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Neanderthals were once considered to be subhuman brutes with low intelligence and capable of communicating through little more than a series of grunts. However, research fuelled by a fascination into the plight of the Neanderthals who mysteriously died out some 30,000 years ago, has revealed that Neanderthals were not as primitive as once believed. New research has now revealed that Neanderthals most likely had a sophisticated form of speech and language not dissimilar to what we have today.
It was long believed that our ancient human ancestors, including the Neanderthals, lacked the necessary cognitive capacity and vocal hardware for speech and language. However, an international team of scientists led by Associate Professor Stephen Wroe, a zoologist and palaeontologist from the University of New England, has made a revolutionary discovery which challenges the notion that Homo sapiens are unique in their capacity for speech and language.
The research team utilised latest 3D x-ray imagining technology to examine a 60,000-year-old Neanderthal hyoid bone discovered in the Kebara Cave in Israel in 1989. The hyoid bone, otherwise called the lingual bone, is a small, u-shaped bone situated centrally in the upper part of the neck, beneath the mandible but above the larynx. The function of the hyoid is to provide an anchor point for the muscles of the tongue and for those in the upper part of the front of the neck.
The Neanderthal remains found in the Kebara Cave, Israel. Photo source
The hyoid bone, which is the only bone in the body not connected to any other, is the foundation of speech and is found only in humans and Neanderthals. Other animals have versions of the hyoid, but only the human variety is in the right position to work in unison with the larynx and tongue and make us the chatterboxes of the animal world. Without it, scientists say we'd still be making noises much like chimpanzees.
Location of the Hyoid bone
The discovery of the modern-looking hyoid bone of a Neanderthal man in the Kebara Cave led its discoverers to argue many years ago that the Neanderthals had a descended larynx, and thus human-like speech capabilities.
“To many, the Neanderthal hyoid discovered was surprising because its shape was very different to that of our closest living relatives, the chimpanzee and the bonobo. However, it was virtually indistinguishable from that of our own species. This led to some people arguing that this Neanderthal could speak,” said Professor Wroe.
However, other researchers have claimed that the morphology of the hyoid was not indicative of the larynx's position and that it was necessary to take into consideration the skull base, the mandible and the cervical vertebrae and a cranial reference plane. It was also argued that the fact that the Neanderthal hyoid was the same shape as humans did not necessarily mean they were used in the same way.
However, through advances in 3D imaging and computer modelling, Professor Wroe’s team was able to examine this issue. By analysing the mechanical behaviour of the fossilised bone with micro x-ray imaging, they were able to build models of the hyoid that included the intricate internal structure of the bone. They then compared them to models of modern humans.
The results showed that in terms of mechanical behaviour, the Neanderthal hyoid was basically indistinguishable from our own, strongly suggesting that this key part of the vocal tract was used in exactly the same way.
“From this research, we can conclude that it’s likely that the origins of speech and language are far, far older than once thought,” said Professor Wroe. The first proto-Neanderthal traits appeared as early as 350,000 – 600,000 years ago, which means that, potentially, language has been around for this period of time or even earlier.
Featured image: Depiction of the Hyoid bone in a Neanderthal. Image source .
Like the Denisovan genome recovered from a finger bone, a Neanderthal toe from the very same Siberian cave of wonders has yielded up secrets of humanity’s past. Not surprisingly, the ancestral web evident from the genomic analysis published in Nature is quite consistent with the story of our past found in the Bible’s book of Genesis.
The high-quality complete genomic sequence obtained from the bone—a Neanderthal woman’s toe—confirms other genetic data suggesting that Neanderthals and Denisovans had mixed with each other and with early modern humans. The extent of the intermingling of people groups seems somewhat limited, however, as we would expect in the wake of humanity’s dispersion from the Tower of Babel.
“Admixture seems to be common among human groups,”1 says lead author Kay Prüfer. “Nevertheless,” Prüfer, Svante Pääbo, and their colleagues write, “Our analyses show that hominin2 groups met and had offspring on many occasions in the Late Pleistocene, but that the extent of gene flow between the groups was generally low.”3
Scientists to grow 'mini-brains' using Neanderthal DNA
S cientists are preparing to create “miniature brains” that have been genetically engineered to contain Neanderthal DNA, in an unprecedented attempt to understand how humans differ from our closest relatives.
In the next few months the small blobs of tissue, known as brain organoids, will be grown from human stem cells that have been edited to contain “Neanderthalised” versions of several genes.
The lentil-sized organoids, which are incapable of thoughts or feelings, replicate some of the basic structures of an adult brain. They could demonstrate for the first time if there were meaningful differences between human and Neanderthal brain biology.
“Neanderthals are the closest relatives to everyday humans, so if we should define ourselves as a group or a species it is really them that we should compare ourselves to,” said Prof Svante Pääbo, director of the genetics department at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, where the experiments are being performed.
Pääbo previously led the successful international effort to crack the Neanderthal genome, and his lab is now focused on bringing Neanderthal traits back to life in the laboratory through sophisticated gene-editing techniques.
The lab has already inserted Neanderthal genes for craniofacial development into mice (heavy-browed rodents are not anticipated), and Neanderthal pain perception genes into frogs’ eggs, which could hint at whether they had a different pain threshold to humans. Now the lab is turning its attention to the brain.
“We’re seeing if we can find basic differences in how nerve cells function that may be a basis for why humans seem to be cognitively so special,” said Pääbo.
The research comes as the longstanding stereotype of Neanderthals as gormless and thuggish is being rewritten by emerging evidence that they buried their dead, produced cave art and had brains that were larger than our own.
Prof Svante Pääbo, director of evolutionary genetics at the Max Planck Institute for Evolutionary Anthropology. Photograph: Christian Jungeblodt
In the basement beneath Pääbo’s office, scientists are working to extract DNA – the code of life – from ancient human and animal fossils excavated at sites across the world. The team’s success relies on taking obsessive precautions against contamination: a speck of dust floating in through a window can contain more DNA than the few milligrams of powdered ancient bone under analysis. Researchers shower and don spacesuit-style uniforms before entering rooms kept sterile by UV lights and a sophisticated air filtration system.
It was under these stringent working conditions in 2010 that his team reassembled the code of the Neanderthal genome from heavily degraded samples taken from four females who lived in Europe tens of thousands of years ago.
The genome revealed Neanderthals interbred with our ancestors – and successfully enough that all non-Africans today carry 1-4% of Neanderthal DNA. And since people acquired slightly different genes, collectively about a third of the Neanderthal genome is still floating around in modern populations.
However, there are also genetic dead zones: large stretches of the Neanderthal genome that nobody inherited, possibly because they conferred disadvantages to health, fertility, cognition or physical appearance.
Evolutionary timeline
55m years ago
15m years ago
Hominidae (great apes) split off from the ancestors of the gibbon.
8m years ago
Chimp and human lineages diverge from that of gorillas.
4.4m years ago
Ardipithecus appears: an early "proto-human" with grasping feet.
4m years ago
Australopithecines appeared, with brains about the size of a chimpanzee’s.
2.3m years ago
Homo habilis first appeared in Africa.
1.85m years ago
First "modern" hand emerges.
1.6m years ago
Hand axes are a major technological innovation.
800,000 years ago
Evidence of use of fire and cooking.
700,000 years ago
Modern humans and Neanderthals split.
