mostly known from sites 30 – 100 TYO and 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, revealing details such that some Neanderthals had pale skin like modern Europeans, and they shared one of our genes associated with speech.  There is a great deal of debate about Neanderthals’ 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 speciated 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

The species 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 our species as “modern humans”, to distinguish sapiens from the extinct members 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 cross-breeding, this clade originated somewhere between 30,000 and 2,000,000 years ago!  Most scientists would agree that the departure of Neanderthals from Africa several hundred thousand years ago was the last significant speciation event.  The Heidelbergs left behind in Africa were apparently our parent species.  There is no definitive line where heidelbergensis ends or sapiens begins.

Of course, the pre-sapiens Heidelbergs, like Rhodesian Man, 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 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.

Anatomical, genetic, and behavioral modernity will all be elaborated further in this chapter.  For now, suffice it to say that Homo sapiens joined the human races over the last few hundred thousand years, apparently in Africa.  That brings us back around to the debate opened in Chapter 6 with multiregionalism.  Let us now take a closer look at the flipside of modern human origins – recent African evolution.

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

Chapter 6 introduced the multiregional aspect of human evolution, which we now know is partly true.  After several hundred thousand years of separation, Neanderthals and modern humans never quite lost the capacity to mate with each other.  In that literal biological sense, the ergaster branch of humanity has been a single species the whole time.

Going further, the multiregional model originally asserted that modern humans evolved continuously and simultaneously across four continents ever since erectus colonized Asia.  This strong conclusion has not held up against recent evidence.  Recall that the basis for belief in multiregional origins was regional continuity.  The idea was that we could line up a series of European skulls and, as they progressed from old to new, their features would gradually morph from Neanderthal to modern.  Likewise, another timeline of skulls from China would blend smoothly from erectus to modern.  In reality, no such lineup of skulls is available, 17 and the fossil evidence that does exist can be interpreted in different ways. 18

Instead, today’s best evidence indicates that early Eurasian humans lived in small scattered patches, 19  20 and their contributions to the modern human species have been minor afterthoughts.  The prolonged isolation of populations such as Neanderthal, Asian erectus, and floresiensis is evident in their persistently different anatomies, so it is appropriate to call them different species.  African populations eventually grew larger and denser, and that is where most of the evolution toward the modern form took place.

In fact, Africans also suffered periodic population losses and fragmentation.  The southern continent endured a series of “megadroughts”, when even tropical Africa had deserts. 21 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. 22

At other times, African populations were more robust and interconnected.  This is where the multiregional model still finds a place in the story.  There is now good evidence of multiregional evolution on an African scale.  That is, some modern features first appeared in northern Africa, others in southern or eastern Africa, and over time they blended together into the modern human composite. 23 Multiregionalism, which was originally proposed as an explanation for present-day racial diversity, is now ironically useful for explaining human commonalities.

Modern humans established a 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 For unknown reasons, those pioneering populations did not persist or expand.

It wasn’t until 50 – 70 TYA that sapiens migrated from Africa in great numbers.  Although the Sahara Desert is virtually uninhabitable now, it has gone through numerous wet and dry cycles 26 that may have served as a “pump” for these migrations.  There is evidence that southeastern Africans were drawn to northern Africa during a “green Sahara” phase in MIS 5 and were then forced to evacuate when it was desiccated again in MIS 4. 27 It was this latest phase of migration that led to permanent settlement of the entire Old World.

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

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, but we know frustratingly few details about this takeover.  We can’t help but wonder if Homo sapiens entered this world in a bloody genocidal campaign.  Fortunately, there’s not much evidence of that, though, knowing human nature, it would be surprising if there were no interspecies skirmishes.  It’s probably a more important factor that modern humans were simply better survivors, and they outcompeted archaic human species that were already endangered.

The most significant interactions were with Neanderthals and Denisovans, who both mated with AMH.  Neanderthals occupied the Levant when modern humans first entered that region.  The two species coexisted near the Sinai gateway for millennia, and this was probably their mating nexus. 28 Neanderthal DNA is present in almost all modern human populations outside of sub-Saharan Africa. 29 This suggests that our modern ancestors 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. 30 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. 31 There is mixed evidence that Neanderthals grew up faster than modern humans. 32  33 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.  Some authors speculate that Neanderthals resisted Cro-Magnon expansion. 34 As the harsh MIS 2 ice age took hold, Neanderthals retreated to southern Europe and Cro-Magnons filled the void.  The two species probably shared Europe briefly around 40 TYA. 35 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. 36 One of the genes important for survival at high altitudes was passed from Denisovans to modern Tibetans. 37

