Did humans speak through cave art? New paper links ancient drawings and language’s origins

When and where did humans develop language? To find out, look deep inside caves, suggests an MIT professor.

Stock image of a cave painting in South Africa [Credit: MIT]

More precisely, some specific features of cave art may provide clues about how our symbolic, multifaceted language capabilities evolved, according to a new paper co-authored by MIT linguist Shigeru Miyagawa.

A key to this idea is that cave art is often located in acoustic “hot spots,” where sound echoes strongly, as some scholars have observed. Those drawings are located in deeper, harder-to-access parts of caves, indicating that acoustics was a principal reason for the placement of drawings within caves. The drawings, in turn, may represent the sounds that early humans generated in those spots.

In the new paper, this convergence of sound and drawing is what the authors call a “cross-modality information transfer,” a convergence of auditory information and visual art that, the authors write, “allowed early humans to enhance their ability to convey symbolic thinking.” The combination of sounds and images is one of the things that characterizes human language today, along with its symbolic aspect and its ability to generate infinite new sentences.

“Cave art was part of the package deal in terms of how homo sapiens came to have this very high-level cognitive processing,” says Miyagawa, a professor of linguistics and the Kochi-Manjiro Professor of Japanese Language and Culture at MIT. “You have this very concrete cognitive process that converts an acoustic signal into some mental representation and externalizes it as a visual.”

Cave artists were thus not just early-day Monets, drawing impressions of the outdoors at their leisure. Rather, they may have been engaged in a process of communication.

“I think it’s very clear that these artists were talking to one another,” Miyagawa says. “It’s a communal effort.”

The paper, “Cross-modality information transfer: A hypothesis about the relationship among prehistoric cave paintings, symbolic thinking, and the emergence of language,” is published in the journal Frontiers in Psychology. The authors are Miyagawa; Cora Lesure, a PhD student in MIT’s Department of Linguistics; and Vitor A. Nobrega, a PhD student in linguistics at the University of Sao Paulo, in Brazil.

Re-enactments and rituals?

The advent of language in human history is unclear. Our species is estimated to be about 200,000 years old. Human language is often considered to be at least 100,000 years old.

“It’s very difficult to try to understand how human language itself appeared in evolution,” Miyagawa says, noting that “we don’t know 99.9999 percent of what was going on back then.” However, he adds, “There’s this idea that language doesn’t fossilize, and it’s true, but maybe in these artifacts [cave drawings], we can see some of the beginnings of homo sapiens as symbolic beings.”

While the world’s best-known cave art exists in France and Spain, examples of it abound throughout the world. One form of cave art suggestive of symbolic thinking — geometric engravings on pieces of ochre, from the Blombos Cave in southern Africa — has been estimated to be at least 70,000 years old. Such symbolic art indicates a cognitive capacity that humans took with them to the rest of the world.

“Cave art is everywhere,” Miyagawa says. “Every major continent inhabited by homo sapiens has cave art. … You find it in Europe, in the Middle East, in Asia, everywhere, just like human language.” In recent years, for instance, scholars have catalogued Indonesian cave art they believe to be roughly 40,000 years old, older than the best-known examples of European cave art.

But what exactly was going on in caves where people made noise and rendered things on walls? Some scholars have suggested that acoustic “hot spots” in caves were used to make noises that replicate hoofbeats, for instance; some 90 percent of cave drawings involve hoofed animals. These drawings could represent stories or the accumulation of knowledge, or they could have been part of rituals.

In any of these scenarios, Miyagawa suggests, cave art displays properties of language in that “you have action, objects, and modification.” This parallels some of the universal features of human language — verbs, nouns, and adjectives — and Miyagawa suggests that “acoustically based cave art must have had a hand in forming our cognitive symbolic mind.”

Future research: More decoding needed

To be sure, the ideas proposed by Miyagawa, Lesure, and Nobrega merely outline a working hypothesis, which is intended to spur additional thinking about language’s origins and point toward new research questions.

Regarding the cave art itself, that could mean further scrutiny of the syntax of the visual representations, as it were. “We’ve got to look at the content” more thoroughly, says Miyagawa. In his view, as a linguist who has looked at images of the famous Lascaux cave art from France, “you see a lot of language in it.” But it remains an open question how much a re-interpretation of cave art images would yield in linguistics terms.

The long-term timeline of cave art is also subject to re-evaluation on the basis of any future discoveries. If cave art is implicated in the development of human language, finding and properly dating the oldest known such drawings would help us place the orgins of language in human history — which may have happened fairly early on in our development.

“What we need is for someone to go and find in Africa cave art that is 120,000 years old,” Miyagawa quips.

