Processed : Homo Sapiens & Upper Paleolithic – Robert Jurmain reference book
- Describe the time frame and geographic locations for the earliest evidence of modern humans in Africa as well as elsewhere in the Old World.
- Compare the different models accounting for the origin and dispersal of modern humans and evaluate how fossil and genetic evidence support these models.
- Explain from the archaeological evidence how and why modern human behavior in the Upper Paleolithic differed from that of their Middle Paleolithic predecessors.
- What anatomical characteristics define modern, as compared with premodern, humans? Assume that you’re analyzing an incomplete skeleton that may be early modern H. sapiens. Which portions of the skeleton would be most informative, and why?
- What recent evidence supports a partial replacement model for an African origin and later dispersal of modern humans? Do you find this evidence convincing? Why or why not? Can you propose an alternative that has better data to support it?
- Why are the fossils recently discovered from Herto so important? How does this evidence influence your conclusions in question 2?
- What archaeological evidence shows that modern human behavior during the Upper Paleolithic was significantly different from that of earlier hominins? Do you think that early modern H. sapiens populations were behaviorally superior to the Neandertals? Be
careful to define what you mean by “superior.” - Why do you think some Upper Paleolithic people painted in caves? Why don’t we find such evidence of cave painting from a wider geographical area?
Our last hominin cousin disappeared several thousand years ago. Perhaps about 80,000 ya, modern peoples in the Middle East encountered beings that walked on two legs, hunted large animals, made fire, lived in caves, and fashioned complex tools. These beings
were the Neandertals. Sometime, probably close to 200,000 ya, the first modern Homo sapiens populations appeared in Africa. Within 150,000 years or so, their descendants had spread across most of the Old World, even expanding as far as Australia (and somewhat later to the Americas).
Who were they, and why were these early modern people so successful? What was the fate of the other hominins, such as the Neandertals, who were already long established in areas outside Africa? Did they evolve as well, leaving descendants among some living human populations? Or were they completely swept aside and replaced by African emigrants?
In this chapter, we’ll discuss the origin and dispersal of modern H. sapiens.
All contemporary populations are placed within this species (and the same subspecies as well). Most paleoanthropologists agree that several fossil forms, dating back as far as 100,000 ya, should also be included in the same fully modern group as us. In addition, some recently discovered fossils from Africa also are clearly H. sapiens, but they show some (minor) differences from living people and could thus be described as nearmodern. Still, we can think of these early African humans as well as their somewhat later relatives as “us.”
These first modern humans, who evolved by 195,000 ya, are probably descendants of some of the premodern humans. In particular, African populations of H. heidelbergensis are the most likely ancestors of the earliest modern H. sapiens. The evolutionary events that took place as modern humans made the transition from more ancient premodern forms and then dispersed throughout most of the Old World were relatively rapid, and they raise several basic questions:
- When (approximately) did modern humans first appear?
- Where did the transition take place? Did it occur in just one region or in several?
- What was the pace of evolutionary change? How quickly did the transition occur?
- How did the dispersal of modern humans to other areas of the Old World (outside their area of origin) take place?
- What does archaeological evidence tell us about important cultural characteristics of early modern people that allowed them to quickly and successfully disperse throughout the Old World after about 50,000 ya?
These questions concerning the origins and early dispersal of modern Homo sapiens continue to fuel much controversy among paleoanthropologists. And it’s no wonder, for at least some early H. sapiens populations are the direct ancestors of all contemporary humans. They were much like us skeletally, genetically, and (most likely) behaviorally. In fact, it’s the various hypotheses regarding the behaviors and abilities of our most immediate predecessors that have most fired the imaginations of scientists and laypeople alike. In every
major respect, these are the first hominins that we can confidently refer to as fully human.
Something New and Different: The “Little People”
As we’ve seen, by 25,000 ya, modern humans had dispersed to all major areas of the Old World, and they would soon journey to the New World as well. But at about the same time, remnant populations of earlier hominins still survived in a few remote and isolated corners. Populations of Homo erectus in Java managed to survive on this island long after their cousins had disappeared from other areas (for example, China and East Africa). What’s more, even though they persisted well into the Late Pleistocene, physically these Javanese hominins were still similar to other H. erectus individuals.