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 somewhat assimilated them into the gene pool while retaining only slight traces of their physical appearance.  But their extinction cannot be explained by assimilation alone.  A major advantage that modern humans had over their sister species 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 species 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 (New York, 2009), Kindle edition, p. 109.
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  3.  Thomas Holtz, “GEOL 204 Dinosaurs, Early Humans, Ancestors & Evolution” lecture notes, University of Maryland (Spring, 2018), https://www.geol.umd.edu/~tholtz/G204/lectures/204sapiens.html (accessed and saved 8/05/18).
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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).  I regard this article with a grain of salt, owing in part to a confessed skepticism of Russian journalism.  A related article in DailyMail.com mentioned a 2017 meeting with international scientists to corroborate that the artifacts were Denisovan-made, but if there ever was such a meeting I can not find its report.
  9. Debbie Argue et al., “The affinities of Homo floresiensis based on phylogenetic analyses of cranial, dental, and postcranial characters”, Nature vol. 107 (June, 2017), pp. 107-133. https://www.sciencedirect.com/science/article/pii/S0047248417300866 (Paysite with abstract accessed 8/12/18). Summarized by Australian National University, “Origins of Indonesian hobbits finally revealed”, Phys.org (4/21/2017), https://phys.org/news/2017-04-indonesian-hobbits-revealed.html (accessed and saved 8/12/18).
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  12. National Geographic has sponsored the Dinaledi excavations, and it has an outstanding general-interest summary of this species and its discovery at https://news.nationalgeographic.com/2015/09/150910-human-evolution-change/ (9/10/2015, accessed and saved 8/13/18).
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  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).
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  17. Paul Pettitt, “Multi-regional Evolution and Modern Human Emergence in Asia and Australasia”, The Human Past, Richard Scarre, ed., Thames & Hudson (London, 2005), p. 130.
  18. Richard G. Klein, “The Out-of-Africa Hypothesis and Its Multiregional Alternative”, The Human Career, 3rd edition, The University of Chicago Press (Chicago, 2009) pp. 627 – 631.
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  21. Andrew S. Cohen et al., “Ecological consequences of early Late Pleistocene megadroughts in tropical Africa”, PNAS vol. 104 no. 42 (10/16/2007), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2034256/ (accessed and saved 8/26/18).
  22. Christopher Seddon, “The long African dawn”, Humans: from the beginning, Glanville Publications (revised ebook, 2015) Ch. 10.
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  26. 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).
  27. 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).
  28. Sriram Sankararaman et al., “The Date of Interbreeding between Neandertals and Modern Humans”, PLOS Genetics 8(10): e1002947. https://doi.org/10.1371/journal.pgen.1002947 (accessed and saved 9/02/18).
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  30. 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 (abstract accessed 9/02/18).  Related master’s thesis by co-author Lia Tarle, “Clothing and the Replacement of Neanderthals by Modern Humans”, Simon Fraser University (Fall 2012), summit.sfu.ca/system/files/iritems1/12498/etd7482_LTarle.pdf (accessed and saved 9/02/18).
  31. Michael P. Richards et al., “Neanderthal diet at Vindija and Neanderthal predation: The evidence from stable isotopes”, PNAS vol. 97 no. 13, 7663-7666 (6/20/2000), http://www.pnas.org/content/97/13/7663 (accessed and saved 9/02/18).
  32. Tanya M. Smith et al., “Dental evidence for ontogenetic differences between modern humans and Neanderthals”, PNAS 107(49) 20923-20928 (12/07/2010), http://www.pnas.org/content/107/49/20923 (accessed 9/02/18).
  33. Antonio Rosas, “The growth pattern of Neandertals, reconstructed from a juvenile skeleton from El Sidron (Spain)”, Science vol. 357, Issue 6357, pp. 1282-1287 (9/22/2017), http://science.sciencemag.org/content/357/6357/1282 (accessed 9/02/18).
  34. Clive Finlayson, The Humans Who Went Extinct, Oxford University Press (New York, 2009).
  35. 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).
  36. Sharon R. Browning et al., “Analysis of Human Sequence Data Reveals Two Pulses of Archaic Denisovan Admixture”, Cell vol. 173, issue 1, pp. 53-61.E9 (3/22/2018), https://www.cell.com/cell/comments/S0092-8674(18)30175-2 (accessed and saved 9/02/18).
  37. Emilia Huerta-Sanchez et al., “Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA”, Nature vol. 512 pp. 194ff., https://www.nature.com/articles/nature13408 (accessed 9/02/18).  Free but non-downloadable copy accessible by linking through summary article, https://www.nationalgeographic.com/science/phenomena/2014/07/02/sex-with-extinct-humans-passed-high-altitude-gene-to-tibetans/ (accessed 9/02/18, link at very bottom of article).
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