At a minimum, a further consideration of cave art as part of our cognitive development may reduce our tendency to regard art in terms of our own experience, in which it probably plays a more strictly decorative role for more people.

“If this is on the right track, it’s quite possible that … cross-modality transfer helped develop a symbolic mind,” Miyagawa says. In that case, he adds, “art is not just something that is marginal to our culture, but central to the formation of our cognitive abilities.”

Author: Peter Dizikes | Source: Massachusetts Institute of Technology [February 21, 2018]

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Brain size of human ancestors evolved gradually over 3 million years

Modern humans have brains that are more than three times larger than our closest living relatives, chimpanzees and bonobos. Scientists don't agree on when and how this dramatic increase took place, but new analysis of 94 hominin fossils shows that average brain size increased gradually and consistently over the past three million years.

Models of human ancestors brain size compared to modern day humans
[Credit: Matt Wood, UChicago]

The research, published this week in the Proceedings of the Royal Society B, shows that the trend was caused primarily by evolution of larger brains within populations of individual species, but the introduction of new, larger-brained species and extinction of smaller-brained ones also played a part.

"Brain size is one of the most obvious traits that makes us human. It's related to cultural complexity, language, tool making and all these other things that make us unique," said Andrew Du, PhD, a postdoctoral scholar at the University of Chicago and first author of the study. "The earliest hominins had brain sizes like chimpanzees, and they have increased dramatically since then. So, it's important to understand how we got here."

Du began the work as a graduate student at the George Washington University (GW). His advisor, Bernard Wood, GW's University Professor of Human Origins and senior author of the study, gave his students an open-ended assignment to understand how brain size evolved through time. Du and his fellow students, who are also co-authors on the paper, continued working on this question during his time at George Washington, forming the basis of the new study.

"Think about the entrance to a building. You can reach the front door by walking up a ramp, or you can take the steps," Wood said. "The conventional wisdom was that our large brains had evolved because of a series of step-like increases each one making our ancestors smarter. Not surprisingly the reality is more complex, with no clear link between brain size and behavior."

Modern human brains (left) are more than three times larger than our closest relatives, chimpanzees (right)
[Credit: Andrew Du, UChicago]

"The moral is this: When you don't understand something ask a bunch of bright and motivated students to figure it out," he said.

Du and his colleagues compared published research data on the skull volumes of 94 fossil specimens from 13 different species, beginning with the earliest unambiguous human ancestors, Australopithecus, from 3.2 million years ago to pre-modern species, including Homo erectus, from 500,000 years ago when brain size began to overlap with that of modern-day humans.

The researchers saw that when the species were counted at the clade level, or groups descending from a common ancestor, the average brain size increased gradually over three million years. Looking more closely, the increase was driven by three different factors, primarily evolution of larger brain sizes within individual species populations, but also by the addition of new, larger-brained species and extinction of smaller-brained ones. The team also found that the rate of brain size evolution within hominin lineages was much slower than how it operates today, although why this discrepancy exists is still an open question.

The study quantifies for the first time when and by how much each of these factors contributes to the clade-level pattern. Du said he likens it to how a football coach might build a roster of bigger, strong players. One way would be to make all the players hit the weight room to bulk up. But the coach could also recruit new, larger players and cut the smallest ones.

"That's exactly what we see going on in brain size," he said. "The dominant process is like the players hitting the gym. They're evolving larger brains within a population. But we also see speciation events adding larger-brained daughter species, or recruiting bigger players, and we see extinction, or cutting the smallest players too."

Source: University of Chicago Medical Center [February 20, 2018]

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Did humans domesticate themselves?

Human 'self-domestication' is a hypothesis that states that among the driving forces of human evolution, humans selected their companions depending on who had a more pro-social behavior. Researchers from a team of the UB led by Cedric Boeckx, ICREA professor at the Department of Catalan Philology and General Linguistics and member of the Institute of Complex Systems of the University of Barcelona (UBICS), found out new genetic evidence for this evolutionary process.

Craniofacial differences between modern humans and Neanderthals (top)
and between dogs and wolves (bottom) [Credit: PLOS ONE]

The study, published in the science journal PLOS ONE, compared the genomes of modern humans to those of several domesticated species and their wild animal type, in order to look for overlapping genes that were associated with domestication traits, such as docility or a gracile physiognomy. The results showed a statistically significant number of genes associated with domestication which overlapped between domestic animals and modern humans, but not with their wild equals, like Neanderthals.

According to the researchers, these results reinforce the human self-domestication hypothesis and "help to shed light on one aspect that makes us human, our social instinct."