400,000 years ago
Neanderthals begin to spread across Europe and Asia.
300,000 years ago
200,000 years ago
60,000 years ago
Modern human migration from Africa that led to modern-day non-African populations.
“We want to know whether among those things, is there something hiding there that really sets us apart?” Pääbo said. “Is there a biological basis for why modern humans went on to become millions and eventually billions of people, spread across the world and have culture?”
It is not certain that the contrasting fates of the two species are linked to differences in cognition, but Pääbo said: “It’s tempting to think that, yes.”
The latest work focuses on differences in three genes known to be crucial for brain development. Using the editing technique Crispr, changes have been introduced into human stem cells to make them closer to Neanderthal versions.
The stem cells are coaxed using chemical triggers to become neurons, which spontaneously clump together and self-organise into miniature brain-like structures that grow to a few millimetres in diameter. The lack of any sensory input means the internal wiring is haphazard and varies from one blob to the next.
“You start the organoid growing and leave it for nine months and see what happens,” said Gray Camp, a group leader at the institute who is overseeing the organoid experiments. “You don’t get a well-formed human brain at all, but you see multiple regions have kind of formed you can study the synapses and electrical activity and early developmental differences.”
The scientists will compare the Neanderthalised organoids and the fully human ones to assess the speed at which the stem cells divide, develop and organise into three-dimensional brain structures and whether the brain cells wire up differently.
“A dream result would be that the [genetic] changes make for longer or more branched neuronal outgrowth,” said Pääbo. “One would say it would be a biological basis for why our brain would function differently.”
The work won’t reveal which species is “smarter”, but could hint at differences in the ability to plan, socialise and use language.
The lab is also looking at how Neanderthal genes that are commonly found in the DNA of people with European and Asian ancestry influence brain development. By growing organoids from cells taken from living people and looking at how the Neanderthal genes switch on and off, the team can see whether a person’s brain development is subtly influenced by their ancient Neanderthal ancestry.
“We can regrow your Neanderthal brain,” said Camp. “We can monitor that and resurrect the functionality of those neanderthal genes.”
The team are not the first to contemplate resurrecting Neanderthal biology. The Harvard professor George Church previously suggested that a cloned Neanderthal baby could be created if an “adventurous female human” were prepared to act as a surrogate. Such a scenario, Pääbo counters, is not only ethically unpalatable but unachievable with today’s technology, which allows for only a handful of genetic edits at a time rather than the 30,000 required for fully Neanderthal tissue.
Pääbo said he finds comments like Church’s frustrating because “then other people like me have to look like the boring, non-visionary guy, saying it’s not possible and think about the ethics.”
Do blobs of brain come with their own ethical considerations? “Yes, at some point one can of course ask, when does a developing brain become an individual? But that is far into the future.”
Modern humans and Neanderthals split into separate lineages around 400,000 years ago, with our ancestors remaining in Africa and the Neanderthals moving north into Europe. About 60,000 years ago, the archaeological record reveals, there was a mass migration of modern humans out of Africa that brought the two species face-to-face once more. The revelation that Neanderthals interbred with humans and were far more sophisticated than previously thought has led some to suggest the two lineages should be merged into a single species, but Pääbo and others disagree.
How Could Language Have Evolved?
PLOS Biology, August 26, 2014
Citation: Bolhuis JJ, Tattersall I, Chomsky N, Berwick RC (2014) How Could Language Have Evolved? PLoS Biol 12(8): e1001934. doi:10.1371/journal.pbio.1001934
The evolution of the faculty of language largely remains an enigma. In this essay, we ask why. Language’s evolutionary analysis is complicated because it has no equivalent in any nonhuman species. There is also no consensus regarding the essential nature of the language “phenotype.” According to the “Strong Minimalist Thesis,” the key distinguishing feature of language (and what evolutionary theory must explain) is hierarchical syntactic structure. The faculty of language is likely to have emerged quite recently in evolutionary terms, some 70,000–100,000 years ago, and does not seem to have undergone modification since then, though individual languages do of course change over time, operating within this basic framework. The recent emergence of language and its stability are both consistent with the Strong Minimalist Thesis, which has at its core a single repeatable operation that takes exactly two syntactic elements a and b and assembles them to form the set
Citation: Bolhuis JJ, Tattersall I, Chomsky N, Berwick RC (2014) How Could Language Have Evolved? PLoS Biol 12(8): e1001934. Copyright: © 2014 Bolhuis et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: JJB is funded by Utrecht University and by Netherlands Organization for Scientific Research (NWO) grants (ALW Open Competition and NWO Gravity and Horizon Programmes) (http://www.nwo.nl/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. It is uncontroversial that language has evolved, just like any other trait of living organisms. That is, once—not so long ago in evolutionary terms—there was no language at all, and now there is, at least in Homo sapiens. There is considerably less agreement as to how language evolved. There are a number of reasons for this lack of agreement. First, “language” is not always clearly defined, and this lack of clarity regarding the language phenotype leads to a corresponding lack of clarity regarding its evolutionary origins. Second, there is often confusion as to the nature of the evolutionary process and what it can tell us about the mechanisms of language. Here we argue that the basic principle that underlies language’s hierarchical syntactic structure is consistent with a relatively recent evolutionary emergence. Conceptualizations of Language The language faculty is often equated with “communication”—a trait that is shared by all animal species and possibly also by plants. In our view, for the purposes of scientific understanding, language should be understood as a particular computational cognitive system, implemented neurally, that cannot be equated with an excessively expansive notion of “language as communication” [1]. Externalized language may be used for communication, but that particular function is largely irrelevant in this context. Thus, the origin of the language faculty does not generally seem to be informed by considerations of the evolution of communication. This viewpoint does not preclude the possibility that communicative considerations can play a role in accounting for the maintenance of language once it has appeared or for the historical language change that has clearly occurred within the human species, with all individuals sharing a common language faculty, as some mathematical models indicate [1]–[3]. A similar misconception is that language is coextensive with speech and that the evolution of vocalization or auditory-vocal learning can therefore inform us about the evolution of language (Box 1) [1],[4]. However, speech and speech perception, while functioning as possible external interfaces for the language system, are not identical to it. An alternative externalization of language is in the visual domain, as sign language [1] even haptic externalization by touch seems possible in deaf and blind individuals [5]. Thus, while the evolution of auditory-vocal learning may be relevant for the evolution of speech, it is not for the language faculty per se. We maintain that language is a computational cognitive mechanism that has hierarchical syntactic structure at its core [1], as outlined in the next section. Box 1. Comparative Linguistics: Not Much to Compare A major stumbling block for the comparative analysis of language evolution is that, so far, there is no evidence for human-like language syntax in any nonhuman species [4],[41],[42]. There is no a priori reason why a version of such a combinatorial computational system could not have evolved in nonhuman animals, either through common descent (e.g., apes) or convergent evolution (e.g., songbirds) [1],[18]. Although the auditory-vocal domain is just one possible external interface for language (with signing being another), it could be argued that the strongest animal candidates for human-like syntax are songbirds and parrots [1],[41],[42]. Not only do they have a similar brain organization underlying auditory-vocal behavior [4],[43],[44], they also exhibit vocal imitation learning that proceeds in a very similar way to speech acquisition