Study looks at human cultural adaptation and the effects of ancient climate change


November 1, 2022

Most species adapt through genetic evolution. But humans, uniquely, also adapt through culture — we come up with good ideas, share them with each other, and build on the discoveries of others. Culture is central to the global success of our species, but why did it evolve in the first place?

ASU researcher Thomas J. H. Morgan and colleagues believe that one clue to why culture developed comes from our ancestors’ adaptation to environmental changes. They published the result of a set of experiments to investigate this hypothesis in the Proceedings of the Royal Society B this week. wood people in a network Download Full Image

From about two million to 10,000 years ago, a period covering much of human evolution, the global climate was extremely unstable. These unpredictable conditions are thought to be a key driver in human evolution. Genetic evolutionary changes would not have occurred quickly enough for our ancestors to adapt. Culture, however, is faster than genetic change, leading to the evolution of culture as a means to rapidly adapt to changing circumstances.

Questions about the hows and whys of culture and evolution are often addressed through purely mathematical simulations. However, simulating something as complex as the human mind is a challenge. To get around this, the researchers invited human participants to take part directly in a simulation by inhabiting a simulated online world and making decisions for simulated human ancestors. In this way, real human psychology was fed directly into the evolutionary simulation. The researchers’ goal was to see whether real human decision-making produces a culture that can respond to a changing climate and so test the hypothesis that culture itself evolved to keep up.

The researchers recruited 4,800 people to take part. Each participant was put in a group of 40 people and then challenged to figure out what to do in their virtual world. Participants were even given simulated genes that controlled whether they could learn from others or not, and successful participants “reproduced.” Newly recruited participants inherited their simulated genes from successful participants.

Depending on their simulated genes, participants could try to figure the world out on their own or learn from the decisions of the previous participants. But every so often, the virtual world changed, rendering old information from previous participants out of date. As the simulation progressed, the researchers monitored how well the group performed.

The researchers explored different ways people could learn from each other across different simulations by sharing information about what a wider range of people thought or letting them make independent decisions if they were unhappy with this shared information. Though these strategies helped participants succeed, they still didn’t prevent severe issues when the environment changed.

“Some participants engaged carefully and critically with their group’s culture, and some were even contrary mavericks who consistently did the opposite of what others were doing. But most people just went along with the majority, drawing on the accumulated expertise of past generations to make quick and effective decisions,” said Morgan, a research scientist with the Institute of Human Origins and associate professor with the School of Human Evolution and Social Change.

The general result pattern was that while the “world” was stable, the groups evolved to focus on cultural learning. But when the environment changed, cultural transmission of information could not keep up, and so groups evolved to return to individual learning.

The results hint that while there are some signs of people using culture to learn from each other to adapt and solve the problem of climate change in their simulated world, it trades off against the need to faithfully learn valuable information from previous generations. And sometimes, in order to adopt to new circumstances, participants needed to ignore some past information. However, ignoring information could lead to missing out on valuable insights from the past.  

“Some participants verified the accuracy of information they learn from others or seek out up-and-coming traits,” Morgan said. “However, these people are in the minority, and most people simply go along with the group. The tendency to conform causes severe problems when local conditions change, as many people keep doing things that are no longer a good idea, which we call cultural inertia.”

Nonetheless, there are good reasons to conform: Culture contains many good ideas, and being overly skeptical means that participants miss out and end up ignoring the accumulated experience from past generations. Thus, culture finds itself in a trade-off: The flexibility required to track rapid change works against the fidelity required to take advantage of cultural knowledge.

“Everything humans have done since the dawn of agriculture has happened in a 10,000-year blip of remarkable climactic stability. These results highlight the precariousness of humanity’s position should instability return. Culture has enabled us to do amazing things, but it’s not clear that it could handle the kind of instability that was common up to just a few thousand years ago,” Morgan said.

“For the human past, this means culture didn’t just evolve as a means of rapid adaptation, but part of its benefit also comes from the valuable ideas that can be passed down and would be unlikely to be discovered anew each generation. For the human future, this shows there are limitations to the speed with which we can adapt to new conditions, such as climate change, and we should plan accordingly.” 

Research article: The experimental evolution of human culture: flexibility, fidelity and environmental instability by Thomas J. H. Morgan, Jordan W. Suchow, Thomas L. Griffiths, can be accessed online at https://royalsocietypublishing.org/doi/full/10.1098/rspb.2022.1614.

Julie Russ

Assistant director, Institute of Human Origins

480-727-6571

ASU part of international team to study links between climate, geology, human evolution

Study possible thanks to $1.2M Keck Foundation grant


July 8, 2021

Arizona State University researchers will help lead a $1.2 million, multi-institution project that will use a new theoretical framework and state-of-the-art technology to tackle a long-standing question: How did ecological factors millions of years ago affect the evolution of our ancestors?

The possible answers so intrigued the W.M. Keck Foundation that it awarded the international team one of its largest grants to explore this question. Map of Hadar and Woranso-Mille research sites Map of the two research sites in Ethiopia — Hadar and Woranso-Mille — research sites where significant ancient hominin fossils have been discovered and are now under comparison for why there were different species living closely together, but not overlapping spatially. Google Earth image. Download Full Image

The funds will support a systematic, integrated investigation into why two adjacent, world-renowned fossil study areas in the Afar region of Ethiopia — Hadar and Woranso-Mille — have revealed strikingly different records of our human genus’s early predecessors.