A new type of evidence: the genomes of extinct human relatives

Self-domestication would occur in species that display anatomical and behavioural features which are typical of domestic animals in comparison to their wild types. However, in these cases, domestication would have taken place without any other species domesticating the others. Several studies proposed the hypothesis stating that humans -and other species such as bonobos- domesticated themselves. The aim of this study was to find out biological evidence of the self-domestication by looking at a new type of data that has become available: the genomes of our extinct relatives, such as Neanderthals or Denisovans.

"One reason that made scientists claim that humans are self-domesticated lied within our behavior: modern humans are docile and tolerant, like domesticated species, our cooperative abilities and pro-social behaviour are key features of our modern cognition," says Cedric Boeckx. "The second reason is that modern humans, when compared to Neanderthals, present a more gracile phenotype that resembles the one seen in domesticates when compared to their wild-type cousins," added the expert.

To identify signs of a self-domestication process in humans, researchers made a list of genes associated with domestication features in humans, out of the comparison with the genome in Neanderthals and Denisovans, extinct human species. Then, they compared this list to the genome from some domesticated animals and their wild relatives, for instance, dogs compared to wolves, and cattle compared to wisents.

Results showed that this overlap was only relevant between domesticated species and humans. "Those modern humans' selected genes under selection may prove central to a relevant process of domestication, given that these interactions may provide significant data on relevant phenotypic traits," said Boeckx.

Intersection between modern humans and domesticated species

Researchers also employed other statistical measures, including control species, to certify these results. Their aim was to rule out the fact that these genes could be randomly overlapped between humans and domesticated animals when compared, so they compared the genomes among other great apes. "We found that chimpanzees, orangutans and gorillas do not show a significant overlap of genes under positive selection with domesticates. Therefore, it seems there is a 'special' intersection between humans and domesticated species, and we take this to be evidence for self-domestication," Boeckx said.

Researchers note that there is still more experimental work to do in order to find out the anatomical, cognitive and behavioural characteristics that are associated with these genes. "We suspect it will cover the anatomical, cognitive, and behavioral characteristics that researchers used to motivate the idea of self-domestication. We think that the overlap we found could help us explain our special mode of cognition and why we are strikingly cooperative, but this remains to be put to the test. In a sense, what we did is narrow down the set of genes to examine experimentally," concluded Cedric Boeckx.

Source: Universidad de Barcelona [February 15, 2018]

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Interdisciplinary approach yields new insights into human evolution

The evolution of human biology should be considered part and parcel with the evolution of humanity itself, proposes Nicole Creanza, assistant professor of biological sciences. She is the guest editor of a new themed issue of the Philosophical Transactions of the Royal Society B, the oldest scientific journal in the world, that focuses on an interdisciplinary approach to human evolution.

Credit: iStock

Stanford professor Marc Feldman and Stanford postdoc Oren Kolodny collaborated with Creanza on the special issue.

"Within the blink of an eye on a geological timescale, humans advanced from using basic stone tools to examining the rocks on Mars; however, our exact evolutionary path and the relative importance of genetic and cultural evolution remain a mystery," said Creanza, who specializes in the application of computational and theoretical approaches to human and cultural evolution, particularly language development. "Our cultural capacities-to create new ideas, to communicate and learn from one another, and to form vast social networks-together make us uniquely human, but the origins, the mechanisms, and the evolutionary impact of these capacities remain unknown."

The special issue brings together researchers in biology, anthropology, archaeology, economics, psychology, computer science and more to explore the cultural forces affecting human evolution from a wider perspective than is usually taken.

"Researchers have begun to recognize that understanding non-genetic inheritance, including culture, ecology, the microbiome, and regulation of gene expression, is fundamental to fully comprehending evolution," said Creanza. "It is essential to understand the dynamics of cultural inheritance at different temporal and spatial scales, to uncover the underlying mechanisms that drive these dynamics, and to shed light on their implications for our current theory of evolution as well as for our interpretation and predictions regarding human behavior."

In addition to an essay discussing the need for an interdisciplinary approach to human evolution, Creanza included an interdisciplinary study of her own, examining the origins of English's contribution to Sranan, a creole that emerged in Suriname following an influx of indentured servants from England in the 17th century.

Creanza, along with linguists Andre Sherriah and Hubert Devonish of the University of the West Indes and psychologist Ewart Thomas from Stanford, sought to determine the geographic origins of the English speakers whose regional dialects formed the backbone of Sranan. Their work combined linguistic, historical and genetic approaches to determine that the English speakers who influenced Sranan the most originated largely from two counties on opposite sides of southern England: Bristol, in the west, and Essex, in the east.

"Thus, analyzing the features of modern-day languages might give us new information about events in human history that left few other traces," Creanza said.

Author: Liz Entman | Source: Vanderbilt University [February 13, 2018]

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