in human infants [4],[41],[42]. This ability is absent in our closest relatives, the great apes [1],[4]. In addition, like human spoken language, birdsong involves patterned vocalizations that can be quite complex, with a set of rules that govern variable song element sequences known as “phonological syntax” [1],[4],[41],[42],[45]. Contrary to recent suggestions [46],[47], to date there is no evidence to suggest that birdsong patterns exhibit the hierarchical syntactic structure that characterizes human language [41],[48],[49] or any mapping to a level forming a language of thought as in humans. Avian vocal-learning species such as parrots are able to synchronize their behavior to variable rhythmic patterns [50]. Such rhythmic abilities may be involved in human prosodic processing, which is known to be an important factor in language acquisition [51]. The Faculty of Language According to the “Strong Minimalist Thesis” In the last few years, certain linguistic theories have arrived at a much more narrowly defined and precise phenotype characterizing human language syntax. In place of a complex rule system or accounts grounded on general notions of “culture” or “communication,” it appears that human language syntax can be defined in an extremely simple way that makes conventional evolutionary explanations much simpler. In this view, human language syntax can be characterized via a single operation that takes exactly two (syntactic) elements a and b and puts them together to form the set
As the text below and Figure 1 shows, merge also accounts for the characteristic appearance of displacement in human language—the apparent “movement” of phrases from one position to another. Displacement is not found in artificially constructed languages like computer programming languages and raises difficulties for parsing as well as communication. On the SMT account, however, displacement arises naturally and is to be expected, rather than exceptional, as seems true in every human language that has been examined carefully. Furthermore, hierarchical language structure is demonstrably present in humans, as shown, for instance, by online brain imaging experiments [7], but absent in nonhuman species, e.g., chimpanzees taught sign language demonstrably lack this combinatorial ability [8]. Thus, before the appearance of merge, there was no faculty of language as such, because this requires merge along with the conceptual atoms of the lexicon. Absent this, there is no way to arrive at the essentially infinite number of syntactic language structures, e.g., “the brown cow,” “a black cat behind the mat” [9]–[11], etc. This view leaves room for the possibility that some conceptual atoms were present antecedent to merge itself, though at present this remains entirely speculative. Even if true, there seems to be no evidence for an antecedent combinatorial and hierarchical syntax. Furthermore, merge itself is uniform in the contemporary human population as well as in the historical record, in contrast to human group differences such as the adult ability to digest lactose or skin pigmentation [12]. There is no doubt that a normal child from England raised in northern Alaska would readily learn Eskimo-Aleut, or vice versa there have been no confirmed group differences in the ability of children to learn their first language, despite one or two marginal, indirect, and as yet unsubstantiated correlative indications [13]. This uniformity and stability points to the absence of major evolutionary change since the emergence of the language faculty. Taken together, these facts provide good evidence that merge was indeed the key evolutionary innovation for the language faculty. Figure 1. The binary operation of merge (X,Y) when Y is a subset of X leads to the ubiquitous phenomenon of “displacement” in human language, as in Guess what boys eat. Left: The circled structure Y, corresponding to what, the object of the verb eat, is a subset of the circled structure X, corresponding to boys eat what. Right: The free application of merge to X, Y in this case automatically leads to what occupying two syntactic positions, as required for proper semantic interpretation. The original what remains as the object of the verb so that it can serve as an argument to this predicate, and a copy of what, “displaced,” is now in the position of a quantificational operator so that the form can be interpreted as “for what x, boys eat x.” Typically, only the higher what is actually pronounced, as indicated by the line drawn through the lower what. doi:10.1371/journal.pbio.1001934.g001 It is sometimes suggested that external motor sequences are “hierarchical” in this sense and so provide an antecedent platform for language [14]. However, as has been argued [15], motor sequences resemble more the “sequence of letters in the alphabet than the sequences of words in a sentence” ([15], p. 221). (For expository purposes, we omit here several technical linguistic details about the labelling of these words see [16].) Along with the conceptual atoms of the lexicon, the SMT holds that merge, plus the internal interface mappings to the conceptual system, yields what has been called the “language of thought” [17]. More narrowly, the SMT also suffices to automatically derive some of the most central properties of human language syntax. For example, one of the most distinctive properties of human language syntax is that of “displacement,” along with what is sometimes called “duality of semantic patterning.” For example, in the sentence “(Guess) what boys eat,” “what” takes on a dual role and is interpreted in two places: first, as a question “operator” at the front of the sentence, where it is pronounced and second, as a variable that serves as the argument of the verb eat, the thing eaten, where it is not pronounced (Figure 1). (There are marginal exceptions to the nonpronunciation of the second “what” that, when analyzed carefully, support the picture outlined here.) Given the free application of merge, we expect human languages to exhibit this phenomenon of displacement without any further stipulation. This is simply because operating freely, without any further constraints, merge derives this possibility. In our example “(Guess) what boys eat,” we assume that successive applications of merge as in our earlier example will first derive
The Nature of Evolution Evolutionary analysis might be brought to bear on language in two different ways. First, evolutionary considerations could be used to explain the mechanisms of human language. For instance, principles derived from studying the evolution of communication might be used to predict, or even explain, the structural organization of language. This approach is fraught with difficulties. Questions of evolution or function are fundamentally different from those relating to mechanism, so evolution can never “explain” mechanisms [18]. For a start, the evolution of a particular trait may have proceeded in different ways, such as via common descent, convergence, or exaptation, and it is not easy to establish which of these possibilities (or combination of them) is relevant [18],[19]. More importantly, evolution by natural selection is not a causal factor of either cognitive or neural mechanisms [18]. Natural selection can be seen as one causal factor for the historical process of evolutionary change, but that is merely stating the essence of the theory of evolution. As we have argued, communication cannot be equated with language, so its evolution cannot inform the mechanisms of language syntax. However, evolutionary considerations—in particular, reconstructing the evolutionary history of relevant traits—might provide clues or hypotheses as to mechanisms, even though such hypotheses have frequently been shown to be false or misleading [18]. One such evolutionary clue is that, contrary to received wisdom, recent analyses suggest that significant genetic change may occur in human populations over the course of a few hundred years [19]. Such rapid change could also have occurred in the case of language, as we will argue below. In addition, as detailed in the next section, paleoanthropological evidence suggests that the appearance of symbolic thought, our most accurate proxy for language, was a recent evolutionary event. For instance, the first evidence of putatively symbolic artifacts dates back to only around 100,000 years ago, significantly after the appearance on the planet of anatomically distinctive Homo sapiens around 200,000 years ago [20],[21], The second, more traditional way of applying evolutionary analysis to language is to attempt to reconstruct its evolutionary history. Here, too, we are confronted with major explanatory obstacles. For starters, language appears to be unique to the species H. sapiens. That eliminates one of the cornerstones of evolutionary analysis, the comparative method, which generally relies on features that are shared by virtue of common descent (Box 1) [1],[4],[18]. Alternatively, analysis can appeal to convergent evolution, in which similar features, such as birds’ wings and bats’ wings, arise independently to “solve” functionally analogous problems. Both situations help constrain and guide evolutionary