ASU’s Institute of Human Origins has a more than 40-year history of exploration and discovery in Hadar, starting with the 1974 discovery of “Lucy,” the 3.2-million-year-old Australopithecus afarensis fossil, by the institute's Founding Director Donald Johanson. Since then, scientists have found hundreds more fossils of Lucy’s species at Hadar, but no other hominin species that might have lived at the same time.

Only 30 miles north of Hadar, a research project at Woranso-Mille that began in 2005, led by the institute's new director, Yohannes Haile-Selassie, has yielded ample fossils from not only Lucy’s species, but at least two others — including one whose foot appears to be adapted to tree climbing. Some of these different species existed at the same time.

Haile-Selassie and Kaye Reed, a research associate with the Institute of Human Origins and President’s Professor with the School of Human Evolution and Social Change; Beverly Saylor of Case Western Reserve University; and Naomi Levin of the University of Michigan are co-principal investigators on the W. M. Keck Foundation awarded project. Case Western Reserve University is the lead institution for the award.

Other participating institutions include Addis Ababa University, Aix Marseille University, University of Barcelona, Berkeley Geochronology Center, Ohio University and the University of Southern California. 

Haile-Selassie and Reed will lead efforts to compare and analyze the fossil record from Hadar and Woranso-Mille to assess links between rift setting, landscape-scale heterogeneity and mammal diversity, including among hominins.

“This multidisciplinary integration of physical, chemical and biological evidence will enable us to assess differences in the ecology of closely related early human ancestors and provide insights into the origins of our own genus,” said Haile-Selassie, who is a professor with the ASU School of Human Evolution and Social Change.

The transformative aspect of this project is that it is attempting, for the first time, to directly compare Hadar and Woranso-Mille to examine the environmental selective pressures that might have driven human evolution.

Seizing this opportunity involves engaging some 30 scientists whose expertise ranges from geology and paleoanthropology to geochronology and paleoclimate, including Christopher Campisano, Institute of Human Origins research associate and associate professor in the School of Human Evolution and Social Change; David Feary, research professor in the School of Earth and Space Exploration; and Denise Su, who will join the Institute of Human Origins and the School of Human Evolution and Social Change as a research associate and associate professor in August.

Over the next three years, the team will gather samples and data from both areas to gain a more detailed understanding of the two sites as they existed more than 3 million years ago.

Reed will refine the reconstructions of habitats using fauna, isotopes and depositional data for specific areas within the Hadar stratigraphy and work with Su to compare the differences in mammals and habitats between the two sites.

“This is the first time we have the opportunity to compare the paleoecology of unique fauna and hominins from adjacent areas in the same time period,” Reed said. “It will give us a level of detail that we haven’t had and enable us to explore why there were different species living close together but not overlapping spatially. It’s very exciting.”

Campisano will lead the geologic efforts at Hadar, guiding and working with a team of geoscientists that are new to Hadar to collect high-resolution samples and data at particular time intervals to compare to Woranso-Mille.

“Better integrating Hadar’s geology and paleoenvironments with adjacent project sites has been a goal of mine for more than a decade,” Campisano said. “The chance to do this, and with a suite of new-to-Hadar analytical techniques, is an intriguing opportunity.”

Su will primarily be responsible for the reconstruction of the paleoenvironment at Woranso-Mille using the faunal evidence and integrating the geologic, isotopic and paleobotanic data.

“Woranso-Mille is the only Pliocene site that documents at least two contemporaneous hominin species. Reconstructing its paleoenvironment will be crucial to understanding how the hominins shared the landscape,” Su said.

Rounding out the ASU team is Feary, who will be developing a high-resolution 3D model of the Hadar focus area using recently developed aerial photogrammetric techniques as a base for the geological and habitat reconstructions.

“The W.M. Keck Foundation award provides an amazing opportunity to use new research tools to address fundamental paleoenvironmental and human evolution questions,” Feary said.

If successful, this project will reveal the spatial context of hominin diversity records — one of the great challenges to understanding human evolution and a fundamental question of biodiversity. 

“This project builds on decades of field studies, laboratory analyses and museum work, that together with the differences in hominin species in neighboring but distinct geological landscapes provide an unprecedented opportunity to understand the ecological characteristics that influence human diversity and evolution,” said Saylor, who is the lead investigator on the project.

Haile-Selassie added, “This project takes human origins research to another level. Understanding how tectonics and rifting may have played a role in the diversity or lack of diversity in early human ancestors, and how these forces may have shaped the landscapes and associated climates in which our earlier ancestors diversified or went extinct would be a major breakthrough in paleoanthropology.” 

Ethiopia’s Authority for Research and Conservation of Cultural Heritage and the Afar Regional Government will be facilitating local permits for this research.

The W. M. Keck Foundation was established in 1954 in Los Angeles by William Myron Keck, founder of The Superior Oil Company. One of the nation’s largest philanthropic organizations, the W. M. Keck Foundation supports outstanding science, engineering and medical research. The foundation also supports undergraduate education and maintains a program within southern California to support arts and culture, education, health and community service projects.

ASU has received a number of awards from the Keck Foundation; the most recent was a Science and Engineering grant in 2018 related to materials science.

Julie Russ

Assistant director, Institute of Human Origins

480-727-6571