Even more surprising, it seems that other populations possibly branched off from some of these early inhabitants of Indonesia and either intentionally or accidentally found their way to other, smaller islands to the east. There, under even more extreme isolation pressures, they evolved in an astonishing direction. In late 2004, the world awoke to the startling announcement that an extremely small-bodied, small-brained hominin had been discovered in Liang Bua Cave, on the island of Flores, east of Java. Dubbed the “Little Lady of Flores” or simply “Flo,” the remains consist of an incomplete skeleton of an adult female (LB1) as well as additional pieces from approximately 13 other individuals, which the press has collectively nicknamed “hobbits.” The female skeleton is remarkable in several ways, though in some ways similar to the Dmanisi hominins. First, she was barely 3 feet tall—as short as the smallest australopith—and her brain, estimated at a mere 417 cm3 (Falk et al., 2005), was no larger than that of a chimpanzee (Brown et al., 2004). Possibly most startling of all, these extraordinary hominins were still living on Flores just 13,000 ya (Morwood et al., 2004, 2005; Wong, 2009)! Where did they come from? As we said, their predecessors were perhaps H. erectus populations like those found on Java. How they got to Flores—some 400 miles away, partly over open ocean—is a mystery. There are several connecting islands, and to get from one to another these hominins may have drifted across on rafts; but there’s no way to be sure of this. What’s more, these little hominins were apparently living on Flores for a very long time; recently discovered stone tools have been radiometrically dated to at least 1 mya (Brumm et al., 2010). Such an ancient date, as well as the overall similarities to the Dmanisi hominins, suggest to some researchers that Homo floresiensis may derive from an early migration of early Homo to Southeast Asia (Jungers et al., 2009; Wong, 2009).
In other words, this highly unusual hominin might have evolved from ancestors that left Africa even before H. erectus did. How did they get to be so physically different from all other known hominins? Here we’re a little more certain of the answer. Isolated island populations can quite rapidly diverge from their relatives elsewhere. Among such isolated animals, natural selection frequently favors reduced body size. For example, remains of dwarfed elephants have been found on islands in the Mediterranean as well as on some channel islands off the coast of southern California. And perhaps most interesting of all, dwarf elephants also evolved on Flores; they were found in the same geological beds with the little hominins. The evolutionary mechanism (called “insular dwarfing”) thought to explain such extreme body size reduction in both the elephants and the hominins is an adaptation to reduced resources, with natural selection favoring smaller body size (Schauber and Falk, 2008). Other than short stature, what did the Flores hominins look like? In their cranial shape, thickness of cranial bone, and dentition, they most resemble H. erectus, and specifically those from Dmanisi. Still, they have some derived features that also set them apart from all other hominins. For that reason, many researchers have placed them in a separate species, Homo floresiensis. Immediately following the first publication of the Flores remains, intense controversy arose regarding their interpretation (Jacob et al., 2006; Martin et al., 2006). Some researchers have argued that the small-brained hominin (“Flo,” technically called LB1) is actually a pathological modern H. sapiens individual afflicted with a severe disorder (microcephaly has been proposed, among others). The researchers who did most of the initial work reject this conclusion and
provide some further details to support their original interpretation (for example, Dean Falk and colleagues’ further analysis of microcephalic endocasts; Falk et al., 2009).
The conclusion that among this already small-bodied island population the one individual found with a preserved cranium happened to be afflicted with a severe (and rare) growth defect is highly unlikely. Yet, it must also be recognized that long-term, extreme isolation of hominins on Flores leading to a new species showing dramatic dwarfing and even more dramatic brain size reduction is quite unusual. So where does this leave us? Because a particular interpretation is unlikely, it’s not necessarily incorrect. We do know, for example, that such “insular dwarfing” has occurred in other mammals.
For the moment, the most comprehensive analyses indicate that a recently discovered hominin species (H. floresiensis) did, in fact, evolve on Flores (Nevell et al., 2007; Tocheri et al., 2007; Falk et al., 2008; Schauber and Falk, 2008; Jungers et al., 2009). The more detailed studies of hand and foot anatomy suggest that in several respects the morphology is like that of H. erectus (Nevell et al., 2007; Tocheri et al., 2007) or even early Homo (Jungers et al., 2009). In any case, the morphology of the Flores hominins
is different in several key respects from that of H. sapiens, even those who show pathological conditions. There is some possibility that DNA can be retrieved from the Flores bones and sequenced. Although considered a long shot due to poor bone preservation, analysis of this DNA would certainly help solve the mystery.