explanation. Lacking both, as in the case of language, makes the explanatory search more difficult. In addition, evolutionary analysis of language is often plagued by popular, naïve, or antiquated conceptions of how evolution proceeds [19],[22]. That is, evolution is often seen as necessarily a slow, incremental process that unfolds gradually over the eons. Such a view of evolutionary change is not consistent with current evidence and our current understanding, in which evolutionary change can be swift, operating within just a few generations, whether it be in relation to finches’ beaks on the Galapagos, insect resistance to pesticides following WWII, or human development of lactose tolerance within dairy culture societies, to name a few cases out of many [19],[22]–[24]. Language leaves no direct imprint in the fossil record, and the signals imparted by putative morphological proxies are highly mixed. Most of these involve speech production and detection, neither of which by itself is sufficient for inferring language (see Box 2). After all, while the anatomical potential to produce the frequencies used in modern speech may be necessary for the expression of language, it provides no proof that language itself was actually employed. What is more, it is not even necessary for language, as the visual and haptic externalization routes make clear. Moreover, even granting that speech is a requirement for language, it has been argued convincingly [25],[26] that equal proportions of the horizontal and vertical portions of the vocal tract are necessary for producing speech. This conformation is uniquely seen in our own species Homo sapiens. In a similar vein, the aural ability of nonhuman primates like chimpanzees or extinct hominid species such as H. neanderthalensis to perceive the sound frequencies associated with speech [26],[27] says nothing about the ability of these relatives to understand or produce language. Finally, neither the absolute size of the brain nor its external morphology as seen in endocasts has been shown to be relevant to the possession of language in an extinct hominid (Figure 2) [28]. Recent research has determined that Neanderthals possessed the modern version of the FOXP2 gene [29], malfunctions in which produce speech deficits in modern people [4],[30]. However, FOXP2 cannot be regarded as “the” gene “for” language, since it is only one of many that have to be functioning properly to permit its normal expression. Figure 2. A crude plot of average hominid brain sizes over time. Although after an initial flatlining this plot appears to show consistent enlargement of hominid brains over the last 2 million years, it is essential to note that these brain volumes are averaged across a number of independent lineages within the genus Homo and likely represent the preferential success of larger-brained species. From [20]. Image credit: Gisselle Garcia, artist (brain images). doi:10.1371/journal.pbio.1001934.g002 Box 2. The Infamous Hyoid Bone A putative relationship between basicranial flexion, laryngeal descent, and the ability to produce sounds essential to speech was suggested [52] before any fossil hyoid bones, the sole hard-tissue components of the laryngeal apparatus, were known. It was speculated that fossil hyoids would indicate when speech, and by extension language, originated. A Neanderthal hyoid from Kebara in Israel eventually proved very similar to its H. sapiens homologue, prompting the declaration that speech capacity was fully developed in adult H. neanderthalensis [53]. This was soon contested on the grounds that the morphology of the hyoid is both subsidiary [25] and unrelated [26] to its still-controversial [36] position in the neck. A recent study [54] focuses on the biomechanics, internal architecture, and function of the Kebara fossil. The authors conclude that their results “add support for the proposition that the Kebara 2 Neanderthal engaged in speech” ([54], p. 6). However, they wisely add that the issue of Neanderthal language will be fully resolved only on the basis of fuller comparative material. While the peripheral ability to produce speech is undoubtedly a necessary condition for the expression of vocally externalized language, it is not a sufficient one, and hyoid morphology, like most other lines of evidence, is evidently no silver bullet for determining when human language originated. In terms of historically calibrated records, this leaves us only with archaeology, the archive of ancient human behaviors—although we have once again to seek indirect proxies for language. To the extent that language is interdependent with symbolic thought [20], the best proxies in this domain are objects that are explicitly symbolic in nature. Opinions have varied greatly as to what constitutes a symbolic object, but if one excludes stone and other Paleolithic implements from this category on the fairly firm grounds that they are pragmatic and that the techniques for making them can be passed along strictly by imitation [31], we are left with objects from the African Middle Stone Age (MSA) such as pierced shell beads from various 100,000-year-old sites (e.g., [32]) and the 80,000-year-old geometrically engraved plaques from South Africa’s Blombos Cave [33] as the earliest undisputed symbolic objects. Such objects began to be made only substantially after the appearance, around 200,000 years ago, of anatomically recognizable H. sapiens, also in Africa [34]. To be sure, this inference from the symbolic record, like much else in paleontology, rests on evidence that is necessarily quite indirect. Nevertheless, the conclusion lines up with what is known from genomics. Our species was born in a technologically archaic context [35], and significantly, the tempo of change only began picking up after the point at which symbolic objects appeared. Evidently, a new potential for symbolic thought was born with our anatomically distinctive species, but it was only expressed after a necessary cultural stimulus had exerted itself. This stimulus was most plausibly the appearance of language in members of a species that demonstrably already possessed the peripheral vocal apparatus required to externalize it [20],[22]. Then, within a remarkably short space of time, art was invented, cities were born, and people had reached the moon. By this reckoning, the language faculty is an extremely recent acquisition in our lineage, and it was acquired not in the context of slow, gradual modification of preexisting systems under natural selection but in a single, rapid, emergent event that built upon those prior systems but was not predicted by them. It may be relevant to note that the anatomical ability to express language through speech was acquired at a considerable cost, namely the not-insignificant risk of adults choking to death [25],[36], as simultaneous breathing and swallowing became impossible with the descent of the larynx. However, since this conformation was already in place before language had demonstrably been acquired (see Box 2), the ability to express language cannot by itself have been the countervailing advantage. Finally, there has been no detectable evolution of the language faculty since it emerged, with no known group differences. This is another signature of relatively recent and rapid origin. For reasons like these, the relatively sudden origin of language poses difficulties that may be called “Darwin’s problem.” The Minimalist Account of Language—Progress towards Resolving “Darwin’s Problem” The Strong Minimalist Thesis (SMT) [6], as discussed above, greatly eases the explanatory burden for evolutionary analysis, since virtually all of the antecedent “machinery” for language is presumed to have been present long before the human species appeared. For instance, it appears that the ability to perceive “distinctive features” such as the difference between the sound b, as in bat, as opposed to p, as in pat, might be present in the mammalian lineage generally [37],[38]. The same holds for audition. Both comprise part of the externalization system for language. Furthermore, the general constraint of efficient computation would also seem plausibly antecedent in the cognitive computation of ancestral species. The only thing lacking for language would be merge, some specific way to externalize the internal computations and, importantly, the “atomic conceptual elements” that we have identified with words. Without merge, there would be no way to assemble the arbitrarily large, hierarchically structured objects with their specific interpretations in the language of thought that distinguish human language from other animal cognitive systems—just as Darwin insisted: “A complex train of thought can be no more carried out without the use of words, whether spoken or silent, than a long calculation without the use of figures or algebra” ([39], p. 88). With merge, however, the basic properties of human language emerge. Evolutionary analysis can thus be focused on this quite narrowly defined phenotypic property, merge itself, as the chief bridge between the ancestral and modern states for language. Since this change is relatively minor, it accords with what we know about the apparent rapidity of language’s emergence. No one knows for sure when language evolved, but fossil and genetic data suggest that humanity can probably trace its ancestry back to populations of anatomically modern Homo sapiens (people who would have looked like you and me) who lived around 150,000 to 200,000 years ago in eastern or perhaps southern Africa [4,5,6]. Because all human groups have language, language itself, or at least the capacity for it, is probably at least 150,000 to 200,000 years old. This conclusion is backed up by evidence of abstract and symbolic behaviour in these early modern humans, taking the form of engravings on red-ochre [7, 8]. The archaeological record reveals that about 40,000 years ago there was a flowering of art and other cultural artefacts at modern human sites, leading some archaeologists to suggest that a late genetic change in our lineage gave rise to language at this later time [9]. But this evidence derives mainly from European sites and so struggles to explain how the newly evolved language capacity found its way into the rest of humanity who had dispersed from Africa to other parts of the globe by around 70,000 years ago. About 400,000 years ago, Neanderthals settled across Eurasia in groups of between about twelve and twenty-four people. Individual groups formed alliances with other groups nearby. Though Neanderthals died out in most of Eurasia somewhere around 40,000 years ago, some may have survived on the Iberian Peninsula for significantly longer. Either way, before they went completely extinct, Neanderthals had a long and successful run. Over the course of about 360,000 years they adapted to climate change of two sorts — rapid warming and quick cooling. They shared terrain with threatening megafauna such as straight-tusked elephants, hippopotami, cave lions, cave bears, cave hyenas, rhinoceroses, and scimitar-toothed cats. They used fire and made precise, stone-tipped wooden spears and cutting tools. They twisted plant fibers into three-ply rope that might have been used to make bags, fishing nets, sleeping mats, and sails. They made ornaments and other beautiful but non-functional objects. They may have worn shells and feathers. Yet Neanderthals’ intelligence has long been denigrated. Neanderthals and ancestral Homo sapiens (humans) looked a lot alike, though Neanderthals had a more ape-like appearance. When, in 1829 the first Neanderthal skull was discovered in Belgium, the scientific community was decidedly not interested in what they thought was a deformed human head. This isn’t surprising. Charles Darwin wouldn’t set out his basic ideas about evolution in On the Origin of Species by Means of Natural Selection for another thirty years. Yet another twelve years would pass before, in The Descent of Man, and Selection in Relation to Sex, he would suggest for the first time that humans descended from apes. This is to say that the discovery of the Neanderthal skull in Belgium preceded scientific consensus that there was any such thing as evolution, much less an evolutionary precursor to modern humans. No one examined the skull closely for another hundred years. In 1848, still a good twenty-three years before The Descent of Man was published, a second Neanderthal skull was found, this one at Gibraltar, which is at the southern tip of Spain’s Iberian Peninsula. That skull met the same fate as the first it was ignored. Finally, by 1856 when the skeleton of a barrel-chested male Neanderthal was discovered in Germany in the Neander Valley (“thal” is the Old German word for “valley”), the idea of “transmutation” within and between species was at least within the borderlands of scientific discourse. This may be why a few paleontologists took interest in the Neanderthal skeleton. However, the skeleton’s posture seemed hunched, the ribcage looked wide, and the skull and bones were thicker than those of modern humans. The general reaction to the strange skeleton was one of fascinated repulsion. It seemed like it might be the bones of some savage, evolutionary dead-end. Homo stupidus is the name zoologist Ernest Haeckel gave to that particular skeleton’s bones. (Haeckel’s astonishing ethnocentrism and lack of imagination regarding Neanderthals aside, he was an important scientist of his day. He coined the phrase “ontogeny recapitulates phylogeny.” By this he meant that an organism’s prenatal development is a quick, summary expression of its species’ evolutionary development. That idea has since been disproven, but not before it caught the fancies of generations of biology students thrilled to learn that developing human fetuses have gills. Which they do not, but they do have slits in places corresponding to where gills would grow if humans were fish.) Perhaps because most Christian Europeans of the time still believed in the God-made-the-world-and-mankind-in-six-days-and-rested-on-the-seventh origin story, Haeckel’s characterization of Neanderthals as knuckle draggers went generally unchallenged. How could they have anything whatsoever to do with us? In 1908 another Neanderthal skeleton was discovered near La Chapelle-aux-Saints in central France. Marcellin Boule, a geologist, paleontologist, and physical anthropologist at the Muséum National d’Histoire Naturelle in Paris, would probably have read Haeckel on the matter of H. stupidus. Boule reacted to the La Chapelle-aux-Saints discovery’s primate-like posture, thick bones and skull, low-vaulted cranium, and brow ridges by describing the skeleton as subhuman. He did so even though, as an eminent paleontologist and anthropologist, he had surely read Darwin’s 1871 The Descent of Man and therefore knew that ancestral humans might have looked like primates. Even so, he didn’t seem to factor into his calculus the possibility that Neanderthals were anything but the ugly remains not of pre-humans but of humans’ unpleasant, failed, and very distant cousins (at best). This is ironic, for before Neanderthals went extinct, they enjoyed 360,000 years of lively history. If any of the modern crises (nuclear war, pandemic, climate change) wipe humans out, the Neanderthals’ run will have been twice as long as that of H. sapiens. Fast-forward a few decades after Boule. With a discovery in 1957 in the Shanidar Cave in northern Iraq, the picture of Neanderthal intelligence started to clarify. Working with local Kurds, a team from Columbia University found graves that appeared to have been created as long as 65,000 years ago. Inside the graves were the bones of eight adult and two infant Neanderthals. Fossilized flower pollens surrounded one of the skeletons, a sign that Neanderthals had mortuary practices and burial rituals and, possibly, a mythology about life after death. Healed injuries and set bones on some of the skeletons showed that Neanderthals had a functional folk medicine. The skeleton of a Neanderthal found at Shanidar cave in Irbil and datable to about 45000 years ago, . [+] is displayed at the Iraqi National Museum in Baghdad, Iraq, (AP Photo/Hadi Mizban) Perhaps just as importantly, the Shanidar Cave findings also revealed a trait that may have been common among Neanderthals — extraordinary compassion. “Healed injuries and set bones” doesn’t begin to describe the state of some of the Shanidar Cave skeletons. As reported by the IB Times, one of the skeletons retrieved from the cave had many injuries including a blind eye, a missing (and possibly amputated) lower arm, and two broken legs. He was also partially deaf, and he had a fractured C5 vertebrae. Another of the Shanidar Cave skeletons had a degenerative joint disorder that would have made walking difficult. Even though both men’s injuries had been very long-standing when they died, and both were so disabled that they could probably not take care of themselves, they had been able to stay alive for years. As discoveries at the Shanidar Cave and many other sites have continued, more evidence of intelligence and compassion has emerged. Meanwhile, in the popular world, the idea of Neanderthals as slouched, hairy brutes persists, possibly fueled by something as inane (and, to be clear, completely harmless) as caveman cartoons. Only within the past few decades have scientists begun to realize that Neanderthals may have been as cognitively advanced as the ancestral H. sapiens that, about 55,000 years ago, settled alongside Neanderthals in Europe and Asia. For example: · About 65,000 years ago, Neanderthals may have created cave paintings in Spain. These paintings were originally attributed to ancestral H. sapiens, but they pre-dated H. sapiens’ arrival in the area by many thousands of years. If the paintings were, indeed, made by Neanderthals, they suggest a capacity for symbolic thinking — and perhaps for language, as well. Picture shows neanderthal cave-paintings inside the Andalusian cave of Ardales, on March 1, 2018. · There is no written record of Neanderthal language. Even so, they very well may have been capable of spoken communication. If so, they may have gained their genetic capacity for language from the same source that ancestral H. sapiens did. Neanderthals and humans share two evolutionary changes in FOXP2, a gene that has been implicated in the development of speech and language. The gene may have come from Neanderthals’ and humans’ common ancestor. · According to the team of anthropologists that discovered the three-ply Neanderthal rope, the use of twisted fibers suggests that they may have understood mathematical concepts like pairs, sets, and numbers. · Analysis of the calcified food on Neanderthal teeth reveals a little about their folk medicine. They seem to have treated illnesses with poplar, (a natural source of aspirin) and the mold Penicillium, which is the source of the antibiotic, penicillin. Neanderthal childhood had much in common with human childhood. While adult Neanderthals had brains larger than those of their human counterparts, brain size at birth was comparable to that of modern human newborns. The ribcages of Neanderthal children were wider, but their skeletons took about as long as those of modern human children to mature. In a 2014 issue of the Oxford Journal of Archeology archeologists from the University of York argued that, just like lower primates, great apes, and humans, Neanderthal children probably played, at least when conditions were safe to do so. Playing is a way to pass time while parents work — but it’s also essential to skill building and to the creation of group bonds. If the pattern from primates held true for Neanderthal children, peek-a-boo as well as various throwing and swinging activities may have been games of choice. When Neanderthal children died, they were lovingly buried, sometimes along with artifacts that may have been toys. Radiocarbon dating published in 2015 in the journal Nature indicated that Neanderthals disappeared without a trace a few thousand years after ancestral H. sapiens arrived from Africa and shared Eurasia with them. No definitive answer to the question of why Neanderthals went extinct has proven reliable, though: · Competition between ancestral H. sapiens and Neanderthals has long been a leading contender among the various scenarios. · The rapid cooling of the last Ice Age may have killed off the Neanderthals. · Disease contracted from humans is another contender. · Considering that Neanderthal populations were probably always small, inbreeding, wars, disease, and natural disasters may have been enough to cause populations to collapse like dominoes. One occasionally promulgated theory explaining the demise of Neanderthals is that the women may have had prolonged periods of postpartum infertility, possibly because their babies’ higher metabolic demands required them to be weaned later than babies of ancestral H. sapiens. This could have reduced birth rates, which might have made Neanderthal populations especially vulnerable. This November, however, in a paper in the journal Proceedings of the Natural Academy of Sciences of the United States of America (PNAS), a team of scientists from Italy and the U.K. called that idea into question. The scientists had examined three baby teeth found in northeastern Italy. The growth lines in the enamel and calcified food on the teeth showed that Neanderthal children were introduced to solid foods at five or six months — about when most modern human children are given their first food. After Ernest Haeckel’s uproarious idea of Homo stupidus finally wore thin, the binomial (two-word) name Homo neanderthalensis was suggested for Neanderthals in 1863. As do all binomial names in scientific nomenclature, it identifies the genus (in this case “Homo,” which is Latin for “man” or “person”), and then identifies the species. In this case “neanderthalensis” (“-ensis” being a Latin suffix meaning “pertaining to” or “originating in”) refers to the entire species. (The absence of a third name in the string signifies the absence of any subspecies whatsoever.) Similarly, in common scientific nomenclature, humans are identified by a genus name (Homo) and then a species name, “sapiens” (Latin for “wise”). In the case of H. sapiens, the use of “sapiens” with no third name in the string indicates the assumption that no sapiens subspecies exists. Except that one might have, about between about 400,000 and 40,000 years ago. After all, in biological terms a species is defined as organisms that share common characteristics and that are capable of successfully breeding. Neanderthals and H. sapiens fit that bill. Forty thousand years ago, Neanderthals looked only slightly different from H. sapiens, and their lives, cognitive competencies, and emotional capabilities seem to have been in many ways similar. They had a common ancestor. They even interbred. Anywhere from one to four percent of the DNA of non-African modern humans are of Neanderthal origin. When H. sapiens and Neanderthals shared areas of Eurasia, Neanderthal DNA may have comprised from six to nine percent of human DNA. Why do the scientific names of Neanderthals and humans not make any reference to each other? Are we humans so enraptured with the idea of ourselves as special or “chosen” that we are unable to recognize Neanderthals as the fellow Homo species members that they might have been? Are we too repulsed by their more primitive look to see them clearly? Back in the 1970s, Neanderthals were called H. sapiens neanderthalensis — wise humans of the Neanderthal kind. H. sapiens sapiens was the moniker for humans. It will be interesting to see whether, as dating technologies improve and any understanding of human and Neanderthal commonality deepens, scientists decide to revisit the questions of nomenclature and of who, exactly, Neanderthals were and who we humans are now. These advances bring researchers together in exciting new ways. Over 140 new Nazca Lines , ancient images carved into a Peruvian desert, were discovered using artificial intelligence to sift through drone and satellite imagery. With the wealth of high-resolution satellite imagery online, teams are also turning to crowdsourcing to find new archaeological sites. Although new partnerships among archaeologists and scientific specialists are not always tension-free , there is growing consensus that studying the past means reaching across fields. The Open Science movement aims to makes this work accessible to all. Scientists including archaeologists are sharing data more freely within and beyond the academy. Public archaeology programs, community digs and digital museum collections are becoming common. You can even print your own copy of famous fossils from freely available 3D scans , or an archaeological coloring book in more than 30 languages. Efforts to make archaeology and museums more equitable and engage indigenous research partners are gaining momentum as archaeologists consider whose past is being revealed . Telling the human story requires a community of voices to do things right. In two new studies, genetic researchers have shown that about 20 percent of the Neanderthal genome survives in modern humans of non-African ancestry and identified exactly which areas of the human genome retain segments of Neanderthal DNA. Neanderthal. Image credit: Trustees of the Natural History Museum, London. About 30,000 years ago, Homo sapiens migrating out of Africa began encountering Neanderthals, a lineage that had diverged from modern humans hundreds of thousands of years before. Despite their differences, Homo sapiens and Neanderthals mingled, and over time, produced children with genes from both lineages. Today, the biological remnants of that collision between two distinct populations remain alive in the genomes of Europeans and East Asians. The first study, reported in the journal Nature, examines how Neanderthals influence the genetic composition of modern humans. Study’s senior author Dr David Reich of Harvard Medical School said: “the goal was to understand the biological impact of the gene flow between Neanderthals and modern humans.” “We reasoned that when these two groups met and mixed, some new traits would have been selected for and remained in the human genome, while some incompatibilities would have been selected against and removed.” “As methods to analyze ancient DNA continue to improve, we are able to get at answers to ever more fine-grained questions about our evolutionary history,” added Dr Elizabeth Tran of the National Science Foundation, who was not involved in the studies. Dr Reich and his colleagues analyzed genetic variants in 846 people of non-African heritage, 176 people from sub-Saharan Africa, and a 50,000-year-old Neanderthal. They showed that nine previously identified human genetic variants known to be associated with specific traits likely came from Neanderthals. These variants affect lupus, biliary cirrhosis, Crohn’s disease, optic-disk size and type 2 diabetes and also some behaviors, such as the ability to stop smoking. The team expects that more variants will be found to have Neanderthal origins. The team also measured how Neanderthal DNA present in human genomes today affects keratin production and disease risk. “Neanderthal ancestry is increased in genes affecting keratin filaments. This fibrous protein lends toughness to skin, hair and nails and can be beneficial in colder environments by providing thicker insulation. It’s tempting to think that Neanderthals were already adapted to the non-African environment and provided this genetic benefit to humans,” Dr Reich said. The scientists also found that some areas of the modern non-African human genome were rich in Neanderthal DNA, which may have been helpful for human survival, while other areas were more like ‘deserts’ with far less Neanderthal ancestry than average. “The barren areas were the most exciting finding. It suggests the introduction of some of these Neanderthal mutations was harmful to the ancestors of non-Africans and that these mutations were later removed by the action of natural selection,” said lead author Dr Sriram Sankararaman from the Harvard and MIT’s Broad Institute and Harvard Medical School. The team showed that the areas with reduced Neanderthal ancestry tend to cluster in two parts of our genomes: genes that are most active in the male germline and genes on the X chromosome. This pattern has been linked in many animals to a phenomenon known as hybrid infertility, where the offspring of a male from one subspecies and a female from another have low or no fertility. Dr Reich explained: “this suggests that when ancient humans met and mixed with Neanderthals, the two species were at the edge of biological incompatibility.” “Present-day human populations, which can be separated from one another by as much as 100,000 years, are fully compatible with no evidence of increased male infertility. In contrast, ancient human and Neanderthal populations apparently faced interbreeding challenges after 500,000 years of evolutionary separation.” The second study, published online in the journal Science, tests an innovative, fossil-free method for sequencing archaic DNA. Co-authors Dr Benjamin Vernot and Dr Joshua Akey, both from the University of Washington, analyzed whole-genome sequencing data from 379 Europeans and 286 East Asians to identify Neanderthal lineages that persist in the modern DNA. “We found evidence that Neanderthal skin genes made Europeans and East Asians more evolutionarily fit, and that other Neanderthal genes were apparently incompatible with the rest of the modern human genome, and thus did not survive to present day human populations,” Dr Vernot said. The scientists observed that certain chromosomes arms in humans are tellingly devoid of Neanderthal DNA sequences, perhaps due to mismatches between the two species along certain portions of their genetic materials. For example, they noticed a strong depletion of Neanderthal DNA in a region of human genomes that contains a gene for a factor thought to play an important role in human speech and language. The results suggest that significant amounts of population-level DNA sequences might be obtained from extinct groups even in the absence of fossilized remains, because these ancient sequences might have been inherited by other individuals from whom scientists can gather genomic data. Therein lies the potential to discover and characterize previously unknown archaic humans that bred with early humans. “The fossil free method of sequencing archaic genomes not only holds promise in revealing aspects of the evolution of now-extinct archaic humans and their characteristic population genetics, it also might provide insights into how interbreeding influenced current patterns of human diversity,” Dr Vernot said. “In the future, I think scientists will be able to identify DNA from other extinct hominin, just by analyzing modern human genomes.” “From our end, this was an entirely computational project. I think it’s really interesting how careful application of the correct statistical and computational tools can uncover important aspects of health, biology and human history. Of course, you need good data, too.” Sriram Sankararaman et al. The genomic landscape of Neanderthal ancestry in present-day humans. Nature, published online January 29, 2014 doi: 10.1038/nature12961 Benjamin Vernot and Joshua M. Akey. Resurrecting Surviving Neandertal Lineages from Modern Human Genomes. Science, published online January 29, 2014 doi: 10.1126/science.1245938 F or David Reich, research can be a harrowing experience. The 44-year-old Harvard University geneticist says he now goes to bed terrified he will wake up to find his team’s recent, stunning discoveries about human ancestry have been proved wrong. “We are now making so many startling insights I sometimes fear it must all be incorrect,” he says. To be fair to Reich, no one has yet found any hint his results are invalid. “That still doesn’t stop me worrying,” he insists. Reich’s work as a leader of prehistoric population studies includes the discovery that all people of non-African descent carry small amounts of Neanderthal DNA, showing that Homo sapiens – at one stage – must have interbred with this long-dead species of ancient humans. Reich was also involved in uncovering the existence of Denisovans, a previously unknown species of ancient humans, using DNA found in fossil scraps in a Siberian cave. In addition, he has discovered that 5,000 years ago northern Europe was overrun by invaders from central Asia, a migration of profound importance – for those newcomers became the first people of the British Isles. These remarkable recreations of our past are outlined in Reich’s book Who We Are and How We Got Here, in which he chronicles the spectacular rise of ancient DNA studies in the last few years. Thanks to this remarkable new science, we now know that about 70,000 years ago, our planet was remarkably rich in terms of its human variety. It was populated by modern humans, Neanderthals – and the Denisovans who, Reich has recently discovered, must have existed as at least two separate varieties: Siberian Denisovans and the more recently discovered Australo-Denisovans from south-east Asia. In addition, we also know that the Hobbit folk – Homo floresiensis, a race of tiny humans whose remains were discovered in 2003 – were then thriving in Indonesia. In those not too distant days, there were many ways to be a human, it transpires. A recreation of the face of a Neanderthal. Photograph: Jose A Astor/Alamy Stock Photo The ingrained notion – that there has only ever been one species of human being, Homo sapiens – is a latterday fiction born of our own self-important view of ourselves. Think instead of the bar scene from Star Wars with all those various people playing and drinking, says the Israeli palaeontologist Yoel Rak. That gives a far better flavour of our evolutionary past. In making constant new discoveries about humanity, Reich and his Harvard team are now plunging into uncharted academic waters. “We are going out on a limb on so many different studies,” he says. “It is very lonely and somewhat terrifying. We don’t have the comfort of standing on the shoulders of others. We are the first. That’s why I worry.” Reich’s influence in this field has been immense and the output of his department monumental. This year alone he has been involved in producing an analysis that reveals the existence of a previously unknown group of ancient Native Americans from fossil remains uncovered in Alaska a study that shows the ancient British people who built Stonehenge and other great neolithic monuments were almost completely replaced by invaders from central Asia 5,000 years ago and a paper that indicates there were at least two waves of settlers, from Taiwan and then Papua New Guinea, which were responsible – 3,000 years ago – for the settling of one of the last pockets of the planet to be reached by humans, Vanuatu. Ancient DNA studies are overturning our oversimplified vision of our past and are the outcome of a late 20th-century revolution in molecular biology that gave scientists the power to study DNA, the material from which our genes are made, with startling precision. For the first time, the exact structure and makeup of a gene could be determined and the detailed origins of many inherited illnesses and cancers outlined, setting in motion the slow, ongoing task of developing new treatments. By contrast, the study of ancient DNA, which uses the same basic technology, began late but has since flowered far more dramatically. “It is in the area of shedding light on human migrations – rather than in explaining human biology – that the genome revolution has been a runaway success,” says Reich. The field’s hesitant start is understandable. In samples from living animals, DNA exists in long, healthy, easily analysed strands. However, DNA starts to decay the moment an organism dies and those strands quickly fragment. And the longer the passage of time, the shorter the fragments become. This disintegration poses problems. If, for example, you want to study Neanderthals, who dominated Europe for around 400,000 years and who were close in evolutionary terms to Homo sapiens, DNA from their fossils is going to be in minuscule pieces. The last member of this doomed species died more than 40,000 years ago, after all. Genetic material taken from Neanderthal fossils is also likely to be contaminated with large amounts of DNA from bacteria and vegetation – and sometimes from researchers. Trying to create a genome from these sullied scraps has been likened, by writer Elizabeth Kolbert, to reassembling “a Manhattan telephone book from pages that have been put through a shredder, mixed with yesterday’s trash and left to rot in a landfill”. Nevertheless, scientists have persevered and in 2007, geneticist Svante Pääbo, of the Max Planck Institute for Evolutionary Anthropology, decided to assemble a team of experts to sequence a Neanderthal genome that would be billions of DNA units in length. Reich, an innovator in the field of studying population mixtures, was asked to join and has since played a key role in the fledgling field’s remarkable development. Clean rooms were built, advanced gene sequencers purchased and DNA extracted from Neanderthal bones that had been found in Vindija cave in Croatia. A Neanderthal genome was slowly spliced together from pieces of DNA only a few dozen units in length. It was a brilliant achievement though Reich makes clear progress was halting. “The Neanderthal sequences we were working with had a mistake approximately every 200 DNA letters,” he reveals in his book. These errors were not due to differences between humans and Neanderthals, it should be pointed out, but to errors made in analysing DNA. It was Reich’s task to get round these problems and help create a meaningful genome of a Neanderthal. From that, scientists could assess just how closely we were related to these ancient people. His tests succeeded and subsequently showed, to everyone’s surprise, that many modern humans carry small amounts of Neanderthal DNA in their genomes. “Non-African genomes today are around 1.5 to 2.1% Neanderthal in origin,” he says. So yes, Homo sapiens and Neanderthals had a common ancestor, about 500,000 years ago, before the former evolved as a separate species – in Africa – and the latter as a different species in Europe. Then around 70,000 years ago, when modern humans emerged from Africa, we encountered the Neanderthals, most probably in the Middle East. We briefly mixed and interbred with them before we continued our slow diaspora across the planet. In doing so, those early planetary settlers carried Neanderthal DNA with them as they spread out over the world’s four quarters. Hence its presence in all those of non-African origin. By contrast, Neanderthal DNA is absent in people of African origins because they remained in our species’s homeland. Reich has since established that such interbreeding may have occurred on more than one occasion. More importantly, his studies show that “Neanderthals must have been more like us than we had imagined, perhaps capable of many behaviours that we typically associate with modern humans”. They would, most likely, have had language, culture and sophisticated behaviours. Hence the mutual attraction. That itself is intriguing. However, there is another key implication of Reich’s work. Previously, it had been commonplace to view human populations arising from ancestral groupings like the trunk of a great tree. “Present populations budded from past ones, which branched from a common root in Africa,” he states. “And it implies that if a population separates then it does not remix, as fusions of branches cannot occur.” But the initial separation of the two lines of ancient humans who gave rise to Neanderthals and to Homo sapiens – and then their subsequent intermingling – shows that remixing does occur. Indeed, Reich believes it was commonplace and that the standard tree model of populations is basically wrong. Throughout our prehistory, populations have split, reformed, moved on, remixed and interbred and then moved on again. Alliances have shifted and empires have fallen in a perpetual, sliding global Game of Thrones. An illustration is provided by the puzzling fact that Europeans and Native Americans share surprising genetic similarities. The explanation was provided by Reich who has discovered that a now nonexistent group of people, the Ancient North Eurasians, thrived around 15,000 years ago and then split into two groups. One migrated across Siberia and gave rise to the people who crossed the Bering land bridge between Asia and America and later gave rise to Native Americans. The other group headed west and contributed to Europeans. Hence the link between Europeans and Native Americans. No physical specimen of the Ancient North Eurasian people had ever been discovered when Reich announced their existence. Instead, he based his analysis on the ghostly impact of their DNA on present-day people. However, the fossil remains of a boy, recently found near the Siberian village of Mal’ta, have since been found to have DNA that matches the genomes of Ancient North Eurasians, giving firmer physical proof of their existence. “Prior to the genome revolution, I – like most others – had assumed that the big genetic clusters of populations we see today reflect deep splits of the past. But in fact the big clusters today are themselves the result of mixtures of very different populations that existed earlier. There was never a single trunk population in the human past. It has been mixtures all the way down.” Instead of a tree, a better metaphor would be a trellis, branching and remixing far back into the past, says Reich, whose work indicates that the idea of race is a very fluid, ephemeral concept. However, he is adamant that it is a very real one and takes issue with those geneticists who argue that there are no substantial differences in traits between populations. “This is a strategy that we scientists can no longer afford and that in fact is positively harmful,” he argues. Plenty of traits show differences between populations: skin colour, susceptibility to disease, the ability to breath at high altitudes and the ability to digest starch. More to the point, uncovering these differences is only just beginning. Many more will be discovered over the decades, Reich believes. Crucially, we need to be able to debate the implications of their presence at varying levels in different populations. That is not happening at present and that has dangerous implications. “If as scientists we wilfully abstain from laying out a rational framework for discussing human differences, we will leave a vacuum that will be filled by pseudoscience, an outcome that is far worse than anything we could achieve by talking openly,” says Reich. The genome revolution provides us with a shared history, he adds. “If we pay proper attention, it should give us an alternative to the evils of racism and nationalism and make us realise that we are all entitled equally to our human heritage.” DNA from an ancient man in Siberia shows how Stone Age people spread into Asia. Unearthed by an ivory carver from a Siberian riverbank, a man's 45,000-year-old thigh bone reveals when people first mated with Neanderthals, an international genetics team reports Wednesday. The Ust'-Ishim man's thigh bone is the oldest human bone found so far outside of Africa and the Middle East, according to the report in the journal Nature. It's nearly twice as old as the next oldest from a modern human, which comes from a boy who died elsewhere in Siberia some 24,000 years ago. Scientists collected DNA from the bone and analyzed the ancient man's complete genetic map, or genome. The DNA narrows down the time when mating first brought Neanderthal genes into the human gene pool: from 50,000 to 60,000 years ago. "It's really exciting that we now have a really high-quality genome sequence of an early modern human that is this old," says study author and genetics expert Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Recent DNA studies led by Max Planck's Svante Pääbo, another author of the new study, have found traces of Neanderthal in modern people. Typically about 1.6 to 2.1 percent of the genes in people of Eurasian descent are Neanderthal in origin. (Related: "Neanderthals Died Out 10,000 Years Earlier Than Thought, With Help From Modern Humans.") Archaeological finds show that Neanderthals and modern humans overlapped in the Middle East as long as 100,000 years ago, says paleoanthropologist John Hawks of the University of Wisconsin in Madison. But the new DNA findings seem to rule out mating taking place until much later. Previous studies put the timing of the earliest human-Neanderthal mating anywhere from 86,000 to 37,000 years ago. The researchers narrowed that range to 50,000 to 60,000 years ago by calculating the loss of Neanderthal genes over time since the gene swapping occurred. The Ust'-Ishim man had about 2.3 percent Neanderthal genes, but modern people typically have less than 2.1 percent. Using the mutation rate as a genetic "clock," the researchers extrapolated back to determine the era when modern humans picked up genes from Neanderthals. "I think the paper is pretty convincing on this," Hawks says. But he cautions that the idea of a single time of human mating with Neanderthals "almost certainly is an oversimplification. The contacts could have extended over a longer period." A possible second, more recent, episode may explain slightly higher numbers of Neanderthal genes common today in East Asians, according to the study. The femur shaft turned up on the banks of the Irtysh River near Ust'-Ishim, Russia, in 2008. A Russian ivory carver and historian named Nikolay Peristov collected the bone after it eroded from a bluff above the river in western Siberia. It was identified as human, based on its teardrop-shaped cross section, in 2010.
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